[img_inline align=”right” src=”http://padnws01.mcmaster.ca/images/jeffhealey.jpg” caption=”A study by McMaster’s Jeff Healey, associate professor of medicine, says that an irregular heartbeat that isn’t felt but can be picked up by a pacemaker is associated with a significantly increased risk of stroke. File photo.”]An irregular heartbeat that you don't even feel but can be picked up by a pacemaker is
associated with a significantly increased risk of stroke, says a new McMaster University
study.

The report, published in the New England Journal of Medicine, says that of nearly 2,600
patients without a history of atrial fibrillation but with a recently implanted pacemaker,
more than one-third had episodes when the heartbeat would become rapid and
irregular for more than six minutes.

In 85 per cent of these patients, the irregular heartbeat did not cause any symptoms
and was only detected by the modern pacemakers. Those who had one of these
asymptomatic atrial arrhythmias in the first three months had more than twice the risk
of stroke or embolism compared to others.

The international research team based at the Population Health Research Institute was
led by Dr. Jeff Healey, an associate professor of medicine in the Michael G. DeGroote
School of Medicine at McMaster.

“This study suggests that silent atrial fibrillation is very common and may be the cause
of many strokes that previously could not be explained. In all, atrial fibrillation may be
responsible for nearly 1 in 5 strokes,” said Healey. “This is an important observation as
we have very effective and specific therapies to prevent stroke in patients with atrial
fibrillation, once this heart rhythm disturbance is identified.”

The Asymptomatic Stroke and Atrial Fibrillation Evaluation in Pacemaker Patients Trial
(ASSERT) was a prospective cohort study conducted in 23 countries with 136 centres, to
explore the relationship between device-detected atrial arrhythmias and stroke. The
study participants were 65 years old or older, with a history of hypertension but no
history of atrial fibrillation. They were followed for approximately 2.5 years.

The study was sponsored by St. Jude Medical Inc.