Efficacy of type 1C antiarrhythmic agents for treatment of resistant atrial fibrillation

Antiarrhythmic drug therapy of atrial fibrillation

In the post-AFFIRM era, treatment of AF has become the treatment of symptoms. In some patients, this will be simple rate control, but there remain a significant cohort of patients in whom rate control alone does not give acceptable symptom relief. In this group, antiarrhythmic therapy still has a role, and the AFFIRM trial indicates that this therapeutic strategy is without significant deleterious effect on mortality. The choice of antiarrhythmic agent must be individualized according to underlying cardiac pathologies and comorbidities, however. Most recently, the introduction of dofetilide has widened the therapeutic options in patients with severe heart disease, and the Canadian Trial of Atrial Fibrillation indicated the superior efficacy of amiodarone at low doses. The release/ development of newer Class III antiarrhythmic agents may offer hope for the benefits of amiodarone without the serious adverse effects with long-term therapy.

Pilsicainide for conversion and maintenance of sinus rhythm in chronic atrial fibrillation: a placebo-controlled, multicenter study

BACKGROUND

Pilsicainide is a newly synthesized antiarrhythmic agent with class Ic properties. Various antiarrhythmic agents have been used to convert atrial fibrillation (AF) to sinus rhythm or decrease the rate of relapse of AF.

METHODS

We randomly assigned 62 patients with chronic AF to oral treatment of either a placebo (10 patients) or 150 mg/day of pilsicainide (52 patients) for 4 weeks before electrical cardioversion. Before oral administration of pilsicainide, 41 patients underwent transesophageal echocardiography to investigate whether there was thrombus formation in the heart chambers. Patients without pharmacologic defibrillation underwent direct current cardioversion to restore sinus rhythm. After successful cardioversion, all patients continued to receive pilsicainide and were monitored for up to 2 years.

RESULTS

Before cardioversion, 11 patients in the pilsicainide group (21%) reverted to sinus rhythm. No patients in the placebo group reverted to sinus rhythm. Direct current cardioversion was performed in 51 patients; however, 8 patients were not converted to sinus rhythm (5 patients receiving pilsicainide, 3 patients receiving placebo), and 3 patients needed intracardiac cardioversion to convert to sinus rhythm. Asymptomatic bradyarrhythmias were observed in 5 patients in the pilsicainide group. During the follow-up period, 33 patients (71%) in the pilsicainide group remained in sinus rhythm at 1 month; this number decreased to 23 patients (49%) at 3 months, 20 (43%) at 6 months, 16 (34%) at 12 months, 16 (34%) at 18 months, and 16 (34%) at 24 months. All patients receiving placebo continued to receive placebo after the cardioversion, and AF recurred a few days after cardioversion in all cases. No independent discriminant variables were identified in the groups between maintenance and nonmaintenance of sinus rhythm. Although no serious side effects regarding pilsicainide have been documented, one patient died of acute myocardial infarction, most likely not related to pilsicainide administration.

CONCLUSIONS

Pilsicainide is effective in restoring or maintaining sinus rhythm in patients with chronic AF lasting longer than an average duration of 22 months. No major adverse effects were observed.

SD3212, a new antiarrhythmic drug, raises atrial fibrillation threshold in isolated rabbit hearts

SD3212 is a new antiarrhythmic drug which has class I, III, and IV effects. The purpose of this study was to elucidate the electrophysiological effects of this compound on a rabbit atrial fibrillation model, and to test a hypothesis that atrial fibrillation threshold is a quantitative indicator of atrial vulnerability. Whole hearts were excised from rabbits, and the aortas cannulated to perfuse the coronary arteries. Atrial fibrillation was induced with a burst stimulation of 50 Hz for 1 s while 3 microM acetylcholine (ACh) was perfused. When the right atrial appendage was paced at 200-ms intervals, SD3212 prolonged interatrial conduction time: control 30 +/- 1.2 ms, ACh 33 +/- 1.4 ms, ACh + SD 1 microM 37 +/- 2.4 ms, ACh + SD 3 microM 52 +/- 8.1 ms. The drug also prolonged the effective refractory period: control 80 +/-3.0 ms, ACh 48 +/- 3.8 ms, ACh + SD 1 microM 65 +/- 4.7 ms, ACh + SD 3 microM 98 +/- 15 ms. The rate of induction of atrial fibrillation by rapid pacing was 26% in Tyrode's solution, 85% in the presence of ACh, and 38% in the presence of ACh + SD 1 microM. The atrial fibrillation threshold decreased from 8.6 +/- 0.8mA (control) to 2.5 +/- 0.7 mA in the presence of ACh. It increased again to 7.8 +/- 1.0 mA in the presence of SD3212 (1 microM). SD3212 prolonged both the conduction time and refractory period. A reversed use-dependency was not prominent. These features caused antifibrillatory effects. Thus, the atrial fibrillation threshold seems to be a good quantitative indicator of atrial vulnerability.

Antiarrhythmic drug therapy in the management of atrial fibrillation

Antiarrhythmic drugs have been used for the acute conversion of atrial fibrillation to sinus rhythm, as well as for the long-term maintenance of sinus rhythm. In recent years, concerns regarding antiarrhythmic drug efficacy as well as safety have prompted a re-examination of the indications for antiarrhythmic therapy in patients with atrial fibrillation. This review will focus on the safety and efficacy of antiarrhythmic therapy in the acute and chronic management of patients with atrial fibrillation.

Propafenone for conversion and prophylaxis of atrial fibrillation. Propafenone Atrial Fibrillation Trial Investigators

Pharmacologic therapy is widely used for restoration of sinus rhythm and prevention of recurrences of atrial fibrillation. Because concerns have been raised about their potential proarrhythmic effects, therapeutic regimens should be evaluated by placebo-controlled studies to determine their efficacy and safety. One hundred thirty-six patients with persistent atrial fibrillation were randomized to receive propafenone 2 mg/kg over 30 minutes, followed by oral propafenone 150 mg 3 times daily or matching placebo. Nonresponders to intravenous therapy underwent direct-current cardioversion. Both responders to intravenous therapy and converters to sinus rhythm after direct-current cardioversion were followed for 6 months in a double-blind oral treatment period of propafenone 150 mg 3 times daily or matching placebo. Pharmacologic conversion to sinus rhythm was achieved in 29% of the patients taking propafenone and in 17% of patients taking placebo (p > or = 0.10). Subsequent direct-current cardioversion in nonresponders was equally successful (70%) in both groups (p > or = 0.10). The proportion of patients free from recurrent symptomatic arrhythmia at 6 months was 67% for the propafenone and 35% for the placebo group (p < 0.01). Time to atrial fibrillation relapse was more favorable with propafenone than with placebo (p < 0.001). The incidence of drug-related side effects was 10% in the propafenone group and 14% in the placebo group. Thus, "slow" infusion of propafenone seems to be of limited value for terminating atrial fibrillation. Oral propafenone at a low dosage 150 mg 3 times daily is well tolerated and effective in maintaining sinus rhythm for 6 months after pharmacologic or electrical restoration of sinus rhythm.

Effects of oral propafenone administration before electrical cardioversion of chronic atrial fibrillation: a placebo-controlled study

OBJECTIVES

Our aim was to evaluate the benefits and risks of administering propafenone before electrical defibrillation for chronic atrial fibrillation.

BACKGROUND

In this context, an antiarrhythmic drug-although potentially useful in preventing early recurrence of arrhythmia-could adversely affect the defibrillation threshold and reduce the cardioversion success rate.

METHODS

We randomly assigned 100 patients with chronic atrial fibrillation to oral treatment with either placebo (51 patients) or 750 mg/day of propafenone (49 patients) for 48 h before administration of direct current shock. After successful cardioversion, all patients received propafenone therapy and were followed up for 48 h.

RESULTS

Before defibrillation, three patients in the propafenone group (6.1%) had reversion to sinus rhythm and one had sustained ventricular tachycardia. Shock efficacy (82.4% vs. 84.4%) and the cumulative effective energy (395 +/- 258 vs. 421 +/- 236 J) were not different between the placebo and propafenone groups. In the propafenone group, 11 patients had their arrhythmia transformed into atrial flutter and required a lower energy level for arrhythmia conversion than did the other patients with continued atrial fibrillation (245 +/- 197 vs. 493 +/- 215 J, p < 0.01); the latter patients showed a trend (p < 0.10) toward higher energy requirements than that of patients who received placebo. The incidence of asymptomatic bradyarrhythmias was higher in the propafenone group (28.9% vs. 7.1%, p < 0.02), but more patients who received placebo had early recurrence of atrial fibrillation (16.7% vs. 0%, p < 0.02). Two days after cardioversion, more patients given propafenone (73.5% vs. 52.9%, p < 0.05) were discharged from the hospital with sinus rhythm. During the in-hospital stay, propafenone was withdrawn from six patients (6.6%) because of side effects.

CONCLUSIONS

Propafenone, given before electrical cardioversion for chronic atrial fibrillation does not affect the mean defibrillation threshold or the rate of successful arrhythmia conversion. It decreases the recurrence of atrial fibrillation early after shock, thus allowing more patients to be discharged from the hospital with sinus rhythm.

Atrial anatomy and function postcardioversion: insights from transthoracic and transesophageal echocardiography

Echocardiography provides a valuable tool for the evaluation and assessment of atrial function in patients with atrial fibrilation (AF). Atrial morphology after restoration of sinus rhythm is dynamic, with a decrease in atrial size if sinus rhythm is maintained and atrial growth among those with sustained AF. Restoration of electrocardiographic sinus rhythm is frequently accompanied by relatively depressed atrial mechanical function, with recovery that appears to be related to multiple factors, including the duration of AF before cardioversion and the mode of cardioversion. Such delay appears to confer ongoing risk for thrombus formation and thromboembolism in the days after cardioversion and argues strongly for the need to maintain therapeutic anticoagulation during the pericardioversion and postcardioversion period.

Safety and utility of flecainide acetate in the routine care of patients with supraventricular tachyarrhythmias: results of a multicenter trial. The Flecainide Supraventricular Tachycardia Study Group

Patients with supraventricular arrhythmias have been safely and effectively treated with flecainide. We conducted an open-label, 20-center trial to define further the safety and efficacy profile of oral flecainide in patients with supraventricular arrhythmias, including atrial tachycardias (ectopic or multifocal), atrial-ventricular tachycardias (reentrant), paroxysmal atrial fibrillation/flutter (PAF), and chronic atrial fibrillation (CAF). Our study population of 151 patients with documented supraventricular arrhythmias requiring treatment included 67 with paroxysmal supraventricular tachycardia (PSVT), 67 with PAF (symptoms < 15 days), and 17 with CAF (symptoms > of = 15 days)> The initial flecainide dose of 100 mg twice daily could be increased by 50 mg bid every 4 days to a maximum of 200 mg twice daily. Patients who were effectively treated could receive flecainide for 1 year. The study was terminated April 26, 1989, in response to interim results reported by the Cardiac Arrhythmia Suppression Trial (CAST). All patients were removed from the study by August 1989. At study termination 87% of PSVT, 73% of PAF, and 56% of CAF patients had improved symptomatically while on flecainide therapy. Eleven patients experienced cardiac adverse experiences: proarrhythmic events (3 patients), new or worsened congestive heart failure (7 patients), sinus pauses (1 patient). Cardiac side effects appeared to be more frequent in patients in the CAF group (5/17 patients), all of whom had structural heart disease. Overall, 45 (67%) PSVT, 43 (64%) PAF, and 9 (56%) CAF patients reported at least 1 noncardiac adverse experience; the most common were abnormal vision, dizziness, and headaches. One patient from the CAF group died; the death was considered to be unrelated to flecainide. Flecainide appears to be safe and effective treatment for patients with supraventricular arrhythmias of a variety of mechanisms and appears particularly effective for patients with PSVT. The efficacy is lowest and side effects most frequent in patients with CAF, as seen with other trials of antiarrhythmic medication in these patients. In the context of the CAST experience and other trials of antiarrhythmic drugs in patients with CAF, the balance of risk and benefit of therapy should be considered carefully before initiating treatment.

Cardioversion of atrial fibrillation

Cardioversion to sinus rhythm should be considered for all patients in atrial fibrillation in order to improve cardiac performance and perhaps to reduce the long-term risk of thromboembolic complications. Different methods of cardioversion, whether electrical or pharmacological, exist and there is often uncertainty about performing the procedure. In particular, there is often confusion about the use of anti-arrhythmic drugs and the suitable length of anticoagulant therapy required pre- and post-cardioversion. This review discusses the current understanding of electrical and pharmacological cardioversion of atrial fibrillation, the clinical effects and the role of prophylactic anti-arrhythmic and anticoagulant therapy in this procedure.