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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 presented Monday at the American Heart Association (AHA; Dallas) sessions in Orlando by cardiologists from Allegheny General Hospital (AGH; Pittsburgh).

Prevalent in about 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. 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 age 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, MD, 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, he 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 FDA-approved 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,” Biederman said.

Over the course of many years of reviewing the transesophageal echocardiograms of patients with and without PFO, 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.

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 1 cm long and .25 cm 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,” Biederman said.

In other news from the AHA conference this week:

• PreMD (Toronto) said its non-invasive skin cholesterol test has demonstrated the ability to detect risk of cardiovascular disease in asymptomatic subjects, according to data presented yesterday. This study marks the largest clinical trial to date to evaluate levels of skin cholesterol in asymptomatic individuals, the company said. Titled, “Increased Skin Cholesterol Identifies Individuals at Increased Cardiovascular Risk: The Predictor of Advanced Subclinical Atherosclerosis (PASA) Study,” the study supports the usefulness of non-invasive skin cholesterol measurements for cardiovascular disease risk assessment.

Results of the PASA Study showed that skin cholesterol content, measured by PreMD’s skin cholesterol test, was associated with carotid intima-media thickness (CIMT) and the presence of carotid plaque. This association was observed in subjects across all ranges of cardiovascular risk, particularly in those at low and intermediate risk, based on traditional cardiovascular risk factors. CIMT and carotid plaque are both well-established markers for risk of future heart attack and stroke, according to the company.

PreMD’s skin cholesterol test non-invasively measures the amount of cholesterol that has accumulated in the skin tissues. The test is cleared for sale in Canada and Europe but the company is not yet cleared for use in asymptomatic subjects in the U.S.