Practice Question
A 64-year-old man is brought to the emergency department 4 days after an acute myocardial infarction. He was treated with thrombolytics at an outside hospital and was clinically improving until this morning when he developed sudden-onset shortness of breath. His temperature is 37.1°C, blood pressure is 88/60 mmHg, and pulse is 112/min. Examination reveals jugular venous distension, a new harsh holosystolic murmur with a palpable thrill heard best at the left lower sternal border, and bilateral crackles. Right heart catheterization shows an oxygen saturation step-up from the right atrium to the right ventricle. Which of the following is the most likely diagnosis?
Answer is B! Interventricular septal rupture occurs 3–5 days post-MI (LAD or RCA territory) and presents with sudden cardiogenic shock, a harsh holosystolic murmur with thrill at the left lower sternal border, and a pathognomonic O₂ step-up from RA to RV on right heart cath, reflecting left-to-right shunting through the defect. This distinguishes it from papillary muscle rupture, which causes acute MR with a soft apical murmur but no O₂ step-up. Definitive treatment is surgical patch repair.