BACKGROUND: Stroke is the third leading cause of death in the United States, and for 30 to 40 percent of the most common kind of stroke, no cause can be identified (Source: Ohio State University).

When patients suffer a stroke with no identifiable cause, the condition is called cryptogenic stroke. These types of strokes usually strike people younger than 55 (Source: Texas Heart Institute Journal).

Experts hypothesize that many cryptogenic strokes are caused by small emboli, or blood clots, that travel from the legs to the right atrium of the heart. These blood clots pass through a hole in the heart into the left atrium and then travel to the brain, producing a stroke.

Some doctors think atrial fibrillation -- or an irregular heartbeat -- could be the cause of many strokes labeled as cryptogenic. Atrial fibrillation causes the heart to beat either too fast or too slow, which in turn affects the flow of blood through the heart.

When the heart beats too slowly, blood can pool in the heart and cause blood clots to form, which increases a person's risk of stroke. When the heart beats too quickly, the amount of blood in the lower chamber of the heart decreases, causing fatigue and tiredness.

TREATING A MYSTERY CONDITION: Treatment of stroke -- whether or not atrial fibrillation is identified as the cause -- usually involves anti-clotting medications like aspirin, clopidogrel (Plavix) or warfarin (Coumadin). If a hole in the heart -- called a patent foramen ovale, or PFO -- is identified as a cause, surgery to close the hole is also an option. One recent study found hat surgery to close PFO can, in some circumstances, actually increase a patient's risk of stroke.

IDENTIFYING THE CAUSE: Researchers at the Ohio State University Medical Center are trying to identify how many strokes with no identifiable cause are actually caused by atrial fibrillation. They are doing this with a new monitoring system.

A patient who has suffered a cryptogenic stroke is implanted with a device that continuously monitors the heart's electrical activity. That activity is transmitted to a third-party monitoring center, where technicians contact physicians if they observe abnormal heart rhythms.

Doctors also use a hand-held device to program patients' monitors. Mahmoud Houmsse, M.D., lead researcher of the study, says he believes intermittent atrial fibrillation -- or atrial fibrillation that comes and goes -- may account for close to 50 percent of cryptogenic strokes.

FOR MORE INFORMATION, PLEASE CONTACT:
Doug Flowers
Medical Center Communications
Ohio State University Medical Center
(614) 293-3737