Duration of atrial fibrillation and risk of stroke

Episodes of atrial fibrillation (afib) — a chaotic, irregular heart rhythm — can last for minutes, hours, days, or much longer. The condition encourages blood clots to form in the heart; the clots can then escape and lead to a stroke. New research suggests that even intermittent bouts of afib (which were previously considered to be low risk) may increase a person’s risk of stroke.

The study included nearly 2,000 people who wore a small skin patch that continuously monitored their heart rates for 14 days. All of them had paroxysmal (intermittent) afib and were not taking anti-clotting medications. Researchers then tracked the participants’ incidence of stroke over the following five years. They found that afib that lasted more than 11% of the total monitoring time was associated with a threefold increase in stroke risk.

The findings suggest that the amount of time spent in afib (known as afib burden) is related to the risk of stroke. Measuring that burden may help doctors to assess better a person’s need for stroke prevention strategies, say the authors. The study was published online May 16 by JAMA Cardiology.