Moving Toward the Goal of Painless Atrial Cardioversion

Patrice Wendling

May 11, 2017

CHICAGO, IL — New research suggests patients with paroxysmal atrial fibrillation (AF) might escape the pain caused by a standard high-energy biphasic shock but still achieve AF cardioversion if treated using a series of very low-energy pulses[1].

AF was converted with low-energy multistage electrotherapy (MSE) in nine of 16 consecutive AF ablation patients in whom cardioversion thresholds were measured.

The mean lowest cardioversion energy and voltage with MSE was 0.57 J and 45.6 V, which falls well below the 7.3 J and 10.6 J reported for implanted cardiac devices with biphasic shock and the 60 V–threshold associated with mild or no patient discomfort.

Dr Fu Siong Ng

"You deliver a lot less energy over a longer time, which is a totally different mechanism of stopping fibrillation," principal investigator Dr Fu Siong Ng (Imperial College London, UK) told heartwire from Medscape at the Heart Rhythm Society 2017 Scientific Sessions, where the first-in-human, observational study was presented.

The researchers previously reported that MSE terminates AF with significantly less energy and lower peak voltage than biphasic shock in dogs[2] and studied its safety and feasibility in an unpublished cohort of 20 humans.

Compared with the instantaneous blast of a single biphasic shock, MSE delivers a sequence of intracardiac far-field and near-field stimuli over up to 1 second through leads in the right atrium.

Based on the preclinical work, MSE is thought to work by destabilizing the drivers of atrial fibrillation, inhibiting reanchoring, and then stopping any meandering wave fronts, Ng explained.

In the present study, the nine patients (mean age 61 years; 77% male) had been diagnosed with AF for an average of 48 months and had a mean ejection fraction of 64.3%.

In all, 35 AF episodes were converted by MSE at 0.65 J/44.0 V, with wide variation between patients of both conversion energy (1.45–0.04 J) and voltages (75–10 V).

Eight of the nine patients received MSE under conscious sedation, with one under general anesthesia. This limited the ability to quantitatively measure pain, although there were no reports of pain or visible diaphragmatic contraction, Ng said. No adverse events were also reported.

The next steps will be to optimize the pulses and perform MSE while patients are awake to better determine pain thresholds. Ultimately, early cardioversion with MSE may reduce AF symptoms and facilitate wider acceptance of cardiac electronic implantable devices for treating AF.

"It's a nice proof of concept and we're excited about it, but it's still early days and more work needs to be done before we can get this in something implantable that is sub–pain threshold, which will cardiovert atrial fibrillation as it occurs," he said.

The study was sponsored by Cardialen. Ng reports no relevant financial relationships; disclosures for the coauthors are listed in the abstract.

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