European Journal Supplements (2003) 5 (Supplement H), H40—H44

Cardioversion of atrial : how and when? Downloaded from https://academic.oup.com/eurheartjsupp/article/5/suppl_H/H40/527907 by guest on 29 September 2021

Ph. Ricard, K. Yaïci, J.P. Rinaldi, M. Bergonzi and N. Saoudi Division of , Centre Hospitalier Princesse Grace, Monaco

Restoration of in patients with persistent (AF) can be KEYWORDS Antiarrhythmic agents; achieved either by pharmacological or electrical cardioversion. Pharmacological Anticoagulant therapy; cardioversion is effective especially when the duration of AF is short (<7 days). In Atrial fibrillation; contrast for long duration episodes external cardioversion is the technique of Biphasic waveform; choice. The success rate ranges from 64 to 96%. The development of new Electrical cardioversion defibrillators delivering shocks with biphasic waveforms is associated with a higher success rate with lower energies. For some patient who had failed external cardioversion, internal cardioversion should be proposed. One major concern is the prevention of embolic complications. For this purpose, long term (>3 weeks) anticoagulation with warfarin or short term anticoagulation with heparin when the presence of atrial thrombus has been ruled out by transoesophageal echocardiogram has been shown to be effective. © 2003 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved

Introduction serious adverse events, especially ventricular , can occur. In contrast, electrical CV Two different strategies are available in the has been shown to be safe and effective, and it is management of patients with persistent atrial therefore the technique of choice when AF is fibrillation (AF). The first consists of restoration persistent. It is important to recall that the and maintenance of sinus rhythm, whereas the prevention of embolic complications should be the second permits AF while controlling ventricular same whatever technique of CV is chosen. The rate. Although the superiority of the first strategy present review focuses on electrical CV of AF. relative to the other has not been clearly demonstrated,1,2 restoration of sinus rhythm is a desirable end-point. Reasons to prefer restoration Technical aspects of external and maintenance of sinus rhythm are the relief of cardioversion symptoms, prevention of induced cardiomyopathy and prevention of thromboembolic Several techniques of electrical CV have been complications. Cardioversion (CV) of AF can be described. Although external CV is the most achieved with the use of antiarrhythmic drugs or commonly used technique, internal CV can be with electrical shocks. Pharmacological CV is beneficial in some patients. Regardless of which widely used for AF of short duration (<7 days). Its technique is chosen, R-wave synchronization of efficiency is less than that of electrical CV, and shocks is mandatory to avoid induction of ventricular arrhythmias, which may occur if the Correspondence: Ph. Ricard, MD, Division of Cardiology, Centre shocks are delivered on the T wave. Knowledge of Hospitalier Princesse Grace, avenue Pasteur, Monaco the technical aspects of CV is important because (Principauté) 98000 they affect the success rate with shocks.

01520-765X/03/0H0040 + 05 $35.00/0 © 2003 The European Society of Cardiology, Published by Elsevier Science Ltd. All rights reserved. Cardioversion of atrial fibrillation: how and when? H41

A high-energy impulse of short duration is Table 1 Technical features affecting the success rate of delivered through the chest using two electrodes. external cardioversion The density of current reaching the heart depends Position and size of the electrodes on the electrical current delivered and on the Contact between skin and electrodes resistance of the heart, the rib cage and the skin. Pressure on electrodes Therefore, several technical factors are involved Energy and number of shocks delivered in the success of external CV (Table 1). Waveform of the shocks The position and size of the electrodes are Thoracic impedance (obesity, lung disease, etc.) crucial for optimal results. Two types of electrodes are available: paddles and self-adhesive Downloaded from https://academic.oup.com/eurheartjsupp/article/5/suppl_H/H40/527907 by guest on 29 September 2021 electrodes. The latter allow the choice of any the serum level of myocardial enzymes. However, position, especially anterior-posterior, with in a recent study in 72 patients given an average optimal contact between skin and electrodes, shock energy in excess of 400 J, the serum levels whereas the former makes it possible to apply of T and troponin I did not vary pressure on the electrodes. The optimal electrode significantly but the level of creatine kinase-MB size ranges from 8 to 12 cm.3 It has been shown increased after the shocks in 10% of the patients.9 that, when small electrodes are used, the current The increase in concentration of creatine kinase- density is 20 times greater between the paddles MB was correlated with the energy delivered. than at the margin of the heart.4 Therefore, this Most external defibrillators deliver a high current density between electrodes can monophasic damped sine waveform. However, induce myocardial injury. Alternatively, when the biphasic waveforms, in the implantable electrodes are too large the current density cardioverter—defibrillator, have been shown to be through the heart is too low to achieve CV. In a associated with lower thresholds as randomized controlled study of 301 patients, compared with the monophasic waveforms. Their Botto et al.5 compared an anterior-lateral paddle use for external CV has provided encouraging position (right infra-clavicular and ventricular results. Two types of biphasic waveforms are apex) with an anterior-posterior paddle position available for external CV: rectilinear and (sternum and left scapular). When high-energy truncated exponential (Fig. 1). Only three studies shocks (>4 J/kg) were delivered, the anterior- dealing with external CV with biphasic waveforms posterior location was associated with a higher have been published to date. In a prospective success rate (87%) than with the anterior-lateral single-centre study, Ricard et al.10 demonstrated position (76%). In contrast to this, Kerber et al.6 that a 150 J impedance-compensated exponential did not find any significant difference between biphasic waveform shock was more effective than these two positions. Because the superiority of a 150 J monophasic shock (success rate 86% vs one position compared with the other has not 59%; P = 0.02). If sinus rhythm was not restored, been clearly demonstrated, it is suggested that if then a second 150 J biphasic shock or a 360 J one position fails then the other should be tried. monophasic shock was delivered, resulting in a The energy and number of shocks delivered are cumulative percentage of patients in sinus rhythm important for optimal outcome. In a prospective of 96% for the biphasic group vs 92% for the study conducted in 198 patients, Ricard et al.7 monophasic group (no significant difference). A showed that the cumulative percentage of CV was double-blind prospective multicentre study 22% for shocks of 40—50 J, 48% for those of 80— demonstrated the superiority of the biphasic 100 J, 75% for those of 160—200 J and 96% for waveform for shocks with energies lower than 200 those of 360 J. Therefore, it is recommended that J (i.e. 100, 150 and 200 J).11 The cumulative one starts with a first shock of 200 J. This strategy percentages of patients in sinus rhythm after allows a high success rate while keeping completion of the protocol (200 J biphasic shock vs cumulative energies as low as possible. The reason 360 J monophasic shock) were 91% in the biphasic to select the lowest effective energy is that high- group and 85% in the monophasic group (no energy shocks may be associated with some significant difference). Rectilinear biphasic potential side effects. Experimental studies have waveform was used in the third study.12 The shown a clear relationship between high energies sequence of the shocks was 70, 120, 150 and 170 J and myocardial injury. For example, the for the biphasic group and 100, 200, 300 and 360 J deleterious haemodynamic effect of three shocks for the monophasic group. In that study the of 50 J is very low.8 This is in keeping with the cumulative success rates were 94% in the biphasic results of some clinical studies that showed either group and 79% in the monophasic group; in a transient ST-segment elevation or an increase in contrast to the two previous studies, the H42 Ph. Ricard et al.

(a) 100 Damped sine Exponential 80 v v 60

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Patients (%) Patients 20

0 Downloaded from https://academic.oup.com/eurheartjsupp/article/5/suppl_H/H40/527907 by guest on 29 September 2021 CV 1 min 2 weeks 1 year Duration (ms) Duration (ms) Time (b) Rectilinear Exponential Fig. 2 Proportion of patients in sinus rhythm after electrical cardioversion. (From Tieleman et al.16) v v 96%.7,14 This difference can be accounted for by differences in the patients studied and the definition of success. For example, in some studies the occurrence of at least two consecutive P waves is defined as success,11 whereas in others success means sinus rhythm 3 days after CV.15 The latter definition appears less accurate because it Duration (ms) Duration (ms) does not allow distinction between early recurrence of AF and failure of the technique. Fig. 1 1 (a) Monophasic and (b) biphasic waveforms available Although the success rate with CV is high, for external cardioversion and defibrillation. recurrence of AF is common, especially during the first 2 weeks following the procedure (Fig. 2).16 It is difference in this study was statistically significant estimated that early recurrence of AF, within 2 min (P = 0.005). In the study, 50% of the patients who after the shock, occurs in about 5—10% of cases. For received monophasic shocks without success were these reasons, several authors have proposed that successfully cardioverted with biphasic shocks. patients be treated with antiarrhythmic drugs Independent factors for successful CV were before CV. Pre-treatment with such drugs not only biphasic shocks, thoracic impedance and duration decreases the number of immediate recurrences but of AF. In addition, the biphasic waveform was also increases, in some cases, the success rate of CV. found to induce less dermal injury than did the For example, in a prospective study conducted in monophasic waveform. 100 patients, Bianconi et al.17 compared two pre- treatments (one with and the other with placebo) 48 h before the procedure. Although Clinical aspects of external the success rate of CV was not significantly different cardioversion between the groups (84% vs 82%), the percentage of patients in sinus rhythm 48 h after external CV was External CV is performed under general anaesthesia significantly greater in the propafenone group than using short-acting agents (such as propofol) so that in the placebo group. In another study, pre- recovery after the procedure is rapid. As mentioned treatment with 1 month before CV led above, R-wave synchronization is mandatory to to a rate of patients in sinus rhythm of 23% before avoid induction of ventricular , and the CV (vs 3% in the placebo group) and a rate of 88% energy of the first shock, if a monophasic waveform after CV (vs 65% in the placebo group).18 Finally, is used, should be 200 J. , a new class III drug, administered before In a large series of patients, Van Gelder et al.13 shock increased the rate of success (100% vs 72% in found, using multivariate analysis, that the the placebo group).19 After crossover, all patients following factors were predictive of success: who had failed external CV and who were pre- young age, short duration of AF and presence of treated with an ibutilide infusion were successfully . On the other hand, cardiomegaly, cardioverted during an additional series of shocks. enlargement of the left and underlying Therefore, pre-treatment with a class I or class III heart disease were associated with failure. antiarrhythmic drug before electrical external CV, Overall, the success rate of CV ranges from 64% to should be routine. Cardioversion of atrial fibrillation: how and when? H43

Complications associated with external internal CV was more effective than external CV, cardioversion and the rate of recurrence of AF was similar in both groups.14 This technique is no longer used, and low- Complications of external CV, such as systemic energy internal CV (<15 J) is preferred because it emboli, pulmonary oedema, hypotension, sinus removes the need for general anaesthesia — only arrest, or fibrillation, sedation is required. Two different techniques are myocardial injury and pacemaker dysfunction, are available. The first makes use of two catheters, one uncommon. However, their detection and positioned in the right atrium and the other in the prevention are mandatory. coronary sinus or in the left . In

The incidence of systemic emboli following the second technique a single catheter, holding two Downloaded from https://academic.oup.com/eurheartjsupp/article/5/suppl_H/H40/527907 by guest on 29 September 2021 external CV has been reported to range from 1% to coils located in the right atrium and in the left 7% in case—control studies when anticoagulation pulmonary, is used. Several studies have shown that was not used.20,21 Two strategies can be applied to low-energy internal CV is effective and safe. In a prevent embolic complications before and after CV population of patients, some of whom had failed when the duration of AF is longer than 48 h. In the external CV, the success rate ranged from 70% to first strategy, oral anticoagulation (to achieve an 92%, and no ventricular arrhythmia was induced international normalized ratio of 2.0—3.0) is given when the shocks were synchronized on the R wave for 3—4 weeks before the shock.22 More recently, a and when the RR interval preceding the shock was new transoesophageal guided greater than 500 ms.24,25 In a prospective strategy based on a short period of anticoagulation multicentre randomized study of 141 patients, the with heparin and detection of intra-cardiac thrombi defibrillation threshold was significantly lower in was proposed. A multicentre study comparing the the group with paroxysmal AF than in the group two strategies in 1222 patients was conducted.23 with chronic AF (2.0 J vs 3.6 J; P < 0.05).24 In a The two strategies resulted in similar incidences of recent study, Ricard and Lévy26 compared the stroke (0.50% in the conventional group vs 0.81% in single-catheter technique with the two-catheter the transoesophageal echocardiography group). technique and found that the duration of the Because recovery of mechanical function of the procedure was significantly shorter with the former atrium can be delayed for several weeks after than with the latter. They suggested that the single- restoration of sinus rhythm, it is recommended that catheter technique was more practical and time oral anticoagulation be continued for at least efficient. Because the biphasic waveform is 4 weeks after CV. The recommendations for available for external CV, it is likely that the prevention of embolic complications are applicable number of patients treated with internal CV will whichever technique of CV is chosen (pharmaco- decrease in the future. Indications for internal CV logical, or electrical external or internal). are failure of external CV and possibly the presence Dysfunction of pacemakers or implantable of emphysema, obesity, pacemaker or defibrillator, defibrillators can be induced by external CV. or drug infusion pumps, or when general Measures to prevent such complications should be anaesthesia is contraindicated. undertaken routinely. The two most common complications are changes in the programming of the device and exit block resulting in loss of ventricular capture. Therefore, the anterior- Indications for electrical cardioversion posterior position of the electrodes should be of atrial fibrillation preferred over the anterior-lateral position because the current density reaching the device is lower Because the strategy for the management of with the former. When the patient is dependent on patients with AF is still a matter of debate, the pacemaker, temporary pacing is mandatory. indications for CV of AF may vary between centres. Examination of the device should be performed We propose that CV be performed in the following before and after CV. situations: • first AF episode of duration more than 48 h; • chronic or paroxysmal AF (duration >48 h) in Internal electrical cardioversion highly symptomatic patients; • chronic or paroxysmal AF (duration >48 h) in Internal CV of AF was first performed using high- patients with a previous complication of AF; and energy shocks (>200 J) delivered between an • AF due to myocardial infarction, angina, or heart electrode positioned in the right atrium and a back failure that does not respond to pharmacological plate. A prospective randomized study showed that therapy. H44 Ph. Ricard et al.

CV is possible but not mandatory in the following 8. Ditchey RV, Le Winter MM. Effects of direct-current electri- situations: cal shocks on systolic and diastolic left ventricular function • AF with duration less than 48 h when in dogs. Am Heart J 1983;105:727—31. 9. Lund M, French JK, Johnson RN, et al. Serum troponin T and haemodynamic tolerance is good; I after elective cardioversion. Eur Heart J 2000;21:245—53. • frequent recurrences (more than three within 10. Ricard P, Lévy S, Boccara G, et al. External cardioversion of 6 months) despite the use of antiarrhythmic atrial fibrillation: comparison of biphasic versus monopha- drugs; and sic waveform shocks. Europace 2001;3:96—9. • chronic AF in asymptomatic patients. 11. Page RL, Kerber RE, Russel JK, et al. Biphasic versus monophasic shock waveform for conversion of atrial fibrilla- CV is not indicated or contraindicated in the tion: the results of an international randomized, double-blind following cases: multicenter trial. J Am Coll Cardiol 2002;39:1956—63. Downloaded from https://academic.oup.com/eurheartjsupp/article/5/suppl_H/H40/527907 by guest on 29 September 2021 • hyperthyroidism; 12. Mitall S, Ayati S, Stein KM, et al. Transthoracic cardiover- • acute infection or inflammatory diseases; sion of atrial fibrillation: comparison of rectilinear biphasic • digitalis toxicity; versus damped sine wave monophasic shocks. Circulation 2000;101:1282—7. • hypokalaemia; 13. Van Gelder IC, Crijns HJ, Van Gilst WH, Werver D, Lie KI. • non-compensated heart failure (except Prediction of uneventful cardioversion and maintenance of emergency situations); sinus rhythm for direct-current electrical cardioversion of • contraindication to general anaesthesia; chronic atrial fibrillation and flutter. Am J Cardiol 1991; • left atrial thrombus; 68:41—6. 14. Lévy S, Lauribe P, Dolla E, et al. A randomized comparison • severe chronic alcoholic intoxication; of external and internal cardioversion of chronic atrial fib- • life expectancy <1 year in asymptomatic rillation. Circulation 1992;86:1415—20. patients; and 15. Lundstrom T, Ryden L. Chronic atrial fibrillation. Long-term • paroxysmal AF with very frequent episodes. results of direct current cardioversion. Acta Med Scand 1988;223:53—9. 16. Tieleman RG, Van Gelder IC, Crijns HJ, et al. Early recur- rences of atrial fibrillation after electrical cardioversion: a Conclusion result of fibrillation-induced electrical remodeling of the atria? J Am Coll Cardiol 1998;31:167—73. AF is the most common arrhythmia and the 17. Bianconi L, Mennumi M, Luckic V, et al. Effect of oral strategy for its management remains a matter of propafenone administration before electrical cardioversion of chronic atrial fibrillation: a placebo-controlled study. J debate. Electrical CV is widely used to restore Am Coll Cardiol 1996;28:700—6. sinus rhythm and has been shown to be safe and 18. Capucci A, Villani GQ, Aschieri D, et al. Oral amiodarone effective. Biphasic waveforms have been increases the efficacy of direct-current cardioversion in introduced for external CV and represent an restoration of sinus rhythm in patients with chronic atrial important breakthrough in the field. fibrillation. Eur Heart J 2000;21:66—73. 19. Oral H, Souza JJ, Michaud GF, et al. Facilitating transtho- racic cardioversion of atrial fibrillation with ibutilide pre- References treatment. N Engl J Med 1999;340:1849—54. 1. Planning and Steering Committees of the AFFIRM study for 20. Bjerkelund CJ, Orning OM. The efficacy of anticoagulant the NHLBI AFFIRM investigators. Atrial fibrillation follow-up therapy in preventing embolism related to D.C. electrical investigation of rhythm management: the AFFIRM study cardioversion of atrial fibrillation. Am J Cardiol 1969;23: design. Am J Cardiol 1997;79:1198—202. 208—16. 2. Hohnloser SH, Kuck KH, Lilienthal J. Rhythm or rate control 21. Arnold AZ, Mick MJ, Mazurek RP, et al. Role of prophylactic in atrial fibrillation—Pharmacological Intervention in Atrial anticoagulation for direct current cardioversion in patients Fibrillation (PIAF): a randomised trial. Lancet 2000;356: with atrial fibrillation or atrial flutter. J Am Coll Cardiol 1789—94. 1992;19:851—5. 3. Ewy GA. The optimal technique for electrical cardioversion 22. Hart RG, Halperin JL. Atrial fibrillation and thromboem- of atrial fibrillation. Clin Cardiol 1994;17:79—84. bolism: a decade of progress in stroke prevention. Ann 4. Peleaka B. A high voltage defibrillator and the theory of Intern Med 1999;131:688—95. high voltage defibrillation. In: Proceedings of the Third 23. Klein AL, Grimm RA, Murray RD, et al. Use of transesophageal International Conference of Medical Electronics. Charles C echocardiography to guide cardioversion in patients with Thomas, Springfield. 1960:265. atrial fibrillation. N Engl J Med 2001;344:1411—20. 5. Botto GL, Politi A, Bonini W, et al. External cardioversion of 24. Lévy S, Ricard P, Lau CP, et al. Multicenter low energy atrial fibrillation: role of paddle position on technical effi- transvenous atrial defibrillation (XAD) trial results in dif- cacy and energy requirements. Heart 1999;82:726—30. ferent subsets of atrial fibrillation. J Am Coll Cardiol 1997; 6. Kerber RE, Jensen SR, Grayzel J, et al. Elective cardiover- 29:750—5. sion: influence of paddle-electrode location and size on 25. Ricard P, Socas AG, Taramasco V, Guenoun M, Levy S. success rate and energy requirements. N Engl J Med 1981; Cardioversion of atrial fibrillation with low energy internal 305:658—62. shocks. Arch Mal Coeur 1997;90:1605. 7. Ricard P, Lévy S, Trigano J, et al. Prospective assessment of 26. Ricard P, Lévy S. A randomized comparison of a single the minimum energy needed for external electrical car- catheter technique versus the conventional two catheter dioversion of atrial fibrillation. Am J Cardiol 1997;79:815— technique for low energy internal cardioversion of atrial 16. fibrillation [abstract]. Eur Heart J 2000;21:730.