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A-fib -- an abnormal heart rhythm -- is common after heart surgery, and it's linked to stroke and heart failure. But two new studies suggest that botox injections during surgery temporarily freeze nerve bundles in the heart, preventing the dangerous complication.
The effect lasted over three years, long after the botox itself dissipated, said lead researcher Dr. Jonathan Steinberg.
"Atrial fibrillation typically lengthens hospital stays and can have complications. Other drugs have been tried, but nothing has come out that is a solid, reliable performer, and there is no standard of care," said Steinberg. He is director of the SMG Arrhythmia Center at the Summit Medical Group in Short Hills, N.J.
In his study, 60 patients undergoing heart bypass surgery were randomly assigned to either botox or an inactive placebo. All received implantable cardiac monitors that tracked occurrence of atrial fibrillation.
In the botox group, risk of a-fib dropped immediately after surgery, and fell fivefold to ninefold each year of the three-year follow-up, the researchers found.
Also during follow-up, significantly fewer botox recipients were hospitalized for a-fib or needed treatment for it compared to the placebo group.
Botox, or botulinum toxin, blocks signals from the nerves to the muscles. It's a well-known tool in cosmetic surgery, and some doctors use it to treat neurological disorders including migraine, excessive sweating and eye muscle problems.
In heart surgery, Steinberg said the drug appears to interrupt "cardiac neural traffic."
He believes the findings suggest a new approach to treatment.
In the other study, Dr. Nathan Waldron and colleagues randomly assigned 130 patients to receive an injection of either botox or placebo while undergoing heart bypass surgery.
"Injecting botulinum toxin into fat pads surrounding the heart during cardiac surgery may be a promising strategy to reduce atrial fibrillation after cardiac surgery, but further study is needed," said Waldron, an assistant professor of anesthesiology at Duke University in Durham, N.C.
The reduction in a-fib risk among the botox group wasn't statistically significant -- only 11 percent -- but the episodes were shorter and less severe, researchers found. This finding may be due to the small size of the study, Waldron's team said.
Dr. Gregg Fonarow is director of the cardiomyopathy center at the University of California, Los Angeles, and co-director of the UCLA preventative cardiology program.
Developing effective and safe strategies to lower a-fib risk after surgery has been a challenge, he said.
"These new studies, while modest in size, suggest that there is the potential for epicardial fat pad injection of botulinum toxin performed during the cardiac surgery to lower the risk of postoperative atrial fibrillation," Fonarow said.
However, additional studies involving larger numbers of patients are needed, he added.
The reports were recently published online in the journal HeartRhythm.
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