Five days after a first large transmural anterior MI, a 72-year-old hypertensive woman suddenly collapses. She is unresponsive with a palpable carotid pulse momentarily lost; the monitor shows organized QRS complexes with no recordable blood pressure and no pulse. Bedside echo shows pericardial effusion with diastolic collapse of the right ventricle. What is the most likely mechanism?

• A Rupture of the interventricular septum
• B Ventricular tachycardia degenerating to ventricular fibrillation
• C Rupture of a posteromedial papillary muscle
• D Rupture of the left ventricular free wall with hemopericardium ✓

Explanation

Free wall rupture peaks 3 to 7 days after a transmural MI, when coagulative necrosis is maximal and granulation tissue has not yet strengthened the wall. Blood escapes into the pericardium causing tamponade, and the classic rhythm is pulseless electrical activity: organized complexes without a mechanical output. Septal rupture produces a pansystolic murmur and shock without effusion, papillary muscle rupture produces acute mitral regurgitation, and primary ventricular arrhythmia would show a disorganized rhythm rather than organized QRS complexes.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.