Non-rheumatic atrial fibrillation as a risk factor for stroke.

The association between non-rheumatic atrial fibrillation (AF) and stroke has been studied in 402 patients consecutively admitted to a stroke unit. Brain infarction patients with sinus rhythm (n = 196) and non-rheumatic AF (n = 92) were further compared. Some findings supported an embolic origin of the stroke: half of the deceased AF patients (n = 24) at autopsy either had left atrial thrombosis or arterial embolism compared to none of the ten with sinus rhythm. Patients with AF also had a higher mortality and more severe brain lesions, findings compatible with a sudden occlusion of blood flow. However, these differences might also be explained by an atherothrombotic occlusion with impaired autoregulation in the ischaemic region in conjunction with heart failure, which was more common in the AF patients. Other findings supporting an atherothrombotic mechanism were: the prevalence of AF was higher (19-29%) in all kinds of stroke, including haemorrhage, than in age-matched controls (3-9%). Also patients with previous AF and no present embolic source resembled the whole AF group and differed from patients with sinus rhythm. Thus embolism is a plausible cause of stroke in many AF patients, whereas an atherothrombotic origin is more likely in others. Characteristics identifying the mechanism in an individual case were not found.