Cardiac Rupture (Content Rupture) Complicating Myocardial Infarction

Pathological Basis

Three Types of Cardiac Rupture

1. Ventricular Free Wall Rupture

• Frequency: Least common of the three rupture types, but the most lethal. Accounts for ~10% of AMI fatalities.
• Timing: Usually 1-5 days after infarction.
• Mechanism: Transmural infarction of the left ventricular free wall leads to perforation - blood enters the pericardial space (hemopericardium) causing cardiac tamponade.
• Clinical features: Sudden tearing pain, rapid hemodynamic collapse - hypotension, tachycardia, elevated JVP, muffled heart sounds, pulsus paradoxus (Beck's triad).
• Diagnosis: Echocardiography is the test of choice in the ED; pulmonary artery catheterization shows near-equalization of right atrial, RV mid-diastolic, and RV systolic pressures.
• Outcome: Fatal in >90% of cases.
• Treatment: Emergency surgical repair.

2. Ventricular Septal Rupture (Post-MI VSD)

• Frequency: Most common of the three rupture types (though more often detected clinically than free wall rupture).
• Associated infarct: More common with anterior wall MI and extensive three-vessel coronary artery disease.
• Mechanism: Septal perforation creates a left-to-right shunt (VSD), leading to right heart volume overload and pulmonary edema.
• Clinical features: Chest pain, dyspnea, sudden new holosystolic murmur best heard at the lower left sternal border, often with a palpable thrill.
• Diagnosis:
  • Doppler echocardiography (procedure of choice)
  • Pulmonary artery catheter: O₂ step-up >10% from right atrium to right ventricle is diagnostic
• Treatment: Surgical. The size of the defect determines the degree of left-to-right shunt and overall prognosis.

3. Papillary Muscle Rupture

• Frequency: ~1% of AMI patients. Follows ventricular septal rupture in frequency.
• Associated infarct: More common with inferior MI; typically with a small- to modest-sized infarct (unlike free wall/septal rupture).
• Timing: Usually 3-5 days after AMI.
• Mechanism: The posteromedial papillary muscle is most commonly ruptured because it has a single blood supply (usually from the right coronary artery), making it vulnerable. The anterolateral papillary muscle has dual supply and is affected 6-10 times less frequently. Rupture causes acute severe mitral regurgitation.
• Clinical features: Acute onset dyspnea, pulmonary edema, new holosystolic murmur of MR (distinguished from VSD murmur - VSD has thrill at left sternal border, papillary muscle rupture murmur may radiate differently).
• Diagnosis: Echocardiography (can distinguish partial papillary muscle rupture from other causes of MR).
• Treatment: Surgical (mitral valve repair or replacement). Intra-aortic balloon pump as bridge.

Summary Comparison

Key Points

• All three forms represent mechanical complications of MI caused by rupture of infarcted tissue.
• The window of highest risk is 3-7 days post-MI, when enzymatic lysis peaks.
• Early reperfusion therapy (PCI) has significantly reduced the incidence of all rupture complications.
• Echocardiography is the cornerstone of rapid diagnosis for all three.
• All require surgical intervention - medical therapy alone is insufficient.