Answer
C: Mitral regurgitation
Educational Objective
Diagnose acute mitral regurgitation due to papillary muscle rupture.
Critique
The most likely diagnosis is acute mitral regurgitation. This patient has evidence of a recent inferolateral myocardial infarction and decompensated heart failure. The mitral regurgitation is likely secondary to papillary muscle dysfunction (or rupture) and/or ventricular dysfunction. In acute mitral regurgitation, heart failure symptoms may occur abruptly because there has not been time for adaptive chamber dilatation. The murmur of acute mitral regurgitation may be present only in early diastole, owing to rapid diastolic equalization of ventricular and atrial pressures caused by the high volume overload. In cases of severe mitral regurgitation, a diastolic rumble occurs because of the large regurgitant volume during diastole. If present, the systolic murmur of acute mitral regurgitation is typically soft and ends before A2. It is best heard along the left sternal border and base of the heart, generally without a thrill.
In patients with aortic stenosis, the murmur characteristically gets louder and then softer (crescendo-decrescendo) during systole; it is loudest at the second right intercostal space, with radiation to the carotid arteries. These findings are not present in this patient.
Left ventricular free wall rupture is an often fatal complication of myocardial infarction that occurs 3 to 7 days after the initial event. Patients most commonly present with cardiac tamponade (due to hemopericardium), pulseless electrical activity, and death. Patients with cardiac tamponade typically do not have a heart murmur or a preserved or exaggerated x descent in the jugular venous pulse, as seen in this patient.
Most patients with mild to moderate tricuspid regurgitation are asymptomatic. Examination reveals a systolic murmur that is loudest at the left lower sternal border and increases with inspiration. Symptoms and signs of right-sided heart failure, such as fatigue, elevated jugular venous pulse, and lower extremity edema, may be found; however, tricuspid regurgitation does not cause volume overload in the lungs, as was observed in this patient.
Key Point
Acute severe mitral regurgitation is associated with papillary muscle rupture following acute myocardial infarction.
Bibliogrpahy
Kutty RS, Jones N, Moorjani N. Mechanical complications of acute myocardial infarction. Cardiol Clin. 2013;31:519-31, vii-viii. [PMID: 24188218] doi:10.1016/j.ccl.2013.07.004