A 65-year-old man is admitted with NSTEMI. Troponin I is elevated at 3.8 ng/mL. He is started on aspirin, ticagrelor, and low-molecular-weight heparin. On day 3, he develops a new harsh holosystolic murmur at the lower left sternal border, worsening dyspnea, and a right heart catheterization shows a step-up in oxygen saturation from right atrium to right ventricle. What is the most likely complication?

• A Acute mitral regurgitation due to papillary muscle rupture
• B Left ventricular free wall rupture
• C Pericarditis
• D Ventricular septal defect ✓

Explanation

The step-up in oxygen saturation from right atrium to right ventricle on oximetry during right heart catheterization is pathognomonic for a ventricular septal defect (VSD), a mechanical complication of MI. Left-to-right shunting causes oxygenated blood to enter the right ventricle, raising its oxygen saturation. Papillary muscle rupture also produces a new murmur but causes acute mitral regurgitation without an RA-to-RV oxygen step-up; V-waves in the pulmonary capillary wedge tracing would be expected instead.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.