A 65-year-old diabetic male develops a large anterior STEMI and undergoes primary PCI. Forty-eight hours later, a new loud pansystolic murmur is heard at the left sternal border; blood pressure drops to 80/50 mmHg. Oxygen step-up is confirmed on right heart catheterisation. Which mechanical complication is most likely?
- A Acute mitral regurgitation from papillary muscle rupture
- B Free wall rupture with pseudoaneurysm
- C Ventricular septal defect (post-infarction VSD) ✓
- D Acute severe tricuspid regurgitation
Correct answer: C. Ventricular septal defect (post-infarction VSD)
Explanation
Post-infarction ventricular septal defect (VSD) typically occurs 3–7 days after anterior STEMI, presenting with a harsh pansystolic murmur at the lower left sternal border, haemodynamic deterioration, and an oxygen step-up at right ventricular level on Swan-Ganz catheterisation (RV saturation exceeds RA saturation by >5%). Acute MR from papillary muscle rupture produces a murmur but no oxygen step-up. Posterior STEMI more commonly causes papillary muscle rupture; anterior STEMI more commonly causes VSD.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.