Cardiac arrhythmias are electrical malfunctions that throw the heart out of rhythm, causing many of the 330,000 sudden cardiac deaths each year in the United States. Most fatal arrhythmias occur in aging patients when scar tissue left by a heart attack interferes with the heart's electrical system. As many as 1,000 deaths each year, however, are caused by Long QT Syndrome (LQTS), the focus of the long-running grant renewal. LQTS occurs mostly in teens with otherwise healthy hearts. Research into this infrequently occurring medical condition has provided insights into much more common, post-heart attack arrhythmias.
The QT interval is part of the heart's electrical signature as recorded by an electrocardiogram (ECG). It represents the time it takes for the heart's lower chambers to "electrically recover" after each heartbeat. In LQTS patients, the QT electrical recovery time is prolonged, which makes the heart more susceptible to fatal arrhythmias. The condition may go unnoticed until sports, strong emotions or even loud noises knock the heart out of rhythm, causing loss of pulse and rapid, chaotic heart rhythm with loss of consciousness (syncope). In some cases, the dangerous heart rhythm stops on its own, but in others it deteriorates into a fatal rhythm (ventricular fibrillation). Sudden death will then occur if the heart is not restarted with a defibrillator. Some families have lost one or more children before realizing that their family has an inherited heart condition.
As a result of work led by Arthur Moss, M.D., professor of Medicine at the Medical Center, over more than two decades, researchers have achieved an 80 percent reduction in life-threatening events via drug treatment (e.g. beta blockers) and device advances, results achieved in Rochester area patients first. Through related articles published in medical journals, word of the success in Rochester has spread to help patients worldwide. The new grant will enable the team to further hone each patient's risk factor assessment, and to develop even more effective treatment to prevent sudden death in this and related conditions, by continuing to analyze LQTS population data.
In 1979, Moss helped to launch the International LQTS Registry, a database of families with the LQTS trait. By following families and patients with this disorder, gene hunters used the registry to track down more than 500 genetic mutations involving ten genes that cause versions of LQTS. By following the outcomes of patients in the registry over many years, researchers are now drawing more accurate conclusions about each patient's risk.
"It has been tremendously exciting to continue this line of research from the early days of trying to understand the nature of the disease to recent successes in developing new therapies for it," Moss said. "We presented our research findings in April at the American College of Cardiology meeting in which we identified a new drug, ranolazine, that will be useful in treating patients with some forms of LQTS. Our longstanding program in basic and clinical research is leading to new, and more effective treatment for patients with heart disease."
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