9 - The Point
A first‐year medical student is examining a standardized patient with a structurally normal heart. The student is having difficulty auscultating the splitting of the second heart sound. At what area on the patient's chest would the student have the best opportunity of hearing this sound? a) Left second and third interspace b) Midsternum c) Right second interspace d) Lower left sternal border e) Apex
a) Left second and third interspace The pulmonic area is the left second and third interspace close to the sternum. The mitral area is at the apex. The right second interspace overlies the aortic valve. The tricuspid space is the lower left sternal border. The midsternum does not correspond to the anatomic location of any of the four cardiac valves; however, it is important to remember that murmurs radiate and must be interpreted in the setting of the clinical scenario.
A 70‐year‐old retired business executive presents to the Emergency Department with progressive shortness of breath and two‐pillow orthopnea. On physical examination, the blood pressure is 145/90 mm Hg, there is jugular venous distension, lower extremity pitting edema to the knee, and a blowing holosystolic murmur heard best at the lower left sternal border. No other murmurs or thrills are auscultated on physical exam. Which of the following interventions is to most likely to improve the patient's symptoms? a) Removal of intravascular volume with diuresis b) Replacement of the mitral valve c) Replacement of the aortic valve d) Decrease in blood pressure e) Repair of a ventricular septal defect
a) Removal of intravascular volume with diuresis This patient is in heart failure based upon the symptoms and physical examination findings. The murmur is consistent with tricuspid regurgitation that may be the result of ventricular dilation and failure of the valve to completely close. Symptoms often improve with diuresis. Based upon the examination, the murmur is not consistent with underlying mitral or aortic valve disease. Although the blood pressure is high, it is not high enough to cause this degree of symptomatology. A ventricular septal defect is a holosystolic murmur heard within the left third to fifth interspaces, but is often associated with a thrill.
A 45‐year‐old physician is placed on a β‐blocker for hypertension. Prior to medication administration, the patient's heart rate is 75 beats per minute with a cardiac output of 5 liters per minute. Following initiation of the medication, the heart rate decreases to 60 beats per minute without a change in stroke volume. What would be the expected new cardiac output? a) 5 liters per minute b) 4 liters per minute c) 10 liters per minute d) 3 liters per minute e) 6 liters per minute
b) 4 liters per minute Cardiac output is the product of heart rate and stroke volume. Therefore, if the heart rate decreases by 20%, the cardiac output would decrease by 20% if the stroke volume did not change.
On routine physical examination, a 40‐year‐old teacher is found to have a single second heart sound. The most likely explanation for this finding is what? a) Auscultation occurred during inspiration. b) Auscultation occurred during expiration. c) The patient has a right bundle branch block. d) The patient has a left bundle branch block. e) The patient has pulmonic stenosis.
b) Auscultation occurred during expiration. During expiration, the components of S , A , and P fuse into a single sound. During inspiration, the right heart filling time is increased thereby delaying closure of the pulmonic valve and splitting S into two audible components. Pulmonic stenosis and a right bundle branch block delay the P component and cause fixed splitting of S . A left bundle branch block delays the A component and causes paradoxical splitting
A 55‐year‐old truck driver with obstructive sleep apnea has diastolic heart failure. An echocardiogram demonstrates significant biatrial enlargement. What portion of his electrocardiogram would likely be abnormal? a) S wave b) R wave c) P wave d) T wave e) QRS complex
c) P wave The P wave is the result of atrial depolarization and would therefore have changes associated with atrial enlargement. The QRS complex, R wave, and S wave are a result of ventricular depolarization, whereas the T wave is a result of ventricular repolarization.
A newborn baby has an embryologic defect affecting the aortic valve. What other cardiac valve is most likely to be affected? a) Pyloric valve b) Mitral valve c) Pulmonic valve d) Eustachian valve e) Tricuspid valve
c) Pulmonic valve The pulmonic and aortic valves are semilunar valves and have similar embryologic origin. The tricuspid and mitral valves are atrioventricular valves. The pyloric valve is located between the stomach and small intestine. The Eustachian valve lies at the junction of the inferior vena cava and right atrium.
A 77‐year‐old man is experiencing progressive shortness of breath and dizziness. The patient undergoes cardiac catheterization, and the systolic blood pressure measured in the left ventricle is 180 mm Hg, while the systolic blood pressure measured in the aorta is 140 mm Hg. The patient is most likely experiencing symptoms related to what valvular condition? a) Mitral stenosis b) Aortic insufficiency c) Mitral regurgitation d) Aortic stenosis e) Pulmonic stenosis
d) Aortic stenosis Patients with aortic stenosis often experience dyspnea with exertion, chest pain, or dizziness. The calcification of the aortic valve and narrowing of the valve area effectively decreases the blood flow from the left ventricle to the aorta. Given the obstruction created from the narrowing of the aortic valve, the pressure within the left ventricle is often higher than that seen in the aorta. Aortic insufficiency is associated with blood flow from the aorta to the left ventricle during diastole and is often not associated with differences in systolic blood pressure. Mitral stenosis involves narrowing of the valve between the left atrium and left ventricle while mitral regurgitation involves the flow of blood from the left ventricle to the left atrium during systole when the mitral valve is normally closed. Pulmonic stenosis involves valvular obstruction between the right ventricle and pulmonary artery.
A 55‐year‐old actress sustains a heart attack and the follow‐up electrocardiogram demonstrates a left bundle branch block. What would be the likely duration of the QRS complex? a) 95 milliseconds b) 100 milliseconds c) 75 milliseconds d) 90 milliseconds e) 125 milliseconds
e) 125 milliseconds The QRS complex is the duration of ventricular depolarization and is normally less than 100 milliseconds. Therefore, a left bundle branch block would extend ventricular depolarization and cause lengthening of the QRS complex and its duration.
A 20‐year‐old college student is experiencing dyspnea on exertion and palpitations. On cardiac auscultation, the second heart sound is split and fixed on both inspiration and expiration. What is the most likely cardiac condition associated with this finding? a) Pulmonic stenosis b) Left bundle branch block c) Right bundle branch block d) Tricuspid stenosis e) Atrial septal defect
e) Atrial septal defect Patients with an atrial septal defect often experience dyspnea as well as atrial arrhythmias. Fixed splitting of the second heart sound occurs in atrial septal defects and right heart failure and does not vary with respiration. A left bundle branch block causes paradoxical splitting secondary to the delayed closure of the aortic valve. Wide splitting of the second heart sound is secondary to a delayed closure of the pulmonic valve and is often found in right bundle branch blocks and pulmonic stenosis. Tricuspid stenosis would not usually affect the second heart sound as it is a component of S .
An elderly patient with a history of smoking two packs of cigarettes a day for 50 years complains to her physician of progressive shortness of breath. On cardiac examination, the physician feels the most prominent palpable impulse to be in the xiphoid area. This is most likely a result of what condition? a) Mitral regurgitation b) Aortic stenosis c) Hypertrophic cardiomyopathy d) Hypertension e) Pulmonary hypertension
e) Pulmonary hypertension Pulmonary hypertension may arise from underlying lung disease from smoking such as emphysema or chronic obstructive pulmonary disease. Pulmonary hypertension often results in right ventricular hypertrophy. Aortic stenosis, hypertrophic cardiomyopathy, and hypertension all cause left ventricular hypertrophy and would displace the point of maximal impulse (PMI) lateral to the midclavicular line. Mitral regurgitation is often not associated with ventricular hypertrophy.
