Doctors now make more informed decisions on how to treat an electrical disorder of the heart – be it with drugs, an implanted device or nothing – thanks to a series of decades-long, Rochester-based studies. The two latest studies in the series, published recently in the journal Circulation, further defined the ideal treatments for the youngest and oldest of patients with Long QT syndrome (LQTS) and concluded that they are not the same. Another conclusion is that the risk of fatal events in children is relatively low, and that implanted devices, while clearly important for some high-risk patients, may create more risk than the condition itself in some cases. That may change, however, if that patient survives past 40, when the same device becomes a lifesaver.

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 behind by a heart attack interferes with the heart’s electrical system. As many as 1,000 deaths each year, however, are caused by LQTS.

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. QTc is the QT interval corrected for heart rate, a more accurate measure. In LQTS patients, QTc reset 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.

The LQTS syndromes were discovered 50 years ago, but researchers are still fine-tuning treatment recommendations. When is a drug or device warranted? If so, which procedures are right for which patients, and when is the best time to intervene? The competing risks of the disease itself, versus those created by invasive treatments, often complicate decision-making.

“Even when effective treatment is available, it doesn’t always translate immediately into use by the affected patients, if the awareness is not there,” said Ilan Goldenberg, M.D., research assistant professor of Cardiology in the Department of Medicine at the University of Rochester Medical Center, and first author of the Circulation paper. “Our study found surprisingly that just one in five children diagnosed with LQTS received appropriate drug treatment, beta blockers, known for years to cut their risk of death by 50 percent or more.”

Arthur Moss, M.D., professor of Medicine at the University of Rochester Medical Center, and an author on the current paper, in 1979 helped to launch the International LQTS Registry, a database of families with the LQTS trait. By following generations of affected families, 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, and by identifying groups of patients at high risk, researchers are closing in on more accurate ways to reduce the risk. In the current issue of Circulation, separate studies looked at risk of fainting or sudden cardiac death in two groups of registry patients, the youngest (under 13) and the oldest (over 40).

Hart Risk in Children

For the current report about LQTS in children, the authors reviewed data on more than 3000 children who were enrolled in the registry before their teenage years, focusing predominantly on fatal or near-fatal events. The team reaffirmed that abnormally long QTc period (greater than 500 ms) in boys and fainting spells (syncope) in both boys and girls are significant predictors of aborted cardiac arrest or sudden cardiac death during childhood.

The syncope association with risk was time-dependent: the more recent the syncope, the greater the risk for a cardiac event. Girls accounted for 63 percent of the children in the registry, and they had a slightly but statistically significant longer baseline QTc. That said, boys had a higher rate of events (5 percent for boys, 1 percent for girls).

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