Several million older Americans have been diagnosed with atrial fibrillation, the abnormal heart rhythm abbreviated as A-fib, because they experienced symptoms such as palpitations, dizziness, and shortness of breath.
Yet many others may have the heart condition without realizing it, raising their risk of stroke, according to a new study coauthored by Main Line Health cardiologist Peter R. Kowey.
Kowey and his coauthors monitored 385 older patients who were at risk of A-fib due to diabetes, high blood pressure, and other telltale indicators but who had not been diagnosed with the rhythm disorder. Physicians implanted a slender wireless rhythm-recording device beneath each patient’s collarbone.
The longer the patients were followed, the more they experienced at least one episode of A-fib lasting six minutes or more, the authors reported in the journal JAMA Cardiology.
Six months into the study, 20.4 percent of patients were found to have A-fib. After one year, that figure rose to 27.1 percent. By 30 months, 40 percent of patients were determined to have suffered at least one episode of this type of abnormal rhythm.
According to the U.S. Centers for Disease Control and Prevention, 9 percent of people aged 65 and up have been diagnosed with atrial fibrillation.
Kowey, of Main Line’s Lankenau Heart Institute, said the disease was clearly more common than that, but he could not say just how common because the new study focused only on patients deemed to be at high risk.
Patients with atrial fibrillation are typically counseled to take blood-thinning medications called anticoagulants. That is because during an episode of A-fib, the patient’s blood may stagnate and form a dangerous clot, leading to a stroke.
Yet strokes can occur weeks after the heart rhythm has returned to normal, suggesting that they might not be directly caused by A-fib, Kowey said. Instead, the higher rate of stroke may stem from a related symptom: scarring on the atrial walls.
“People are starting to believe that A-fib is a signal that the atrium is sick,” Kowey said.
The rate of stroke in older people is about 1 percent to 2 percent per year. Among those diagnosed with A-fib, the risk is roughly three times that high, Kowey said.
After the study, anticoagulants were prescribed for 72 patients who were found to have undiagnosed A-fib. Kowey said patients in the general population with “silent” A-fib may also benefit from taking the drugs, though trials are underway to make sure.
The study was funded by Medtronic, which made the wireless monitors that were implanted in the patients.