A 58-year-old man with hypertension and diabetes presents with acute anterior wall myocardial infarction. Regarding the complications and sequelae of acute MI, all of the following are true EXCEPT:
A. Dressler syndrome typically occurs within 1–2 weeks of acute MI and is mediated by autoimmune mechanisms
B. Papillary muscle rupture leads to acute mitral regurgitation and is more common in inferior wall infarcts
C. Cardiac rupture is most common in the first 3–5 days post-infarction and occurs more frequently in transmural infarcts
D. Ventricular free wall rupture carries a mortality rate exceeding 90% if not immediately surgically repaired
Explanation
Complications of Acute Myocardial Infarction
Key Point
Dressler syndrome (post-MI pericarditis) typically occurs 1–2 weeks to several months after acute MI — NOT within 1–2 weeks as stated in Option A. The classic teaching is that Dressler syndrome presents weeks to months post-infarction (most commonly 2–10 weeks), distinguishing it from early pericarditis (which occurs within the first 1–4 days due to direct epicardial inflammation).
Timing of Post-MI Pericarditis
Table
Type
Timing
Mechanism
Early pericarditis
1–4 days post-MI
Direct epicardial inflammation from transmural necrosis
Dressler syndrome
2 weeks to months (classically 2–10 weeks)
Autoimmune (anti-myocardial antibodies)
Option A is FALSE because it states Dressler syndrome occurs "within 1–2 weeks," which is too early. The autoimmune mechanism is correct, but the timing is wrong — Dressler syndrome is a delayed phenomenon occurring weeks to months after MI.
Why the Other Options Are TRUE (and thus not the answer)
Option B (Cardiac rupture, 3–5 days, transmural): Correct. Free wall rupture peaks at 3–5 days post-MI, when the necrotic myocardium is maximally softened before adequate fibrosis. Transmural infarcts are at highest risk. (Robbins & Cotran Pathologic Basis of Disease, 10th ed.)
Option C (Papillary muscle rupture → acute MR, more common in inferior MI): TRUE overall. The posteromedial papillary muscle has a single blood supply (RCA/PDA), making it more vulnerable to ischemia than the anterolateral papillary muscle (dual supply from LAD and LCx). Posteromedial PM rupture is therefore more common in inferior wall MI (RCA territory). This is a correct general statement. (Harrison's Principles of Internal Medicine, 21st ed.)
Option D (Free wall rupture >90% mortality): Correct. Ventricular free wall rupture leads to hemopericardium and cardiac tamponade; mortality exceeds 90% without immediate surgical repair.
Clinical Pearl
The posteromedial papillary muscle is supplied solely by the posterior descending artery (RCA in right-dominant circulation), making it more susceptible to ischemic rupture than the anterolateral papillary muscle, which has dual blood supply. This is why papillary muscle rupture is more common in inferior MI overall — a well-established fact in cardiology (Braunwald's Heart Disease, 12th ed.).
High-YieldNEET PG
For NEET PG/INI-CET, remember that Dressler syndrome = delayed (weeks to months), autoimmune, with fever, pleuritis, and pericarditis. Early post-MI pericarditis (days 1–4) is a separate entity caused by direct inflammation, not autoimmunity.
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