Botulinum toxin amazes cardiologists

Botulinum toxin amazes cardiologists

Cardiologists have now also discovered a possible therapeutic use for the active ingredient known as wrinkle-smoothing botulinum toxin: for the suppression of atrial fibrillation after bypass operations. But there are still many question marks.

NOVOSIBIRSK. The cardiologists present were astonished by the research results of a group of Russian colleagues presented for the first time at the Heart Rhythm Society (HRS) congress in Boston in May 2015.

In a small, randomized, controlled pilot study, they had an unusual therapeutic approach - the intraoperative infiltration of botulinum toxin into the epicardial adipose tissue - the effects of which on atrial fibrillation after surgical myocardial revascularization had been tested - with astonishing success.

The group around the cardiologist Dr. Evgeny Pokushalov from Novosibirsk has now published her study results in the journal "Circulation: Arrhythmias and Electrophysiology" (Circ Arrhythm Electrophysiol 2015, online October 20).

For the study, 60 patients with indications for aortocoronary bypass surgery were recruited at two centers in Russia. All participants had previously had paroxysmal atrial fibrillation, which indicated an increased risk of postoperative development of atrial fibrillation as a result of cardiac surgery.

After randomization into two treatment groups, the patients were injected with either botulinum toxin or normal saline (placebo) into epicardial fat pads following the bypass operation. As is well known, botulinum toxin temporarily blocks the release of acetylcholine from synaptic vesicles and thus inhibits the cholinergic transmission of excitation by nerve cells.

There were no complications from the injections. For continuous cardiac rhythm monitoring, all study participants received an implantable event recorder, the recordings of which were evaluated after 7, 14, 21 and 30 days as well as after 3.6, 9 and 12 months.

The results on the short-term effect of intraoperative injections within the first 30 days had already been published in the specialist journal JACC in August 2014. They largely meet expectations.

Postoperative atrial fibrillation was then recorded in two (7 percent) of 30 patients in the botulinum toxin group and nine (30 percent) of 30 patients in the control group - a significant difference in favor of toxin injection (p = 0.024).

A real surprise, however, are the effects that followed up until the end of the study. In this phase, the arrhythmia-suppressing effects of botulinum toxin should actually have declined according to the expectations of the study authors.

But surprisingly, she didn't: Between 30 days and the end of the study after 12 months, not a single patient developed atrial fibrillation in the botulinum toxin group, compared to seven (27 percent) of 30 patients in the control group (p = 0.002).

With this data, intraoperative botulinum toxin injection has not yet qualified as a treatment option to be included in the guidelines for protection against atrial arrhythmias in cardiac surgery. This requires confirmation of the positive results in larger studies, according to a statement by the American Heart Association (AHA) on the publication of the study.

The study authors also see it that way. If the clinical benefit is confirmed in further studies, the method, which is still to be classified as experimental, could also prove to be a possible option for heart valve surgery, which also often leads to atrial fibrillation.

The hope that percutaneous coronary intervention could improve the prognosis in stable CHD was not fulfilled in the largest study to date. However, a benefit could be shown.

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