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 pansystolic murmur radiating to the right sternal border, what is the most likely cause?

Interventricular Septal Rupture (Ventricular Septal Defect)

The most likely diagnosis is interventricular wall rupture (Option B), presenting as a post-MI ventricular septal defect (VSD), which characteristically produces a pansystolic murmur radiating to the right sternal border in the setting of acute hemodynamic deterioration 3-7 days after myocardial infarction. 1

Clinical Presentation and Timing

• Mechanical complications of acute coronary syndrome typically present within the first week after myocardial infarction, with ventricular septal rupture most commonly occurring 3-5 days post-MI 1
• The classic presentation includes recurrent chest pain or a new murmur accompanied by disproportionate heart failure, cardiogenic shock, or sudden hemodynamic deterioration 1
• This patient's presentation at day 5 with hypotension and tachycardia fits the expected timeline for post-infarction mechanical complications 1

Distinguishing Auscultatory Features

• Ventricular septal rupture produces a harsh pansystolic (holosystolic) murmur that is loudest at the lower left sternal border but characteristically radiates to the right sternal border due to the left-to-right shunt across the interventricular septum 1

• The murmur may be accompanied by a palpable thrill and is associated with acute hemodynamic compromise 1

• Mitral regurgitation from papillary muscle rupture (Option C) would produce a pansystolic murmur but radiates to the axilla, not the right sternal border, making this diagnosis less likely given the described radiation pattern 1

• Free wall rupture (Option A) typically presents with sudden cardiovascular collapse, cardiac tamponade, and electromechanical dissociation rather than a new murmur, as blood accumulates in the pericardial space 1

• Pseudoaneurysm (Option D) is usually discovered incidentally or presents with a late complication rather than acute hemodynamic deterioration with a new murmur in the first week 1

Pathophysiology

• The stenotic defect in the interventricular septum creates turbulent flow from the high-pressure left ventricle to the lower-pressure right ventricle throughout systole 1
• This left-to-right shunting causes acute right ventricular volume overload and reduced forward cardiac output, manifesting as hypotension and compensatory tachycardia 1
• The use of intra-aortic balloon pump (IABP) has been shown to reduce left-to-right shunting and improve hemodynamics in patients with ventricular septal rupture 1

Immediate Management Priorities

• Transfer to a facility with cardiac surgical expertise is mandatory, as medical therapy alone carries extremely high early mortality 1
• Short-term mechanical circulatory support devices are reasonable for hemodynamic stabilization as a bridge to definitive surgical repair 1
• Early corrective surgery remains the treatment of choice, though the risk is highest when performed in the setting of cardiogenic shock 1
• Delayed surgical intervention may be considered to allow hemodynamic stabilization with mechanical support, recovery from end-organ injury, and infarct tissue maturation to facilitate more durable repair 1

Critical Diagnostic Confirmation

• Transthoracic echocardiography should be performed emergently to visualize the ventricular septal defect, assess the size and location of the rupture, quantify the shunt, and evaluate biventricular function 1
• Doppler echocardiography will demonstrate the characteristic left-to-right flow across the interventricular septum 1

Common Pitfall

• Do not delay transfer to a specialized center even if the patient appears temporarily stable, as hemodynamic deterioration can be precipitous and unpredictable in previously stable patients with mechanical complications 1