Embolism and atrial fibrillation. A longitudinal follow-up.

Six hundred and forty-nine patients with proven chronic atrial fibrillation were followed for a total of 1,436 patient-years without anticoagulation. The patient were divided into 7 disease groups with each having an average age ranging from 39 to 69 years. Eleven per cent of the patients had systemic embolism prior to being registered for the follow-up. The diseases which had the highest incidence of embolism prior to being followed were the same as those producing the highest rate of systemic embolism while under observation. The disease groups were rheumatic valvular (predominantly mitral stenosis) and ischemic heart diseases. Their embolic rate were 3.9 to 5.1 emboli per 100 pt-yr. Other disease groups with lower embolic rates of 0 to 0.9 per 100 pt-yr were heart failure, non-rheumatic mitral regurgitation, atrial septal defect and thyrotoxicosis. Since the incidence of systemic embolism varied according to the primary disease, and since the hemorrhagic complication of anticoagulant therapy is finite, it is advised that low risk group may not benefit greatly from anticoagulation. However, the true low risk group has still to be properly determined.