For AFib Cardioversion in Obesity, Dual Energy Might Be the Answer

PHILADELPHIA – As an initial treatment strategy for treatment of atrial fibrillation (AF) in patients with obesity, dual energy cardioversion is substantially more reliable and just as safe as conventional single energy cardioversion, a multicenter randomized trial shows.

When treated with dual direct current cardioversion (DCCV), only 2% of patients with obesity failed to cardiovert on the first shock versus 14% (P = .002) of those treated with a conventional single DCCV, reported Joshua D. Aymond, MD, a fellow in electrophysiology at Ochsner Health, New Orleans.

Of the 14 patients in the single DCCV arm who did not convert on the first shock, 12 cardioverted when switched to dual energy. The remaining two cardioverted on the second dual shock.

In the dual DCCV group, of the two patients who did not cardiovert on the first dual shock, one did on the second. The other also cardioverted on a second shock, but this second shock was not delivered for 2 weeks, during which time the patient received a course of amiodarone-based anti-arrhythmic therapy.

No disadvantages seen with dual energy

The greater efficacy of a first shock with dual DCCV was achieved with no apparent disadvantages. There were no differences in post-procedure chest discomfort and no procedure-related adverse events in either arm, Dr. Aymond said.

The rising prevalence of obesity in the United States has created the need for a more effective first-line strategy for AF, noted Dr. Aymond, who presented the results of this study at the annual scientific sessions of the American Heart Association.

Cardioversion, which he characterized as the treatment of choice for AF, "fails to restore sinus rhythm in 20% to 35% of obese patients versus less than 10% of non-obese patients," he said. The higher failure rate in patients with obesity is becoming a more common clinical issue not only due to the rising rates of obesity but a corresponding rise in AF, which is a related phenomenon.

"The risk of atrial fibrillation is increased by 50% relative to those who are not obese," Dr. Aymond explained.

In this study, 200 patients at three participating centers were randomized to single DCCV or double DCCV after exclusions that included ventricular tachycardia and respiratory instability. The baseline characteristics were comparable. All 101 patients in the single DCCV group and 99 patients in the dual DCCV group were available for the intention-to-treat analysis.

200 vs. 400 joules delivered across the heart

In the study protocol, patients were fitted with four chest pads, two located adjacent but above the heart and two adjacent but below the heart. For single DCCV, 200 joules of energy were delivered from the upper right pad to the lower left pad across the heart. For dual DCCV, another 200 joules were delivered simultaneously from the upper left to the lower right across the heart. The total dose in the dual DCCV group was 400 joules.

The primary outcome was restoration of sinus rhythm of any duration immediately after DCCV. Safety, including clinical events, was a secondary outcome. Only the patients were blinded to the energy they received.

On univariate analysis, the odds ratio for successful cardioversion with dual DCCV was nearly eightfold higher (OR 7.8; P = .008) than single DCCV. On a simple multivariable analysis, when the researchers controlled for just age, sex, and body mass index, the odds ratio rose (OR 8.5; P = .007).

On a comprehensive multivariable analysis adding control for such characteristics as left ventricular ejection fraction (LVEF), obstructive sleep apnea, and antiarrhythmic drugs, the advantage of dual DCCV climbed above 12-fold (OR 12.6; P = .03).

The study is addressing a relevant and persistent question, said the AHA-invited discussant Jose A. Joglar, MD, program director, Clinical Cardiac Electrophysiology Fellowship, University of Texas Southwestern Medical Center, Dallas.

Dr. Joglar pointed out that alternatives to single DCCV for patients more difficult to cardiovert have been "sought for decades." He noted that a variety of techniques, including dual DCCV, have been evaluated in small studies and case reports.

Alternatives for obese outlined

Several have shown promise, Dr. Joglar said. As one of several examples, he cited a 20-patient study that randomized patients to adhesive patches, like those employed in the Aymond trial, or handheld paddles. Both patches and paddles were applied with manual pressure while a 200-joule shock was delivered. The proportion of patients who cardioverted on the first shock was almost two times higher in the group after the first shock with the paddles (50% vs. 27%; P = .01). Dr. Joglar said the study supports the principle that 200 joules delivered by adhesive patches is inadequate for treatment of AF in many patients with obesity.

Dr. Joglar also cited studies suggesting that single DCCV delivered with higher energy than 200 joules appears to improve cardioversion success rates, but he indicated that this study with dual DCCV in the front-line setting provides evidence for another alternative.

"This is the first such trial with dual defibrillators as an initial strategy," he said, calling the groups well matched and the superiority of dual DCCV "impressive." He cautioned that the study size was well powered for the endpoint but perhaps small for evaluating relative safety.

Yet, "the study adds credibility and confidence for the use of dual DCCV, especially in difficult or refractory patients," he said. He is less certain that it establishes dual DCCV as a standard first-line therapy in all patients with obesity. This would require additional studies to compare it to other types of strategies such as those he mentioned.

As an option for improving cardioversion in first-line treatment, dual DCCV "can be added to a list of other techniques, such as manual pressure or a higher initial dose with single DCCV," he said.

Dr. Aymond and Dr. Joglar report no potential conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.