Cardiac

Which structure is the primary or natural pacemaker?

SA node Rationale- With an intrinsic rate of 60 to 100 beats/min, the sinoatrial node is the primary pacemaker in a healthy heart. The atrioventricular node beats 40 to 60 beats/min. Ventricular tissue must have an electrical impulse to contract. Purkinje fibers beat 15 to 40 beats/min.

Why is the measurement of the QT interval important?

an increased QT interval increases the risk for Torsades de Pointes. Rationale- A prolonged QT interval is significant because it can predispose the patient to the development of polymorphic ventricular tachycardia, known also as torsades de pointes. A long QT interval can be congenital, as a result of genetic inheritance, or it can be acquired from an electrolyte imbalance or medications.

Through what mechanism does enalapril decrease blood pressure?

blocks the conversion of angiotensin I to angiotensin II.

Which statement regarding the autonomic nervous system's role in the regulation of heart rate is true?

both sympathetic and parasympathetic influences are normally active.

Which clinical manifestations are indicative of left ventricular failure?

cool, pale extremities weak peripheral pulses rales. Rationale- Patients presenting with left ventricular failure have one of the following: (1) decreased exercise tolerance, (2) fluid retention, or (3) discovery during examination of noncardiac problems. Clinical manifestations of left ventricular failure include decreased peripheral perfusion with weak or diminished pulses; cool, pale extremities; and, in later stages, peripheral cyanosis.

The patient is admitted with a diagnosis of cardiogenic shock. The patient's heart rate (HR) is135 beats/min with weak peripheral pulses. The patient has bilaterally crackles in the bases of the lungs. O2 saturation is 90% on 4L/NC. The practitioner orders diuretics and vasodilators. What response should the nurse expect after starting the medications?

decreased preload and after load. Rationale- Vasodilators are used to decrease afterload, and diuretics are used to decrease preload.

What is the physiologic effect of left ventricular afterload reduction?

decreased systemic vascular resistance. Rationale- After load is defined as the pressure the ventricle generates to overcome the resistance to ejection created by the arteries and arterioles. After a decrease in afterload, wall tension is lowered. The technical name for afterload is systemic vascular resistance (SVR).

What effect does ventricular tachycardia have on CO?

decreases cardiac output due to a decrease in SV. Rationale- Tachycardia is detrimental to anyone with ischemic heart disease because it decreases the time for ventricular filling, decreases stroke volume, and compromises cardiac output. Tachycardia increases heart work and myocardial oxygen demand while decreasing oxygen supply by decreasing coronary artery filling time.

Which findings is a reliable indicator of repercussion after fibrinolytic surgery?

dysrythmias RATIONALE- Initially, when there is reperfusion, ischemic chest pain ceases abruptly as blood flow isrestored. Another reliable indicator of reperfusion is the appearance of various "reperfusion"dysrhythmias. Premature ventricular contractions, bradycardias, heart block, ventricular tachycardia, and (rarely) ventricular fibrillation may occur.

A patient reports that he has been having "indigestion" for the last few hours. Upon furtherreview the nurse suspects the patient is having of chest pain. Cardiac biomarkers and a 12-lead electrocardiogram (ECG) are done. What finding is most significant in diagnosing an acute coronary syndrome (ACS) within the first 3 hours?

elevated Troponin I levels Rationale- the elevation of Troponin I and troponin T occurs 3 to 6 hours after acute myocardial damage. Because troponin I is found only in cardiac muscle, it is a highly specific biomarker for myocardial damage.

Which signs and symptoms would indicate successful reperfusion after administration of a fibrinolytic agent? (Select all that apply.)

intermittent, multifocal PVC's -rapid resolution of ST elevation -rapid rise in CKMB fraction

Why is a new-onset of atrial fibrillation serious?

it increases the patients risk for a stroke. Rationale- In atrial fibrillation the atria do not contract normally; they quiver. This increases the chance of the blood clotting in the atria because of a lack of complete emptying of the atria. These clots can break free and cause embolic strokes and pulmonary emboli.

What parameter is used to assess the contractility of the left side of the heart?

left ventricular stroke work index.

What is the name of the valve that allows blood flow into pulmonary artery?

pulmonic valves

Depolarization of one myocardial cell will likely result in what physiologic response?

quick depolarization and spread to all the heart. Rationale- The cardiac muscle is a functional syncytium in which depolarization started in any cardiac cell is quickly spread to all of the heart.

Which hemodynamic alteration is the most common cause of a decrease in cardiac output in the postoperative cardiovascular patient?

reduced preload Rationale- In most patients, reduced preload is the cause of low postoperative cardiac output. To enhance preload, volume may be administered in the form of crystalloid, colloid, or packed red blood cells.

What is the rationale for administrating a fibrinolytic agent to a patient experiencing acute ST-elevation myocardial infarction (STEMI)?

restoration of blood flow via lysis of the thrombus. Rationale- The administration of a fibrinolytic agent results in the lysis of the acute thrombus, thus recanalizing, or opening, the obstructed coronary artery and restoring blood flow to the affected tissue. After perfusion is restored, adjunctive measures are taken to prevent further clot formation and reocclusion.

What type of atrioventricular (AV) block can be described as a gradually lengthening PR interval until ultimately the final P wave in the group fails to conduct?

second degree AV block; type 1.

Which statement regarding the difference between stable and unstable angina is accurate?

stable angina responds predictably well to nitrates. Rationale- Stable angina is predictable and caused by similar precipitating factors each time; typically, it is exercise induced. Pain control is usually achieved by rest and by sublingual nitroglycerin within 5 minutes.

Which intervention is an essential aspect of the patient teaching plan for the patient with chronic heart failure?

stressing the importance of compliance w/diuretic therapy. Rationale- Primary topics of education include (1) the importance of a daily weight, (2) fluid restrictions, and (3) written information about the multiple medications used to control the symptoms of heart failure. Reduction or cessation of diuretics usually results in sodium and water retention, which may precipitate heart failure.

Which step of impulse conduction is most conducive to atrial kick?

the conduction delay at the AV node, allowing time for filling. Rationale-

A patient is admitted with right- and left-sided heart failure. The nurse's assessment revealsthat the patient has 3+ pitting edema on the sacrum, blood pressure of 176/98 mm Hg, and bilateral crackles in the lungs. The patient is experiencing shortness of breath and chestdiscomfort. On the basis of this information, how would the nurse evaluate the patient'spreload status?

the patient is experiencing HF and has too much preload. Rationale- Whereas a patient with hypovolemia has too little preload, a patient with heart failure has too much preload.

What is the rationale for giving the patient additional fluids after a cardiac catheterization?

the radiopaque contrast acts as an osmotic diuretic. Rationale-Fluid is given for rehydration because the radiopaque contrast acts as an osmotic diuretic. Fluid is also used to prevent contrast-induced nephropathy or damage to the kidney from the contrast dye used to visualize the heart structures.

Which is an example of a physiological shunt?

the thebesian vessel returning deoxygenated blood to the left ventricle.

Why are vasopressors used cautiously in the treatment of critical care patients?

they increase after load Rationale- Vasopressors are not widely used in the treatment of critically ill cardiac patients because the dramatic increase in afterload is taxing to a damaged heart.

Adenosine is an antidysrhythmic agent that is given primarily for what reason?

to convert SVT's.

What is the function of the atrioventricular (AV) valves?

to prevent back flow of blood into the atria during ventricular contraction. Rationale- The atrioventricular (AV) valves are open during ventricular diastole (filling) and prevent backflow of blood into the atria during ventricular systole (contraction). Semilunar valves prevent the backflow of pulmonic and aortic blood back into the ventricles.

The atrioventricular (AV) node delays the conduction impulse from the atria (0.8-1.2 seconds) for what reasons?

to provide time for the ventricles to fill during diastole.

What is the major factor influencing the patients response to ATRIAL FLUTTER?

ventricular response rate

A patient is diagnosed with third-degree heart failure. The nurse reviews the patient'smedication list. Which classifications of drugs should be avoided with this patient? (Select all that apply.)

-Nsaids -antidysrythmics -calcium channel blockers

Which patients would be a candidate for fibrinolytic therapy? (Select all that apply.)

-The patient's chest pain started 3 hours ago, and her electrocardiogram (ECG) shows a new left bundle branch block. -The patient's chest pain started 1 hour ago, and his ECG shows ST elevation. Rationale- Eligibility criteria for administering fibrinolytics include chest pain of less than 12 hours'duration and persistent ST elevation. Exclusion criteria include recent surgery, cerebrovascular accident, and trauma.

Which mechanisms responsible for a myocardial infarction (MI)?

-coronary artery thrombosis -plaque rupture -coronary artery spasm near the ruptured plaque. Rationale- The three mechanisms that block the coronary artery and are responsible for the acute reduction in oxygen delivery to the myocardium are (1) plaque rupture, (2) new coronary artery thrombosis, and (3) coronary artery spasm close to the ruptured plaque.

A patient suddenly develops a wide QRS complex tachycardia. The patient's heart rate is 220beats/min and regular; blood pressure is 96/40 mm Hg; and respiratory rate is 22 breaths/min, and the patient is awake without compl

Adenosine 6mg rapid IV push

An echocardiogram reveals an ejection fraction of 55%. On the basis of this information, howwould the patient's cardiac function be described?

Adequate Rationale- Ejection fraction is expressed as a percent, with normal being at least greater than 50%. An ejection fraction of less than 35% indicates poor ventricular function (as in cardiomyopathy), poor ventricular filling, obstruction to outflow (as in some valve stenosis conditions), or a combination of these.

The nursing management plan for a patient with angina would include which intervention?

Assessment and documentation of chest pain episodes. Rationale- Nursing interventions focus on early identification of myocardial ischemia, control of chest pain, recognition of complications, maintenance of a calm environment, and patient and family education. It is important to document the characteristics of the pain and the patient'sheart rate and rhythm, blood pressure, respirations, temperature, skin color, peripheral pulses, urine output, mentation, and overall tissue perfusion.

What does the P wave component of the electrocardiographic waveform represent?

Atrial contraction (depolarization)

A patient presents with atrial fibrillation, a heart rate of 156 beats/min, and a blood pressure of 124/76 mm Hg. The practitioner orders diltiazem, a calcium channel blocker, to be given slowly by intravenous push. Why did the practitioner choose this medication to treat thispatient's atrial tachyarrhythmia?

Diltiazem decreases the calcium influx into the atrioventricular (AV) nodal tissue and decreases the speed of impulse conduction. Rationale- Calcium channel-blocking drugs, such as verapamil and diltiazem, inhibit the inward Ca++ current into pacemaker tissue, especially the atrioventricular (AV) node. For this reason, they are used therapeutically to slow the rate of atrial tachydysrhythmias and protect the ventricle from excessive atrial impulses.

A patient is admitted with an acute myocardial infarction (MI). What common complication should the nurse anticipate in this patient?

Dysrhythmias Rationale- Many patients experience complications occurring either early or late in the postinfarction course. These complications may result from electrical dysfunction or from a cardiac contractility problem. Cardiac monitoring for early detection of ventricular dysrhythmias is ongoing.

Why is mixed venous oxygen saturation (SVO2) monitoring helpful in the management of the critically ill patient?

It can detect an imbalance between oxygen supply and metabolic tissue demand.

Which serum lipid value is a significant predictor of future acute myocardial infarction (MI) in persons with established coronary artery atherosclerosis?

LDL levels Rationale- Both the LDL-C and total serum cholesterol levels are directly correlated with risk for coronary artery disease, and high levels of each are significant predictors of future acute myocardial infarction in persons with established coronary artery atherosclerosis. LDL-C is the major atherogenic lipoprotein and thus is the primary target for cholesterol-lowering efforts.

Which calcium channel blocker is beneficial in the treatment of patients with coronary artery disease or ischemic stroke?

Nicardipine Rationale- Nicardipine was the first available intravenous calcium channel blocker and as such could be more easily titrated to control blood pressure. Because this medication has vasodilatory effects on coronary and cerebral vessels, it has proven beneficial in treating hypertension in patients with coronary artery disease or ischemic stroke. Nifedipine is available only in an oral form, but in the past it was prescribed sublingually during hypertensive emergencies.

A patient becomes unresponsive. The patient's heart rate is 32 beats/min in an idioventricularrhythm; blood pressure is 60/32 mm Hg; SpO2 is 90%; and respiratory rate is 14 breaths/min. Which intervention would the nurse do first?

Notify the physician and obtain a temporary pacemaker. Rationale- Rather than trying to abolish the ventricular beats, the aim of treatment is to increase the effective heart rate (HR) and reestablish dominance of a higher pacing site such as the sinus node or the AV junction. Usually, a temporary pacemaker is used to increase the HR until the underlying problems that caused failure of the other pacing sites can be resolved.

Which phase is the final repolarization phase of the action potential?

Phase 3

Which factors influence SV?

Preload, After load, and Contractility.

Which classification of dysrhythmia is most common with an inferior wall infarction in the first hour after ST segment elevation myocardial infarction (STEMI)?

Sinus bradycardia Rationale-Sinus bradycardia (heart rate less than 60 beats/min) occurs in 30% to 40% of patients who sustain an acute myocardial iNnfarRctioIn (MGI).BIt.iCs moMre prevalent with an inferior wallUSNT O infarction in the first hour after ST segment elevation MI.

A patient has been admitted in hypertensive crisis. Which medication would the nurse expect the practitioner to order for this patient?

Sodium Nitroprusside Rationale- Sodium nitroprusside is frequently the first drug used to lower blood pressure in hypertensive emergency. Sodium nitroprusside is useful because of its half-life of seconds. It is not suitable for long-term use because of development of a metabolite that causes cyanide-like toxicity.

The nurse is caring for a patient with these vital signs: blood pressure 220/110, pulse 108, respiratory rate 24, temperature 103° F, and oxygen saturation of 94% on oxygen 2L nasal cannula. The patient is responsive and denies chest pain. The physician has ordered a work-up for coronary artery disease (CAD). These findings are suggestive of which diagnosis?

Stage 2 HTN Rationale- Stage 2 hypertension is defined as a systolic blood pressure of 160 mm Hg or above and a diastolic blood pressure of 100 mm Hg or above.

A patient with a serum potassium level of 6.8 mEq/L may exhibit what type of electrocardiographic changes?

Tall, peaked T waves

What is the effect of preload on cardiac output?

As preload increases, cardiac output increases until it overstretches the ventricle and cardiac output decreases. Rationale- According to the Frank-Starling law of the heart, if preload increases stroke volume, then cardiac output may increase. If, however, preload causes excessive left ventricular stretch, it can actually decrease cardiac output and may result in congestive heart failure.

ST segment monitoring for ischemia has gained increasing importance with the advent of thrombolytic therapy. What is the most accurate method for monitoring the existence of true ischemic changes?

12 lead ECG

Which of the following values reflects a normal cardiac output at rest?

5.8L/min Rationale- The normal cardiac output in the human adult is approximately 4 to 8 L/min. It is approximately 4 to 6 L/min at rest and increases with exercise.

The patient has a heart rate (HR) of 84 beats/min and a stroke volume (SV) of 65 mL. Calculate the cardiac output (CO).

5460 Rationale- The patient has a heart rate (HR) of 84 beats/min and a stroke volume (SV) of 65 mL. Calculate the cardiac output (CO).

A patient is admitted with hypertrophic cardiomyopathy. The nurse would expect the medical management of this patient to include which intervention?

Administer beta blockers. Rationale- beta-blockers to decrease left ventricular workload,

Which cardiac biomarker is elevated in decompensated heart failure?

BNP levels Rationale- n decompensated heart failure, ventricular distension from volume overload or pressure overload causes myocytes in the ventricle to release B-type natriuretic peptide (BNP). With greater ventricular wall stress, more natriuretic peptide is released from the myocardium, reflected as an elevated BNP level.

Which diagnostic test is most effective for measuring overall heart size?

CXR

Which clinical manifestation is usually the first symptom of peripheral arterial disease (PAD)?

Cramping while walking Rationale- Arterial occlusion obstructs blood flow to the distal extremity. The lack of blood flow produces ischemic muscle pain known as intermittent claudication. This cramping, aching pain while walking is often the first symptom of peripheral arterial occlusive disease. The pain is relieved by rest and may remain stable in occurrence and intensity for many years.

What are the clinical manifestations of right-sided heart failure?

Elevated CVP and sacral edema. Rationale- The common manifestations of right ventricular failure are the following: jugular venous distention, elevated central venous pressure, weakness, peripheral or sacral edema, hepatomegaly (enlarged liver), jaundice, and liver tenderness. Gastrointestinal symptoms include poor appetite, anorexia, nausea, and an uncomfortable feeling of fullness.

5. Which criteria are representative of the patient in normal sinus rhythm?

Heart rate, 88 beats/min; rhythm regular; PR interval, 0.18 second; QRS, 0.06 second Rationale- The parameters for normal sinus rhythm are heart rate, 60 to 100 beats/min; rhythm, regular; PR interval, 0.12 to 0.20 second; and QRS, 0.06 to 0.10 second.

What characteristic is associated with junctional escape rhythms?

P wave may be present or absent. Rationale- Characteristics of a junctional escape rhythm include a rate of 40 to 60 beats/min, regular rhythm, present or absent P waves, PR less than 0.12 seconds, and QRS between 0.06 and 0.10 seconds.

Which electrocardiographic (ECG) abnormality is most often found in ventricular dysrhythmias?

wide QRS complexes Rationale- The usual conduction pathway through the ventricles is not used, and the wave of depolarization must spread from cell to cell. As a result, the QRS complex is prolonged and is always greater than 0.12 second. It is the width of the QRS, not the height that is important in the diagnosis of ventricular ectopy.

Mechanical contraction of the heart occurs during which phase of the cardiac cycle?

Phase 2 Rationale- During phases 1 and 2, an electrical plateau is created, and during this plateau, mechanical contraction occurs. Because there is no significant electrical change, no waveform appears on the electrocardiogram (ECG). During phase 0 (depolarization), the electrical potential changes rapidly from a baseline of -90 mV to +20 mV and stabilizes at about 0 mV. Because this is a significant electrical change, it appears as a wave on the ECG as the QRS. During phase 3 (repolarization), the electrical potential again changes, this time a little more slowly, from 0 mV back to -90 mV. This is another major electrical event and is reflected on the ECG as a T wave. During phase 4 (resting period), the chemical balance is restored by the sodium pump, but because positively charged ions are exchanged on a one-for-one basis, no electrical activity is generated, and no visible change occurs on the ECG tracing.

A patient reports feeling dizzy after standing quickly. Which finding could provide a clue regarding the cause?

Poor skin turgor and extended tenting. Rationale- Poor skin turgor could suggest dehydration. Dehydration can cause orthostatic hypotension because of low capacitance reserves from hypovolemia.

The patient's admitting 12-lead ECG shows tall, peaked P waves. What diagnosis could be responsible for this finding?

Pulmonary Edema Rationale- Tall, peaked P waves occur in right atrial hypertrophy and are referred to as P pulmonale because this condition is often the result of chronic pulmonary disease. Ischemia occurs when the delivery of oxygen to theNtissRuesIis inGsufBfi.cieCnt tMo meet metabolic demand. CardiacUSNT O ischemia in an unstable form occurs because of a sudden decrease in supply, such as when the artery is blocked by a thrombus or when coronary artery spasm occurs.

What major clinical finding is present in a patient w/ventricular fibrillation?

Pulselessness Rationale-In ventricular fibrillation (VF), the patient does not have a pulse, no blood is being pumped forward, and defibrillation is the only definitive therapy. No forward flow of blood or palpable pulse is present in VF.

A patient is admitted with a diagnosis of acute myocardial infarction. The monitor pattern reveals bradycardia. Occlusion of which coronary artery most likely resulted in bradycardia from sinoatrial node ischemia?

Right Rationale- The right coronary artery provides the blood supply to the sinoatrial and atrioventricular (AV) nodes in more than half the population.

On returning from the cardiac catheterization laboratory, the patient asks if he can get up in the chair. What should the nurse tell the patient?

you cannot get up because you may start bleeding. Rationale- After catheterization, the patient remains flat for up to 6 hours (varies by institutional protocol and catheter size) to allow the femoral arterial puncture site to form a stable clot. Most bleeding occurs within the first 2 to 3 hours after the procedure.

Which physiologic effects can be associated with physical exercise? (Select all that apply.)

Decreased LDL Increased HDL Decreased triglycerides Decreased incidence of depression.

Place the following components of the cardiac conduction pathway in the correct anatomic order?

SA node AV node Inter nodal pathways Bundle of His Bundle branches Purkinje fibers

A patient presents with atrial flutter with an atrial rate of 280 beats/min and a ventricular rate of 70 beats/min. Which statement best explains this discrepancy in rates?

The atrioventricular (AV) node does not conduct all the atrial signals to the ventricles. Rationale- The atrioventricular (AV) node does not allow conduction of all these impulses to the ventricles. In this case, the rhythm would be described as atrial flutter with a 4:1 AV block, indicating that only one of every four atrial signals is conducted to the ventricles.

What dysrhythmia is most frequently associated with sudden cardiac death?

Ventricular tachycardia Rationale- When the onset of symptoms is rapid, the most likely mechanism of death is ventricular tachycardia, which degenerates into ventricular fibrillation.

What is the formula for calculating mean arterial pressure (MAP)?

adding the systolic pressure and two diastolic pressures and then dividing by 3. Rationale- The mean arterial pressure is one-third systole and two-thirds diastole.