Journal of Interventional Cardiac Electrophysiology 9, 229–233, 2003  C 2003 Kluwer Academic Publishers. Manufactured in The Netherlands. Atrial Fibrillation: The Role of Atrial Defibrillation Massimo Santini and Renato Ricci Department of Cardiology, San Filippo Neri Hospital, Via Martinotti, 20, 00135 Rome, Italy Abstract. Dual defibrillator implantation represents an emerging option to treat patients with drug refractory atrial fibrillation. Atrial antitachycardia pacing and cardioversion have been demonstrated to be highly effective in treating spontaneous tachyarrhythmias and may reduce atrial fibrillation burden by preventing atrial remodeling. Device implantation has been associated to improved quality of life and reduced hospitalization rate. Patient selection and tailored device programming are critical as regard to clinical outcome. Individual psychological profile analysis as well as underlying heart disease and atrial fibrillation clinical patterns represent the main drivers for the right strategy. Controlled studies are needed in order to define the subset of patients who can benefit more from device implantation. Key Words. atrial fibrillation, atrial defibrillator, dual chamber defibrillator, internal cardioversion, shock tolerance Introduction Atrial fibrillation is the most common arrhythmia in clinical practice and its incidence is increasing due to the aging of the population. The arrhythmia is associated to increased hospitalizations [1], higher mortality [2], heart failure, acute myocardial infarction, stroke [3] and quality of life impairment [4]. Due to limited and usually temporary efficacy of antiarrhythmic drugs [5], several non pharmacological therapies have been developed to treat drug refractory atrial fibrillation. The Dual Defibrillator The dual defibrillator combines the features of conventional dual chamber defibrillators with the capability of preventing, detecting and treating supraventricular tachyarrhythmias. It has been demonstrated to be effective in patients with conventional indication for defibrillator implantation [6–8]. Efficacy of antitachycardia pacing on regular atrial tachycardia has been reported to be as high as 50–70% and efficacy of high frequency burst as high as 20–30% on atrial fibrillation. Shock success rate approached 90% and strongly depended on appropriate programming of deliv- ered energy. Atrial therapies were associated to significant reduction of arrhythmia duration and reduced atrial fibrillation burden [9]. The Dual Defibrillator for Drug Refractory Atrial Fibrillation Hundred and forty-six patients with drug refractory atrial fibrillation without any prior ventricular tachyarrhythmia have been enrolled in the Worldwide Jewel AF-Only Trial [10]. During one-year follow-up, 4913 treated episodes were available for stored electrogram analysis and therapy efficacy evaluation. Appropriate atrial tachyarrhythmia detection was near 100%. It is worthwhile to stress that the atrial arrhythmia detected at very early onset was very commonly a well organized atrial tachycardia. In the AF-Only group, among 3116 episodes treated by antitachy pacing, 67% were classified as atrial tachycardia. Considering that slower and regular arrhythmias can be more easily treated by pacing techniques, early delivery of atrial antitachycardia pacing may increase success rate and prevent the need for atrial shock. Very few data are available about cost effectiveness of dual defibrillator implantation in patients without ventricular tachyarrhythmias. Data from ongoing trials, reported only as abstracts [11,12], in which patients with drug refractory, paroxysmal or persistent atrial fibrillation, with or without sinus bradycardia, were enrolled, showed a favourable impact of defibrillator implantation on hospitalisations and quality of life, if evaluated by using the Symptom Checklist/Frequency and Severity Scale and SF-36 questionnaire. Early delivery of atrial shock after atrial fibrillation onset may prevent atrial remodeling [13], induced by long lasting atrial tachyarrhythmias. Prevention of atrial remodeling may increase sinus rhythm periods, may reduce atrial Address for correspondence: Massimo Santini, Department of Cardiology, San Filippo Neri Hospital, Via Martinotti, 20, 00135 Rome, Italy. E-mail: m.santini@rmnet.it; renatopietroricci@tin.it Received 28 October 2003; accepted 20 February 2003 229 230 Santini and Ricci fibrillation burden in the long-term follow-up and may avoid permanent atrial fibrillation development. Preliminary data from stand-alone atrial defibrillator experience [14,15] showed a progressive reduction of atrial fibrillation episode number and burden during the follow-up. In the Jewel “AF only” study [10], after 1-year follow-up 94% of patients were in sinus rhythm and device therapy was active in 91.3%. Reversal of tachycardiomyopathy to normal left ventricular function has been reported after atrial defibrillator implantation [16]. In this setting atrial defibrillation play a critical role and programming of atrial shocks is a major task to be dealt with. In particular timing, energy, configuration and mode (automatic, manual in-hospital or self activated) of atrial shocks need individual tailoring and careful analysis of patient clinical and psychological status. Psychological Issues Quality of life, psychological well being and patient acceptance have been studied in patients receiving implanted cardioverter-defibrillators for ventricular life-threatening and atrial arrhythmias [17]. These studies demonstrated that the patients with paroxysmal atrial fibrillation have the worst quality of life, due to intolerable symptoms, and that women had worse quality of life in comparison with men. Highly symptomatic patients who have less than one arrhythmia episode per month are likely to find acceptable shock related pain, while those who have the tendency to amplify benign symptoms, usually do not accept shocks. Psychologically distressed patients may have worse scores on the majority of quality of life scales and usually show less treatment satisfaction and more negative attitudes. It has been demonstrated in patients wearing a defibrillator that quality of life scores inversely correlated with anxiety and depression [18] and that as far as shock number increased, the percentage of psychologically distressed patients rose from 10 to 50% [19]. Shock Tolerance As regard to energy programming, we observed that shock tolerance was weakly related to the delivered energy and strongly depending on the number of atrial shocks and on their efficacy in restoring sinus rhythm [7]. This finding is consistent with the studies on shock tolerance performed during endocavitary low energy cardioversion [20]. According to that, in symptomatic atrial tachyarrhythmias success probability should be the main driver to select optimal shock energy programming, since the success itself is the main determinant of patient compliance. Setting the initial shock energy at too low level may lead to persistence of severe symptoms combined with unacceptable pain. This data has been recently confirmed by Steinhaus et al. [21] who demonstrated that patients wearing a defibrillator could not distinguish differences in discomfort between shocks of 0.4 and 2 J, but perceived the second shock as more painful than the first, regardless of the energy delivered. It is worth noting that also a low energy shock of 0.4 J may be supramaximal for the activation of pain fibers and skeletal muscle contraction. As a consequence, further attempts at reducing defibrillation threshold may not be followed by increased patient tolerance. The Authors stressed the point that, in spite of discomfort involved, the majority of patients would tolerate low energy internal shocks if delivered not more frequently than once a month. Patient Selection In our opinion, from the clinical point of view, the best candidate for shock therapy should have these characteristics: – paroxysmal or persistent atrial fibrillation with very uncomfortable and debilitating symptoms (more than 24 hours without returning in sinus rhythm); – heart failure symptoms development; – drug refractoriness or intolerance (two or more drugs, including amiodarone); – need for frequent electrical cardioversions (more than one in the previous year); – high probability after the procedure to remain in sinus rhythm for a reasonable period of time. The last point is the most difficult to be defined. Heart failure, valvular heart disease, left atrial dysfunction as well as prior repetitive cardioversion with short-term recurrence of the arrhythmia should identify the patients with low probability of remaining in sinus rhythm. As a matter of fact, no conclusive data is available in this field. From the psychological point of view, the “ideal patient” should be an active person, without any significant past/present psychological distress (i.e. depression or high anxiety), able to understand his disease and the device with its risks and benefits. He should be ready to accept a device that shocks him for a non-life threatening condition. Recommendations in Atrial Defibrillator Setting As far as shock delivery mode is concerned, three options are available: