The presence of a tract in the inner wall of the atrial septum appears to be a strong predictor for elevated stroke risk in patients with patent foramen ovale, according to a presentation at the annual meeting of the American Heart Association.

Patent foramen ovale has a prevalence of roughly 25 percent of the general population. Although most patients survive into adulthood without any significant symptoms, patency is the most likely cause of stroke in patients under the age of 55 years.

According to Robert Biederman, MD, principal investigator and presenter of the study and a cardiologist at the Gerald McGinnis Cardiovascular Institute, patent foramen ovale is considered to be a factor in as many as 40 percent of patients who have an ischemic stroke of unknown cause.

Although a number of effective techniques exist to close the defect, including newer percutaneous therapies, the procedures are approved for use in the U.S. by the Food and Drug Administration only after a patient has had a second stroke or a myocardial infarction.

Over the course of many years of reviewing trans-esophageal echocardiograms of patients with and without the defect, Biederman began noticing an anatomical feature of the atrial septum that was more often apparent patients who had strokes. The anomaly was a septal tract between the septum primum and septum secundum.

In the current analysis, the researchers retrospectively and blindly analyzed trans-esophageal echocardiography 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 1.0 centimeter long and 0.25 centimeter wide).

Of the patients studied, 19 had a history of stroke and 81 had no prior stroke. Among the stroke patients, 9 had a patent foramen ovale and 8 of those (89 percent) had a Type C, large-tract, septum. Of the 81 non-stroke patients, only 4 (5 percent) 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 percent in those patients with patent foramen ovale 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," Biederman said.

Although completed too late to be included in the abstract, the retrospective analysis of was recently extended to 250 patient cases with the same significant prognostic capability.