Dr. Subramaniam Krishnan

IRVINE — UC Irvine cardiologists have found a pouchlike structure inside the heart's left atrial chamber that may be a potent source of stroke-causing blood clots.

About 80 percent of the 700,000-plus strokes that occur annually in the U.S. are due to blood clots blocking a brain artery. In up to a third of these cases, the clots' origin cannot be determined. Study co-author Dr. Subramaniam Krishnan said the discovery of this left atrial pouch could provide answers and inform neurologists' efforts to prevent stroke recurrences.

Krishnan and Dr. Miguel Salazar of UC Irvine first spotted the pouch during autopsy research. Subsequent ultrasound and CT scans of patients' hearts confirmed the finding. The researchers estimate that the anatomical feature, which Krishnan likened to a kangaroo pouch, is present in 30 percent to 35 percent of individuals. Study results appear in the January issue of Journal of the American College of Cardiology: Cardiovascular Interventions.

"The cul-de-sac nature of the heart pouch can promote stagnation of the blood, forming clots that can travel into the brain and cause a stroke," Krishnan said. "It was thought that the body of the left atrium was largely smooth and unlikely to be a source of blood clots, but we have found that not to be true for roughly one in three people."

Krishnan and UC Irvine neurologist Dr. Mark Fisher currently are studying the prevalence of the left atrial pouch in patients who already have had strokes. "This finding points to a potentially important cause of strokes," Fisher said. "The presence of this pouch could change how neurologists treat these patients and lead to new therapeutic strategies for preventing strokes."

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