Reported to the American Heart Association Scientific Sessio

作者：杨超月

　　PITTSBURGH, and ORLANDO, Fla., Nov. 5 /PRNewswire/ -- The presence of a tract, or separation, in the inner wall of the heart''s atrial septum appears to be a strong predictor of elevated stroke risk among patients with patent foramen ovale (PFO), according to a study being presented today at the American Heart Association Scientific Sessions by cardiologists from Allegheny General Hospital (AGH) in Pittsburgh.

Prevalent in approximately 25% of the general population, PFO is a small hole in the atrial septum, the wall separating the heart''s two upper chambers, that fails to close after fetal development. Called a foramen ovale, the hole enhances fetal circulation in utero.

Though most patients with PFO survive into adulthood without any significant symptoms, it is the most likely cause of stroke in patients under the age of 55.

The condition predisposes patients to stroke when small blood clots that form in the extremities pass through the PFO into the heart''s left ventricle where they can travel to the brain or other organs.

According to Robert Biederman, M.D., principal investigator of the AGH study and a cardiologist at the hospital''s Gerald McGinnis Cardiovascular Institute, PFO is considered to be a factor in as many as 40% of patients who have an ischemic stroke of unknown cause.

He said the discovery of precise anatomical marker that identifies which patients with PFO are at risk for stroke or heart attack would be a significant advancement that may lead to earlier and more aggressive therapeutic intervention.

"Current standard of care for patients with PFO who have suffered a transient ischemic attack, or mini-stroke, is to treat them with a blood thinning drug to prevent recurrent blood clots. These medications are not 100% effective, however, and associated risks are considerable, particularly with long-term use," Biederman said.

Anticoagulant medications are difficult to manage in any patient, Dr. Biederman said, but younger people are especially poor candidates because of their active lifestyles.

Though a number of effective techniques exist to close a PFO, including newer percutaneous therapies that do not require major surgery, the procedures are approved for use by the Food and Drug Administration only after a patient with PFO has suffered a second stroke or heart attack.

"PFOs have been studied extensively for a way to better determine who benefits most from a prophalactic closure of the hole. Until now, that answer has been elusive. Though our findings are clearly preliminary and will require a more extensive and prospective investigation, we believe this is an extremely critical and promising development in our understanding about the pathology of this disease," Dr. Biederman said.

Over the course of many years of reviewing the transesophageal echocardiograms of patients with and without PFO, Dr. Biederman began noticing an anatomical feature of the atrial septum that was more often apparent in those with PFO who had suffered strokes. The anomaly was a septal track formation, or a clear passageway between the atrial septum''s two wall layers - - the septum premum and secundum.

Following up on this observation, Biederman and his team performed a blinded retrospective analysis of transesophageal echocardiograpy (TEE) studies from 100 patients. The study identified three classifications of septal tract formation: Type A -- "absent" or very minimal track formation; Type B -- "intermediate" sized tract formation; or Type C -- "present," or a large tract formation (defined as a separation one centimeter long and .25 centimeter wide).

Of the patients studied, 19 suffered strokes and 81 had not. Among the stroke patients, nine had a PFO and eight of those (89%) had a Type C septum. Of the 81 non-stroke patients, only four (5%) fell into the Type C classification.

"If these results hold true, we may in the near future have the ability to reduce the risk of stroke by 90% in those PFO patients at greatest risk simply by evaluating this specific morphological feature of their atrial septum. Those patients theoretically could undergo a minimally invasive surgical repair of the foramen ovale and forgo a life-long dependency on blood thinning medication," Dr. Biederman said.

Although completed too late to be included in the abstract being presented to the AHA today, Biederman''s retrospective analysis of TEE studies was recently extended to 250 patient cases. He said results from the larger group showed the same significant prognostic capability.

"For someone who has a known PFO and has suffered a stroke, it is a very frightening and disconcerting prospect to be waiting for that second event before a corrective intervention is allowed. These are typically young and otherwise healthy individuals who suddenly find themselves dependent on daily medication and at risk of another, potentially devastating neurological or cardiovascular injury," said Dr. Biederman.

"Our study suggests for the first time the possible existence of an easily identifiable marker for stroke risk that would allow us to more effectively care for these patients and lessen the morbidity and mortality associated with PFO."

Source: Allegheny General Hospital
　　