The Value of Quinidine in the Prevention of Atrial Fibrillation after Mitral Valvuloplasty

ATRIAL FIBRILLATION is the characteristic arrhythmia of the advanced stages of mitral stenosis, being present in 40 per cent of such cases. Paradoxically, mitral valve surgery, which relieves the obstruction and reduces the hemodynamic overload of the left atrium, frequently precipitates either transient or permanent atrial fibrillation. The reported incidence of this disorder after mitral operation ranges from 24 to 47 per cent.'-6 In the patient with normal sinus rhythm undergoing mitral valve surgery atrial fibrillation thus constitutes the most common operative complication. Physiologic studies clearly indicate that atrial fibrillation compromises cardiac function. Restoration of normal sinus rhythm has been shown to increase the cardiac output at rest and especially after exercise.7-10 It has been observed that patients with atrial fibrillation have generally lower cardiac outputs, higher pulmonary vascular resistance, and higher left atrial and pulmonary arterial pressures than do patients with mitral stenosis in sinus rhythm."1 12 The ventricular rate in atrial fibrillation is unstable and prone to acceleration to more than 100 per minute. In some fully digitalized patients ventricular rates as high as 170 have been recorded following moderate exercise or administration of atropine.13 Occasionally in the presence of this arrhythmia congestive failure cannot be controlled, even though the heart rate is slow, until normal sinus rhythm has been restored. It has furthermore been shown that atrial