International Journal of Cardiology 114 (2007) 16 – 21 www.elsevier.com/locate/ijcard
DC cardioversion of persistent atrial fibrillation: A comparison of two protocols Lana Boodhoo *, Andrew R.J. Mitchell, George Bordoli, Guy Lloyd, Nikhil Patel, Neil Sulke Department of Cardiology, Eastbourne General Hospital, Eastbourne, UK Received 11 September 2005; received in revised form 30 October 2005; accepted 17 November 2005 Available online 27 April 2006
Abstract Background: Current guidelines for transthoracic direct-current cardioversion (DCCV) of atrial fibrillation (AF) recommend a step-up energy protocol. The aim of this study was to compare such a protocol with a protocol involving a high initial energy shock, anteroposterior paddle position and reversal of shock polarity, on cardioversion efficacy, total energy delivery, use of sedation and patient tolerability. Methods: 261 patients (mean age 71 T10 years, 62% male) referred for elective DCCV of persistent AF were enrolled. Patients were randomised to either protocol A: (1) 200 J anteroapical, (2) 360 J anteroapical, (3) 360 J anteroposterior; or protocol B: (1) 360 J anteroapical, (2) 360 J anteroposterior, and (3) 360 J posteroanterior. All procedures were performed under sedation with intravenous diazepam. Results: Protocol B improved shock success rates (protocol A first shock success rate = 42%, protocol B = 68%, p < 0.001; protocol A second shock success rate = 72%, protocol B 86%, p = 0.006; protocol A third shock success rate = 83%, protocol B = 92%, p = 0.03) and required fewer shocks to achieve sinus rhythm (1.3 T 0.6) compared with protocol A (1.6 T 0.7, p < 0.001). There were no differences in cumulative energy used (protocol A 473 T 286 J, protocol B 436 T 273 J, p = 0.24) or sedation requirements (protocol A diazepam 22.1 T 9.0 mg, protocol B 21.7 T 8.9 mg, p = 0.75). Both protocols were equally well tolerated by patients. Conclusion: High initial energy increased success rates and decreased the number of shocks but resulted in similar cumulative energy delivery, sedation use and patient tolerability compared with a conventional step-up protocol. D 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Cardioversion; Atrial fibrillation; Sedation
1. Introduction Direct-current (DC) cardioversion is the most effective method for restoring sinus rhythm in patients with persistent atrial fibrillation (AF) and current guidelines recommend starting with at least 200 joules (J) for monophasic external cardioversion and progressing to higher energies [1]. The delivered energy, paddle position and paddle pressure may influence the cardioversion success rate [2– 5]. Reversed shock polarity has been used when previous attempts to cardiovert have failed but this approach has not been * Corresponding author. Department of Cardiology, The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE, United Kingdom. Tel.: +44 151 228 1616; fax: +44 151 220 8573. E-mail address:
[email protected] (L. Boodhoo). 0167-5273/$ - see front matter D 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2005.11.108
supported by the literature [6]. Cardioversion has been traditionally performed under general anaesthesia but there is a gradual shift to using intravenous benzodiazepines for sedation during elective DC cardioversion of atrial arrhythmias. This technique has been shown to be safe, effective, cost-efficient and to improve patient turnover [7 –10]. If the initial cardioversion shock fails to restore sinus rhythm, however, repeated shocks under sedation may lead to an increase in sedation requirement. 1.1. Study aims We compared a recommended step up energy protocol to one utilising a high initial energy shock, anteroposterior paddle position, and reversed shock polarity for the cardioversion of persistent AF. The primary endpoint was
L. Boodhoo et al. / International Journal of Cardiology 114 (2007) 16 – 21
cardioversion success rate. Secondary endpoints were total energy delivery, sedation requirements, complication rates and patient acceptability and tolerability.
2. Materials and methods 2.1. Patients All patients attending for elective cardioversion of persistent AF from June 2002 to August 2003 at Eastbourne General Hospital were invited to participate in the study. The study was performed in accordance with the Declaration of Helsinki and the protocol was approved by the Local Research and Ethics Committee. All patients gave written informed consent. Inclusion criteria were AF of greater than 24 h duration that required external cardioversion and no reversible cause of AF. At least 4 weeks of anticoagulation with warfarin with an International Normalised Ratio (INR) of greater than 2.0 was required. Patients were excluded for the following reasons: Serum potassium less than 3.5 mmol/l, INR less than 2.0, known allergy to any drug normally used in the procedure, clinical evidence of digitalis toxicity, or resting oxygen saturation measured by oximetry of less than 90%. Patients cardioverted for atrial arrhythmias other than AF were excluded from the analysis. 2.2. Protocols for cardioversion Cardioversions were performed as day-case procedures in the cardiac care unit under sedation with intravenous diazepam with the patient in the fasted state. Diazepam was given as Diazemuls (Dumex, Exeter, UK) 10 mg bolus with increments of 2.5 mg until adequate sedation was obtained. Patients were randomised in a single blind manner to either of the following shock protocols: protocol A (i) 200 J anteroapical, (ii) 360 J anteroapical, (iii) 360 J anteroposterior; or protocol B (i) 360 J anteroapical, (ii) 360 J anteroposterior, (iii) 360 J posteroanterior. The end point of the procedure was either restoration of sinus rhythm or the delivery of all three shocks. All cardioversions were done with a Physio-Control Lifepak 9 defibrillator (Physio Control Corp, Washington, USA) that applied monophasic waveforms through hand-held electrodes. Non-adhesive contact pads were applied to the patient in the required positions (3M healthcare, Neuss, Germany). For the anterolateral configuration, the anterior electrode position was the right infraclavicular area, and the lateral electrode position was at the left ventricular apex. For the anteroposterior configuration the anterior electrode was located over the body of the sternum, and the posterior electrode was a specifically designed back electrode of 12 cm diameter and was situated interscapularly. For the posterior – anterior configuration, the anterior electrode was located interscapularly and the posterior electrode over the body of the
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sternum. Manual pressure of at least 8 kg was applied to the paddles for all shocks. Successful cardioversion was defined as the restoration and maintenance of sinus rhythm at discharge 2 h postprocedure as documented on a 12-lead ECG. Patient perception was assessed prior to discharge, at 24 h and 48 h post-procedure by custom-designed questionnaires [10]. These evaluated using 15-point visual analogue scales of anxiety, discomfort, pain, unpleasantness, and side effects. Patients were also asked whether they were willing to repeat the procedure and sedation if medically indicated. Postprocedure questionnaires were returned in pre-paid envelopes. All patients were reviewed 6 weeks post-cardioversion with a 12-lead ECG. 2.3. Statistical analysis Values are expressed as means T standard deviation (S.D.). Fisher’s Exact Test was used to compare categorical variables. Unpaired Student’s t-tests were used for comparisons of continuous variables between groups. A p value of 0.05 was considered significant.
3. Results During the study period, 338 patients attended for daycase DC cardioversion of atrial arrhythmias. Fifty patients underwent more than one cardioversion procedure and only the first procedure was included. Twenty-seven patients who were cardioverted for atrial arrhythmias other than AF were excluded from the analysis. Two hundred and sixty-one patients were therefore included in the final analysis. The patient demographics are listed in Tables 1 and 2. The mean age was 71 T10 years, and 38% of patients were female. The mean BMI was 26 T 4 kg/m2, and mean left atrial diameter and ejection fraction were 4.5 T 0.8 cm and 58 T 18%, respectively. Both groups were similar in age, gender, weight, height, body mass index, left atrial diameter, duration of AF, ejection fraction, alcohol consumption, underlying aetiology and antiarrhythmic medication use.
Table 1 Patient demographics Protocol
A
B
p
n Female (%) Age (years) Height (cm) Weight (kg) Body mass index (kg/m2) Left atrial diameter (cm) Ejection fraction (%) Alcohol intake (units/week) Duration AF >6 months (%)
125 38 70 T 10 173 T 11 79 T 17 26 T 4 4.8 T 0.8 65 3 72
136 39 72 T 10 172 T 11 79 T 18 27 T 4 4.4 T 0.8 65 2 70
0.80 0.11 0.77 0.81 0.50 0.17 0.78 0.36 0.65
AF: atrial fibrillation.
L. Boodhoo et al. / International Journal of Cardiology 114 (2007) 16 – 21 p=0.03
Table 2 Aetiology and antiarrhythmic drug treatment Protocol Aetiology Hypertension Ischaemic heart disease Valvular heart disease Congestive cardiac failure Pulmonary Antiarrhythmic drug use Digoxin Class I (disopyramide, flecainide, propafenone) Class II (atenolol, bisoprolol) Class III (amiodarone, sotalol) Class IV (verapamil, diltiazem)
A (%)
B (%)
p
57 11 6 6 6
43 9 1 1 1
0.15 0.88 0.90 0.18 0.18
26 3 15 35 2
32 4 15 40 3
0.36 0.99 0.99 0.47 0.99
ns: non-significant.
Cumulative success (%)
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100 90 80 70 60 50 40 30 20 10 0
p=0.006 p
