Cardiovascular system USLME (MCQs)

15. A 35-year-old man with no significant medical history presents to his primary care physician with a 2-week history of progressive shortness of breath that occurs with activity. He previ- ously exercised regularly and has never had symptoms like this before, but now he finds that he can walk only one block before becom- ing symptomatic. He has also noticed a 7-lb (3.2-kg) weight gain during this time. He does not smoke or use alcohol or illicit drugs and has not traveled recently. In addition, he has no family history of cardiac disease and does not have any sick contacts, but recalls having an upper respiratory infection about a month ago that improved on its own. Physical exami- nation reveals crackles in his lungs bilaterally and an S3 gallop. X-ray of the chest reveals car- diomegaly. What is the most likely mechanism causing this patient's heart failure? (A) Antibodies to a variety of cardiac proteins that ca

A 15. The correct answer is B. This patient is most likely experiencing congestive heart failure (CHF) secondary to dilated cardiomyopathy (DCM), which is characterized by dilation and impaired contraction of one or both ventricles. Symptoms of CHF include dyspnea (especially on exertion), orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema with weight gain. DCM may also present with arrhythmias such as atrial fibrillation, or sudden cardiac death. DCM has a variety of etiologies includ- ing idiopathic, myocarditis, ischemic, drug- induced, hypertension, infiltrative disease, HIV infection, connective tissue disease, and the chemotherapeutic agent doxorubicin. In this case the most likely cause of the patient's DCM is viral myocarditis following his upper respiratory infection several weeks ago. Viruses known to cause myocarditis include coxsackie- virus, influenza virus, adenovirus, echovirus, cytomegalovirus, and HIV. These viruses cause myocarditis with subsequent DCM by inflict- ing direct cytotoxicity via receptor-mediated entry of the virus into cardiac myocytes. Pa- tients with myocarditis may present initially with symptoms of chest pain or arrhythmias with ECG changes; in others, symptoms of heart failure may be the initial manifestation, as in this patient. Answer A is incorrect. Antibodies to a variety of cardiac proteins causing immune-mediated damage to myocytes is the suspected mecha- nism of injury in familial DCM. This disorder is usually inherited in an autosomal dominant manner and therefore is associated with a sig- nificant family history of CHF. Given the patient's recent history of an upper respiratory infection and lack of a family history of cardiac disease, viral myocarditis leading to DCM is the more likely etiology of his CHF.

18. Jugular venous pressure (JVP) curves are de- signed to show the pressure changes that nor- mally take place in the right atrium through- out the cardiac cycle. A JVP curve consists of two, or sometimes three, positive waves and two negative troughs. A normal JVP curve is shown in the image. Which of the following points on the normal jugular venous tracing in the image would be most prominently affected in tricuspid regurgitation? (A) A and C (B) A and Y (C) C and X (D) V and Y

A 18. The correct answer is C. In tricuspid regurgi- tation, blood flows back into the atria during ventricular systole. This would affect the C and X waves, replacing them with a large positive deflection. This positive deflection joins the C wave and the V wave, creating the "CV wave." The C wave is thought to be due to pressure on the tricuspid valve during ventricular sys- tole. If the valve allows backflow during ven- tricular systole, the pressure would drastically increase in the atria. The downward move- ment of the ventricle causes the X descent dur- ing ventricular systole. This would also be re- placed by a positive deflection from blood regurgitating into the atria during ventricular systole. Answer A is incorrect. These points are not the most likely to be affected in tricuspid regurgitation. Answer B is incorrect. These points are not the most likely to be affected in tricuspid regurgitation. Answer D is incorrect. These points are not the most likely to be affected in tricuspid regurgitation. The V wave is increased pressure because of right atrial filling against a closed tricuspid valve. With tricuspid regurgitation, not much change is seen with the V wave itself, but rather it is the end point for the new CV wave change.

22. A baby is observed at birth to be noncyanotic. The mother is known to have been infected with rubella during the pregnancy. On physi- cal examination the patient is found to have a continuous murmur that is present in both sys- tole and diastole. A nonsteroidal anti-inflam- matory drug is prescribed, and on follow-up the murmur has disappeared. Which of the fol- lowing is the most likely congenital lesion? (A) Patent ductus arteriosus (B) Tetralogy of Fallot (C) Transposition of the great vessels (D) Truncus arteriosus (E) Ventricular septal defect

A 22. The correct answer is A. A patent ductus arte- riosus (PDA) rarely causes cyanosis. PDAs are associated with maternal rubella infection dur- ing pregnancy. During fetal development, the ductus arteriosus remains patent through the action of prostaglandin I2 (PGI2). PDAs at birth are closed with indomethacin, a non- steroidal anti-inflammatory drug that inhibits PGI2 formation. Remember that there are, in general, three congenital heart lesions that cause late cyanosis due to left to right shunt: ventricular septal defect, atrial septal defect, and PDA. The classic murmur heard with PDA is a continuous machinelike murmur.

3. A 50-year-old man with diabetes receives the results of a fasting lipid profile that reveals hy- percholesterolemia. To reduce the patient's mortality risk, his physician recommends life- style changes and initiates therapy with a sta- tin. Which of the following mechanisms de- scribes the action of statins in reducing serum levels of LDL cholesterol? (A) Competitive inhibition of 3-hydroxy- 3-methylglutaryl coenzyme A reductase (B) Inactivation of 3-hydroxy-3-methylglutaryl coenzyme A synthase (C) Negative feedback to decrease thiolase ac- tivity (D) Noncompetitive inhibition of citrate syn- thase (E) Positive feedback to increase 3-hydroxy- 3-methylglutaryl coenzyme A lyase activity

A 3. The correct answer is A. 3-Hydroxy-3-methyl- glutaryl coenzyme A reductase (HMG-CoA re- ductase) catalyzes the rate-limiting step in the synthesis of cholesterol. The enzyme converts 3-hydroxy-3-methylglutaryl coenzyme A (HMG- CoA) to mevalonic acid, a cholesterol precursor. Statins competitively inhibit HMGR by ob- structing part of the enzyme's active site and preventing sufficient interaction with HMG- CoA to produce mevalonate. The consequent decrease in intrahepatic cholesterol causes up- regulation of hepatic LDL cholesterol receptors, ultimately lowering plasma LDL cholesterol levels. Diabetes mellitus is considered a cardiac heart disease equivalent, and by the ATP III rec- ommendations, the target LDL cholesterol of a diabetic patient is <100 mg/dL, with pharmaco- therapy initiated at levels >130 mg/dL.

30. Drugs such as cholestyramine and colestipol have been shown to decrease circulating serum LDL cholesterol and to slightly elevate triglyc- erides. These drugs work by which of the fol- lowing mechanisms? (A) Binding and excretion of bile-soluble lipids (B) Decreased peripheral lipolysis (C) Increased lipoprotein lipase activity (D) Inhibition of cholesterol absorption at the small intestine brush border (E) Inhibition of the rate-limiting enzyme of cholesterol formation (F) Retention of bile acid resins in hepatocyte

A 30. The correct answer is A. Cholestyramine and colestipol are bile acid resins that promote binding and excretion of dietary fats that are bile-soluble. This prevents such fats from en- tering the blood stream effectively. They de- crease serum LDL and total cholesterol levels.

36. A 76-year-old woman visits the emergency department complaining of increased fatigue. She states that she tires easily even with very low lev- els of activity. Her temperature is 36.7° C (98.1° F), heart rate is 123 beats/min, and blood pres- sure is 85/43 mm Hg. The woman has a history of coronary artery disease and diabetes. She also notes a recent traumatic episode when her grandson kicked her in the chest when she was picking him up. On physical examination, her doctor notices a disappearing arterial pulse on inspiration. The doctor orders an echocardio- gram to confirm the diagnosis. What invasive procedure will be necessary to treat this patient? (A) Angioplasty (B) Aortic valve replacement (C) Mitral valve replacement (D) Pericardiocentesis (E) Surgical reduction of an aortic aneurys

A 36. The correct answer is D. This patient has car- diac tamponade. Although Beck's clinical triad of jugular venous distension, muffled heart sounds, and hypotension is more specific, the clinician must sometimes rely on other phys- cial findings. Pulsus paradoxus (systolic blood pressure that drops >10 mm Hg during inspira- tion) is usually present. Pulsus paradoxus could also be detected by noting extra beats on car- diac auscultation while simultaneously palpat- ing the radial pulse. Pericardiocentesis is re- quired immediately and may be life-saving. The fluid that has filled the pericardial mem- brane is removed, thereby reversing the pres- sure levels that led to the elevated intracardiac pressure, limited ventricular filling, and re- duced cardiac output that ultimately caused her symptoms of fatigue and pulsus paradoxus.

43. A 32-year-old man with diabetes presents to his physician with orthostatic hypotension. This suggests a deficiency in the normal physiologic response carried out by arterial baroreceptors located in the aortic arch and the carotid sinus. What is the normal physiologic response to hypotension? (A) Decreased baroreceptor afferent firing in the aortic arch leads to increased sympa- thetic efferent firing (B) Decreased baroreceptor afferent firing in the carotid sinus leads to increased para- sympathetic efferent firing (C) Decreased baroreceptor afferent firing in the carotid sinus leads to increased sympa- thetic efferent firing (D) Increased baroreceptor afferent firing in the aortic arch leads to increased parasym- pathetic efferent firing (E) Increased baroreceptor afferent firing in the carotid sinus leads to increased para- sympathetic efferent firing

A 43. The correct answer is C. The carotid sinus baroreceptor sends an afferent signal via the glossopharyngeal nerve to the medulla, which in turn responds with a sympathetic efferent signal that causes vasoconstriction, increased heart rate, increased contractility, and in- creased blood pressure. Answer A is incorrect. The baroreceptor lo- cated in the aortic arch responds only to an increase in blood pressure.

9. A 56-year-old woman arrives in the emergency department complaining of dizziness and headache. Her blood pressure is 210/140 mm Hg. She is currently not taking any medica- tions and has not seen a doctor for several years. The physician decides to address her hy- pertension urgently. Which of the following drugs is contraindicated in this patient? (A) Intravenous diltiazem (B) Intravenous labetalol (C) Intravenous metoprolol (D) Oral captopril (E) Sublingual nifedipine

A 9. The correct answer is E. Nifedipine is a dihydropyridine class calcium channel blocker that could be used in the long-term control of hy- pertension. However, in the case of a hyperten- sive emergency, nifedipine used sublingually can cause dangerous fluctuations in blood pressure that are difficult to control and can lead to more harm than good. Answer A is incorrect. Diltiazem is a benzo- thiazepine class calcium channel blocker that reduces myocardial demand and also causes vasodilation. It is not contraindicated in this patient. Answer B is incorrect. Labetalol is a com- bined α/β-blocker that has effects on both re- ceptors. It can be used in a hypertensive situa- tion as an emergent option for treatment. It is not contraindicated in this patient. Answer C is incorrect. Metoprolol is a β-blocker used to treat angina by reducing heart rate and contractility. It also reduces the metabolic demand of the myocardium. It is of- ten used to control hypertension, but is not contraindicated in this patient. Answer D is incorrect. Captopril is an angio- tensin-converting enzyme inhibitor used in the control of chronic hypertension. It is especially useful for patients who have signs of renal dis- ease and can slow the progression of damage to the ki

16. A 25-year-old pregnant woman goes to her gy- necologist for her 36-week checkup. She com- plains of light-headedness when she goes to bed at night. In the office, her blood pressure is 120/70 mm Hg while sitting upright and 90/50 mm Hg while lying supine. Which of the following is the most likely cause of this hy- potension? (A) Cardiogenic shock (B) Inferior vena cava compression (C) Neurogenic shock (D) Third spacing of fluid (E) Vasodilation

B 16. The correct answer is B. Inferior vena cava (IVC) compression is common in women dur- ing the third trimester of pregnancy. The large uterus compresses the IVC, decreasing venous return to the heart. This reduction in preload reduces stroke volume, thus reducing cardiac output. Recall that mean arterial pressure = cardiac output × total peripheral resistance; an acute decrease in either of these parameters will reduce blood pressure

17. A 48-year-old obese man presents to his pri- mary care physician with complaints of lower leg pain that occurs after he walks a few city blocks and is relieved with rest. He has no other complaints. His blood pressure is 165/85 mm Hg, his pulse is 83/min, and his respira- tory rate is 18/min. After further questioning, he admits to smoking two packs of cigarettes per day. Which of the following types of vessels is most likely involved in the pathologic pro- cess surrounding this patient's symptoms? (A) Arteries (B) Arterioles (C) Capillaries (D)Veins (E) Venules

B 17. The correct answer is A. This patient is pre- senting with intermittent claudication. Com- bined with his history of smoking, this points to peripheral arterial disease, which is often the presenting sign of atherosclerosis. Peripheral atherosclerosis targets areas of high turbulence typically found at branching arterial sites; the most common sites are the abdominal aorta and iliac arteries, femoral and popliteal arteries (which is causing the calf pain in this patient), and tibial and peroneal arteries. Medical ther- apy with antiplatelet drugs such as aspirin has had moderate success, with surgical revascular- ization reserved for severe cases. Risk factors for atherosclerosis include smoking, hyperten- sion, diabetes mellitus, hyperlipidemia, and a positive family history. Answer B is incorrect. Arterioles help provide the dynamic regulation of blood flow through the capillary beds. Although they are the site of principle resistance in blood flow, they do not have the turbulence necessary to predispose to atherosclerotic formation. They, along with small muscular arteries, are the major site af- fected by hypertension.

26. A 72-year-old woman has a 1-month history of left-sided jaw pain when chewing food, head- ache, fever, and fatigue. Laboratory studies re- veal an elevated erythrocyte sedimentation rate. Which of the following arteries is most likely involved? (A) External carotid artery (B) Facial artery (C) Ophthalmic artery (D) Postauricular artery (E) Superficial temporal artery

B 26. The correct answer is E. This individual is likely suffering from giant cell (temporal) ar- teritis (GCA), the most common systemic vasc- ulitis in adults. GCA, which affects large to small arteries, typically presents in people >50 years old and is more common in women. Pa- tients commonly present with constitutional symptoms (anorexia, fatigue, weight loss), uni- lateral temporal or occipital headache with overlying scalp tenderness, jaw claudication, and impaired vision. The superficial temporal artery is the most commonly affected artery in patients with GCA and is affected in this pa- tient. On biopsy, affected arteries are character- ized by nodular thickening that reduces the size of the lumen, granulomatous inflamma- tion with mononuclear and giant cells, and fragmentation of the internal elastic mem- brane. GCA is treated with high-dose corticos- teroids to reduce inflammation rapidly and prevent permanent blindness. Answer A is incorrect. GCA typically affects branches of the external carotid artery, such as the superficial temporal artery. It can also af- fect branches of the internal carotid artery, such as the ophthalmic artery. Unilateral vision loss can also be caused by a cholesterol em- bolus from a plaque on the common or inter- nal carotid artery, but not the external carotid artery.

33. A 57-year-old white man presents to his pri- mary care physician with dyspnea. He says that he likes to maintain his yard and garden, but that he has recently had trouble doing the work, and becomes short of breath even walk- ing up the one flight of stairs in his house. On further questioning, he says that sometimes he wakes up short of breath in the middle of the night. Physical examination demonstrates pit- ting ankle edema. Which of the following find- ings would also be expected in this patient? (A) Decreased sympathetic outflow (B) Decreased venous pressure (C) Increased aldosterone secretion (D) Increased effective arterial blood volume (E) Increased glomerular filtration r

B 33. The correct answer is C. This individual is presenting with signs typical of CHF. In CHF, there is a decrease in effective arterial blood volume due to the inability of the heart to ef- fectively pump blood, which stimulates the renin-angiotensin-aldosterone axis to increase the tubular absorption of Na+ to help increase intravascular volume. Answer B is incorrect. The venous pressure would actually be increased due to the inability of the heart to effectively pump blood to the arterial system; this would lead to a passive congestion of blood in the venous circulation. This increased venous pressure can result in passive congestion of the liver known as a "nut- meg" liver.

35. A 73-year-old man with a history of hyperten- sion and type 2 diabetes mellitus presents with the sudden onset of right-sided paralysis. An ul- trasound study shows significant atherosclerosis in a major artery that is embryologically derived from one of the aortic arches. The ar- tery that is most likely involved in this patient's paralysis is derived from which of the following aortic arches? (A) First aortic arch (B) Second aortic arch (C) Third aortic arch (D) Fourth aortic arch (E) Sixth aortic arch

B 35. The correct answer is C. Given his age and his history of hypertension and diabetes, this patient is most likely presenting with a stroke. Part of the workup for stroke includes an ultra- sound to evaluate the carotid arteries, which in this case showed significant atherosclerosis, the likely cause of the man's stroke. The common carotid arteries, as well as the proximal part of the internal carotids, have their embryologic origins in the third aortic arch. Remember this by noting that "C" is the third letter of the al- phabet. The aortic arches are responsible for the major arteries in the head and neck re- gions, while the descending aorta is the origin for the arteries in the rest of the body. Answer A is incorrect. The first aortic arch gives rise to the maxillary artery, which is not involved in the pathophysiology of stroke. Answer B is incorrect. The second aortic arch gives rise to the stapedial (Second = Stapedial) and hyoid arteries, neither of which is involved in stroke. Answer D is incorrect. The fourth aortic arch gives rise to the adult arch of the aorta on the left and the proximal part of the right subcla- vian artery on the right. In theory, it is possible for an embolus from an aortic arch thrombus to travel up the carotid and cause a stroke, but this is not a likely scenario and would not be evaluated by ultrasound. Similarly, a subcla- vian embolus may travel up the vertebral arter- ies to cause a posterior stroke, but this would not be evaluated by ultrasound.

37. A 60-year-old woman dies in a car accident. On autopsy, the cause of death is determined to be a massive brain hemorrhage due to a skull fracture. An additional abnormality, shown below in the image of the opened left atrium, is also found and determined to be un- related to the cause of death. This abnormality could have led to which of the following physi- cal examination findings when the woman was alive? (A) Continuous murmur throughout both dias- tole and systole, loudest at the end of ven- tricular systole (B) Decrescendo murmur in early ventricular diastole (C) Sharp, high-pitched sound in early ventricular diastole, followed by a decrescendo, crescendo murmur (D) Sharp, high-pitched sound in early ventric- ular systole, followed by a crescendo, decrescendo murmur (E) Sharp, high-pitched sound in mid ven- tricular systole, followed by a uniform murmur

B 37. The correct answer is C. This image shows mi- tral stenosis, causing a classic "fish-mouth" ap- pearance due to the fusion of the valve leaflets. Mitral stenosis often causes a sharp, high- pitched opening snap at the beginning of dias- tole, due to the opening of the stiffened mitral valve leaflets, followed by a decrescendo- crescendo murmur. The shape of the murmur of mitral stenosis is unique and occurs because the pressure gradient between the left atrium and left ventricle is the greatest when the mitral valve opens and decreases during rapid and slow ventricular filling (decrescendo) and then intensifies slightly during atrial contraction at the end of ventricular diastole (crescendo). The murmur of mitral stenosis is low-pitched and is best heard at the apex of the heart. This woman may have had rheumatic heart disease, which is the most common cause of mitral stenosis. Answer A is incorrect. A patent ductus arterio- sus causes a continuous murmur as blood flows from the higher-pressure aorta to the lower- pressure pulmonary artery during both diastole and systole. The murmur increases during ven- tricular systole as the pressure in the aorta in- creases, reaches a maximum at the end of ven- tricular systole, and decreases throughout diastole, as the pressure in the aorta decreases. This patient, however, has a stenotic mitral valve, not a patent ductus arteriosus. Answer B is incorrect. Aortic or pulmonic re- gurgitation, not mitral stenosis, would cause a decrescendo murmur that would be loudest in early diastole, when the pressure gradient be- tween the aorta and the left ventricle is the greatest, and would decrease throughout dias- tole as the left ventricular pressure increases. Answer D is incorrect. Aortic stenosis leads to a crescendo-decrescendo murmur best heard at the right sternal border duri

38. A 3-year-old boy comes to the pediatrician with fever, conjunctivitis, erythema in the oral mu- cosa, and cervical lymphadenopathy. The boy suddenly becomes hypotensive and goes into cardiac arrest and dies shortly thereafter. Au- topsy shows aneurysmal dilations of the left cir- cumflex and right coronary arteries. The boy's disease is characterized as a self-limiting dis- ease that most commonly affects the coronary arteries. Which of the following diseases is the correct diagnosis? (A) Buerger's disease (B) Kawasaki's disease (C) Polyarteritis nodosa (D) Takayasu's arteritis (E) Wegener's granulomatosis

B 38. The correct answer is B. This is Kawasaki's disease, which typically affects infants and children under 5 years old is self-limiting. It in- volves the mouth, skin, and lymph nodes at first, but if left untreated the patient may have arrhythmias due to inflammation of the outer membranes of the heart. The most common histopathologic sign of Kawasaki's disease is acute necrotizing vasculitis of small and medium-sized vessels. Answer A is incorrect. Buerger's disease is characterized as an idiopathic, segmental thrombosing vasculitis with intermittent clau- dication, superficial nodular phlebitis, and cold sensitivity. Patients are usually young men (20- 40 years old) who are also heavy smokers. Answer C is incorrect. PAN is characterized by cotton-wool spots, microaneurysms, and pal- pable purpura. This condition most often arises in the fourth or fifth decades of life, and is twice as likely to occur in men. It is also associ- ated with hepatitis B. The cardinal histopatho- logic sign is inflammation throughout the en- tire arterial wall. PAN predominantly affects the kidneys, peripheral nervous system, and gastrointestinal tract and can lead to symptoms such as renal failure, mononeuritis multiplex, and bowel infarction. Up to 80% of patients with PAN have P-ANCA, an antibody against myeloperoxidase. Answer D is incorrect. Takayasu's arteritis is characterized by weak pulses in the upper ex- tremities, fever, arthritis, and night sweats. The condition most often arises in women under the age of 40 years (9:1 female predominance). The classic pulselessness is a result of chronic inflammation and subsequent narrowing of the aorta and its branches, making it a large-vessel vasculitis. Answer E is incorrect. Wegener's granuloma- tosis is characterized by necrotizing granulo- mas in the lung and upper airways togethe

45. A patient presents for treatment of his severe essential hypertension. He is being treated with numerous medications for high blood pressure, and hydralazine was recently added to his med- ication regimen. He explains that he has been experiencing flushing and headaches since his last visit, when hydralazine therapy was started. Which of the following is an adverse effect of hydralazine? (A) Angina (B) Cardiotoxicity (C) First-dose orthostatic hypotension (D) Nephrotoxicity (E) Pulmonary embolism

B 45. The correct answer is A. At toxic levels of hydralazine, the body may compensate with se- vere reflex tachycardia as well as with salt and water retention. Because of these compensa- tions, a patient with cardiac disease may experi- ence angina as a result of increased oxygen de- mand secondary to increased cardiac output or increased heart rate. Hydralazine works by in- creasing cyclic guanosine monophosphate, which induces smooth muscle relaxation. This smooth muscle relaxation occurs more in the arterioles than in the veins and thus reduces the afterload on the heart Answer B is incorrect. Hydralazine does not have any direct cardiotoxic effects. Many other drugs do, such as digoxin or theophylline, if given out of their therapeutic range Answer C is incorrect. Prazosin, an α-blocker, may cause first-dose orthostatic hypotension. Answer D is incorrect. Hydralazine does not directly cause nephrotoxicity. The most com- mon drug classes associated with nephrotoxic- ity include penicillins, cephalosporins, sulfon- amides, and nonsteroidal anti-inflammatory drugs. Answer E is incorrect. Pulmonary embolism (PE) typically occurs in the setting of preexist- ing risk factors such as surgery, extended peri- ods of venous stasis in the lower extremities, pregnancy, or disease states such as malignancy or autoimmunity. Hydralazine treatment alone does not increase the risk for PE.

8. This image depicts the administration of drug X, which produces an increase in systolic, dia- stolic, and mean arterial pressure. Drug Y is then added, resulting in little or no change to the blood pressure. Drug X is then readminis- tered, causing a net decrease in blood pressure. Which of the following drug combinations are drug X and drug Y, respectively? A) Epinephrine, phentolamine (B) Isoproterenol, clonidine (C) Norepinephrine, propranolol (D) Phenylephrine, metoprolol (E) Phenylephrine, phentolamine

B 8. The correct answer is A. Epinephrine is a non- selective agonist of α and β adrenergic recep- tors. Administering a large dose of epinephrine causes an increase in blood pressure via an in- creased heart rate and contractility through stimulation of β1 receptors (the β2 effect is minimal) and increased systemic vascular resis-

10. A 65-year-old man presents to the emergency department with chest pain that he noticed af- ter climbing a set of stairs. The emergency physician sends him for an exercise stress test. Which of the following physiologic mecha- nisms does the heart use to deal with increased work demand during an exercise stress test? (A) Decreased coronary artery diameter (B) Decreased metabolite production (C) Decreased oxygen extraction (D) Increased coronary blood flow (E) Increased oxygen extraction

C 10. The correct answer is D. An increase in myocardial contractility due to exercise leads to in- creased oxygen demand by the cardiac muscle and increased oxygen consumption, causing local hypoxia. This local hypoxia causes vaso- dilation of the coronary arterioles, which then produces a compensatory increase in coronary blood flow and oxygen delivery to meet the de- mands of the cardiac muscle. Oxygen extraction from heart muscle is maximized. In- creased demand can be met only by increasing blood flow. Answer C is incorrect. The heart cannot in- crease or decrease its oxygen extraction. Even if this were the primary means of supplying the extra demand for oxygen, the heart would re- spond by increasing oxygen extraction, not decreasing.

14. A 67-year-old woman presents to the emer- gency department with dizziness, syncope, and palpitations. She states she is taking a medica- tion for "heart troubles" but cannot remember its name. Results of an ECG are shown in the image. Which of this patient's current medica- tions might have caused this abnormal ECG pattern (A) Adenosine (B) Bretylium (C) Propranolol (D) Quinidine (E) Verapamil

C 14. The correct answer is D. The ECG shows tor- sades des pointes. Quinidine is a class IA anti- arrhythmic agent used in the treatment of su- praventricular arrhythmias. Quinidine slows conduction and can increase the QT interval, leading to torsades de pointes. Answer A is incorrect. Adenosine is used both to diagnose and to treat supraventricular tach- yarrhythmias. However, it is not associated with torsades des pointes. Answer B is incorrect. Although the class III antiarrhythmics tend to be associated with tor- sades des pointes, especially sotalol, bretylium is an exception. Answer C is incorrect. Propranolol is a class II antiarrhythmic but is not associated with tor- sades des pointes. β-Blockers such as propra- nolol are used to suppress abnormal pacemak- ers by decreasing the slope of phase 4 (slow diastolic depolarization in pacemaker cells). Answer E is incorrect. Bepridil, not verapamil, is a calcium channel blocker and class IV anti- arrhythmic associated with torsades des pointes. Verapamil and diltiazem are two calcium chan- nel blockers used in the prevention of nodal arrhythmias (e.g., supraventricular tachycar- dia).

2. A 28-year-old African-American man presents to the physician with fever, weight loss, and ab- dominal pain. His blood pressure is 168/92 mm Hg, his pulse is 83/min, and his respira- tory rate is 18/min. On physical examination, there is palpable purpura on his lower extremi- ties; a fundoscopic examination reveals fluffy, white spots on his retina. His past medical his- tory is significant for a previous hepatitis B in- fection. An arterial biopsy is shown in the im- age. Which of the following is the most prominent morphologic feature of the affected arteries in this patient's disease process? (A) Caseating necrosis (B) Eosinophilic infiltrate (C) Fibrinoid necrosis (D) Granulomatous inflammation (E) Langhans' giant cells (F) Onion skinning

C 2. The correct answer is C. This individual is likely suffering from polyarteritis nodosa (PAN), which is characterized by necrotizing immune complex inflammation of small or medium-sized arteries. PAN is typically associ- ated with fever, malaise, weight loss, abdomi- nal pain, headache, myalgias, and hyperten- sion. There are no diagnostic serologic tests specific for PAN. Patients with classic PAN are ANCA-negative and may have low titers of rheumatoid factor or antinuclear antibodies, both of which are nonspecific findings. In pa- tients with PAN, appropriate serologic tests for active hepatitis B infection must be performed as up to 30% of patients with PAN are positive for hepatitis B surface antigen. Histologically, the intense inflammatory infiltrate in the arte- rial wall and surrounding connective tissue is associated with fibrinoid necrosis and disrup- tion of the vessel wall. Answer A is incorrect. Caseating necrosis is as- sociated with tuberculosis infections. The gran- uloma of tuberculosis is referred to as a tuber- cle, and is characterized by central caseous necrosis and often by Langhans' giant cells. These lesions often coalesce and rupture into bronchi. The caseous contents may liquefy and be expelled, resulting in cavitary lesions. Answer B is incorrect. Eosinophilic infiltrate is a more prominent feature in Churg-Strauss syndrome, a necrotizing vasculitis of small and medium-sized muscular arteries, capillaries, veins, and venules. Patients with Churg-Strauss syndrome often present with severe asthma attacks, pulmonary infiltrates, and mononeuri- tis multiplex, along with nonspecific symptoms such as weight loss, fever, malaise, and an- orexia. Answer D is incorrect. Granulomatous infil- trate is a more prominent feature in giant cell arteritis (also known as temporal arteritis), an inflammator

24. A 62-year-old man was admitted to the inten- sive care unit for overwhelming sepsis. The pa- tient has received 4 L of normal saline bolus fluids. Empirical antibiotics were begun with no improvement in his condition. His blood pressure is 60/30 mm Hg, pulse is 112/min, temperature is 40.6° C (105° F), and respira- tory rate is 23/min. The physician orders intra- venous norepinephrine. Which of the follow- ing is a direct effect of norepinephrine in this clinical scenario? (A) Bradycardia (B) Bronchoconstriction (C) Coronary vasodilation (D) Decreased inotropy (E) Periphearl vasodilation

C 24. The correct answer is C. Norepinephrine, a potent direct-acting α-agonist and a moderate β-agonist, can be useful in cases of septic shock because it stimulates peripheral vasoconstric- tion. However, the coronary vasculature ex- presses both α- and β-adrenergic receptors, with a net effect of vasodilation of the coronary vessels when catecholamines are present in high levels. Norepinephrine also exerts a mild inotropic effect as a β1-agonist, but this effect may not be clinically relevant. Successful treat- ment of septic shock involves fluids, proper an- tibiotics, and pressors (i.e., norepinephrine) if the blood pressure is unresponsive to fluid re- suscitation. Pressors are given to maintain tis- sue perfusion.

29. A 24-year-old man presents to the emergency department with a fever, chills, night sweats, malaise, and fatigue that started 3 days ago. In the past day he has also become short of breath. He admits to using intravenous drugs regularly. At presentation, the patient is shak- ing and appears pale. Physical examination is remarkable for a temperature of 39.4° C (103° F), hypoxia to 88% on room air, jugular venous distention, bilaterally decreased breath sounds at the bases with dullness to percussion at the bases, and a grade III/VI systolic murmur heard best at the lower left sternal border. The pa- tient states that he never had anything wrong with his heart before. Which pathogen is most likely responsible for this patient's condition? (A) Enterococcus faecalis (B) Haemophilus aphrophilus (C) Staphylococcus aureus (D) Streptococcus bovis (E) Viridans streptococci

C 29. The correct answer is C. This patient is pre- senting with a classic case of acute bacterial endocarditis (ABE). Endocarditis is often char- acterized by constitutional symptoms (fever, malaise, chills), new-onset cardiac murmur, and a combination of other signs and symp- toms (e.g., Janeway lesions, Osler nodes, and Roth spots). Acute and subacute endocarditis can be differentiated based on history, as the acute case will have a more severe and sudden onset, as in this patient. ABE is also most often seen in cases of intravenous drug use and in- dwelling catheters, and Staphylococcus aureus is the most common bacterial pathogen iso- lated in these cases because it is part of the skin flora and enters the blood at needle sites. This patient's history of intravenous drug abuse as well as auscultation of a murmur consistent with tricuspid regurgitation both point to a right-sided ABE infection. In right-sided endo- carditis, septic emboli to the lungs leading to bilateral infiltrates are seen more often. This patient is manifesting signs of bilateral infil- trates with signs of hypoxia, decreased breath sounds, and dullness to percussion. It is impor- tant to note that many of the classic signs of endocarditis, such as Janeway lesions, Osler nodes, and Roth spots, are mostly seen as a complication of left-sided endocarditis, in which septic emboli leave the heart and enter the systemic circulation.

31. A 30-year-old patient comes to an ophthalmol- ogist with complaints of decreased vision. On examination, angiomatous lesions are visible in the retina. The patient also has documented cerebellar and spinal hemangioblastomas, bilateral renal cysts, and pancreatic microcystic adenomas. A previous chromosomal analysis on this patient showed a deleted tumor suppressor gene. A detailed family history shows similar problems in the patient's brother, father, aunt, and grandfather. Which of the following is the inheritance pattern of this patient's disease? (A) Autosomal dominant (B) Autosomal recessive (C) Mitochondrial (D) Spontaneous (E) X-linked recessive

C 31. The correct answer is A. This patient has von Hippel-Lindau syndrome, an autosomal domi- nant disorder characterized by abnormal blood vessel growth. The overgrowth of blood vessels leads to angiomas and hemangioblastomas in the retina, brain, and spinal cord, as well as in other regions of the body. Patients also show cystic growths in the kidneys and pancreas, pheochromocytomas, islet cell tumors, and clear cell renal carcinoma. The disease is due to deletion of the VHL tumor suppressor gene on the short arm of chromosome Answer C is incorrect. In mitochondrial in- heritance, children (male and female) of an af- fected mother may exhibit the disease. The dis- ease is not transmitted from fathers to any of their children (only maternal transmission). Von Hippel-Lindau syndrome is not inherited in this mann

40. A 67-year-old woman who has recently begun to take a new antihypertensive medication presents to her primary care physician with complaints of new-onset fatigue and depressed mood. Her physical examination is unremark- able except for a heart rate of 56/min. Labora- tory tests show: Na+: 137 mEq/L K+: 4.0 mEq/L Blood urea nitrogen: 12 mg/dL Creatinine: 0.5 mg/dL Glucose: 82 mg/dL Which of the following is most likely the new medication that this patient has started? (A) Furosemide (B) Hydrochlorothiazide (C) Losartan (D) Metoprolol (E) Nifedipine (F) Prazosin

C 40. The correct answer is D. The patient's primary complaints are fatigue and depression that be- gan after she started a new medication. Her physical examination and laboratory studies are within normal limits and reveal no additional side effects of this new medication. Mild seda- tion and depression are common adverse ef- fects of β-blockers; diarrhea, pruritis, distur- bance of the sleep cycle, exercise intolerance, and a diminished hypoglycemic response can also occur with the use of β-blockers. Of all the medications listed, metoprolol is the only one that may cause depression. Answer A is incorrect. Furosemide is a loop diuretic and thus can cause electrolyte abnor- malities such as hypokalemia and metabolic alkalosis. It is not associated with sedation. Answer B is incorrect. Hydrochlorothiazide, a diuretic, has side effects such as hypokalemia and hyperglycemia. It is not associated with sedation or changes in mood. Answer C is incorrect. Losartan is an angio- tensin receptor blocker; its use can result in hyperkalemia, but it is not associated with sedation. Answer E is incorrect. Nifedipine is a calcium channel blocker that functions primarily on the vasculature. It can be associated with edema, flushing, and dizziness, but is not usu- ally sedating

42. The image depicts the relationship of ventricu- lar pressure and volume in the cardiac cycle. The various phases of the cardiac cycle are labeled I through IV. Which phase occurs between aortic valve closing and mitral valve opening? (A) Phase I (B) Phase II (C) Phase III (D) Phase IV

C 42. The correct answer is D. Isovolumetric relax- ation (phase IV in the image) is the period in which both the aortic and mitral valves are closed, thus keeping ventricular volume con- stant. Ventricular muscle relaxes from its prior contraction to allow for filling. Answer C is incorrect. Ventricular ejection (phase III in the image) is the period between aortic valve opening and closing.

44. A 56-year-old woman presents to her physician because of recent onset of chest pain and dysp- nea. Six weeks earlier the patient suffered an MI. Her physical examination is remarkable for a friction rub over the fifth intercostal space in the midclavicular line together with an ele- vated jugular venous pressure. Which of the following myocardial complications is this in- dividual most likely suffering from? (A) Cardiac arrhythmia (B) Dressler's syndrome (C) Left ventricular failure (D) Thromboembolism (E) Ventricular rupture

C 44. The correct answer is B. Dressler's syndrome is an autoimmune phenomenon that results in fibrinous pericarditis. This delayed pericarditis typically develops 2-10 weeks post-MI and presents clinically as chest pain and a pericar-dial friction rub. It is generally treated with nonsteroidal antiinflammatory agentes or corti-costeroids. Answer A is incorrect. Cardiac arrhythmia is a common cause of post-MI death and typically occurs 2 days post-MI. It does not typically present with a friction rub. Answer C is incorrect. Left ventricular failure occurs in 60% of people who suffer from MI and can present as CHF or cardiogenic shock. Answer D is incorrect. Thromboemboli are typically systemic emboli that originate from mural thrombi and can lead to cerebrovascular accidents, transient ischemic attacks, and renal artery thrombosis. Answer E is incorrect. Ventricular rupture is a cause of post-MI death that typically occurs 4-10 days post-MI. It often presents with persistent chest pain, syncope, and distended jugular veins.

5. A medical student working in the emergency department sees a female baby, born 2 weeks ago, who is brought in by her anxious mother. The mother tells the student that her baby seems "purple," especially her fingers and toes, and looks extremely blue when crying. On physical examination the sleeping baby has mild cyanosis of the face and trunk, but mod- erate cyanosis of the extremities. Which of the following is the most common cause of cyano- sis within the first few weeks of life? (A) Atrial septal defect (B) Patent ductus arteriosus (C) Tetralogy of Fallot (D) Transposition of the great vessels (E) Ventricular septal defect

C 5. The correct answer is C. Tetralogy of Fallot is the most common cause of cyanosis within the first few weeks of life. The skin becomes bluish because of the malformed right-to-left shunt. Infants also have worsening cyanosis with agi- tation, difficulty feeding, and failure to gain weight. Patients may also have clubbing of the fingers and toes or even polycythemia. The four components of the teratology are (1) ven- tricular septal defect, (2) overriding aorta, (3) infundibular pulmonary stenosis, and (4) right ventricular hypertrophy.

7. A 48-year-old man presents to the emergency department 1.5 hours after the onset of severe substernal chest pain radiating to his left arm. The pain is accompanied by diaphoresis and shortness of breath. His blood pressure is 165/94 mm Hg, pulse is 82/min, and respira- tory rate is 18/min. Which of the following tests is the most important tool in the initial evalua- tion of patients in whom acute myocardial in- farction (MI) is suspected? (A) Aspartate aminotransferase (B) Creatine kinase-myocardial bound (C) ECG (D) Echocardiogram (E) Lactate dehydrogenas

C 7. The correct answer is C. ECG is the gold standard for diagnosing MI within the first 6 hours of symptom onset. ECG changes will in clude ST-segment elevation (signifying trans- mural infarct), ST-segment depression (signify- ing subendocardial infarct), and Q waves (signifying transmural infarct). Answer A is incorrect. Aspartate aminotrans- ferase is a nonspecific protein that is found in cardiac, liver, and skeletal muscle cells. Levels peak around 2 days post-MI and are negative at 3 days post-MI. Answer B is incorrect. Serial measurements of creatine kinase-myocardial bound (CK-MB) fraction along with troponin-I are made in every patient with suspected MI. However, since these enzymes take 4-6 hours to accu- mulate in the blood, and ECG results can be obtained faster, ECG is the initial test when triaging a patient with suspected MI. CK-MB levels peak around 24 hours and are negative at 3 days post-MI.

12. A 72-year-old African-American man under- goes hip surgery. On his third hospital day he experiences chest pain, tachycardia, dyspnea, and a low-grade fever. The man goes into car- diac arrest, and efforts to resuscitate him are unsuccessful. On autopsy a massive pulmonary embolus is discovered. Which of the following, if present, would most likely predispose the pa- tient to this event? (A) Factor VIII deficiency (B) Low serum homocysteine levels (C) Mutation in the Factor V gene (D) Overproduction of protein C (E) von Willebrand factor deficiency

D 12. The correct answer is C. A mutation in the Factor V gene, also known as Factor V Leiden, causes resistance to deactivation of Factor V by protein C. Uninhibited Factor V activity leads to a hypercoagulable state, which can lead to deep vein thrombosis and subsequent pulmo- nary embolism. Answer A is incorrect. Factor VIII deficiency (hemophilia A) would actually predispose an individual to bleeding. Factor VIII is an inte- gral part of the intrinsic coagulation cascade. Answer B is incorrect. High, rather than low, homocysteine levels create a hypercoagulable state. Answer D is incorrect. Proteins C and S act as negative regulators of the coagulation cascade. Therefore, a deficiency rather than an overpro- duction in either of these proteins will lead to a hypercoagulable state. Answer E is incorrect. von Willebrand factor is a major factor in promoting blood clotting, and deficiency (von Willebrand disease) leads to bleeding complications.

13. A 70-year-old woman with a history of type 2 diabetes mellitus, a body mass index of 30 kg/ m2, and an MI 10 years prior presents to the emergency department with crushing subster- nal chest pain radiating to her neck and jaw. Emergency cardiac catheterization with percu- taneous coronary intervention (PCI) shows a 99% occlusion of her left anterior descending artery, and an ECG reveals an anterior wall ST segment elevation MI. The patient remains stable after PCI, and echocardiography shows a mildly impaired ejection fraction (EF) of 45%. Three days later, the patient becomes acutely hypotensive and dyspneic, and physical examination reveals a high-pitched holosystolic murmur, loudest at the apex and radiating to the axilla, that had not been heard on previous exams. An emergency echocardiogram shows an EF of 25%. This patient has developed which of the following? (A) Aortic stenosis (B) Dressler's syndrome (C)

D 13. The correct answer is E. This patient has suf- fered rupture of one of the two left ventricular papillary muscles, a complication that may oc- cur 3-10 days after an acute MI, when the in- farcted area of myocardium is replaced with granulation tissue and thus is the most weak. Without the anchor of the papillary muscle, there is severe acute mitral valve regurgitation, diagnosed by a new holosystolic "blowing mur- mur" that is loudest at the apex and radiates to the axilla, a severely reduced stroke volume (hypotension with EF of 25%), and evidence of pulmonary edema (dyspnea). Answer D is incorrect. Rupture of the left ven- tricular (LV) free wall is another complication that can occur 3-10 days post-MI due to weak- ened myocardium; this development, however, would lead to cardiac tamponade, not to mitral regurgitation. In LV free wall rupture, blood accumulates in the pericardium and the con- stricted heart cannot pump effectively, causing a severely decreased stroke volume, systemic hypotension with pulsus paradoxus, jugular venous distension, and decreased heart sounds due to the insulating effects of the fluid around the heart. The holosystolic murmur loudest at the apex and radiating to the axilla detected in this patient is characteristic of mitral regurgita- tion.

19. A 62-year-old breast cancer survivor visits her physician because of weakness, fatigue, fever, and weight gain 5 years following her radiation therapy. The physician also elicits complaints about abdominal discomfort and exertional dyspnea. Physical examination reveals hepato- megaly and jugular venous distention that fails to subside on inspiration, but shows no evi- dence of hypotension or pulsus paradoxus. An echocardiogram shows reduced end-diastolic volumes and elevated diastolic pressures in both ventricles. Which of the following is the most likely diagnosis? (A) Cardiac tamponade (B) Congestive heart failure (C) Constrictive pericarditis (D) Dilated cardiomyopathy (E) Recurrence of breast cancer

D 19. The correct answer is C. Constrictive peri- carditis interferes with the filling of the ventri- cles because of granulation tissue formation in the pericardium. It can follow purulent viral infections, trauma, neoplastic diseases, medi- astinal irradiation, and other chronic diseases. Pericardial thickening and calcification are sometimes apparent on CT and MRI. Answer A is incorrect. Cardiac tamponade is very similar in presentation to constrictive peri- carditis. One defining characteristic of cardiac tamponade is the absence of Kussmaul's sign (failure of cervical venous distention to subside on inspiration). In addition, pulsus paradoxus (decrease in systolic pressure by ≥10 mm Hg during inspiration) is usually present. X-ray of the chest should reveal an enlarged cardiac sil- houette with pericardial effusion. Answer B is incorrect. CHF produces signs and symptoms similar to those of constrictive pericarditis. However, in CHF there would be significant enlargement and hypertrophy of the ventricles. Answer D is incorrect. The echocardiogram results are not consistent with dilated cardio- myopathy, as diastolic volumes are reduced in this patient but end-diastolic volumes are increased in dilated cardiomyopathy. Answer E is incorrect. Breast and lung carci- nomas, lymphomas, and melanomas are the most common metastases to the pericardium and should therefore be considered in this case. However, metastasis causing constrictive pathology is much less common than peri- carditis.

21. A 52-year-old African-American man is brought to the emergency department unresponsive, and efforts to resuscitate him are unsuccessful. On autopsy, it is found that he suffered from a ruptured aneurysm of the aortic root. His dilated aorta, as seen on autopsy, is shown in the image. In addition, inspection of the man's skin revealed several ulcerated lesions. Which of the following is most likely associated with the underlying etiology of this patient's aneu- rysm? 151 (A) Atherosclerosis (B) Congenital medial weakness (C) Cystic medial necrosis (D) Disruption of the vasa vasorum (E) Hypertension

D 21. The correct answer is D. Syphilitic aortitis is characterized by obliterative endarteritis of the vasa vasorum of the media. This disruption of the vasa vasorum can lead to aneurysm, which typically involves the ascending aorta and is a manifestation of tertiary syphilis. Luetic (syphi- litic) aneurysms favor the aortic root, where they can be complicated by atherosclerosis. The patient's skin lesions are the gummas of tertiary syphilis. Answer A is inc

23. A 25-year-old white woman with no past medical history presents to the emergency depart- ment for "a racing heartbeat." It is determined that she has paroxysmal supraventricular tachy- cardia. Which of the following is the drug of choice used for diagnosing and abolishing atrioventricular nodal arrhythmias by virtue of its effectiveness and its low toxicity? (A) Adenosine (B) Bretylium (C) Encainide (D) Lidocaine (E) Sotalol

D 23. The correct answer is A. Adenosine is ex- tremely useful in abolishing atrioventricular (AV) nodal arrhythmias when given in high- dose intravenous boluses. Adenosine works by hyperpolarizing AV node tissue by increasing the conductance of potassium and by reducing calcium current. As a result, the conduction through the AV node is markedly reduced. In addition to this, adenosine's extremely short duration of action (15 seconds) limits the oc- currence of its toxicities (i.e., hypotension, flushing, chest pain, and dyspnea). Answer B is incorrect. Bretylium, a potassium channel blocker (class III), is used when other antiarrhythmics fail. Answer C is incorrect. Encainide is used when ventricular tachycardia progresses to ventricu- lar fibrillation; it is also used in intractable su- praventricular tachycardia. Answer D is incorrect. Lidocaine, a class Ib antiarrhythmic, is used in the treatment of acute ventricular arrhythmias such as post-MI arrhythmias. Answer E is incorrect. Sotalol, which is both a β-adrenergic-receptor blocker (class II) and a potassium channel blocker (class III), is used when other antiarrhythmics fail.

27. A 67-year-old woman with a long history of poorly controlled diabetes mellitus and chronic renal failure is admitted to the hospital for treatment of cellulitis. Two days into her hospi- tal stay she complains of chest pain that is re- lieved when she leans forward. An ECG shows diffuse ST segment elevations with PR depres- sions; her echocardiogram is normal. Which of the following is the most appropriate treatment at this time? (A) Cardiac catheterization (B) Dialysis (C) Nonsteroidal anti-inflammatory drugs (D) Pericardiocentesis (E) Switch her to another antibiotic regimen

D 27. The correct answer is B. The patient is experi- encing pericarditis due to uremia secondary to chronic kidney disease in the setting of long- standing diabetes mellitus. Pericarditis presents with pleuritic, positional chest pain that is of- ten relieved by sitting forward and with a peri- cardial friction rub on physical examination. Diffuse ST segment elevations may be found on ECG, while an echocardiogram may be normal unless an effusion is also present. Peri- carditis has multiple etiologies, including viral (coxsackievirus, echovirus, adenovirus, and HIV), bacterial (tuberculosis or Streptococcus pneumoniae or Staphylococcus aureus in the setting of endocarditis, pneumonia, or post- cardiac surgery), neoplastic, autoimmune, ure- mic, cardiovascular, or idiopathic. Treatment of pericarditis secondary to uremia is dialysis.

28. A 75-year-old woman arrives at the emergency department and states that her left arm is numb. She is diaphoretic. Laboratory studies show an elevated troponin I level and the pa- tient is treated for an acute MI. A subsequent echocardiogram shows a wall motion abnor- mality of the posterior interventricular septum. Stenosis of which of the following arteries would most likely cause this condition? (A) Acute marginal artery (B) Circumflex artery (C) Left anterior descending artery (D) Posterior descending artery (E) Right coronary artery

D 28. The correct answer is D. The posterior de- scending artery is a branch of the right coro- nary artery on the posterior surface of the heart. It courses along the posterior interventricular groove, extending toward the apex of the heart. It has posterior septal perforator branches that run anteriorly in the ventricular septum and supply the posterior one-third of the ventricular septal myocardium. Answer C is incorrect. The left anterior de- scending artery supplies the anterior interven- tricular septum. One of two main branches off the left main coronary artery, it descends the left surface of the heart anteriorly and inferi- orly in the anterior interventricular groove to the apex of the heart. Diagonal, septal perforat- ing, and right ventricular branches come off of it, supplying portions of the anterior aspects of the left atrium, left ventricle, interventricular septum, and right ventricle. Although the left anterior descending artery is the artery that is most commonly occluded in coronary artery occlusion, the posterior descending artery sup- plies the posterior one-third of the intraventric- ular septum, which is the site of abnormality in this case.

4. A 45-year-old man who takes spironolactone and digoxin for his congestive heart failure is admitted to the hospital because he is experi- encing an altered mental status. The ECG changes shown in the image are noted on test- ing. Urinalysis would most likely reveal which of the following? (A) High K+, high Na+, high-normal volume (B) High K+, low Na+, low volume (C) High K+, low Na+, normal volume (D) Low K+, high Na+, high-normal volume (E) Low K+, low Na+, normal volume

D 4. The correct answer is D. The key to answering this question is realizing that it asks for electro- lyte leveles in urine, not serum. The ECG shows peak T waves and widened QRS interval, which are classic changes seen in hyperkalemia. Spironolactone is the most likely medication to affect urinary electrolytes. As an inhibitor of al- dosterone receptors in the collecting tubule and an inhibitor of Na+ channels, spironolactone greatly decreases the excretion of K+ and mildly increases the excretion of Na+. Urine volume will be high-normal because the diuretic will increase saltwater wasting.

49. Cardiac output is a function of stroke volume and heart rate. Stroke volume increases when contractility increases, preload increases, or afterload decreases. There are a number of fac- tors that affect each of these components and ultimately cardiac output. Which of the follow- ing variations would increase cardiac output? (A) β-Blocker treatment (B) Aortic stenosis (C) Cardiac glycoside administration (D) Decreased intracellular calcium concen- tration (E) Increased extracellular sodium concentra- tion

D 49. The correct answer is C. Cardiac glycosides such as digoxin inhibit the Na+-K+-ATPase transport system to increase intracellular sodium concentration, which then increases intracellular calcium concentration via the sodium-calcium exchange carrier mechanism. This increased calcium level augments the cal- cium released to the myofilaments during exci- tation, resulting in a positive inotropic effect. Increased contractility of the heart directly in- creases cardiac output. Glycosides are largely not used today because of the advent of newer drugs that have fewer adverse effects; the out- standing exception is digoxin, which is still widely used to treat heart failure and atrial fibrillation. Answer D is incorrect. A decreased intracellu- lar calcium level would decrease the contrac- tility of the heart, resulting in decreased car- diac output.

1. A physician decides to place a patient on a calcium channel blocker for treatment of her an- gina. Calcium channel blockers can relax the smooth muscle of blood vessels and can also have various effects on cardiac contractility, conduction, and heart rate. Which of the fol- lowing calcium channel blockers would be most effective in reducing heart rate and con- tractility? (A) Dihydropyridine (B) Diltiazem (C) Nifedipine (D) Nimodipine (E) Verapamil

E 1. The correct answer is E. The calcium chan- nel blockers verapamil and diltiazem are both effective in slowing the rate and contractility of the heart. Both drugs decrease the magnitude of inward calcium current through L type cal- cium channels and also decrease the rate of re- covery of the channel. It is this latter effect that depresses the sinus node pacemaker and slows atrioventricular conduction. Verapamil is a stronger negative inotrope than diltiazem, and therefore is more effective in decreasing heart rate and contractility. Answer A is incorrect. Dihydropyridines are the family of drugs to which nifedipine be- longs. The dihydropyridines are more potent vasodilators than verapamil or diltiazem and in general have less potent effects on the heart. Answer B is incorrect. Diltiazem is a calcium channel blocker but is not as effective as vera- pamil in reducing the rate and contractility of the heart. Answer C is incorrect. Nifedipine is least ef- fective in reducing the rate and contractility of the heart; conversely, it is most effective in evoking vasodilation. Although nifedipine has some negative inotropic effect on the heart, the decrease in arterial blood pressure secondary to vasodilation elicits sympathetic reflexes that re- sult in increases in heart rate and inotropy. Answer D is incorrect. Nimodipine is another member of the dihydropyridine family with similar properties, but it is approved only for the management of stroke with subarachnoid hemorrhage.

11. A 16-year-old Japanese exchange student pres- ents to the physician with a history of fevers, joint pain, night sweats, and muscle pain. On physical examination, the patient has extremely weak pulses in her upper extremities. Labora- tory abnormalities in which of the following parameters is most likely? (A) Anti-IgG antibodies (B) Antinuclear antibodies (C) Cytoplasmic antineutrophil cytoplasmic antibody (D) Erythrocyte sedimentation rate (E) Perinuclear antineutrophil cytoplasmic antibody

E 11. The correct answer is D. This individual is most likely suffering from Takayasu's arteritis, which is also known as "pulseless disease." It typically affects medium and large arteries, re- sulting in thickening of the aortic arch and/or proximal great vessels. Symptoms include fevers, arthritis, night sweats, myalgias, skin nodules, ocular disturbances, and weak pulses in the upper extremities. It is most common in young Asian females and is associated with an elevated erythrocyte sedimentation rate. Answer A is incorrect. Anti-IgG antibodies, more commonly known as rheumatoid factors, are associated with rheumatoid arthritis (RA). RA manifests as an inflammatory polyarthritis classically associated with morning stiffness, rheumatoid nodules, and other features. Answer B is incorrect. Antinuclear antibodies are associated with, but not specific for, systemic lupus erythematosus (SLE). While SLE is most common among young to middle-aged females, a classic pattern of rashes, renal disease, and other manifestations would be expected. Answer C is incorrect. C-ANCA is associated with Wegener's granulomatosis, which is char- acterized by pulmonary and renal focal necro- tizing granulomatous vasculitis. Answer E is incorrect. Perinuclear antineutro- phil cytoplasmic antibody (P-ANCA) is com- monly associated with microscopic polyangiitis and Churg-Strauss syndrome. Patients with ei- ther condition would not present with absent pulses.

20. The classic location for an abdominal aortic aneurysm is inferior to the renal arteries and extending to the bifurcation of the common iliac arteries. Repair involves resecting the dis- eased portion of the aorta and replacing it with a synthetic graft. Based on anatomic consider- ations, which of the following visceral arteries would likely be resected along with the dis- eased aortic tissue during the repair of an infra- renal abdominal aortic aneurysm? (A) Gastroduodenal artery (B) Hepatic artery (C) Inferior mesenteric artery (D) Left gastric artery (E) Splenic artery (F) Superior mesenteric artery

E 20. The correct answer is C. The inferior mesen- teric artery originates from the aorta inferior to the renal arteries and superior to the bifurca- tion of the aorta into the common iliac arter- ies. This artery may sometimes be sacrificed during an infrarenal aortic aneurysm repair rather than being re-attached to a healthy seg- ment of aorta. Usually, there is enough collat- eral flow to the hindgut from the superior mes- enteric artery and the hypogastric arteries that the loss of the inferior mesenteric artery does not result in colonic ischemia. Answer A is incorrect. The gastroduodenal ar- tery is a branch of the hepatic artery, which is in turn a branch of the celiac trunk. Answer B is incorrect. The hepatic artery is a branch of the celiac trunk and is found supe- rior to the renal arteries. Answer D is incorrect. The left gastric artery is a branch of the celiac trunk and is found supe- rior to the renal arteries. Answer E is incorrect. The splenic artery is a branch of the celiac trunk and is also found su- perior to the renal arteries. Answer F is incorrect. The superior mesen- teric artery is superior to the renal arteries and thus would not be disrupted in resection of the infrarenal aorta.

32. A 25-year-old Massachusetts college student presents to his primary care physician. He said he first started to notice problems a few months ago after returning from a hike in the woods. He originally had an expanding rash starting on his calf and flu-like symptoms that resolved spontaneously. Recently, he started having symptoms of dizziness, syncope, dyspnea, chest pain, and palpitations for several weeks' dura- tion. His physician obtains an ECG, as shown in the image. The vector that carries the organism responsible for the student's symptoms is also responsible for transmitting which of the following diseases? (A) Babesiosis (B) Epidemic typhus (C) Malaria (D) Plague (E) Rocky Mountain spotted fever

E 32. The correct answer is A. This patient presents with symptoms consistent with Lyme disease. He had a characteristic expanding rash (ery- thema migrans) and resolving flu-like symp- toms. Lyme disease can often lead to cardiac symptoms such as those described, as well as heart block that can require cardiac pacing. Lyme disease is carried by the Ixodes tick. I. scapularis is also the vector of disease for babe- siosis, a malaria-like parasitic disease common in the northeastern corner of the United States. Answer E is incorrect. Rocky Mountain spot- ted fever is caused by Rickettsia rickettsii, a spe- cies of bacteria spread to humans by the ticks of the Dermacentor family such as D. variabi- lis.

41. A dysfunctional myocardial endothelium un- derlies one form of heart disease. In patients with this common disease process, there is a lack of autoregulatory coronary artery vasodila- tion needed to provide increased blood flow in states of increased physical exertion or emo- tional stress. The pathogenesis is most often from severe narrowing of atherosclerotic coro- nary vessels and typically manifests as chest pain, relieved by rest or nitroglycerin tablets. Which of the following is a soluble metabolite that mediates the compensatory coronary artery vasodilation during periods of increased myo- cardial oxygen demand? (A) Acetylcholine (B) Adenosine (C) Carbon dioxide (D) Lactate (E) Norepinephrine

E 41. The correct answer is B. The question describes the pathology associated with stable an- gina. Autoregulation is the process whereby blood flow is altered to meet demands of tissue. The principle factors determining autoregula- tion of blood flow to the heart are local metab- olites including adenosine, oxygen, and nitric oxide. Answer A is incorrect. Parasympathetic inner- vation to the heart via acetylcholine is not a mediator of autoregulation of coronary blood flow. Parasympathetic discharge will decrease heart rate, decrease atrioventricular nodal con- duction velocity, and decrease atrial contractil- ity with little or direct effect on coronary blood flow. Answer C is incorrect. Carbon dioxide is more important for autoregulation of cerebral blood flow. Answer D is incorrect. Lactate, a solute pro- duced by skeletal muscle during nonoxidative metabolism, is a mediator of the autoregula- tion of blood flow to skeletal muscle. Answer E is incorrect. Sympathetic innerva- tion to the heart via norepinephrine is not a mediator of autoregulation of coronary blood flow. Sympathetic discharge will increase heart rate, increase atrioventricular nodal conduc- tion velocity, and increase myocardial contrac- tility, thus increasing oxygen demand with lit- tle direct effect on coronary blood flow

46. A 76-year-old man receives a pacemaker to treat a dangerous form of heart block. This form of heart block is characterized by a con- stant PR interval with randomly blocked QRS complexes. The patient's ECG prior to treat- ment is shown in the image. Which of the fol- lowing is the abnormality responsible for this type of heart block? (A) Atrioventricular nodal abnormality (B) Defect in the His-Purkinje system (C) Independently contracting atria and ventricles (D) Retrograde conduction (E) Sinoatrial nodal abnormality

E 46. The correct answer is B. This is a Mobitz type II second-degree heart block. A defect in the His-Purkinje system is responsible for this type of heart block defect. Answer A is incorrect. In contrast to this pa- tient's findings, atrioventricular nodal abnormali- ties lengthen the PR interval and are responsible for first-degree heart block and Mobitz type I second-degree heart block. Answer C is incorrect. Independently con- tracting atria and ventricles occur in the com- plete absence or ablation of the His-Purkinje system, not simply a defect in the system. Answer D is incorrect. Retrograde conduc- tions would result in an increase in the number of P waves and a decrease in the PR interval. Answer E is incorrect. Sinoatrial nodal abnormalities are responsible for problems in auto- maticity and would not result in randomly dropped QRS complexes.

47. A 56-year-old white man is rushed to the emer- gency department with crushing substernal chest pain. He is morbidly obese, sweating pro- fusely, breathing very rapidly, and clutching at his chest. The patient is stabilized and seems to be doing well when he suddenly goes into cardiac arrest and dies. Which of the following is the most likely cause of death in this patient? (A) Fatal arrhythmia (B) Mural thrombosis (C) Myocardial failure (D) Myocardial rupture (E) Ruptured papillary muscle

E 47. The correct answer is A. Fatal arrhythmias fol- lowing an MI, also known as sudden cardiac death, are the most common cause of death in the first few hours following an infarction. Ar- rhythmias are due to disruption of the conduc- tion system and myocardial irritability follow- ing injury Answer E is incorrect. A ruptured papillary muscle is a possible complication of an infarc- tion, but it most commonly occurs 3-7 days after the ischemic event. Thus, papillary mus- cle rupture would not cause immediate death.

48. A previously healthy 31-year-old woman is seen in the emergency department because of complete visual loss in her right eye. The patient's history is significant for a 3-day history of mal- aise, chills, and fatigue and some oral pain sec- ondary to her recent wisdom tooth removal. Ophthalmologic examination reveals a gray- white retina with an associated cherry-red spot, two blot hemorrhages, and several segmented vessels with optic edema. Physical examination reveals a murmur consistent with mitral valve insufficiency. Which of the following is the most likely cause of this patient's loss of vision? (A) Carotid artery stenosis (B) Collagen vascular disease (C) Diabetes mellitus (D) Endocarditis (E) Hypertensive crisis

E 48. The correct answer is D. Individuals with central retinal artery occlusion typically present with the acute onset of painless monocular visual loss that is usually the result of throm- boembolic phenomena relating to vascular dis- ease. However, since this patient is young and has no consistent prior medical history, one must consider other causes, which in this pa- tient would almost certainly relate to her recent dental procedure, which can lead to bacteremia. In the setting of a murmur and bacteremia, the most likely cause of this pa- tient's symptoms is a septic embolism that orig- inated in the heart and has lodged in the cen- tral retinal artery. Unfortunately, even with treatment, <25% of patients regain useful vision in the affected eye. Answer E is incorrect. Hypertensive crises would be more likely to result in bleeding than thromboembolic phenomena or other causes of central retinal artery occlusion

50. A 54-year-old woman presents to her physician with swelling in her extremities. Palpation pro- duces significant pitting. Which of the follow- ing conditions is the underlying physiologic basis of this physical finding? (A) Decreased capillary permeability (B) Decreased capillary pressure (C) Increased interstitial fluid colloid osmotic pressure (D) Increased interstitial fluid pressure (E) Increased plasma protein level

E 50. The correct answer is C. Net filtration pressure is governed by the equation Pnet = [(Pc - Pi) - (pc - pi)], where Pc is capillary pressure, Pi is interstitial fluid pressure, pc is plasma colloid osmotic pressure, and pi is interstitial fluid col- loid osmotic pressure. Increasing Pc, pi, or the permeability of the capillaries will lead to a net flow of fluid from the capillaries to the intersti- tium. Likewise, decreasing pc and Pi will also lead to net outward flow and edema. Answer A is incorrect. Decreasing capillary permeability would result in fluid being trapped in the vascular space. Answer B is incorrect. Decreased capillary pressure would decrease the amount of fluid in the interstitial space. Answer D is incorrect. Increased interstitial fluid pressure would increase fluid flow back into the vascular space. Answer E is incorrect. Increased plasma pro- tein levels would cause an increase in fluid re- tention in the vascular space.

6. A 55-year-old man with hypertension is pre- scribed an antiarrhythmic agent that alters the flow of cations in myocardial tissue. The image is a trace of a myocardial action potential. Each phase is associated with the opening and/ or closing of various ion channels. Which of the following would be affected by an agent that affects phase 2 of the myocardial action potential? (A) Ligand-gated Ca2+ channels opening (B) Ligand-gated Na+ channels opening (C) Voltage-gated Ca2+ channels opening (D) Voltage-gated Na+ channels closing (E) Voltage-gated Na+ channels opening

E 6. The correct answer is C. Voltage-gated Ca2+ channels open slowly in response to the Na+ upstroke as increasing K+ conductance during phase 2 gradually depolarizes the cell. The re- sult is a slow conduction velocity that prolongs the transmission from the atria to the ventri- cles. Answer A is incorrect. Ion channels in the myocardium are voltage-gated. Answer B is incorrect. Ion channels in the myocardium are voltage-gated. Answer D is incorrect. Closing voltage-gated Na+ channels would hyperpolarize the cell. Answer E is incorrect. Nodal cells lack the voltage-gated Na+ channels that are responsi- ble for the upstroke in ventricular cells.

25. An 85-year-old man dies from aspiration pneu- monia as a complication of Alzheimer's dis- ease. Autopsy reveals a small (230-g) heart that appears grossly dark brown in color. Hematoxy- lin and eosin staining of cardiac muscle cells reveals brownish perinuclear pigmentation. The pathologist determines this phenomenon to be a consequence of age and not a causative agent in the patient's death. Accumulation of which of the following substances is the most likely cause of the brown pigmentation seen most often in the heart, liver, or spleen of the elderly? (A) Bilirubin (B) Calcium (C) Cholesterol (D) Glycogen (E) Iron (F) Lipofuscin

F 25. The correct answer is F. The combination of an atrophic heart and lipofuscin accumulation is referred to as brown atrophy. Lipofuscin is a "wear and tear" pigment that commonly de- posits within hepatocytes, splenocytes, and myocardial cells in the elderly. It is comprised of oxidized and polymerized membrane lipids of autophagocytosed organelles accumulated slowly over years. Answer A is incorrect. Bilirubin can accumu- late and stain internal organs, producing yel- lowish discoloration called jaundice. However, lack of clinical evidence of a hemolytic or ob- structive process in this case makes this option highly unlikely. Answer B is incorrect. Age-related calcifica- tion is most often seen on heart valves. It would not appear brown in color, nor would it be as- sociated with generalized cardiac atrophy. Answer C is incorrect. Cholesterol may accu- mulate as atheromatous plaques in the arteries; however, its accumulation is not associated with cardiac atrophy nor brown pigmentation. Answer D is incorrect. Glycogen storage dis- eases are inherited conditions that appear early in life. Glycogen does not appear pigmented on hematoxylin and eosin stain. Answer E is incorrect. Iron deposits within the heart could also appear as brownish granules. However, this would suggest that the patient suffers from hemochromatosis. The cardiac complications of hemochromatosis include cardiomyopathy and arrhythmia. The patient described in the question stem has an atrophic heart, making iron deposits a less likely option.

39. A 54-year-old woman comes to the physician 3 months after a undergoing a root canal be- cause of persistent general malaise and fever. The symptoms developed slowly over the weeks following her root canal, but have not abated. On physical examination, the patient is found to have a temperature of 38.3° C (101° F). Ophthalmic examination reveals retinal hemorrhages with clear central regions. Exam- ination of the extremities reveals painful red nodules on her digits and dark macules on her palms and soles. On cardiac examination, a click and a systolic murmur are auscultated over the mitral valve. She tells the physician that the click is due to a mechanical valve replacement done 4 years ago due to rheumatic fever as a child. Given this history, which of the following is the most appropriate treat- ment for this patient? (A) Caspofungin (B) Clindamycin (C) Mebendazole (D) Metronidazole (E) Nafcillin (F) Penicilli

F 39. The correct answer is F. This woman is likely suffering from prosthetic valve endocarditis. She may not have taken appropriate prophylac- tic antibiotics before her root canal procedure, and her susceptible mitral valve after rheumatic fever has been exposed to transient bacteremia. Her symptoms, including low-grade persistent fever, new-onset murmur, and insidious onset, suggest subacute bacterial endocarditis. This is further supported by her physical examination, which reveals the presence of Roth spots (reti- nal hemorrhages), Osler's nodes (painful red nodules on digits), and Janeway lesions (dark macules on palms and soles). Given her clini- cal history and symptoms, the bacterium most likely to have caused this episode is Streptococcus sanguis, part of the viridans group. The most appropriate treatment for such an infection is penicillin

34. A number of tests are used to diagnose an MI. Measuring an elevation in the cardiac enzymes aspartate aminotransferase (AST), creatine ki- nase-MB fraction (CK-MB), lactate dehydroge- nase (LDH), and troponin is one indication that a MI has occurred. The image shown is a representation of the average length of time it takes to see an elevation in these four enzymes. What is the correct order of cardiac enzyme el- evation after an MI? (A) AST, CK-MB, troponin, LDH (B) AST, LDH, troponin, CK-MB (C) CK-MB, AST, troponin, LDH (D) CK-MB, troponin, AST, LDH (E) LDH, CK-MB, troponin, AST (F) Troponin, AST, CK-MB, LDH (G) Troponin, CK-MB, AST, LDH

G 34. The correct answer is G. Cardiac troponin I becomes elevated in the first 4 hours after an MI and remains elevated for 7-10 days. CK-MB peaks in the first 24 hours and then falls off. AST is the next to become elevated, as it gradually increases over the first 2 days and then slowly declines; however, it is not specific for damage to the heart. LDH is the last cardiac enzyme to become elevated (by day 2 post-MI) and it remains elevated for up to 7 days post-MI. Note that although troponin is a great enzyme to monitor for new infarcts, CK-MB is the enzyme of choice in the detec- tion of reinfarction within the first week. If re- infarction occurs, the troponin level would still be elevated and thus not useful in detect- ing the new ischemic event. A final marker not mentioned here is myoglobin, which typi- cally rises and falls within 6 hours pst-MI. However, like AST, it is nonspecific since it is found in skeletal muscle and is not used clini- cally to diagnose MI.