Brain Attack: Researchers Pursue Connection Between a Heart Defect and Stroke

Once a stroke sufferer is brought to a hospital, it is often too late to detect the culprit in the body, only the damage it has left behind. Sometimes, the cause may be a blood clot that travels from the venous (vessels that carry blood to the heart) to the arterial circulatory system (vessels that carry oxygen-rich blood away from heart) and into the brain, where it can cause oxygen deprivation and subsequent death to brain tissue.

But on rare occasion, Dr. Jorge Kizer, a cardiologist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center, has witnessed such a cause. Using echocardiogram, Dr. Kizer has detected a blood clot stuck in an anatomical defect of the heart called Patent Foramen Ovale (PFO). "The clot is trapped like a rottweiler trying to exit a house through a small trap door," says Dr. Kizer.

Dr. Kizer explains that a PFO is a tiny hole or flap of tissue between the two atria – the top chambers of the heart – that naturally closes in the majority of infants in the first year of life. But a surprisingly large number of people, as many as one-quarter, maintain this defect throughout life as adults – often without knowing it. And, more importantly, in one per thousand adults yearly, the PFO defect may be associated with stroke.

The cause of stroke in 40 to 45 percent of adults under the age of 55 is a mystery – termed cryptogenic. Amongst these patients, 50 to 60 percent have PFOs, which has led cardiologists, like Dr. Kizer, to suspect that this heart condition may play a role.

Dr. Kizer believes that a combination of the PFO and a genetic predisposition to form clots in the veins of the legs, called thrombophilia, may be the cause of strokes in these young adults. He explains that the PFO acts as a passageway for clots to move from the legs through the arteries of the body and into the brain. Without the opening, clots forming in the legs could not travel to the brain to cause a stroke.

"While it seems alarming that 27 percent of the population has PFO, figures suggest that it is only a very small subset of such individuals who will go on to have clots that block blood flow to a vital organ," says Dr. Kizer.

He explains that people with PFO may never have health concerns, but there are some risk factors. High-risk factors include a large opening or excess tissue on the PFO's flap, and possibly a genetic predisposition to form clots in the leg veins.

Dr. Kizer's research, known as the THICK (Thrombophilia In Cryptogenic stroke) Study, aims to investigate risk factors, like PFO and thrombophilia, for unexplained stroke. The study is ongoing, with anticipated completion in early 2008.

For media inquiries please contact Andrew Klein at 212-821-0560 or ank2017@med.cornell.edu