Electroconversion of atrial fibrillation after mitral valvotomy.

Of a series of IOO consecutive patients undergoing closed mitral valvotomy, 84 were in atrial fibrillation after operation. Fifty-six were treated by DC countershock; 7 returned to sinus rhythm without defibrillation, and in the remaining 2I defibrillation was not attempted. Of those patientsfibrillatingfor more than a year, none remained in sinus rhythm one year after defibrillation, and no patient remained in sinus rhythm for more than 5 weeks when atrialfibrillation had been present for 5 years before operation. A small proportion ofpatients in whom fibrillation had been present for less than a year, or had appeared after operation, maintained sinus rhythm for I to 2 years or more: approximately one-third at i year, and one-quarter at 2 years. Threequarters of those patients in sinus rhythm before and after operation remained in sinus rhythm for 3 years. A large heart, low amplitude f waves, and male sex were also unfavourable features. It is suggested that the development of atrial fibrillation is an event in the natural history of mitral stenosis which depends relatively little on the degree of stenosis or its relief by operation. Though fibrillation is sometimes precipitated by operation, defibrillation postoperatively is only rarely followed by the maintenance of sinus rhythm for more than i to 2 years. The attempt to restore sinus rhythm is only worth while when atrial fibrillation has been present for less than