Interactive Cardiovascular and Thoracic Surgery 3:386-389(2004)
© 2004 European Association of Cardio-Thoracic Surgery
Best evidence topic - Cardiac general |
Is antero-posterior position superior to antero-lateral position for placement of electrodes for external cardioversion of atrial fibrillation?
Darbhamulla V. Nagarajan and
Joel Dunning*
Department of Cardiology, Stepping Hill Hospital, Stockport, Manchester, UK
* Corresponding author. Address: Department of Emergency Medicine, Manchester Royal Infirmary, Oxford road, M13 3BW, Manchester, UK. Tel.: +780-154-8122; fax: +44-161-276-8538
joeldunning{at}doctors.org.uk
Received February 19, 2004;
accepted February 23, 2004
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Abstract
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A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the antero-posterior position is superior to the antero-lateral position for the placement of electrodes for cardioversion of atrial fibrillation. Altogether 167 papers were found using the reported search, of which 5 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that there is no clinical difference between the two positions although if one position fails to convert the patient, the alternative position may still achieve success.
Key Words: Evidence-based medicine; Thoracic surgery; Electric countershock; Atrial fibrillation; Review
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1. Introduction
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A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
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2. Clinical scenario
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You are with a 75-year old lady who had bypass grafting 5-days ago. Pre-operatively she was in sinus rhythm but postoperatively she went into atrial fibrillation (AF) on day 3. Despite 2 days of Amiodarone she remains in AF. She is otherwise well and you elect to attempt cardioversion prior to discharge. In the anaesthetic room you are presented with two gel pads for the cardioversion, and the theatre assistant asks you where you would like them placed before the patient is sedated. You elect for an antero-lateral position as you have never started with an antero-posterior position before, but after the patient cardioverted after 4 attempts in this position you wonder whether you should have tried the antero-posterior position first.
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3. Three-part question
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In [patients undergoing external DC cardioversion for atrial fibrillation] is [antero-posterior position of electrodes better than anterolateral position] in [terms of reverting to sinus rhythm].
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4. Search strategy
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Medline 1966-Feb 2004 using the OVID interface [exp atrial fibrillation/OR atrial fibrillation.mp OR exp atrial flutter/OR atrial flutter.mp OR AF.mp] AND [exp electric countershock/OR cardioversion.mp OR electroversion.mp] AND [paddle$.mp OR position$.mp OR anterior$.mp OR antero$.mp OR lateral.mp OR posterior.mp].
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5. Search outcome
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A total of 167 papers were found of which 5 prospective randomized trials represented the best evidence on this subject. These papers are listed in Table 1 [2–6].
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6. Results
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No papers were found that directly looked at this subject exclusively in patients post cardiac surgery, but 5-prospective randomized trials were found that represent the best evidence on this subject. Of note several other non-randomized studies were found with this search strategy but they were excluded due to absence of randomization.
Kirchhof et al. [2] recently performed a prospective randomized trial (PRCT) with 108 patients. They found a highly significant finding when using manual defibrillator paddles with a 96% conversion rate with the AP positioning compared to a 78% conversion rate using the AL strategy. In addition 2/3rds of patients who were not converted in the AL position were converted in the AP position. They did not demonstrate a lower energy requirement with this strategy, but they did provide a meta-analysis of 3 prior studies [3–5] showing an 82% conversion with AP position versus a 76% conversion rate with AL positioning.
Alp et al. [3] performed a PRCT with 59 patients randomized to the two protocols. They found that only 48% of patients converted in the AP position compared to 77% in the AL position. This study contrasts with the other studies. Their shock protocol was markedly different to other studies in that they started with 360 J, prior to crossing over techniques. In addition although they planned to recruit 136 patients they stopped the study early, when the p value reached 0.05 between groups. Of note it is more usual to use much more stringent P-values of the order of 0.005 when stopping a trial early is considered, in order to prevent reporting findings on the margins of significance.
Botto et al. [4] performed the largest PRCT in this area, with 301 patients randomized to AP or AL cardioversion using disposable gel pad electrodes. They found that the AP position was significantly superior to the AL position and they also found that a lower total energy requirement was needed using this position.
Mathew et al. [5] performed a PRCT in 90 patients. They found no difference between the two positions when using disposable gel pad electrodes. The AP position had a 78% success and the AL group had a success of 84%. This study did not present sample size calculations and Kirchhof et al. [2] suggested that this study was too underpowered to present conclusive negative findings. In addition the mean duration of AF was over a year in this study and thus this may have reduced the successful cardioversion rate.
Chen et al. [6] performed a PRCT in 70 patients. They also found no difference between AP and AL positions although they measured the Trans-Thoracic Impedance with both techniques and found this to be lower in the AP position. Of note this was also a small study.
The American Heart Association/American College of Cardiology/European Society of Cardiology joint guidelines for the treatment of AF [7] state that ‘the superiority of one position over another has not been established’ but they did not reference 4 of the papers listed here [2,3,5,6].
If all the results of the 5 PRCTs are combined we find that 259 of 315 (82%) patients were converted with AP and 240/313 (76.6%) were converted with AL position. This means that the number needed to treat with AP electrodes is 19 for every extra person converted. In addition this is a non significant result with  (Table 1)
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7. Clinical bottom line
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There is no clinically significant difference between the antero-lateral and antero-posterior positioning of pads for cardioversion of AF, although if cardioversion fails in one of these positions the alternative position may still succeed.
doi:10.1016/j.icvts.2004.02.010
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References
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- Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interac Cardiovasc Thorac Surg. 2003;: Available online 15 September 2003 http://www.icvts.org/pdf/icvts205.pdf
- Kirchhof P, Eckardt L, Loh P, Weber K, Fischer RJ, Seidl KH, Bocker D, Breithardt G, Haverkamp W, Borggrefe M. Anterior-posterior versus anterior-lateral electrode positions for external cardioversion of atrial fibrillation: a randomised trial [see comment]. Lancet. 2002;360:1275–1279[CrossRef][Medline]
- Alp NJ, Rahman S, Bell JA, Shahi M. Randomised comparison of antero-lateral versus antero-posterior paddle positions for DC cardioversion of persistent atrial fibrillation. Int J Cardiol. 2000;75:211–216[CrossRef][Medline]
- Botto GL, Politi A, Bonini W, Broffoni T, Bonatti R. External cardioversion of atrial fibrillation: role of paddle position on technical efficacy and energy requirements. Heart. 1999;82:726–730[Abstract/Free Full Text]
- Mathew TP, Moore A, McIntyre M, Harbinson MT, Campbell NP, Adgey AA, Dalzell GW. Randomised comparison of electrode positions for cardioversion of atrial fibrillation. Heart. 1999;81:576–579[Abstract/Free Full Text]
- Chen CJ, Guo GB. External cardioversion in patients with persistent atrial fibrillation: a reappraisal of the effects of electrode pad position and transthoracic impedance on cardioversion success. Jpn Heart J. 2003;44:921–932[CrossRef][Medline]
- Fuster V, Ryden LE, Asinger RW, Cannom DS, Crijns HJ, Frye RL, Halperin JL, Kay GN, Klein WW, Levy S, McNamara RL, Prystowsky EN, Wann LS, Wyse DG, Gibbons RJ, Antman EM, Alpert JS, Faxon DP, Fuster V, Gregoratos G, Hiratzka LF, Jacobs AK, Russell RO, Smith SC, Klein WW, Alonso-Garcia A, Blomstrom-Lundqvist C, De Backer G, Flather M, Hradec J, Oto A, Parkhomenko A, Silber S, Torbicki A. American College of Cardiology/American Heart Association/European Society of Cardiology Board. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation: executive summary. A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to Develop Guidelines for the Management of Patients With Atrial Fibrillation): developed in Collaboration With the North American Society of Pacing and Electrophysiology. J Am Coll Cardiol. 2001;38:1231–1266[Free Full Text]
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Abstract
1. Introduction