Acute Mitral Regurgitation

Sudden development of retrograde blood flow from the left ventricle into the left atrium through an incompetent mitral valve during systole.

Acute, often massive mitral regurgitation in elderly patients is commonly due to chordal rupture or development of a flail mitral valve. The underlying disorder may be myocardial infarction, papillary muscle rupture, infective endocarditis, trauma, or mucoid degeneration of the valve cusps. Chordal rupture, common among the elderly, may be idiopathic and often results in life-threatening heart failure.

Pathophysiology

With sudden valvular incompetence, a large regurgitant volume enters the left atrium, suddenly increasing the volume of the left atrium during systole. During diastole, this increased volume enters and suddenly dilates the left ventricle; left ventricular filling pressure increases sharply because the normal pericardial sac is relatively noncompliant. Left ventricular dilation produces compression of the right ventricle during diastole, increasing right ventricular filling pressure and leading to right-sided heart failure.

Symptoms and Signs

Typically, patients have symptoms of pulmonary edema or acute pulmonary congestion, both of which often develop rapidly. Sinus tachycardia and a harsh, early systolic apical murmur, often with a thrill, are characteristic. The murmur ends early, when the noncompliant left atrium can no longer accept additional volume. The first heart sound is soft, and the accentuated pulmonic component of the second heart sound reflects acute pulmonary hypertension. An early diastolic sound (S₃) is characteristic, and an atrial gallop (S₄) may be present. Severe acute mitral regurgitation often leads to right ventricular failure. The ECG and chest x-ray may be normal initially but soon show pulmonary venous congestion.

Diagnosis and Treatment

Echocardiography confirms the diagnosis and often suggests the etiology. It can differentiate acute mitral regurgitation due to papillary muscle dysfunction or rupture from interventricular septal rupture and can detect the valvular vegetations of infective endocarditis. Transesophageal echocardiography, a safe procedure, allows the valve to be evaluated in greater detail, thus helping to determine whether the valve can be repaired or must be replaced.

Acute pulmonary edema due to acute mitral regurgitation is managed in the same way as that due to other cardiac disorders. Patients with hemodynamic instability, characterized by hypotension with pulmonary edema, require intra-aortic balloon counterpulsation to allow cardiac catheterization and the subsequent induction of anesthesia for surgery. Patients with infective endocarditis require treatment with appropriate antibiotics.

Patients with acute massive mitral regurgitation and clinical deterioration typically require urgent valve surgery.