Daily Practice - Clinical Quiz #1

A 70-year-old woman develops sudden shortness of breath while being monitored in the cardiac telemetry unit. Three days earlier, she underwent percutaneous coronary intervention (PCI) for a right coronary artery (RCA) stenosis after presenting with ST-segment elevation in leads II, III, and aVF.

📋 Examination Findings

Temp: 37°C (98.6°F) Pulse: 120/min RR: 20/min BP: 90/50 mm Hg

Auscultation: New holosystolic murmur best heard at the apex (5th left midclavicular intercostal space).

👉 Question: Post-MI Complication

Which of the following is the most likely cause of her new-onset dyspnea?

A. Ventricular arrhythmia

B. Papillary muscle rupture

C. Ventricular septal rupture

D. Left ventricular free wall rupture

E. Ventricular aneurysm

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✅ Correct Answer:

B. Papillary muscle rupture.

📚 Expert Detailed Answer and Rationale:

This patient's presentation of acute dyspnea, hypotension, and a new apical holosystolic murmur 3 days after an inferior wall MI is a classic scenario for papillary muscle rupture leading to acute severe mitral regurgitation (MR).

B. ✅ Papillary muscle rupture – The posteromedial papillary muscle is particularly vulnerable to ischemia as it typically has a single blood supply from the posterior descending artery (a branch of the RCA). Its rupture leads to flail mitral leaflet, severe MR, acute pulmonary edema, and cardiogenic shock.

A. Ventricular arrhythmia ❌ – While a potential cause of hypotension post-MI, it would not explain the new structural finding of a holosystolic murmur.

C. Ventricular septal rupture ❌ – This also presents with hypotension and a harsh holosystolic murmur, but the murmur is typically loudest at the lower left sternal border, not the apex.

D. Left ventricular free wall rupture ❌ – This is a catastrophic complication leading to hemopericardium and cardiac tamponade. The patient would present with pulseless electrical activity (PEA) and sudden death, not typically a new murmur.

E. Ventricular aneurysm ❌ – This is a late complication (weeks to months post-MI) and presents with heart failure, arrhythmias, or mural thrombus. It does not cause an acute presentation with a new murmur days after an MI.

🧠 High-Yield Points:

• 💡 Timing is key: Mechanical complications like papillary muscle rupture typically occur 2-7 days post-MI.
• 💡 Location, Location, Location: The murmur of acute MR from papillary muscle rupture is at the apex. The murmur of a VSD is at the left sternal border.
• 💡 Blood Supply: The posteromedial papillary muscle's single blood supply from the PDA (usually from RCA) makes it susceptible in inferior MIs. The anterolateral muscle has a dual supply (LAD and LCx) and is less likely to rupture.
• 💡 Diagnosis is confirmed with an urgent echocardiogram.

📖 Read More on: Mechanical Complications of Myocardial Infarction

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💡 Clinical Challenge / Follow-Up:

Imagine the same patient, but the new holosystolic murmur is heard loudest at the lower left sternal border, and you feel a palpable thrill in the same location.

Your Challenge:

1. What is the most likely diagnosis now?
2. What hemodynamic change is responsible for the murmur?

Show Answer

✅ Answer:

1. The diagnosis is now Ventricular Septal Rupture (VSR). The location of the murmur (left sternal border) is the key differentiator.
2. The murmur is caused by blood being shunted from the high-pressure left ventricle to the low-pressure right ventricle across the newly formed septal defect during systole. This creates a significant left-to-right shunt.

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