Randomised comparison of antero-lateral versus antero-posterior paddle positions for DC cardioversion of persistent atrial fibrillation

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Abstract

We designed a prospective, randomised, single-blind trial to compare the relative efficacy of antero-lateral versus antero-posterior paddle positions for DC cardioversion of persistent atrial fibrillation. A total of 59 patients were randomised to cardioversion using standard gel pads placed either in the antero-lateral (AL) or antero-posterior (AP) positions. The first synchronised shock was given at 360 J; if this was unsuccessful, a second shock of 360 J was given in the alternative position. We compared cardioversion success rate and energy requirements with each strategy. With the first 360 J DC shock, a significantly greater proportion of patients were restored to sinus rhythm from the antero-lateral position (18/30) compared to the antero-posterior position (10/29) (P=0.048). For those patients remaining in atrial fibrillation, there was no difference in the proportions cardioverted from the antero-lateral position (4/19) compared to the antero-posterior position (5/12) with the second 360 J DC shock (P=0.22). The total cardioversion success rate was 23/30 (77%) for antero-lateral followed by antero-posterior shocks compared to a success rate of 14/29 (48%) for antero-posterior followed by antero-lateral shocks, and this difference was significant (P=0.024). There was no significant difference in the mean energy delivered for patients randomised to an initial antero-lateral shock (504 J), compared to patients given an initial antero-posterior shock (583 J) (P=0.1). We conclude that the antero-lateral paddle position appears more effective for DC cardioversion of persistent atrial fibrillation.

Introduction

The cardioversion of chronic persistent atrial fibrillation to sinus rhythm is a worthwhile therapeutic goal: it improves cardiac function, symptomatic status, and reduces the risk of thrombo-embolic events.

Electrical (DC) cardioversion has become a routine technique for the cardioversion of AF since its introduction in the 1960s [1]. In most series, DC cardioversion has an initial success rate of 80–90% [2] depending on the population studied. Various guidelines have been proposed for the cardioversion technique itself (including energy level and paddle positions), but there are only limited data from randomised trials. Some authors have recommended an initial shock energy of 200 J with the paddles in the antero-lateral position followed by a further shock of 200–360 J [3]. If this also fails a final attempt is often made with the paddles in the antero-posterior position, and a 200–360 J shock may be delivered.

It is unclear whether the antero-posterior paddle position is more effective than the antero-lateral position. Studies have demonstrated a lower trans-thoracic impedance with the antero-posterior position, theoretically increasing the likelihood of defibrillation [2], but there have been conflicting findings comparing the clinical outcomes of the two positions. Various studies show either improved success in the antero-posterior position [4], [5], decreased success [6], or no difference [7], [8]. Thus, there is still a need to establish the most effective external cardioversion technique.

Section snippets

Methods

The study was performed in a large district hospital in the UK. The local research ethics committee approved the study protocol. Written informed consent was obtained from all study participants. Patients aged over 18 undergoing their first elective DC cardioversion for persistent atrial fibrillation were considered eligible for inclusion in the trial. Exclusion criteria were: pregnancy, permanent pacemaker in situ, serum potassium less than 3.5 mmol/l, severe kyphoscoliosis, and inability to

Statistical analysis

Statistical analysis was on an ‘intention to treat’ basis. Pearson Chi-squared tests were used to compare proportions of patients in sinus rhythm at each end point. The independent sample t-test was used to compare continuous variables between the two subgroups. Data were analysed using Microsoft Excel 97 software. All reported P-values are two-sided. Standard levels of statistical significance (P<0.05) were used.

To calculate the number of patients required to obtain statistical power, a

Results

From July 1998 to July 1999, 72 patients were screened; of whom 59 gave consent and were randomised (Fig. 1). All patients completed the study protocol. At the interim analysis of these 59 patients, a significant difference between the two groups in the cardioversion success rate was observed and so the study was terminated. The analysis from these patients is presented.

Baseline characteristics including age, gender mix, duration of AF, previous history, antiarrhythmic drug treatment, and

Discussion

This study has shown that cardioversion of AF using antero-lateral followed by antero-posterior 360 J DC shocks with standard gel pads is more successful (77%) than similar shocks given in the antero-posterior followed by the antero-lateral position (48%). This suggests that the antero-lateral paddle position is a more effective cardioversion route than the antero-posterior position, although these results may not apply to lower energy shocks. For those patients requiring a second shock, there

Acknowledgments

We are grateful to our nursing and medical colleagues for their help with recruitment of patients.

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