Summary
Background
Several clinical trials have shown inconsistent results regarding the effect of electrode positions on the success of electrical cardioversion.
Aims
The aim of this meta-analysis was to investigate the effect of the anterior-posterior electrode position on the success of electrical cardioversion in patients undergoing external electrical cardioversion for atrial fibrillation.
Methods
Pubmed, EMBASE, the Cochrane Library and the Chinese National Knowledge Infrastructure were searched for randomized controlled trials. The effect of the anterior-posterior electrode position on cardioversion success is presented as a risk ratio with 95% confidence interval.
Results
Ten trials with 1281 patients were included in the analysis. The anterior-posterior electrode position had no advantages in terms of success of electrical cardioversion for atrial fibrillation compared with the anterior-lateral electrode position (risk ratio 1.02, 95% confidence interval 0.96–1.09; P = 0.50). Subgroup analysis showed that patients with a left atrium diameter ≤ 45 mm and lone atrial fibrillation might derive benefits from the anterior-posterior electrode position in terms of success of cardioversion. No evidence of publication bias was detected.
Conclusions
The present analysis suggests that only patients with a left atrium diameter ≤ 45 mm and lone atrial fibrillation might derive benefits from the anterior-posterior electrode position compared with the anterior-lateral electrode position during external electrical cardioversion for atrial fibrillation. However, there was insufficient evidence to support any advantages for the anterior-posterior electrode position in other situations.
Résumé
Justification
Plusieurs essais cliniques ont montré des résultats hétérogènes concernant le positionnement de l’électrode pour le succès d’une cardioversion électrique.
Objectif
L’objectif de cette méta-analyse est d’investiguer l’effet de la position antéro-postérieure de l’électrode sur le succès de la cardioversion électrique chez les patients ayant une indication à une cardioversion électrique externe pour fibrillation atriale.
Méthode
Les bases Pubmed, EMBASE, Cochrane, CNKI ont été systématiquement interrogées pour ce qui concerne les essais cliniques randomisés, contrôlés. L’effet du positionnement antéro-postérieur de l’électrode sur le taux de succès de la cardioversion a été présenté comme un rapport de risque avec les intervalles de confiance à 95 %.
Résultats
Dix études ayant inclus 1281 patients ont été considérées pour analyse. La position antéro-postérieure de l’électrode n’a pas d’avantage sur le taux de succès de la cardioversion électrique pour fibrillation atriale comparativement au positionnement antéro-latéral de l’électrode (rapport de risque 1,02, IC 95 % 0,96–1,09, p = 0,50). L’analyse en sous-groupe montre que les patients ayant un diamètre atrial gauche > 45 mm et une fibrillation atriale isolée, pourraient tirer bénéfice du positionnement antéro-postérieur de l’électrode sur le taux de succès de la cardioversion. Il n’a pas été mis en évidence de publication pour expliquer ces résultats.
Conclusions
Cette méta-analyse suggère que seuls les patients ayant un diamètre atrial gauche < 45 mm et une fibrillation atriale isolée pourraient bénéficier du positionnement antéro-postérieur de l’électrode, comparativement à un positionnement antéro-latéral pendant les cardioversions électriques externes pour fibrillation atriale. Cependant, il n’y a pas suffisamment de preuves pour retenir l’avantage du positionnement antéro-postérieur de l’électrode dans d’autres situations.
Background
Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice, and is associated with an increased risk of cardiovascular morbidity and overall mortality . Although the rate control strategy is acceptable, the rhythm control strategy may be preferable for some patients with AF, especially young patients with persistent AF . In the European Society of Cardiology guidelines for the management of AF, direct-current cardioversion is recommended as an effective method of converting AF to sinus rhythm .
Two electrode positions are used currently for electrode placement: anterior-lateral (AL) and anterior-posterior (AP). As the left atrium is positioned behind the right atrium, an electrical shock filed between the anterior and posterior thorax may be more efficient than that delivered with electrodes in the AL position. Some trials have also shown that AP electrode placement results in a higher conversion rate with the minimum energy shock requirement . However, other studies have found no difference or have even suggested that the AL electrode position may be better . We therefore performed a meta-analysis of randomized clinical trials (RCTs) to test whether the AP electrode position facilitates cardioversion success compared with the AL electrode position during external cardioversion for AF.
Methods
Literature search
A literature search was performed for studies using Pubmed, EMBASE, the Cochrane Library and the Chinese National Knowledge Infrastructure (CNKI) in English and Chinese. The keywords we used were ‘atrial fibrillation’, and ‘electrical cardioversion’. For all relevant publications, the records retrieved with the ‘related articles’ link in Pubmed were reviewed; reference lists were checked for other relevant studies. The final literature search was finished on 31 May 2013. The major inclusion criteria were: the study was an RCT; the study examined the relative efficacy of different electrode positions in terms of electrical cardioversion success. The major reasons for exclusion of studies were: overlapping data; patients aged < 18 years; data published in the form of abstracts rather than in peer-reviewed manuscripts.
Data collection and quality assessment
Two investigators (B.Z., X.L.) independently reviewed all potentially eligible studies using predefined eligibility criteria and collected data from the included trials. Any discrepancy was resolved by consensus. Baseline characteristics of patients were extracted, as well as data on each trial’s intervention and the outcomes assessed. Trial quality was assessed using the Cochrane Collaboration’s tool for assessing risk of bias. The tool comprises the following dominants: random sequence generation; allocation concealment; blinding of participants and personnel; blinding of outcome assessment; incomplete outcome data; selective reporting; and other bias. Each domain was given a score of ‘high’, ‘unclear’ or ‘low’ by two reviewers, independently. The included trials were then sorted into three categories: low risk of bias (all criteria rated as having a low risk of bias); unclear risk of bias (at least one item unclear); or high risk of bias (at least one item at a high risk of bias) .
Statistical analyses
Statistical analyses were performed using Review Manager 5.0.4 software (available from The Cochrane Collaboration at http://www.cochrane.org ) and STATA 11.0 software (StataCorp LP, College Station, TX, USA). The effect of AP electrode position on cardioversion success was presented as a risk ratio (RR) with 95% confidence interval (CI); weighted mean differences and 95% CIs were calculated to investigate the effect of AP electrode position on transthoracic impedance (TTI) for the first shock, mean energy and number of shocks for successful cardioversion. Heterogeneity was evaluated with Cochran’s Q statistic and quality was evaluated by the I 2 statistic. A value of P < 0.1 for the Q test or I 2 > 50% indicated significant between-study heterogeneity. If no heterogeneity was present, a fixed-effect meta-analysis was performed. Alternatively, a random-effect meta-analysis was performed when heterogeneity existed. Publication bias was evaluated by Begg’s and Egger’s methods. Results were considered statistically significant if P < 0.05. Sensitivity analyses were undertaken by omitting one study at a time to examine the influence of one study on the overall summary estimate, and fixed- or random-effect models described above were used.
We explored possible explanations for heterogeneity according to a prior hypothesis, which included differences in baseline characteristics of patients, duration of AF, concurrent treatment with amiodarone, proportion with lone AF, type of electrode and type of defibrillator. Specially, we compared the result of studies grouped by the following factors: mean age; proportion of men; body mass index; duration of AF; proportion with lone AF; concomitant coronary disease; proportion of patients using amiodarone; left atrium diameter (LAD); type of electrode; and type of defibrillator. Recognizing that any cut-off point is arbitrary, we chose cut-off points before analysing the data using two criteria: thresholds had to be biologically sensible; and they had to divide the trials into two subgroups with a (more or less) similar number of trials. In addition, meta-regression analyses were conducted to identify factors contributing to the heterogeneity between studies, in which location of study, size of study, mean age, male sex, mean LAD, coronary artery disease and type of defibrillator, respectively, were introduced as covariants into meta-regressions.
Results
Search results
Our preliminary search yielded 343 potential literature citations. After the evaluation, a total of 333 articles were excluded for different reasons. Ten trials with 1281 patients (634 patients assigned to the AP group and 647 patients assigned to the AL group) were included in the analysis. Of the 10 studies, three studies reported that an AP electrode position was more effective than the AL position for external cardioversion for AF, one study showed that an AL electrode position was more effective than the AP position and six studies showed that AP and AL electrode positions had similar effects on external cardioversion for AF. The characteristics of included studies are shown in Table 1 .
| Study reference | Study size | Study location | Inclusion criteria | Exclusion criteria | Defibrillator type | Criteria for successful cardioversion |
|---|---|---|---|---|---|---|
| 59 | UK | Patients aged > 18 years undergoing their first electrical cardioversion for persistent AF | Pregnancy; permanent pacemaker; potassium < 3.5 mmol/L; kyphoscoliosis | Monophasic | SR maintained ≥ 30 minutes | |
| 301 | Italy | Patients undergoing elective external cardioversion for stable AF | Urgent cardioversion; LAD > 60 mm; duration of AF > 2 years; untreated hyperthyroidism | Monophasic | Interruption of AF for > 10 seconds | |
| 103 | Lithuania | Patients aged > 18 years undergoing elective cardioversion for stable AF | NA | Biphasic | At least one P-wave within 30 seconds | |
| 70 | China | Patients with persistent AF without previous electrical cardioversion for AF | Duration of AF < 1 month; paroxysmal AF; pregnancy; unstable HF; rheumatic heart diseases without PTMC | Monophasic | SR maintained ≥ 60 minutes | |
| 108 | Germany | Patients aged 18–80 years undergoing cardioversion | Patients with implanted pacemaker or defibrillator | Monophasic | SR or organized atrial rhythm | |
| 71 | China | Patients with persistent AF | NA | Monophasic | NA | |
| 90 | UK | Patients undergoing elective cardioversion for AF | Patients with a permanent pacemaker | Monophasic | NA | |
| 123 | Germany | Patients undergoing elective cardioversion for persistent AF | Implanted pacemaker; cardiopulmonary decompensation; electrolyte imbalance; ineffective anticoagulation | Biphasic | Termination of AF with at least two consecutive sinus beats | |
| 62 | Greece | Patients undergoing elective cardioversion for persistent AF | NA | Monophasic | Sinus rhythm after the shock | |
| 294 | UK | Patients undergoing elective cardioversion for AF | Age < 18 years; unable to provide informed consent; atrial flutter; any contraindication to the procedure | Biphasic | SR ≥ 30 seconds |
Baseline characteristics of patients and quality of the included studies
The baseline characteristics of patients enrolled are summarized in Table 2 . There were no significant differences in the baseline characteristics of patients between the two groups. The mean age of patients in the individual trials ranged from 55 to 68 years. The mean proportion of men was 64.9% among patients enrolled. The mean body mass index of patients in individual trials ranged from 24.5 to 29.6 kg/m 2 . Hypertension was present in 38.9% of patients enrolled. We used the Cochrane Collaboration’s tool to evaluate the quality of the included studies. According to the predefined quality assessment criteria indicated above, all trials were evaluated as having a high risk of bias, except for the trial conducted by Kirchhof et al. ( Fig. 1 ).
| Study reference | Age (years) | Male sex | Body mass index | Hypertension | ||||
|---|---|---|---|---|---|---|---|---|
| AP | AL | AP | AL | AP | AL | AP | AL | |
| 66.8 ± 7.9 | 67.8 ± 8.1 | 22 (75.9) | 19 (63.3) | NA | NA | 11 (37.9) | 5 (16.7) | |
| 62 ± 11 | 62 ± 12 | 89 (59) | 94 (62) | NA | NA | 40 (27) | 41 (27) | |
| 62.31 ± 10.37 | 63.84 ± 11.67 | 29 (60.4) | 36 (65.5) | 29.91 ± 5.16 | 29.55 ± 4.78 | 19 (39.6) | 20 (36.4) | |
| 57.6 ± 10.1 | 59.1 ± 14.7 | 27 (69.2) | 20 (64.5) | 25.2 ± 4.7 | 25.3 ± 4.6 | 15 (38.5) | 10 (32.3) | |
| 62 ± 2 | 58 ± 2 | 38 (73.1) | 44 (78.6) | 27 ± 4 | 27 ± 4 | 29 (56) | 22 (39) | |
| 55.1 ± 10.5 | 51.9 ± 9.7 | 34 (91.9) | 30 (88.2) | 25.4 ± 1.9 | 24.5 ± 2.5 | 13 (35.1) | 13 (38.2) | |
| 65.5 ± 10 | 60 (66.7) | 26.5 ± 5.3 | 27.5 ± 4.9 | 19 (21) | ||||
| 67 ± 10 | 66 ± 10 | 40 (67) | 47 (75) | 27.7 ± 4 | 28.2 ± 5 | 26 (44) | 18 (28) | |
| 61.6 ± 7.2 | 60.1 ± 8.6 | 20 (65.6) | 21 (65.6) | 26.8 ± 3.8 | 25.9 ± 40 | 4 (13.5) | 4 (12.5) | |
| 66 ± 14 | 67 ± 10 | 100 (64) | 95 (63) | 29 ± 5 | 28 ± 5 | 81 (52) | 57 (38) | |
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