Evaluating success rates of direct cardioversion for atrial fibrillation in patients with an elevated body mass index: a randomised controlled trial of adhesive patches vs hand-held paddles (DCR-BMI)

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Direct electrical cardioversion (DCR) is an important aspect of atrial fibrillation and/or atrial flutter (AF) management, and is routinely performed to restore normal sinus rhythm. Success rates range from 50 – 93% , depending on left atrial size, AF duration and transthoracic impedance. Total body weight is a key factor in determining transthoracic impedance and therefore cardioversion failure is more frequent in obese patients . In a randomised trial of 201 patients, hand-held paddle electrodes successfully cardioverted 98% patients,compared to 86% with self-adhesive patches (p = 0.001) . This is likely related to the fact that handheld paddles convey a lower transthoracic impedence and hence enable more efficient delivery of energy to the left atrium . The mean body mass index (BMI) in this trial was 28. It is likely that an even greater difference would be observed with paddles in patients with higher BMIs. While a recent large meta-analysis did not demonstrate a difference in cardioversion success rates for different electrode positions / shock vectors (anterior-posterior vs antero-apical, this may not be the case for obese patients. Currently, self-adhesive patches remain more widely utilized in Australian hospitals, due to their ease of use. However with the emerging obesity epidemic, we believe this practice is contributing to an increasing failure of DCR in this patient group. Our study is a multi-centre randomised controlled trial comparing hand-held paddle electrodes and self-adhesive patch electrodes in obese patients (BMI at least 30). We hope to determine whether rates of successful cardioversion for AF are higher in obese patients using hand-held paddle electrodes compared with self-adhesive patch electrodes. We hypothesise that handheld paddle electrodes have a significantly higher efficacy at restoring sinus rhythm in obese patients. Our 2 x 2 design will comprehensively evaluate the best way to cardiovert obese patients (patch vs paddle AND anteroapical vs anteroposterior). Patients will be randomised to one of four arms (2 paddle arms - 1 antero-posterior, 1 antero-apical shock vector & 2 patch arms - 1 antero-posterior, 1 antero-apical shock vector). Cardioversion will proceed until sinus rhythm is restored. Patients in each group will receive up to 2 shocks with the modality they are assigned to (patch or paddle), with the 3rd (final) shock being a cross-over to the alternative modality (patch or paddle). Additional shocks up to 360J may be delivered at the discretion of the clinician, and all patients with failed cardioversions will be offered a referral for an attempted shock up to 360J on a different date. Patients with successful cardioversions will also be contacted at 3 months to determine if they have had a recurrence of AF, and if not, will be asked to have an ECG performed.

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