New medical device indentifies abnormal heart rhythms called atrial fibrillation

May 20 2004

“Atrial fibrillation (AF) accounts for 15 to 20 percent of all strokes,” said lead author Denis Jabaudon, M.D., Ph.D., a resident in the Department of Neurology at the University Hospital Geneva in Geneva, Switzerland. 

It is a potentially deadly condition in which the heart’s two upper chambers quiver instead of beating effectively.  This causes blood to pool and increases the risk of a blood clot.  Clots that travel to the brain can block vessels and cause an ischemic stroke.

The new device, called an event-loop recorder (ELR), is worn by stroke patients and monitors their heartbeat for seven days.  Irregular heartbeats trigger the device to record and store the information.  The physician uses a computer to interpret the stored data. 

Patients also can trigger the device if they experience palpitations or dizziness.  But studies indicate that palpitations are rarely indicative of AF. 

Often, AF causes no symptoms and the first sign of it is a stroke, said project leader Roman Sztajzel, M.D.  That’s because up to 30 percent of AF patients have transient bouts of irregular heart rhythm that may not occur during the standard electrocardiogram (ECG) performed at admission after a stroke or even during a 24-hour ECG recording (commonly called Holter), he said.

“It is important to find everyone with AF, because they are at high risk of a second stroke and anti-clotting drugs can dramatically reduce that risk,” he said.

A team of cardiology and neurology researchers investigated if recording the heart rhythm of patients during several days after a stroke would detect otherwise-hidden cases of AF. 

In the study, researchers screened 149 consecutive patients hospitalized for stroke or transient ischemic attack (TIA or “mini-stroke”).  They detected AF in 22 patients.  Standard ECG identified AF in four patients upon admission and in another six within five days of initial hospitalization.

The researchers performed Holter on the remaining 139 patients, identifying seven (5 percent) with AF.  Next, patients with normal ECGs and Holter underwent ELR monitoring for one week an average of 55 days after hospital admission.  That test identified AF in five of 88 patients (5.7 percent) for whom complete data was available.

“If the ELR test had not been done, these patients could not have been treated (with anti-clotting drugs) and would have remained at high risk for another stroke,” he said, adding that ELR could potentially save lives.

AF becomes more common with increasing age and is thought to affect 10 percent of the people over age 80.  Atrial dilation (an enlarged upper heart chamber) — a condition linked to high blood pressure or heart valve disease — also increases the risk of AF, he said.

ELRs are used clinically in Europe and the United States, although their use has been limited to investigating fainting (which is sometimes a symptom of AF) and unexplained chest pain.  Prior to this study, ELR had not been used in standard stroke examinations, he said.

Researchers say ELR should not replace either of the two standard tests, but should be considered for every patient in which a circulating blood clot is suspected of causing stroke.

“This study indicates that ECG, Holter and ELR should be used sequentially to provide the best opportunity to identify the most AF patients,” the researchers said.

Detecting atrial fibrillation is an important aspect of stroke management, and stroke care in the United States typically includes cardiac monitoring to detect it, said Robert J. Adams, M.D., an American Stroke Association spokesperson. 

“If these findings are confirmed in other studies of similar patients and 6 percent more atrial fibrillation patients are identified, this may well be worth incorporating into widespread practice, especially if predictors can limit the target group that should undergo extended monitoring,” Adams said.

Co-authors are: Juan Sztajzel, M.D.; Katia Sievert; and Theodor Landis, M.D.  Dr. Jabaudon’s research was supported by a grant from Astra-Zeneca, U.S.A.