A group of researchers at the Institute for Heart Vascular and Stroke Care and Massachusetts General Hospital, Boston, led by Jeremy N. Ruskin, MD, performed a comprehensive meta-analysis of all the studies they could find with a mention of the link between atrial fibrillation (A-fib) and silent strokes (SCI, silent cerebral infarction).
They analyzed eleven studies which fulfilled their criteria for quality and study subject parameters: adults (aged 50-84) with or without A-fib, and no history of stroke or heart valve abnormalities (which can cause both stroke and A-fib). They reviewed the records of 5,317 qualified subjects who had MRI and/or CT scan evidence of SCI; they found that having A-fib conferred over a two-fold higher risk of SCI, as compared to those without the arrhythmia.
A-fib affects more than 2.7 million people in the U.S. and is the most common arrhythmia in the elderly, with a projected prevalence of 5.6 to 12.1 million by 2050, the researchers told journalists from MedPage Today. Patients with A-fib have a four- to five-fold increased risk for clinically evident stroke, and they are also at risk for larger brain infarctions and worse outcomes following stroke, compared with the general population. A recent meta-analysis showed A-fib to be associated with a 40% increase in the risk for cognitive impairment. The association was independent of symptomatic stroke history and other comorbid conditions, such as advanced age, hypertension, heart failure, and diabetes.
ACSH s Dr. Gil Ross had this comment: A-fib is most often asymptomatic. But the absence of palpitations the most common warning sign does not mean there is no danger. The ineffective contractions of the heart s upper chambers (the atria), the hallmark of A-fib, allows blood to pool or stagnate in those smaller chambers, and clots form. Those clots, when pumped out into the systemic circulation via the arteries, become emboli. When an embolus of the right size travels to a major brain artery and blocks it, the resultant oxygen deprivation causes death of part of the brain: a stroke (medically, infarction ). We noted recently that two different studies strongly linked strokes of unknown cause to A-fib: patients with A-fib were six-fold more likely to have cryptogenic stroke. Now we see that asymptomatic ( silent ) strokes are also associated with A-fib. This is no surprise; but all these data increase the urgency of communicating to doctors in every field the need for effective anticoagulation therapy in A-fib patients to prevent this devastating outcome.