A 70-year-old male is admitted after a massive anterior myocardial infarction and initially stabilizes with medical management. Several days later, he suddenly develops ventricular tachycardia followed by cardiac arrest. Histologic remodeling of the infarcted myocardium reveals fibroblast infiltration with deposition of type I collagen, replacing large numbers of necrotic cardiac myocytes. Which of the following best explains the principal cause of death in patients following a massive myocardial infarction?
Progressive systolic heart failure from reduced ejection fraction
Acute papillary muscle rupture leading to severe mitral regurgitation
Life-threatening ventricular arrhythmias due to disruption of normal electrical conduction by collagen scar tissue
Recurrent coronary artery thrombosis from endothelial injury
The Correct Answer is C
A. Progressive systolic heart failure from reduced ejection fraction: Heart failure can develop after myocardial infarction due to loss of contractile myocardium and remodeling. However, in this case, the patient experiences sudden ventricular tachycardia and cardiac arrest, which indicates an arrhythmic event rather than gradual pump failure.
B. Acute papillary muscle rupture leading to severe mitral regurgitation: Papillary muscle rupture is a mechanical complication of myocardial infarction that leads to acute mitral regurgitation and pulmonary edema. It typically occurs within the first week post-MI, but the presentation here involves ventricular arrhythmia and sudden death, which is more consistent with electrical instability than valvular failure.
C. Life-threatening ventricular arrhythmias due to disruption of normal electrical conduction by collagen scar tissue: After myocardial infarction, necrotic myocardium is replaced by fibrous scar tissue composed of type I collagen and fibroblasts. This non-conductive scar interrupts normal electrical pathways, creating areas of heterogeneity that predispose to reentrant circuits and life-threatening ventricular arrhythmias, which are a leading cause of sudden death.
D. Recurrent coronary artery thrombosis from endothelial injury: Recurrent thrombosis can precipitate reinfarction, but the acute presentation of ventricular tachycardia and sudden cardiac arrest in a stabilized patient suggests arrhythmic death due to scar-related conduction abnormalities rather than another thrombotic event.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Angina:Chest pain precipitated by exertion and relieved by nitroglycerin is characteristic of stable angina pectoris. It results from transient myocardial ischemia due to a mismatch between oxygen supply and demand, typically caused by atherosclerotic narrowing of coronary arteries. Nitroglycerin relieves pain by causing venodilation, reducing preload and myocardial oxygen demand.
B. Dyspnea:Dyspnea refers to the subjective sensation of shortness of breath. Although it may accompany cardiac ischemia, it is not defined as chest pain and does not specifically describe exertional discomfort relieved by nitroglycerin.
C. Dyspepsia:Dyspepsia describes indigestion or epigastric discomfort related to gastrointestinal causes. While it can sometimes mimic cardiac chest pain, it is unrelated to myocardial ischemia and would not consistently improve with nitroglycerin.
D. Dysphagia:Dysphagia refers to difficulty swallowing and is associated with esophageal or neuromuscular disorders. It does not describe exertional chest pain related to cardiac ischemia.
E. Orthopnea:Orthopnea is shortness of breath that occurs when lying flat and improves with sitting upright, often seen in heart failure. It is distinct from exertional chest pain relieved by nitrates and does not describe anginal symptoms.
Correct Answer is B
Explanation
A. Acute left-sided heart failure:Left-sided heart failure typically presents with pulmonary congestion, dyspnea, orthopnea, and pulmonary rales. While it can eventually lead to right-sided symptoms, this patient’s presentation is dominated by right-sided signs—jugular venous distention, peripheral edema, hepatomegaly—without primary pulmonary edema, making left-sided failure less likely.
B. Cor pulmonale:Cor pulmonale is right ventricular enlargement and dysfunction caused by chronic pulmonary hypertension, often secondary to chronic lung diseases such as COPD. Features include peripheral edema, cyanosis, elevated jugular venous pressure, loud P2 due to pulmonary hypertension, hepatomegaly, and echocardiographic evidence of right ventricular dilation and hypertrophy. The patient’s history of severe COPD and chronic hypoxia strongly supports this diagnosis.
C. Pulmonary embolism:Pulmonary embolism can cause acute right heart strain and dyspnea, but it usually presents suddenly with chest pain, hemoptysis, and often without chronic signs such as peripheral edema or hepatomegaly. Echocardiography may show right ventricular dilation acutely, but chronic hypertrophy is not typical in isolated PE.
D. Dilated cardiomyopathy:Dilated cardiomyopathy affects both ventricles with progressive systolic dysfunction, leading to biventricular heart failure. While it can cause right-sided symptoms, the patient’s chronic COPD history and predominance of right-sided findings point to cor pulmonale rather than primary dilated cardiomyopathy.
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