Transcutaneous Magnetic Stimulation Promising Against VT Storm

Batya Swift Yasgur MA, LSW

February 22, 2022

A small trial of transcutaneous magnetic stimulation (TcMS) of the left stellate ganglion of patients experiencing a ventricular tachycardia (VT) storm shows that TcMS can safely reduce VT burden in these patients.

Investigators, led by Timothy Markman, MD, from the Division of Cardiology and the Penn Brain Science, Translation, Innovation, and Modulation Center at the University of Pennsylvania, Philadelphia, randomized patients with three or more VT episodes in a 24-hour period to receive either TcMS or a sham intervention, and found "substantial" reduction in the number of episodes of VT in the 72-hour period after randomization in the TcMS group.

Encouragingly, TcMS did not interfere with cardiac implantable electronic devices (CIEDs) and carried no safety concerns.

"In this randomized clinical trial, findings support the potential for TcMS to safely reduce the burden of VT in the setting of VT storm in patients with and without cardiac implantable electronic devices," the authors write.

The study was published online February 16 in JAMA Cardiology.

Lowering VT Burden

VT storm, basically multiple episodes of VT over a short period, is associated with "considerable morbidity and mortality," the authors write. "Autonomic neuromodulation via local blockade of the left stellate ganglion provides therapeutic benefit by reducing cardiac sympathetic input" in these patients, they note. However, this strategy is "invasive and limited by associated risks and the need for technically skilled clinicians."

By contrast, TcMS can "noninvasively and nondestructively" modulate nervous system activity. Animal studies have shown that magnetic stimulation targeting cardiac sympathetic innervation can modify arrhythmia risk. Additionally, a feasibility study of TcMS in patients with VT storm conducted by the same investigators showed that it lowered VT burden without producing adverse effects. The current double-blind, randomized pilot study built on that previous work.

To be included in the trial, patients were required to have had three or more episodes of sustained VT in the preceding 24 hours. The researchers randomized 26 patients (mean [SD] age, 64 [13] years; 77% male) to receive either TcMS or sham stimulation (n = 14 and 12, respectively). Half of the patients in the TcMS group had a CIED.

Patients included had a mean of 12.7 (10.3) episodes of VT in the 24 hours preceding randomization and had recurrent VT despite taking a mean of 2.0 (0.6) antiarrhythmic drugs (AADs). At the time of randomization, 11 patients (42%) required mechanical hemodynamic support.

Uniquely Noninvasive and Nondestructive

During the first 24 hours after randomization, VT recurred in 29% (47%) of patients in the TcMS group and 58% (51%) in the sham group (P = .20) — a finding that was not statistically significant. However, in the 72-hour period after randomization, patients in the TcMS group had a mean of 4.5 (7.2) episodes of VT, compared with 10.7 (13.8) in the sham group (incidence rate ratio, 0.42; P < .001) — a significant finding.

Patients in the TcMS group were taking fewer AADs 24 hours after randomization than at baseline (mean, 0.9 [0.8] vs 1.8 [0.4]; P = .001), whereas there was no difference in the sham group between the number of AADs taken after randomization and at baseline (mean, 2.3 [0.8] vs 1.9 [0.5]; P = .20).

TcMS had no clinically significant effect on device function in the group of seven patients with a CIED.

The authors point to several limitations. Although they attempted to make the trial fully blinded, the TcMS resulted in pacing spikes that potentially could have been identified. "In theory, this may have influenced management decisions and led to incomplete blinding."

Additionally, they write, "although no adverse events occurred, conclusions regarding the safety of TcMS in patients with CIEDs are limited, owing to the small number of patients with devices in the TcMS group."

They describe TcMS as "valuable, not only because of its ability to modify neural circuitry, but also because it is uniquely noninvasive and nondestructive," and add that the findings "should inform future investigations of the optimal strategies for TcMS."

"Exciting Breakthrough"

Commenting for theheart.org | Medscape Cardiology, Kenneth Ellenbogen, MD, professor, Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, called the study's findings "novel" and "truly an exciting breakthrough."

Ellenbogen, who is the second vice president of the Heart Rhythm Society and was not involved with the study, said that "doing something soothing for the sympathetic nervous system — which is the part of the nervous system that triggers ventricular arrhythmias — has been around for a while, and it took a long time to develop the minimally invasive procedure that is now done laparoscopically. The ability to do it through this technique — a noninvasive high-intensity magnetic field to get electric currents into this area — is so crazy and so clever. And the results were very impressive, showing a dramatic decrease in the number of episodes of VT in the first 72 hours."

Also commenting for theheart.org | Medscape Cardiology, Kalyanam Shivkumar, MD, PhD, professor of medicine (cardiology), radiology, and bioengineering, and director, UCLA Cardiac Arrhythmia Center and EP programs, said the study is a "much-needed trial of a noninvasive technology that allows you to control a serious heart rhythm."

Shivkumar, who is also the director and chief of Interventional CV Programs, UCLA, and the editor-in-chief of JACC: Clinical Electrophysiology, and was not involved with the current research, said it is "one of the very few studies in patients who present with VT storm and they [the investigators] have shown that this approach actually works, which is highly innovative and an important contribution to the field."

Other nonrandomized research has shown that targeting these nerves — for example, by injecting local anesthetic drugs into the stellate ganglion — can also control this type of ventricular arrhythmia, but with TcMS, it can be done "externally and noninvasively."

Shivkumar hopes that this work will "inspire future studies, in terms of understanding this mechanism and how it can be used in other conditions."

No source of study funding listed. Markman reports no relevant financial relationships. The other authors' disclosures are listed on the original paper. Ellenbogen reports no relevant financial relationships. Shivkumar has developed patents related to neurocontrol of the heart and researched other devices, drugs, and technologies at UCLA, but not has been involved with the technology evaluated in the current study.

JAMA Cardiol. Published online February 16, 2022. Abstract

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