Most patients with ischemic strokes should be monitored for atrial fibrillation, according to a Northwestern Medicine study published in JAMA.
Whether or not a patient has atrial fibrillation (AFib) after a stroke often determines their course of treatment, and these findings show that a significant proportion of patients who suffer ischemic stroke in fact have AFib that can only be detected with an implantable cardiac monitor.
“We’re not saying the atrial fibrillation we found caused the original stroke,” said Richard Bernstein, MD, PhD, professor in the Ken and Ruth Davee Department of Neurology Division of Stroke and Neurocritical Care and lead author of the study. “Finding atrial fibrillation helps us prevent future strokes, regardless of the cause of the original stroke.”
AFib is an erratic or quivering heartbeat that results in abnormal blood flow in the heart. It is the most common heart rhythm disorder in adults and a major contributor to stroke, heart failure and dementia.
Patients with AFib and ischemic stroke are generally treated with blood thinners, which are extremely effective in preventing further strokes. On the other hand, patients whose stroke was not thought to be caused by AFib are treated with aspirin-like drugs. This means that finding AFib after a stroke represents a fork in the road, Bernstein said.
A previous study published in the New England Journal of Medicine, co-authored by Bernstein and Rod Passman, MD, MSCE, the Jules J. Reingold Professor of Electrophysiology, examined patients with stroke of unknown cause who tested negative for the arrhythmia using standard diagnostic procedures. They found about 30 percent of those patients in fact had AFib after 3 years of monitoring. In that study, investigators tested for AFib using a more accurate implantable heart monitor.
“Our standard monitoring techniques had not found AFib, but when we looked long and hard enough, we found it,” Bernstein said.
In the current study, Bernstein and his collaborators examined patients whose stroke was attributed to blocked arteries in the neck or head. The investigators implanted heart monitors and measured variations in heart rhythm for one year, finding about 12 percent of patients had AFib. Less than two percent of patients monitored with standard techniques were found to have AFib, showing that the implantable monitor was necessary to find AFib.
“These are people in whom we had no reason to suspect AFib,” Bernstein said.
Use of implantable monitors did not result in a significant reduction in stroke compared with those without monitoring, but Bernstein cautioned that the study was not designed to show such a reduction. There was a trend for fewer strokes in the monitored group, but the ultimate clinical value of monitoring can only be determined with further research, he said.
“We already use this monitoring for patients with stroke of unknown cause, and this study shows it also has value for patients with a stroke of known cause,” Bernstein said. “I think this could result in big changes in the way 750,000 strokes a year are worked up in the United States.”
Lee Schwamm, MD, the C. Miller Fisher Chair in Vascular Neurology and professor of Neurology at Harvard Medical School, was co-principal investigator of the study.
“What the Stroke AF study demonstrates is that we must lift our eyes up from our precise inspection of the presumed cause of the initial stroke, and refocus our attention on the complete and thorough evaluation of all causes of recurrent stroke,” Schwamm said. “This is especially true for detecting AFib, which we have now found is frequently hidden in plain sight among patients with strokes we previously were content to treat with aspirin.”
This study was funded by Medtronic.