Acute Myocardial Infarction
8 Questions
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Questions and Answers
- 1.
A 62-year-old white woman with a history of coronary artery disease presents to the emergency department with substernal, squeezing chest tightness of 2 hours' duration. The pain is identical to the pain she experienced with her first myocardial infarction. On physical examination, the patient's heart rate is found to be 105 beats/min; a tachycardic regular rhythm without gallop is noted. The patient's lung fields are clear. A chest radiograph is normal, but ECG reveals ST segment elevation in leads I, aVL, V5, and V6. Which of the following statements regarding the management of this patient is true?
- A.
Thrombolytic therapy has been studied in patients with ECG findings other than ST-segment elevation or bundle branch block and has been found to be superior to conventional therapy
- B.
Current recommendations are that the time between a patient's presentation to the emergency department and the administration of thrombolytic therapy not exceed 2 hours
- C.
Coronary angiography is recommended in all patients after thrombolytic therapy has been administered, once they become hemodynamically stable
- D.
Streptokinase therapy is contraindicated in patients who have recently received a dose of streptokinase because of antibodies that form against the drug
Correct Answer
D. Streptokinase therapy is contraindicated in patients who have recently received a dose of streptokinase because of antibodies that form against the drugExplanation
Key Concept/Objective: To understand the basic principles of thrombolytic therapy
The time between a patient's presentation to the emergency department and the administration of thrombolytic therapy should not exceed 60 minutes. Front-loaded tissue plasminogen activator (t-PA) has been found to be superior to the other thrombolytic regimens. However, some physicians prefer the less expensive streptokinase therapy, particularly for patients at low risk of dying (e.g., those with uncomplicated inferior infarctions) and the elderly, who are more likely to have hemorrhagic complications with t-PA than with streptokinase. Streptokinase is contraindicated in patients who have recently received a dose of streptokinase because of antibodies that form against the drug; these antibodies limit the efficacy of repeat doses and increase the risk of allergic reactions. Thrombolytic therapy has been studied in patients with ECG findings other than ST-segment elevation or bundle branch block and has been found to be either of no use or deleterious. Patients treated with thrombolytic therapy in whom complications do not occur are at low risk for reinfarction and death after discharge, and routine performance of coronary angiography and coronary angioplasty does not reduce the occurrence of these adverse events. Coronary angiography is recommended only for patients with hemodynamic instability or for patients in whom spontaneous or exercise-induced ischemia occurs.Rate this question:
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- 2.
A 49-year-old white man who presented to the emergency department with an ST-segment elevation myocardial infarction was given thrombolytics, oxygen, and aspirin. He is now free of chest pain and will be admitted to the coronary care unit for further monitoring. Which of the following statements regarding adjuvant medical therapy for acute myocardial infarction is false?
- A.
Early administration of beta blockers reduces the mortality and the reinfarction rate
- B.
Unless contraindicated, angiotensin-converting enzyme (ACE) inhibitors are indicated in patients with significant ventricular dysfunction after acute myocardial infarction
- C.
When given within 6 hours after presentation to the hospital, I.V. nitroglycerin reduces mortality in patients with myocardial infarction
- D.
Prophylactic therapy with lidocaine does not reduce and may actually increase mortality because of an increase in the occurrence of fatal bradyarrhythmia and asystole
Correct Answer
C. When given within 6 hours after presentation to the hospital, I.V. nitroglycerin reduces mortality in patients with myocardial infarctionExplanation
Key Concept/Objective: To understand the adjuvant medical therapies available for patients with acute myocardial infarction after reperfusion therapy has been administered
Early administration of beta blockers may reduce infarct size by reducing heart rate, blood pressure, and myocardial contractility. It is recommended that all patients with acute myocardial infarction without contraindications receive I.V. beta blockers as early as possible, whether or not they receive reperfusion therapy. Several large, randomized, controlled clinical trials evaluated the use of ACE inhibitors early after acute myocardial infarction; all but one trial revealed a significant reduction in mortality. To determine whether nitroglycerin therapy is beneficial in patients treated with reperfusion, 58,050 patients with acute myocardial infarction in the ISIS-4 trial were randomized to receive either oral controlled-release mononitrate therapy or placebo; thrombolytic therapy was administered to patients in both groups. The results of this study revealed no benefit from the routine administration of oral nitrate therapy in this setting. Previously, routine prophylactic antiarrhythmic therapy with I.V. lidocaine was recommended for all patients in the early stages of acute myocardial infarction. However, studies have revealed that prophylactic therapy with lidocaine does not reduce and may actually increase mortality because of an increase in the occurrence of fatal bradyarrhythmia and asystole.Rate this question:
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- 3.
A 49-year-old white woman was admitted last night with an acute ST-segment elevation myocardial infarction. She underwent left heart catheterization with restoration of blood flow to her left circumflex artery and is currently in the CCU. She has received anticoagulation therapy and has been started on an ACE inhibitor, aspirin, and a beta blocker. Which of the following statements regarding possible complications of acute myocardial infarction is true?
- A.
The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial showed that rhythm-control strategies provided a significant survival advantage when compared with rate-control strategies
- B.
Beta blockers may reduce the early occurrence of ventricular fibrillation
- C.
Severe mitral regurgitation is 10 times more likely to occur with anterior myocardial infarction than with inferior myocardial infarction
- D.
When patients have right ventricular infarction, the left ventricle is almost always spared of any damage
Correct Answer
B. Beta blockers may reduce the early occurrence of ventricular fibrillationExplanation
Key Concept/Objective: To know the complications associated with acute myocardial infarction
Although lidocaine has been shown to reduce the occurrence of primary ventricular fibrillation, mortality in patients receiving lidocaine was increased because of an increase in fatal bradycardia and asystole, and prophylactic lidocaine is no longer recommended if defibrillation can rapidly be performed. Beta blockers may reduce the early occurrence of ventricular fibrillation and should be administered to patients who have no contraindications. The treatment of atrial fibrillation in acute myocardial infarction should be similar to the treatment of atrial fibrillation in other settings. If atrial fibrillation recurs, antiarrhythmic agents may be used, although their impact on clinical outcomes is unproven. Mild mitral regurgitation is common in acute myocardial infarction and is present in nearly 50% of patients. The posterior papillary muscle receives blood only from the dominant coronary artery (the right coronary artery in nearly 90% of patients); thrombotic occlusion of this artery may cause rupture of the posterior papillary muscle, resulting in severe mitral regurgitation. Although nearly all patients with right ventricular infarction suffer both right and left ventricular infarction, the characteristic hemodynamic findings of right ventricular infarction generally dominate the clinical course and must be the main focus of therapy.Rate this question:
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- 4.
A 55-year-old man with a history of hypertension and hyperlipidemia presents to the emergency department with chest pain for the past 4 hours. His symptoms started while he was playing racquetball. The pain is crushing, retrosternal, 9/10 in severity, and radiating to the left arm. It is worse with exertion and associated with mild shortness of breath. In the emergency department, the patient is given aspirin, nitroglycerin, and oxygen and experiences moderate symptomatic improvement. His electrocardiogram shows ST segment elevation in the anterior precordial leads with reciprocal changes inferiorly. Which of the following is the most important next step in the management of this patient?
- A.
Thrombolytic therapy
- B.
Percutaneous coronary intervention (PCI)
- C.
Send cardiac biomarkers
- D.
Intravenous morphine
Correct Answer
B. Percutaneous coronary intervention (PCI)Explanation
Key Concept/Objective: To understand that PCI is the therapy of choice in ST segment elevation myocardial infarction
The time to administration of reperfusion therapy is a critical determinant of outcome and one of the few determinants of early clinical outcome under the control of the physician. Many studies have revealed that patients with myocardial infarction treated most rapidly have a lower mortality and, among survivors, reduced infarct size. This observation has led to recommendations that the time between a patient’s presentation to the emergency department and the administration of thrombolytic therapy not exceed 60 minutes; ideally, this period should not exceed 30 minutes. The most critical interval is the time between symptom onset and the achievement of reperfusion, not the time to the initiation of therapy. Thus, therapy that takes longer to initiate may actually be superior if it achieves reperfusion more
rapidly than another therapy that can be initiated more rapidly (e.g., thrombolytic therapy). The American College of Cardiology/American Heart Association (ACC/AHA) Task Force gave a class I recommendation to the use of PCI for any patient with an acute ST segment elevation myocardial infarction (STEMI) who presents within 12 hours of symptom onset and who can undergo the procedure within 90 minutes of presentation by clinicians skilled in the procedure. When primary PCI is not available or its implementation will be signifi cantly delayed, use of thrombolytic therapy is recommended. Reperfusion therapy, whether PCI or thrombolytics, should not await the availability of results of cardiac biomarkers. The immediate implementation of reperfusion therapy without awaiting biomarker data was given a class I recommendation.Rate this question:
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- 5.
A 50-year-old woman is hospitalized for an acute inferior myocardial infarction for which she has undergone angioplasty to the right coronary artery. On day 4, she develops acute shortness of breath and hypotension. She does not have any chest pain. On examination, she is tachycardic with a 3/6 holosystolic murmur at the apex and bibasilar crackles. An electrocardiogram shows sinus tachycardia, and a chest x-ray shows pulmonary edema. Which of the following is the most appropriate management for this patient’s problem?
- A.
Prompt surgical repair
- B.
Left heart catheterization
- C.
Right heart catheterization
- D.
Anticoagulation
Correct Answer
A. Prompt surgical repairExplanation
Key Concept/Objective: To recognize the signs, symptoms, and treatment of acute mitral regurgitation
Mitral regurgitation may result from injury to any of the components of the mitral valve apparatus, including the papillary muscles and ventricular walls to which they attach. Mild mitral regurgitation is common in acute myocardial infarction and is present in nearly 50% of patients. Severe mitral regurgitation caused by acute myocardial infarction is rare and generally results from partial or complete rupture of
a papillary muscle. The characteristic murmur of severe chronic mitral regurgitation may not be present with acute rupture of a papillary muscle. Instead, a decrescendo systolic murmur is often present, extending less throughout systole as systemic arterial pressure falls and left arterial pressure rises. In many cases, the signifi cance of the murmur is not recognized. The blood supply of the anterior papillary
muscle arises from branches of both the left anterior descending and the circumfl ex arteries; therefore, rupture of the anterior papillary muscle is rare. However, the posterior papillary muscle receives blood only from the dominant coronary artery (the right coronary artery in nearly 90% of patients); thrombotic occlusion of this artery may cause rupture of the posterior papillary muscle, resulting in severe
mitral regurgitation. Severe mitral regurgitation is 10 times more likely to occur with inferior infarction than with anterior infarction. Acute severe mitral regurgitation is poorly tolerated and generally results in pulmonary edema, often with cardiogenic shock. Prompt surgical repair is recommended. Although the mortality associated with mitral valve surgery is high in this setting, approaching 50%, survival
appears to be greater than with medical therapy alone. Therapy aimed at reducing left ventricular afterload, such as use of IV nitroprusside and an intra-aortic balloon pump, reduces the regurgitant volume and increases forward blood fl ow and cardiac
output and may be helpful as a temporizing measure.Rate this question:
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- 6.
A 65-year-old man with diabetes, hyperlipidemia, and tobacco abuse presents to the emergency department with chest pain for the past 3 days. The pain is worse with exertion and was relieved by sublingual nitroglycerin until today, when the pain persisted. It radiates to the jaw and is associated with nausea and diaphoresis. On examination, the blood pressure is 90/50 mm Hg, with a heart rate of 95 beats perminute. He has a 2/6 holosystolic murmur at the right lower sterna border and a jugular venous pressure of 12 mm H2O. An electrocardiogram reveals ST segment depressions in the inferior leads. CK-MB and troponin levels are elevated, and the patient is diagnosed with a non–ST segment elevation myocardial infarction. Which of the following medications should be avoided in the management of this patient?
- A.
Heparin
- B.
Aspirin
- C.
Nitrates
- D.
Angiotensin-converting enzyme inhibitor
Correct Answer
C. NitratesExplanation
Key Concept/Objective: To understand complications of a right ventricular infarction
Right ventricular infarction occurs in approximately one third of patients with acute inferior left ventricular infarction and is hemodynamically signifi cant in approximately 50% of affected patients. Hemodynamically signifi cant right ventricular infarction
associated with anterior infarction or isolated right ventricular infarction is rare. The classic fi ndings associated with hemodynamically signifi cant right ventricular infarction are hypotension with clear lung fi elds and an elevated jugular venous pressure, often
with the Kussmaul sign. Although nearly all patients with right ventricular infarction suffer both right and left ventricular infarction, the characteristic hemodynamic fi ndings of right ventricular infarction generally dominate the clinical course and must be the main focus of therapy. Right ventricular involvement during inferior myocardial infarction is associated with a signifi cant increase in mortality, and aggressive attempts at early reperfusion should be pursued. Prompt recognition of right ventricular involvement is clinically important because therapy that reduces right ventricular fi lling, such as use of nitrates or diuretics, should be avoided.Rate this question:
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- 7.
A 60-year-old female with a history of coronary artery disease presents to a rural emergency department with chest pain for 1 hour. Her pain is similar to the symptoms that she experienced last year when she was diagnosed with a non–ST elevation myocardial infarction. She has been taking her medications as instructed. The electrocardiogram shows anterior ST segment elevations. The nearest catheterizationlaboratory is 3 hours away. Which of the following is the most appropriate next step in the management of this patient?
- A.
Transfer the patient for PCI
- B.
Consult Cardiovascular Surgery for coronary bypass surgery
- C.
Administer thrombolytics if there are no contraindications
- D.
Medical management
Correct Answer
C. Administer thrombolytics if there are no contraindicationsExplanation
Key Concept/Objective: To recognize that thrombolytic therapy is the treatment of choice for ST elevation myocardial infarction when PCI is not available
Thrombolytic therapy has been widely studied in prospective, randomized, controlled trials involving more than 50,000 patients and has been proved to reduce mortality 29% in patients with ST segment elevation treated within 6 hours after the onset of chest pain. The survival benefi t of thrombolytic therapy is maintained for years. The benefi t of thrombolytic therapy is achieved through rapid restoration of blood fl ow in an occluded coronary artery.
Thrombolytic therapy is strongly recommended for patients with ST segment elevation in two or more contiguous leads who have had less than 6 hours of chest pain; for patients with classic symptoms of infarction in whom a bundle branch block precludes detection of ST segment elevation; and for patients presenting with 6 to 12 hours of chest pain, although the expected benefi ts for this last group of patients are fewer.
The ACC/AHA task force recommends the use of PCI for any patient with an acute STEMI who presents within 12 hours of symptom onset and who can undergo the procedure within 90 minutes of presentation by clinicians skilled in the procedure. When primary PCI is not available or its implementation will be signifi cantly delayed, use of thrombolytic therapy is recommended.Rate this question:
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- 8.
A 40-year-old male has been in the hospital for 5 days following an acute myocardial infarction. His catheterization revealed 99% stenosis of the left circumfl ex, and he received one drug-eluting stent without complications. An echocardiogram showed an ejection fraction of 55%. His current medications include aspirin, clopidrogel, and metoprolol. Which of the following medications should be added to this patient’s regimen prior to discharge?
- A.
An angiotensin receptor blocker
- B.
Warfarin
- C.
Furosemide
- D.
Statin
Correct Answer
D. StatinExplanation
Key Concept/Objective: To recognize the benefi ts of statins in patients with a recent myocardial infarction
Recent studies have demonstrated that in patients with coronary artery disease, lipid-lowering therapy with HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors reduces not only fatal and nonfatal infarction but also mortality from all causes. The
Scandinavian Simvastatin Survival Study revealed a 42% reduction in cardiac mortality and a 30% reduction in all-cause mortality in 4,444 men and women with coronary artery disease over the 5.4 years of the study. The reductions in mortality were similar in patients in
the lowest and those in the highest quartiles of serum low-density lipoprotein (LDL) cholesterol. It has been demonstrated that postinfarction patients with an LDL cholesterol level at or above 130 mg/dL benefi t from lipid-lowering therapy within as little as 2 years after the initiation of such therapy. Initial measurement of cholesterol should be made within 24 hours after myocardial infarction; measurement of lipids 24 hours or more after myocardial infarction can be misleading in that cholesterol levels may be reduced below baseline levels during this period and remain low for up to 1 month. Early initiation of statins may be more benefi cial than later initiation. Exercise, weight reduction in overweight patients, avoidance of dietary saturated fat and cholesterol, and smoking cessation have all been reported to favorably infl uence blood lipid levels and should be recommended whether or not lipid-lowering medications are prescribed.Rate this question:
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