Name the two classic mechanical complications of a transmural myocardial infarction and their typical timing.

Name the two classic mechanical complications of a transmural myocardial infarction and their typical timing.

• A. Ventricular aneurysm formation and mural thrombus formation (late complication)
• B. Atrial septal defect with shunt (early)
• C. Free wall rupture causing tamponade (3-7 days) and papillary muscle rupture causing acute severe mitral regurgitation (3-5 days)
• D. Pericarditis with effusion (early)

Answer: (C)

The key concept is that after a transmural MI the infarcted tissue weakens, and the most feared mechanical problems occur in the subacute period as the wall is degraded. The two classic issues are rupture of the free left ventricular wall, which leads to rapid tamponade from blood filling the pericardial space, and rupture of a papillary muscle, which causes acute severe mitral regurgitation. The timing fits the pathophysiology: free-wall rupture typically happens about 3 to 7 days after the infarct, while papillary muscle rupture tends to occur a bit earlier, around 3 to 5 days. Other complications either occur later, such as ventricular aneurysm formation and mural thrombus, or are inflammatory rather than mechanical, like pericarditis with effusion; an atrial septal defect with shunt is not a typical MI complication.

The key concept is that after a transmural MI the infarcted tissue weakens, and the most feared mechanical problems occur in the subacute period as the wall is degraded. The two classic issues are rupture of the free left ventricular wall, which leads to rapid tamponade from blood filling the pericardial space, and rupture of a papillary muscle, which causes acute severe mitral regurgitation. The timing fits the pathophysiology: free-wall rupture typically happens about 3 to 7 days after the infarct, while papillary muscle rupture tends to occur a bit earlier, around 3 to 5 days. Other complications either occur later, such as ventricular aneurysm formation and mural thrombus, or are inflammatory rather than mechanical, like pericarditis with effusion; an atrial septal defect with shunt is not a typical MI complication.