In a patient who had an acute coronary syndrome treated with percutaneous coronary intervention five days ago and now presents with hypotension, tachycardia, and a new pansystolic murmur at the left sternal edge radiating toward the right sternal border, which is the most likely diagnosis: free‑wall rupture, interventricular septal rupture, mitral regurgitation, or pseudoaneurysm?

Ventricular Septal Rupture (Interventricular Wall Rupture)

The most likely diagnosis is interventricular septal rupture (option B), based on the characteristic presentation of a pansystolic murmur radiating to the right sternal border on day 5 post-PCI, combined with acute hemodynamic collapse. 1

Why Ventricular Septal Rupture is the Answer

Timing is Pathognomonic

• VSR typically occurs 3–7 days after acute MI, with day 5 falling squarely within this classic window 1
• In the contemporary PCI era, mechanical complications now present within the first 24 hours to 7 days, making day 5 a typical presentation time 1, 2

The Murmur Pattern is Diagnostic

• A harsh pansystolic murmur radiating to the right sternal border is highly specific for VSR because it reflects turbulent left-to-right flow across the interventricular septum 1
• This radiation pattern along the sternal border is pathognomonic for a septal defect, distinguishing it from mitral regurgitation (which radiates to the axilla) 1, 3
• The murmur occurs at the left lower sternal border and radiates rightward due to the jet direction through the septal defect 2, 3

Hemodynamic Profile Matches VSR

• The combination of hypotension and tachycardia represents cardiogenic shock from the left-to-right shunt 1, 2
• The shunt reduces effective systemic cardiac output while simultaneously increasing pulmonary blood flow, precipitating acute hemodynamic collapse 1
• Up to 80% of VSR patients develop unpredictable rapid hemodynamic deterioration 4

Why the Other Options Are Incorrect

Free Wall Rupture (Option A)

• Free wall rupture occurs predominantly within the first 24 hours post-MI, not on day 5 1
• It presents with cardiac tamponade and hemopericardium, not a pansystolic murmur 1, 5
• Patients typically have sudden cardiovascular collapse requiring immediate pericardiocentesis or surgery, not a murmur radiating to the sternal border 5

Mitral Regurgitation (Option C)

• Papillary muscle rupture causing acute MR can occur 2–7 days post-MI, making the timing plausible 6, 1
• However, the murmur of MR radiates to the axilla, not to the right sternal border 6
• The radiation pattern in this case is inconsistent with mitral regurgitation and points definitively toward a septal defect 1

Pseudoaneurysm (Option D)

• Pseudoaneurysm develops after subacute free wall rupture and represents contained rupture 6
• It does not produce a pansystolic murmur; instead, it may be silent or associated with signs of tamponade 6, 5
• The clinical presentation here (new murmur with shunt physiology) is incompatible with pseudoaneurysm 1

Immediate Diagnostic and Management Steps

Confirm the Diagnosis

• Obtain urgent transthoracic echocardiography immediately to visualize the septal defect and quantify shunt severity using color Doppler 1, 4
• Look for left-to-right flow across the interventricular septum on color Doppler imaging 1, 3
• Right-heart catheterization demonstrating an oxygen step-up at the right ventricular level provides definitive confirmation of the shunt 1

Stabilize Hemodynamics

• Insert an intra-aortic balloon pump (IABP) immediately to reduce afterload, decrease shunt fraction, and stabilize the patient while preparing for surgery 1
• Initiate dobutamine infusion at 5–10 µg·kg⁻¹·min⁻¹ for inotropic support 1
• Target hemodynamic goals: pulmonary wedge pressure ≥15 mmHg and cardiac index >2 L·min⁻¹·m⁻² 1

Proceed to Urgent Surgery

• Urgent surgical repair is mandatory even in hemodynamically stable patients because the defect can enlarge abruptly and cause sudden collapse 1, 7
• Perform concomitant coronary artery bypass grafting during VSR repair when feasible 1
• Without surgical intervention, mortality reaches ~54% within the first week and ~92% within one year 1
• Medical therapy alone results in near-100% mortality, underscoring the absolute necessity of operative management 1, 4

Critical Pitfalls to Avoid

• Do not delay surgery waiting for "stabilization"—unpredictable hemodynamic deterioration can occur suddenly in 80% of patients 4
• Do not mistake this for mitral regurgitation based solely on the presence of a pansystolic murmur; the radiation pattern to the right sternal border is the key distinguishing feature 1, 3
• Do not assume the patient is stable just because they survived to day 5; the defect can enlarge without warning 1, 7