Nov 21 2013
Old Westbury, N.Y. (November 21, 2013) -- New York Institute of Technology researchers continue to find evidence that thyroid hormones may help prevent cardiac problems.
A recent study published in Circulation: Arrhythmia and Electrophysiology by College of Osteopathic Medicine Assistant Professor Youhua Zhang, MD, Ph.D., concluded that normal thyroid hormone levels are required to maintain normal cardiac functioning and prevent arrhythmias and atrial fibrillation -- conditions that result in irregular heartbeat, a “fluttering” of the heart muscle, and sudden death.
The study, "Both Hypothyroidism and Hyperthyroidism Increase Atrial Fibrillation Inducibility in Rats," builds on previous published research led by Professor and Biomedical Sciences Chair A. Martin Gerdes, who has found that restoring thyroid levels in cardiac tissue to normal in several animal models of heart failure resulted in dramatic improvements in heart function and underlying pathology. Based on his previous work, several partnering Long Island cardiologists hope to raise funds to begin enrolling patients in a clinical trial involving treatment of heart failure patients with low thyroid levels. A new treatment and monitoring approach showing safety and efficacy in several animal models of heart failure will be implemented in patients for the first time.
About 2.2 million Americans have atrial fibrillation, while heart failure affects more than 5 million patients in the United States. Many patients diagnosed with heart failure also develop atrial fibrillation. Importantly, about half of cardiac deaths result from arrhythmias.
Zhang’s study, conducted with Gerdes, Assistant Professor Eduard I. Dedkov, MD, Ph.D., and third-year medical student Bianca Lee investigated the effect of low, normal, and high thyroid levels on cardiac electrophysiology and arrhythmia in rats.
Scientists have already established an association between high thyroid hormone levels, or hyperthyroidism, and atrial fibrillation. Ten to twenty-five percent of patients with hyperthyroidism experience atrial fibrillation. The association between lower levels, or hypothyroidism, and atrial fibrillation has not been widely examined.
“We hypothesized that if we normalized thyroid hormone levels, we would probably reduce arrhythmias,” Zhang said. The study confirmed that the high hormone levels increased the risk of atrial fibrillation. But, low levels were also found to increase the risk, leading researchers to conclude that correcting thyroid dysfunction could prevent arrhythmias and atrial fibrillation.
"Since a growing body of evidence suggests that most cardiac patients likely have reduced thyroid function in heart tissue, this study raises the possibility that our fear of using thyroid hormones in heart patients may actually be leading to an increase in arrhythmias," said Gerdes. "This fear of accidentally overdosing with thyroid hormones and triggering arrhythmias is largely driven by a few poorly conducted clinical studies that did just that. Other short-term studies that used safer, low-doses of thyroid hormones in heart failure patients were overwhelmingly positive. I believe it is time to fully explore the possibilities. Recent information has improved our understanding of the problem and should enable thoughtful, long-term human studies of patients with heart failure in the hopes that this will provide symptomatic relief and reduce mortality."