The incidence of sinus rhythm in patients submitted to mitral valvotomy varies between 40 and 60 per cent. In this group atrial fibrillation occurs in the post-operative period in 20 to 50 per cent (Sellors, Bedford, and Somerville, 1953; Wood, 1954 a and b; Dimond and dos Santos, 1954;Heinz and Hultgren, 1957;Ellis, Harken, and Black, 1959;Kittle and Crockett, 1959;Baker and Hancock, 1960;Lowther and Turner, 1962;Black, Lown, and Bartholomay, 1961). The prognosis of atrial fibrillation after mitral valvotomy with and without quinidine therapy is examined in this paper.Subjects. The cardiac rhythms as confirmed by the electrocardiograms of the 331 patients who underwent their first mitral valvotomy at Hammersmith Hospital between 1951 and 1962 were studied. Of these patients, 151 (45%) were in sinus rhythm, 179 (550o) were in atrial fibrillation, and one was in atrial flutter. Post-operative rhythm changes were always confirmed by the cardiogram.
RESULTSPatients in Sinus Rhythm at Mitral Valvotomy. Of the patients who underwent their first valvotomy, 151 were in sinus rhythm and none was given prophylactic quinidine. Forty-six patients developed atrial fibrillation in the post-operative period and 27 of these were treated with digitalis alone; 12 of the 27 (440 %) reverted to sinus rhythm spontaneously, 8 within the first two postoperative weeks, 2 at five weeks, 1 at eleven weeks, and 1 at six months.An attempt to recognize features favouring the spontaneous reversion to normal rhythm revealed that where atrial fibrillation developed in the first post-operative week (19 patients), 12 (60%) reverted to normal rhythm; but where atrial fibrillation developed after the first post-operative week (8 patients), none reverted spontaneously to normal rhythm (Table I). The cardio-thoracic ratio, pre-operative electrocardiographic evidence of right ventricular hypertrophy, other valve lesions,