Mechanical Complications of Myocardial Infarction
Mechanical complications are rare but life-threatening consequences of acute myocardial infarction (MI). They usually occur within the first week after MI, particularly in patients with delayed reperfusion or large transmural infarctions. Early recognition is critical because most cases require urgent surgical intervention.
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Types of Mechanical Complications
1. Papillary Muscle Rupture
Papillary muscle rupture leads to acute severe mitral regurgitation (MR) due to loss of leaflet support.
Key Points
• Usually occurs 2–7 days after MI
• Most commonly involves the posteromedial papillary muscle because it has single blood supply from the PDA
• Causes sudden pulmonary edema and cardiogenic shock
Clinical Features
• Acute dyspnea
• Hypotension
• Loud holosystolic murmur at apex radiating to axilla
Diagnosis
• Echocardiography shows flail mitral leaflet and severe MR.
Management
• Urgent mitral valve surgery
• Hemodynamic stabilization with vasodilators and intra-aortic balloon pump (IABP)
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2. Ventricular Septal Rupture (VSR)
Rupture of the interventricular septum creates a left-to-right shunt, causing rapid hemodynamic deterioration.
Key Points
• Typically occurs 3–5 days after MI
• More common after anterior wall MI
• Leads to acute heart failure and cardiogenic shock
Clinical Features
• Sudden clinical deterioration
• Harsh holosystolic murmur at left lower sternal border
• Palpable thrill
Diagnosis
• Color Doppler echocardiography shows septal defect with left-to-right shunt.
Management
• Urgent surgical repair
• Temporary stabilization with IABP and vasodilators
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3. Free Wall Rupture
Free wall rupture results in hemopericardium and cardiac tamponade, often causing sudden death.
Key Points
• Occurs 3–7 days after MI
• More common in elderly patients, first MI, and anterior MI
• Associated with transmural infarction
Clinical Features
• Sudden hypotension
• Pulseless electrical activity (PEA)
• Signs of cardiac tamponade
Diagnosis
• Echocardiography shows pericardial effusion and tamponade physiology.
Management
• Emergency pericardiocentesis
• Immediate surgical repair
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Other Less Common Mechanical Complications
Left Ventricular Pseudoaneurysm
Occurs when a contained free wall rupture is held by pericardium.
Features
• Narrow neck
• High risk of rupture
• Requires surgical repair
True Left Ventricular Aneurysm
Develops weeks after MI due to scar formation and ventricular remodeling.
Features
• Wide neck
• Rarely ruptures
• Can cause heart failure, arrhythmias, or thrombus formation
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Time Course of Mechanical Complications
Complication Typical Timing After MI
Papillary muscle rupture 2–7 days
Ventricular septal rupture 3–5 days
Free wall rupture 3–7 days
LV pseudoaneurysm Early weeks
True LV aneurysm Weeks to months
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Risk Factors
• Large transmural MI
• Delayed or absent reperfusion therapy
• Advanced age
• Female sex
• First MI
Early reperfusion with primary PCI has significantly reduced the incidence of these complications.
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Key Takeaways
• Mechanical complications usually occur within the first week after MI.
• The three major complications are papillary muscle rupture, ventricular septal rupture, and free wall rupture.
• Patients often present with sudden hemodynamic deterioration.
• Echocardiography is the diagnostic modality of choice.
• Most cases require urgent surgical intervention.
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