DC defibrillation of atrial fibrillation and its hemodynamical effects, studied by radioisotope dilution method.

Abstract

DC cardioversion for chronic atrial fibrillation was carried out in 32 patients for 58 times using a R-synchronized DC cardioverter. The cardioversion was successful in 49 trials out of 58 (85%) and, in 29 patients of 32 (9 %). Nineteen (33 per cent of 58 trials or 59 per cent of 32 patients) have been maintained normal sinus rhythm for the period ranging from two months to two years. There was no intimate relation between the success or maintenance rate of cardioversion and the severity of the underlying disease indicated by functional classification, duration of atrial fibrillation, cardio-thoracic ratio in chest film or preoperative mean left atrial pressure. The most important factor which determined the results of cardioversion was surgical correctability of underlying disease. Quinidine administration at a maintenance dose appeared to be of limited value for the long-term result of successful cardioversion. Resting cardiac index showed slight or not so remarkable increase with cardioversion, although, it showed significant (+24%) increase in exertional cardiac index. Circulating blood volume increased 3 to 4 per cent at rest and 8 per cent on exercise with restoration of normal sinus rhythm. There seemed to run a risk of bringing lung edema for the patient of disturbed mitral function with this increase. Mean pulmonary circulation time showed 18 per cent of shortening at rest and 16 per cent on exercise. Stroke volume on exercise remained unchanged in comparison to the resting level after cardioversion, while it showed remarkable decrease during arrhythmia. This means that increase of heart rate with exercise brings the increase of cardiac output after cardioversion. Atrial fibrillation should be converted immediately after surgical repair of the underlying diseases. Even if recurrence follows within a few days, normal sinus rhythm can be expected to bring some benefits to patients in the postoperative crisis. No remarkable complication has been experienced during this study.