The 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society Comprehensive guidelines for the management of Atrial Fibrillation

The Canadian Cardiovascular Society (CCS) atrial fibrillation (AF) guidelines program was developed to aid clinicians in the management of these complex patients, as well as to provide direction to policy makers and health care systems regarding related issues. The most recent comprehensive CCS AF guidelines update was published in 2010. Since then, periodic updates were published dealing with rapidly changing areas. However, since 2010 a large number of developments had accumulated in a wide range of areas, motivating the committee to complete a thorough guideline review. The 2020 iteration of the CCS AF guidelines represents a comprehensive renewal that integrates, updates, and replaces the past decade of guidelines, recommendations, and practical tips. It is intended to be used by practicing clinicians across all disciplines who care for patients with AF. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system was used to evaluate recommendation strength and the quality of evidence. Areas of focus include: AF classification and definitions, epidemiology, pathophysiology, clinical evaluation, screening and opportunistic AF detection, detection and management of modifiable risk factors, integrated approach to AF management, stroke prevention, arrhythmia management, sex differences, and AF in special populations. Extensive use is made of tables and figures to synthesize important material and present key concepts. This document should be an important aid for knowledge translation and a tool to help improve clinical management of this important and challenging arrhythmia.

Le programme de lignes directrices de la Société canadienne de cardiologie (SCC) en matière de fibrillation auriculaire (FA) a été élaboré pour aider les cliniciens à prendre en charge ces patients complexes, ainsi que pour orienter les décideurs politiques et les systèmes de soins de santé sur des questions connexes. La dernière édition complète des lignes directrices de la SCC en matière de FA a été publiée en 2010. Depuis lors, des mises à jour périodiques ont été publiées, traitant de domaines en évolution rapide. Cependant, en 2020, un grand nombre de développements s'y étaient ajoutés, couvrant un large éventail de domaines, ce qui a motivé le comité à créer une refonte complète des lignes directrices. L'édition 2020 des lignes directrices de la SCC en matière de FA représente un renouvellement complet qui intègre, met à jour et remplace les lignes directrices, les recommandations et les conseils pratiques des dix dernières années. Elle est destinée à être utilisée par les cliniciens praticiens de toutes les disciplines qui s'occupent de patients souffrant de FA. L'approche GRADE (Gradation des Recommandations, de l'Appréciation, du Développement et des Évaluations) a été utilisée pour évaluer la pertinence des recommandations et la qualité des résultats. Les domaines d'intérêt incluent : la classification et les définitions de la FA, son épidémiologie, sa physiopathologie, l'évaluation clinique, le dépistage de la FA, la détection et la gestion des facteurs de risque modifiables, l'approche intégrée de la gestion de la FA, la prévention des accidents vasculaires cérébraux, la gestion de l'arythmie, les différences entre les sexes et la FA dans des populations particulières. Des tableaux et figures ont été largement utilisés pour synthétiser les éléments importants et présenter les concepts clés. Ce document devrait représenter une aide importante pour l'intégration des connaissances et un outil pour aider à améliorer la gestion clinique de cette arythmie importante et difficile à traiter.

2016 Focused Update of the Canadian Cardiovascular Society Guidelines for the Management of Atrial Fibrillation

The Canadian Cardiovascular Society (CCS) Atrial Fibrillation (AF) Guidelines Committee provides periodic reviews of new data to produce focused updates that address clinically important advances in AF management. This 2016 Focused Update deals with: (1) the management of antithrombotic therapy for AF patients in the context of the various clinical presentations of coronary artery disease; (2) real-life data with non-vitamin K antagonist oral anticoagulants; (3) the use of antidotes for the reversal of non-vitamin K antagonist oral anticoagulants; (4) digoxin as a rate control agent; (5) perioperative anticoagulation management; and (6) AF surgical therapy including the prevention and treatment of AF after cardiac surgery. The recommendations were developed with the same methodology used for the initial 2010 guidelines and the 2012 and 2014 Focused Updates. Using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) standards, individual studies and literature were reviewed for quality and bias; the literature review process and evidence tables are included in the Supplementary Material, and on the CCS Web site. The section on concomitant AF and coronary artery disease was developed in collaboration with the CCS Antiplatelet Guidelines Committee. Details of the updated recommendations are presented, along with their background and rationale. This document is linked to an updated summary of all CCS AF Guidelines recommendations, from 2010 to the present 2016 Focused Update

Role of genetic testing in arrhythmogenic right ventricular cardiomyopathy/dysplasia.

In a cohort of patients with confirmed or suspected arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), genetic testing is useful in confirming the diagnosis, particularly in individuals who do not completely fulfil Task Force criteria for the disease, thereby also enabling the adoption of preventive measures in family members. Due to the high percentage of novel mutations that are expected to be identified in ARVC/D, the use of genetic screening technology based on the identification of known mutations seems to have very restricted value. Our results support that the presence of certain genetic variations could play a role in the final phenotype of patients with ARVC/D, where single and compound mutation carriers would have more symptomatic forms of the disease and the polymorphism P366L could be associated to a more benign phenotype.

Rationale and design of ACTIVE: the atrial fibrillation clopidogrel trial with irbesartan for prevention of vascular events.

BACKGROUND: Atrial fibrillation (AF) is the most frequently occurring cardiac arrhythmia with often serious clinical consequences. Many patients have contraindications to anticoagulation, and it is often underused in clinical practice. The addition of clopidogrel to aspirin (ASA) has been shown to reduce vascular events in a number of high-risk populations. Irbesartan is an angiotensin receptor-blocking agent that reduces blood pressure and has other vascular protective effects. METHODS AND RESULTS: ACTIVE W is a noninferiority trial of clopidogrel plus ASA versus oral anticoagulation in patients with AF and at least 1 risk factor for stroke. ACTIVE A is a double-blind, placebo-controlled trial of clopidogrel in patients with AF and with at least 1 risk factor for stroke who receive ASA because they have a contraindication for oral anticoagulation or because they are unwilling to take an oral anticoagulant. ACTIVE I is a partial factorial, double-blind, placebo-controlled trial of irbesartan in patients participating in ACTIVE A or ACTIVE W. The primary outcomes of these studies are composites of vascular events. A total of 14000 patients will be enrolled in these trials. CONCLUSIONS: ACTIVE is the largest trial yet conducted in AF. Its results will lead to a new understanding of the role of combined antiplatelet therapy and the role of blood pressure lowering with an angiotensin II receptor blocker in patients with AF.

Amiodarone reduces procedures and costs related to atrial fibrillation in a controlled clinical trial.

BACKGROUND: Atrial fibrillation is the most common sustained cardiac arrhythmia, and engenders significant health care costs. The impact of various treatment options for atrial fibrillation on hospital costs has not been evaluated in a randomized trial. METHODS: We analysed 1-year follow-up data on 392 patients randomized to low dose amiodarone (200 mg. day(-1)) or alternative first-line therapy (sotalol or propafenone) in a multicentre trial (Canadian Trial of Atrial Fibrillation, CTAF). RESULTS: Patients in the amiodarone group had fewer electrical cardioversions (65 vs 109 for patients in the sotalol/propafenone group, P<0.0001), and pacemaker insertions (4 vs 11, P=0.07). The average amiodarone patient spent fewer days in hospital (0.47 vs 0.97, P=0.01), and incurred lower costs ($532 vs $898, P=0.03), for admissions where atrial fibrillation was the admitting diagnosis. Average total hospital costs per patient for all admissions, as well as average combined hospital and physician costs per patient, showed wide variations within the treatment arms and were not significantly different between groups. CONCLUSION: For patients in whom antiarrhythmic drug therapy is indicated, low dose amiodarone significantly reduces atrial fibrillation-related costs by reducing the number of atrial fibrillation-related procedures.

Atrioventricular interval optimization and exercise tolerance.

Modern pacemakers offer many programming options regarding the AV interval including the ability to vary AV intervals depending on whether atrial activity is paced or spontaneous and to shorten AV intervals with increasing rates. To determine if optimization of these features improves exercise tolerance, 14 patients with intact sinus node function and AV block treated with dual chamber pacemakers were enrolled in a randomized double-blind crossover trial. Doppler echocardiographic measurements of cardiac index and mitral flow were assessed over a range of programmable AV intervals at rest to determine each patient's optimal AV interval. Eleven patients completed serial graded exercise tests with spiroergometry after randomly programming the AV interval three ways in a crossover manner: fixed AV interval = 150 ms without rate adaptation (150/Fixed), fixed AVinterval = 150 ms with rate adaptation (150/R), or optimized AV interval with rate adaptive AV interval shortening (optimized/R). Exercise capacity was determined by maximum oxygen uptake. Ten men and four women, age 64 +/- 8 years, were enrolled. At rest, optimization of the AVintervalimproved the cardiac index by 21% (P < 0.001) and mitral flow by 13.4% (P < 0.001) when compared to least-favorable AV intervals. During exercise, no differences in maximum heart rates were noted. Maximum oxygen uptake was increased in both groups with rate adaptive AVinterval shortening when compared tofixed AVinterval without rate adaptation: 13.9% (adjusted P < 0.04) and 14.6% (adjusted P < 0.02) in optimized/R and 150/R, respectively. No differences were noted between optimized/R and 150/R. In conclusion, rate adaptive AV interval shortening improved exercise tolerance independent of changes in heart rate. However, optimization of the AV interval with Doppler echocardiography at rest did not further improve exercise capacity.

Antiarrhythmic drug therapy in the Multicenter UnSustained Tachycardia Trial (MUSTT): drug testing and as-treated analysis.

OBJECTIVES: Using data from the Multicenter UnSustained Tachycardia Trial (MUSTT), we examined the factors used to select antiarrhythmic drug therapy and their impact on outcomes. BACKGROUND: The MUSTT examined the use of programmed ventricular stimulation (PVS) to guide antiarrhythmic therapy in patients with coronary arteriosclerosis, left ventricular dysfunction and asymptomatic, unsustained ventricular tachycardia (VT). Trial outcomes may reflect factors used to select antiarrhythmic drug therapy. METHODS: We compared subgroups of patients with inducible sustained VT randomized to PVS-guided antiarrhythmic therapy (n = 351), in particular those receiving PVS-guided antiarrhythmic drug therapy (n = 142) versus no antiarrhythmic therapy (controls, n = 353). RESULTS: "Effective" antiarrhythmic drug therapy (i.e., the term "effective" was used to denote therapy that resulted in noninducible VT or hemodynamically stable induced VT) was found for 142 of the 351 patients (43%), most often at the first or second PVS session (125/142, 88%). Mortality among the 142 patients did not differ from that among control patients. Of these 142 patients, the PVS end point was noninducibility in 91 patients and stable VT in 51 patients. Mortality did not differ between these two groups either, but arrhythmia was numerically more frequent in the PVS-induced stable VT group. Mortality was greatest in the few patients receiving propafenone (unadjusted p = 0.07, adjusted p = 0.14 vs. controls), but mortality with all agents did not differ from that of controls, even after adjustment. CONCLUSIONS: Even when presenting the results as favorably as possible, we found no benefit with PVS-guided drug therapy in patients with clinical unsustained VT who had inducible sustained VT. These findings are unaltered by using different end points for PVS or considering the response to individual drugs.

Relationship between pacemaker dependency and the effect of pacing mode on cardiovascular outcomes.

BACKGROUND: A recently completed trial, the Canadian Trial of Physiological Pacing (CTOPP), showed that physiological pacing did not significantly reduce mortality, stroke, or heart failure hospitalization, but it did show that atrial fibrillation occurred less frequently in patients with physiological pacing. Many pacemaker patients experience only transient bradyarrhythmias with an adequate unpaced heart rate (UHR) and are not pacemaker-dependent. The purpose of the present analysis was to determine if pacemaker-dependent patients have an increased benefit from physiological pacing compared with non-pacemaker-dependent patients. METHODS AND RESULTS: Of 2568 patients included in the CTOPP trial, 2244 patients had a pacemaker dependency test performed at the first follow-up visit. The yearly event rate of cardiovascular death or stroke steadily increased with decreasing UHR in the ventricular pacing group, but it remained constant in the physiological pacing group. When the patients were subdivided to UHR 60 bpm, there was an interaction between pacing mode treatment and UHR subgroup. The Kaplan-Meier plot confirmed a physiological pacing advantage only in the UHR

Catheter cryoablation of the atrioventricular node in patients with atrial fibrillation: a novel technology for ablation of cardiac arrhythmias.

INTRODUCTION: Recent animal studies demonstrated the feasibility and safety of applying percutaneous catheter cryoablation technology for ablation of arrhythmogenic sites. The studies also showed that reversible "ice mapping" can be performed before creating permanent lesions. We investigated the feasibility and safety of applying this new technology in man. METHODS AND RESULTS: Cryoablation of the AV node (AVN) using a 9-French quadripolar catheter with a 4-mm electrode tip was attempted in 12 patients (mean age 67.8 +/- 11.4 years) with refractory atrial fibrillation. Whereas technical issues prevented adequate tissue contact in two patients, complete AVN block was obtained in the remaining 10 patients after 4.8 +/- 1.9 cryoapplications lasting 5.5 +/- 0.2 minutes resulting in temperatures of -58.1 degrees +/- 5.4 degrees C. In all patients with sinus rhythm at the time of the procedure, cryomapping at warmer temperatures induced reversible AVN block and allowed confirmation of a successful site before definitive ablation. Intracardiac echocardiography was performed in three patients and allowed visualization of the cryocatheter-endocardial contact and cryolesion formation. No major procedural complications were reported. After 6 months of follow-up, 8 of 10 initially successful patients remained in complete block; 1 had partial recovery of AVN conduction manifested by atrial fibrillation with a slow ventricular response, and 1 fully recovered AVN conduction. CONCLUSION: (1) Catheter cryoablation of the AVN can be performed safely in man. (2) Reversible cryomapping is feasible and may offer an advantage over radiofrequency ablation. (3) Cryocatheter-endocardial contact and cryolesion growth can be monitored with intracardiac echocardiography.

New-onset atrial fibrillation: sex differences in presentation, treatment, and outcome.

BACKGROUND: Although sex differences in coronary artery disease have received considerable attention, few studies have dealt with sex differences in the most common sustained cardiac arrhythmia, atrial fibrillation (AF). Differences in presentation and clinical course may dictate different approaches to detection and management. We sought to examine sex-related differences in presentation, treatment, and outcome in patients presenting with new-onset AF. METHODS AND RESULTS: The Canadian Registry of Atrial Fibrillation (CARAF) enrolled subjects at the time of first ECG-confirmed diagnosis of AF. Participants were followed at 3 months, at 1 year, and annually thereafter. Treatment was at the discretion of the patients' physicians and was not directed by CARAF investigators. Baseline and follow-up data collection included a detailed medical history, clinical, ECG, and echocardiographic measures, medication history, and therapeutic interventions. Three hundred thirty-nine women and 560 men were followed for 4.14+/-1.39 years. Compared with men, women were older at the time of presentation, more likely to seek medical advice because of symptoms, and experienced significantly higher heart rates during AF. Compared with older men, older women were half as likely to receive warfarin and twice as likely to receive acetylsalicylic acid. Compared with men on warfarin, women on warfarin were 3.35 times more likely to experience a major bleed. CONCLUSIONS: Anticoagulants are underused in older women with AF relative to older men with AF, despite comparable risk profiles. Women receiving warfarin have a significantly higher risk of major bleeding, suggesting the need for careful monitoring of anticoagulant intensity in women.

The class III antiarrhythmic drugs dofetilide and sotalol prevent AF induction by atrial premature complexes at doses that fail to terminate AF.

BACKGROUND: Clinical trials suggest that sotalol and dofetilide are much more effective in preventing atrial fibrillation (AF) than in terminating it. This study evaluated potential mechanisms of discordant sotalol and dofetilide effects on AF termination vs. prevention. METHODS: We applied 240-electrode epicardial mapping and programmed stimulation in a vagotonic dog model of AF before and after dofetilide or sotalol. RESULTS: Under control conditions, sustained AF could be induced by single S(2) extrastimuli that caused unidirectional block and macroreentry. Sotalol (2 mg/kg) and dofetilide (0.04 mg/kg) failed to terminate AF in any dog, but prevented AF induction by S(2) stimuli in 19/22 (86%) and 4/5 (80%) of animals, respectively. With sotalol and dofetilide, unidirectional block still occurred, but wavefront reentry failed. The prevention of S(2)-induced reentry was related to large increases in the effective refractory period (ERP) at a BCL of 1000 ms, leading to ERPs that exceeded the conduction delay following S(2). Reverse use-dependent effects resulted in smaller ERP increases at BCLs closer to the AF cycle length. Although the number of zones of reactivation per cycle during sustained AF were decreased by sotalol and dofetilide, the changes were small and insufficient to terminate AF. CONCLUSIONS: Sotalol and dofetilide prevent AF initiation by premature depolarizations at doses that fail to terminate vagotonic AF, by increasing ERP at the basic cycle length beyond the associated conduction delay that leads to reentry.

Role of gender and personality on quality-of-life impairment in intermittent atrial fibrillation.

Patients with atrial fibrillation (AF) report impaired health-related quality of life (QOL). Differences between men and women with AF have not been described and personality attributes such as somatization (tendency to amplify benign bodily sensations) may mediate potential gender differences in QOL. Patients with AF (n = 264, 59% men) who participated in the Canadian Trial of Atrial Fibrillation (n = 403) completed validated QOL questionnaires at baseline, 3 months, and 12 months after antiarrhythmic drug treatment. Women were significantly older than men and a greater proportion had hypertension, but other cardiac variables did not differ between women and men. At baseline, after controlling for significant clinical and demographic factors, women reported worse physical health (p = 0.002) and functional capacity (p < 0.001), but not mental health or general well-being. Women also had more frequent and severe cardiac symptoms than men (both p < 0.001). Physical health improved significantly from baseline to 3 months for women (p = 0.002), but not for men (p = 0.066). Conversely, mental health improved for men (p = 0.007), but not for women. Cardiac symptom frequency and severity improved over time for women and men (all p < 0.001). Tendency to somatize predicted poor QOL, and women had higher scores than men (p = 0.023). However, after controlling for somatization, women still had worse physical function, functional capacity, and symptom burden than men. Independent of cardiac disease severity and age, women with AF had significantly more impaired QOL than men, specifically on domains related to physical rather than emotional functioning. Personality attributes may have a role in influencing QOL outcomes.

Depression and health-care costs during the first year following myocardial infarction.

OBJECTIVE: Depression in the hospital after myocardial infarction (MI) has been associated with a substantial increase in the long-term risk of cardiac mortality, but little is known about other outcomes. This study uses Quebec Medicare data to examine the relationship between post-MI depression and physician costs, including both out-patient care and hospital readmissions. METHODS: The sample consists of 848 1-year survivors of an acute MI who had completed the Beck Depression Inventory (BDI) in hospital. Two hundred sixty subjects had BDI scores of >/=10 (30.7%), indicative of mild to moderate symptoms of depression. Quebec Medicare data during the index admission for an acute MI and during the year following discharge were compared for the patients with elevated BDI scores and those with normal scores. RESULTS: Total costs, in Canadian dollars (out-patient physician charges plus physician costs during admissions plus estimates of associated direct costs), were about 41% higher (p = 0.004) for patients with elevated BDI scores. The difference was primarily related to out-patient and emergency room visits and readmission costs associated with longer stays in hospital wards, and was not accounted for by use of psychiatric services or readmissions for revascularization. CONCLUSION: Results suggest that, in addition to the survival risks associated with post-MI depression, there are increased health care costs linked to both readmissions and out-patient contacts among depressed patients who survive the first post-MI year. The extent to which the increased use of health care may have reduced depression and enhanced survival remains unclear.

Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death. Multicenter Unsustained Tachycardia Trial Investigators.

BACKGROUND: The mortality rate among patients with coronary artery disease, abnormal ventricular function, and unsustained ventricular tachycardia is high. The usefulness of electrophysiologic testing for risk stratification in these patients is unclear. METHODS: We performed electrophysiologic testing in patients who had coronary artery disease, a left ventricular ejection fraction of 40 percent or less, and asymptomatic, unsustained ventricular tachycardia. Patients in whom sustained ventricular tachyarrhythmias could be induced were randomly assigned to receive either antiarrhythmic therapy guided by electrophysiologic testing or no antiarrhythmic therapy. The primary end point was cardiac arrest or death from arrhythmia. Patients without inducible tachyarrhythmias were followed in a registry. We compared the outcomes of 1397 patients in the registry with those of 353 patients with inducible tachyarrhythmias who were randomly assigned to receive no antiarrhythmic therapy in order to assess the prognostic value of electrophysiologic testing. RESULTS: Patients were followed for a median of 39 months. In a Kaplan-Meier analysis, two-year and five-year rates of cardiac arrest or death due to arrhythmia were 12 and 24 percent, respectively, among the patients in the registry, as compared with 18 and 32 percent among the patients with inducible tachyarrhythmias who were assigned to no antiarrhythmic therapy (adjusted P<0.001). Overall mortality after five years was 48 percent among the patients with inducible tachyarrhythmias, as compared with 44 percent among the patients in the registry (adjusted P=0.005). Deaths among patients without inducible tachyarrhythmias were less likely to be classified as due to arrhythmia than those among patients with inducible tachyarrhythmias (45 and 54 percent, respectively; P=0.06). CONCLUSIONS: Patients with coronary artery disease, left ventricular dysfunction, and asymptomatic, unsustained ventricular tachycardia in whom sustained ventricular tachyarrhythmias cannot be induced have a significantly lower risk of sudden death or cardiac arrest and lower overall mortality than similar patients with inducible sustained tachyarrhythmias.

Social support, depression, and mortality during the first year after myocardial infarction.

BACKGROUND: We previously reported that depression after myocardial infarction (MI) increases the long-term risk of cardiac mortality. Other research suggests that social support may also influence prognosis. This article examines the interrelationships between baseline depression and social support in terms of cardiac prognosis and changes in depression symptoms over the first post-MI year. METHODS AND RESULTS: For this study, 887 patients completed the Beck Depression Inventory (BDI) and the Perceived Social Support Scale (PSSS) at about 7 days after MI. Some 32% had BDIs > or =10, indicating mild to moderate depression. One-year survival status was determined for all patients. Follow-up interviews, including the BDI, were conducted with 89% of survivors. There were 39 deaths (35 cardiac). Elevated BDI scores were related to cardiac mortality (P=0.0006), but PSSS scores and other measures of social support were not. There was a significant interaction between depression and the PSSS (P=0. 016). The relationship between depression and cardiac mortality decreased with increasing support. Furthermore, residual change score analysis revealed that among 1-year survivors who had been depressed at baseline, higher baseline social support was related to more improvement in depression symptoms than expected. CONCLUSIONS: Post-MI depression is a predictor of 1-year cardiac mortality, but social support is not directly related to survival. However, very high levels of support appear to buffer the impact of depression on mortality. Furthermore, high levels of support predict improvements in depression symptoms over the first post-MI year in depressed patients. High levels of support may protect patients from the negative prognostic consequences of depression because of improvements in depression symptoms.

Amiodarone to prevent recurrence of atrial fibrillation. Canadian Trial of Atrial Fibrillation Investigators.

BACKGROUND: The restoration and maintenance of sinus rhythm is a desirable goal in patients with atrial fibrillation, because the prevention of recurrences can improve cardiac function and relieve symptoms. Uncontrolled studies have suggested that amiodarone in low doses may be more effective and safer than other agents in preventing recurrence, but this agent has not been tested in a large, randomized trial. METHODS: We undertook a prospective, multicenter trial to test the hypothesis that low doses of amiodarone would be more efficacious in preventing recurrent atrial fibrillation than therapy with sotalol or propafenone. We randomly assigned patients who had had at least one episode of atrial fibrillation within the previous six months to amiodarone or to sotalol or propafenone, given in an open-label fashion. The patients in the group assigned to sotalol or propafenone underwent a second randomization to determine whether they would receive sotalol or propafenone first; if the first drug was unsuccessful the second agent was prescribed. Loading doses of the drugs were administered and electrical cardioversion was performed (if necessary) within 21 days after randomization for all patients in both groups. The follow-up period began 21 days after randomization. The primary end point was the length of time to a first recurrence of atrial fibrillation. RESULTS: Of the 403 patients in the study, 201 were assigned to amiodarone and 202 to either sotalol (101 patients) or propafenone (101 patients). After a mean of 16 months of follow-up, 71 of the patients who were assigned to amiodarone (35 percent) and 127 of those who were assigned to sotalol or propafenone (63 percent) had a recurrence of atrial fibrillation (P<0.001). Adverse events requiring the discontinuation of drug therapy occurred in 18 percent of the patients receiving amiodarone, as compared with 11 percent of those treated with sotalol or propafenone (P=0.06). CONCLUSIONS: Amiodarone is more effective than sotalol or propafenone for the prevention of recurrences of atrial fibrillation.

Cryothermal ablation of the slow pathway for the elimination of atrioventricular nodal reentrant tachycardia.

BACKGROUND: We report the first successful slow pathway ablation using a novel catheter-based cryothermal technology for the elimination of atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: Eighteen patients with typical AVNRT underwent cryoablation. Reversible loss of slow pathway (SP) conduction during cryothermy (ice mapping) was demonstrated in 11 of 12 patients. Because of time constraints, only 2 sites were ice mapped in 1 patient. Seventeen of 18 patients had successful cryoablation of the SP. One patient had successful ice mapping of the SP, but inability to cool beyond -38 degrees C prevented successful cryoablation. A single radiofrequency lesion at this site eliminated SP conduction. No patient has had recurrent AVNRT over 4.9+/-1.7 months of follow-up. During cryoablation, accelerated junctional tachycardia was not seen and was therefore not available to guide lesion delivery. Adherence of the catheter tip during cryothermy (cryoadherence) allowed atrial pacing to test for SP conduction. Cryoablation in the anterior septum produced inadvertent transient PR prolongation consistent with loss of fast pathway conduction in 1 patient and transient (6.5 seconds) 2:1 AV block in another. On rewarming, the PR interval returned to normal, and the AV nodal effective refractory period was unchanged in both. Accelerated junctional tachycardia was seen on rewarming in both but not during cryothermy. CONCLUSIONS: Cryothermal ablation of the SP was achieved in patients with this novel technique. Successful ice mapping of both the SP and fast pathway was demonstrated. The ability to test the functionality of specific ablation sites before production of a permanent lesion may eliminate inadvertent AV block.

Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes. Canadian Trial of Physiologic Pacing Investigators.

BACKGROUND: Evidence suggests that physiologic pacing (dual-chamber or atrial) may be superior to single-chamber (ventricular) pacing because it is associated with lower risks of atrial fibrillation, stroke, and death. These benefits have not been evaluated in a large, randomized, controlled trial. METHODS: At 32 Canadian centers, patients without chronic atrial fibrillation who were scheduled for a first implantation of a pacemaker to treat symptomatic bradycardia were eligible for enrollment. We randomly assigned patients to receive either a ventricular pacemaker or a physiologic pacemaker and followed them for an average of three years. The primary outcome was stroke or death due to cardiovascular causes. Secondary outcomes were death from any cause, atrial fibrillation, and hospitalization for heart failure. RESULTS: A total of 1474 patients were randomly assigned to receive a ventricular pacemaker and 1094 to receive a physiologic pacemaker. The annual rate of stroke or death due to cardiovascular causes was 5.5 percent with ventricular pacing, as compared with 4.9 percent with physiologic pacing (reduction in relative risk, 9.4 percent; 95 percent confidence interval, -10.5 to 25.7 percent [the negative value indicates an increase in risk]; P=0.33). The annual rate of atrial fibrillation was significantly lower among the patients in the physiologic-pacing group (5.3 percent) than among those in the ventricular-pacing group (6.6 percent), for a reduction in relative risk of 18.0 percent (95 percent confidence interval, 0.3 to 32.6 percent; P=0.05). The effect on the rate of atrial fibrillation was not apparent until two years after implantation. The observed annual rates of death from all causes and of hospitalization for heart failure were lower among the patients with a physiologic pacemaker than among those with a ventricular pacemaker, but not significantly so (annual rates of death, 6.6 percent with ventricular pacing and 6.3 percent with physiologic pacing; annual rates of hospitalization for heart failure, 3.5 percent and 3.1 percent, respectively). There were significantly more perioperative complications with physiologic pacing than with ventricular pacing (9.0 percent vs. 3.8 percent, P<0.001). CONCLUSIONS: Physiologic pacing provides little benefit over ventricular pacing for the prevention of stroke or death due to cardiovascular causes.