The patient had rapid decompensation several days after an acute myocardial infarction, suggesting the possibility of a mechanical complication. The differential diagnosis includes papillary muscle rupture, ventricular septal rupture, free wall rupture with tamponade, and pump failure.
Echocardiography is an excellent tool for sorting through the differential diagnosis, and should be performed as early as possible. Echocardiography allows for expeditious evaluation of overall and regional left ventricular performance, and can rapidly diagnose mechanical causes of shock such as acute mitral regurgitation resulting from papillary muscle rupture, acute ventricular septal defect, and free wall rupture. In some cases, echocardiography may reveal findings compatible with right ventricular infarction, or suggest alternative diagnoses such as pericardial tamponade.
The echocardiogram in the question is shows a 4-chamber view, with the ventricles on top, the atria on the bottom, and the thicker left ventricle on the right side of the image. The distal septum and apex are akinetic, and a ventricular septal defect is visible.
The frequency of acute rupture of the interventricular septum has decreased in the reperfusion era to an incidence of less than 1%, but this complication still represents about 4% of patients with cardiogenic shock. Hypertension, advanced age, female gender are predisposing factors. The incidence is bimodal, either within 24 hours, or 3 to 5 days after acute infarction. Early ruptures are due to intramural hematomas that dissect into tissue, and the later ruptures to ongoing tissue necrosis.
Patients with ventricular septal rupture have severe heart failure or cardiogenic shock, with a pansystolic murmur and a parasternal thrill, although both of these findings may be subtle in the presence of a low cardiac output. The hallmark finding is a left-to-right intracardiac shunt (“step-up” in oxygen saturation from right atrium to right ventricle). The diagnosis is most easily made with echocardiography.
Medical therapy consists of mechanical support with an intra-aortic balloon pump and pharmacologic measures, including judicious use of inotropes and afterload reducers. Nitroprusside can be useful to reduce afterload in acute VSD because of its short half-life and titratability. Invasive monitoring is recommended to optimize vasoactive therapy.
- Because septal perforations are exposed to shear forces and removal of tissue by necrosis, the rupture site can expand abruptly, and so operative repair is usually the only viable option for long-term survival. Surgical mortality is quite high (20-50%), especially for inferoposterior ruptures, which tend to be serpiginous and less well circumscribed than anteroapicai ruptures, and so are harder to repair. The timing of surgery has been controversial, but guidelines now recommend that operative repair should be undertaken early, within 48 hours of the rupture.
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