Holes in Heart Not a Common Cause of Stroke in General Population, Study Finds

Wednesday, May 17, 2006

ROCHESTER, Minn. — The following are featured articles from the May issue of Mayo Clinic Proceedings.

Having a hole in the upper chamber of the heart is not as significant in causing stroke in the general population as previous studies have suggested, finds a new Mayo Clinic study. The findings call into question the need for surgeries to close the holes in many such patients.

Known as patent foramen ovale (PFO), a small hole in the upper chamber of the heart is present in one-fourth to one-third of all people. In recent years numerous studies have suggested that PFOs commonly cause stroke by allowing blood clots to pass through the heart, bypass the lungs and go to the brain.

Mayo's study, published in the May issue of Mayo Clinic Proceedings, contradicts previous PFO studies. Past studies may have overestimated the relationship between PFOs and stroke risk due to a variety of biases, Mayo physicians say, including selective referral of cases.

Past studies have led to an increasing use of anticoagulants or PFO closure procedures in patients who have a stroke or warning of a stroke, but when doctors can't identify another cause. Such strokes are known as cryptogenic strokes (strokes of unknown cause) and afflict about 200,000 Americans annually. As many as 50,000 or more of these stroke victims have a PFO.

"Our study indicates that in the majority of these patients, the PFO and the stroke are unrelated," says George Petty, M.D., lead author of the study published in Mayo Clinic Proceedings.

Mayo's population-based study on the relationship between PFOs and cryptogenic strokes involved 1,072 Olmsted County, Minn., residents who underwent transesophageal echocardiography between 1993 and 1997.

The new findings should prompt patients with PFOs and their physicians to carefully consider whether a closure procedure is necessary, says study author, Bijoy Khandheria, M.D. He expects the findings to be controversial in part because PFO closure procedures totaling $2 billion are performed annually.

The study's findings indicate that, in the general population and particularly those over age 55, traditional cardiovascular risk factors are more important than PFO in contributing to cryptogenic strokes. In younger patients, however, PFO may play a more important role in causing cryptogenic stroke. Larger population-based studies are needed to determine the magnitude and nature of the risk for those patients, say Mayo physicians.

Other authors of the PFO study are Irene Meissner, M.D., and David Wiebers, M.D., from Mayo Clinic's Division of Cerebrovascular Diseases and Department of Health Sciences Research; and Jack Whisnant, M.D.; Walter Rocca, M.D.; Teresa Christianson; JoRean Sicks; Michael O'Fallon, Ph.D.; and Robyn McClelland, Ph.D., all from Mayo's Department of Health Sciences Research.

Closing Holes in Heart Important Treatment for Young Stroke Patients, Study Says

Placement of devices to close holes in the heart is a successful treatment for young stroke patients, finds a study involving three medical centers.

No major complications were reported from the 45 patients included in the study, leading physicians to determine that closure of patent foramen ovales (PFOs) and atrial septal defects (ASDs) with transcatheter devices is a safe surgical alternative for children and young adults who have had a stroke. Most patients who underwent device closure procedures for PFOs or ASDs remained symptom-free months afterward.

Published in the May issue of Mayo Clinic Proceedings, the retrospective medical record study involved patients from Mayo Clinic Rochester, the University of Parma in Italy, and Loyola University Medical Center in Illinois, who had been treated between January 1999 and August 2005. Included were patients younger than 35 who had undergone percutaneous closure (through the skin) of PFO or ASD and who had at least one presumed stroke.

Strokes in young patients are rare, but they present difficult clinical decisions when they occur, the study's authors say. Limited research exists on how young stroke patients fare from device closure procedures, prompting study authors to consider patient experiences from three medical centers.

The significance of PFOs in stroke patients has been confusing in part because previous studies have involved older patients and have overlooked the young, active population, says Donald Hagler, M.D., an author of Mayo's PFO study. Young stroke patients, as featured in the current study, often have large PFOs and are at greater risk for paradoxic embolization.

The study demonstrates further need for a large, prospective randomized trial with long-term follow-up to determine whether device closure is the best treatment for young stroke patients, its authors say. A randomized study is under way and may provide additional answers.

Authors for the study are Peter Bartz, M.D., and Allison Cabalka, M.D., from the Division of Pediatric Cardiology at Mayo Clinic; Frank Cetta, M.D., from the Divisions of Pediatric Cardiology and Cardiovascular Diseases at Mayo Clinic and formerly of Loyola University Medical Center; Donald Hagler, M.D., from the Divisions of Pediatric Cardiology and Cardiovascular Diseases at Mayo Clinic; Guy Reeder, M.D., from the Division of Cardiovascular Diseases at Mayo Clinic; Umberto Squarcia, M.D., Aldo Agnetti, M.D., Nicola Carano, M.D., and Bertrand Tachana, M.D., all from the University of Parma; and Enrico Aurier, M.D., from Parma Hospital.

More Data Needed to Determine Whether Holes in Heart Lead to Stroke

Broad interpretations exist on data related to patent foramen ovales (PFOs) and whether they cause stroke, writes a physician in the May issue of Mayo Clinic Proceedings. Lacking, he says, are good estimates of overall risks or variables that could affect prognosis.

Harold Adams Jr., M.D., from the University of Iowa's Department of Neurology, comments on new studies published in Mayo Clinic Proceedings. In an editorial on cardiac disease and stroke, Dr. Adams says articles in the journal serve as a reminder to physicians to exercise caution when a "new" cause of a common disease such as stroke is described.

Additional research will help determine the best course of treatment for patients with PFOs, Dr. Adams says, and will give physicians and patients the necessary data to make educated treatment decisions.

A peer-review journal, Mayo Clinic Proceedings publishes original articles and reviews dealing with clinical and laboratory medicine, clinical research, basic science research and clinical epidemiology. Mayo Clinic Proceedings is published monthly by Mayo Foundation for Medical Education and Research as part of its commitment to the medical education of physicians. The journal has been published for more than 75 years and has a circulation of 130,000 nationally and internationally. Articles are available online at www.mayoclinicproceedings.com.

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To obtain the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news. MayoClinic.com (www.mayoclinic.com) is available as a resource for your health stories.

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To obtain the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news. MayoClinic.com is available as a resource for your health stories.