Dec 1, 2005

Cardiac Scar Pattern Predicts Risk Of Fatal Arrhythmias

Researchers at Johns Hopkins are doing their homework! Using magnetic resonance imaging (MRI) scans of the heart wall, researchers at Johns Hopkins have found that people whose muscle wall thickness contained more than 25 percent scar tissue were approximately nine times more likely to test positive for a fast and dangerous heart rhythm known as ventricular arrhythmia.

Patients at risk of such arrhythmias often have a heart defibrillator implanted, a small device that delivers an electrical shock to restore their cardiac rhythm in case the heart beats too rapidly to pump enough blood to the rest of their body.

United States Centers for Disease Control and Prevention estimate that each year more than 400,000 Americans suffer a sudden cardiac death, at least 30 percent of which are due to arrhythmia.

"If further tests confirm that MRI measurements of scar tissue accurately predict the risk of arrhythmia-related sudden death, these could become the gold standard for screening who really needs or does not need a defibrillator," says the study's senior author, electrophysiologist Henry Halperin, M.D., a professor of medicine, radiology and biomedical engineering at The Johns Hopkins University School of Medicine and its Heart Institute. "While tests are widely available to screen patients with coronary artery disease for risk of sudden cardiac death, tests are not so effective for identifying the many who will die suddenly from arrhythmias."

"Our MRI technique has significant advantages over existing methods because it avoids the risks of infection that come with surgery, it is noninvasive, there are no catheters, and it is relatively easy to perform, taking only 45 minutes," says study co-author and cardiologist Joao Lima, M.D., an associate professor of medicine and radiology at Hopkins.

Lima notes that a patient with an ejection fraction of 60 percent has normal pumping ability, but anything less than 30 percent for a period of nine months or longer is considered low and an immediate risk factor for arrhythmia. He adds that if a patient has an ejection fraction that is slightly above 30 percent, then an electrophysiology test is used to determine if a patient requires a defibrillator. In this test, a thin catheter is inserted into the heart to try to induce an arrhythmia, something that will fail if the heart is healthy and not at risk. However, if it happens once, it is known to be two to four times more likely to happen again, he says.

Daniel      

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Heart disease
About 13 million Americans (about 7 percent of the total population) suffer from coronary artery disease. Coronary artery disease is the leading cause of death in American men and women amounting a staggering 20 percent of all causes of death. About half of all deaths related to cardiovascular diseases occur from coronary artery disease. Through this heart watch blog we will have our humble contribution towards making men and women aware of the risks of heart diseases.