Intravenous sotalol for the termination of supraventricular tachycardia and atrial fibrillation and flutter: a multicenter, randomized, double-blind, placebo-controlled study. Sotalol Multicenter Study Group

Efficacy and safety of intravenously administered dofetilide in acute termination of atrial fibrillation and flutter: a multicenter, randomized, double-blind, placebo-controlled trial. Danish Dofetilide in Atrial Fibrillation and Flutter Study Group

BACKGROUND

This study was designed to assess the efficacy and safety of intravenous dofetilide in acute termination of atrial fibrillation (AF) and flutter (AFL). Dofetilide, an investigational class III antiarrhythmic agent, selectively inhibits the rapid component of the delayed rectifier potassium current, thus prolonging the effective refractory period and duration of the action potential. Dofetilide can be administered intravenously and has a rapid onset of electrophysiologic action.

METHODS AND RESULTS

Ninety-six patients with AF (n = 79) or AFL (n = 17) with a median arrhythmia duration of 62 days (range 1 to 180) were randomized to placebo (n = 30) or 8 micrograms/kg IV dofetilide (n = 66) over 30 minutes. Conversion was defined as termination of the atrial arrhythmia within 3 hours from the start of infusion. The conversion rate was 30.3% after dofetilide and 3.3% after placebo (P <.006). Conversion rate was higher in AFL than in AF: 64% versus 24% (P =. 012). In nonconverters, there was no statistically significant difference between the change in heart rate among the dofetilide-treated compared with the placebo-treated patients (P =. 42). Torsade de pointes ventricular tachycardia developed in 2 patients (3%). In both patients, drug infusion was discontinued before the event because of prolongation of the QT interval.

CONCLUSIONS

Intravenous dofetilide is effective in acute termination of AF and AFL of medium duration, with a particularly high efficacy rate in AFL. A small but serious risk of proarrhythmia must be anticipated.

Sotalol: An important new antiarrhythmic

Sotalol, the most recently approved oral antiarrhythmic drug, has a unique pharmacologic profile. Its electrophysiology is explained by nonselective beta-blocking action as well as class III antiarrhythmic activity (including fast-activating cardiac membrane-delayed rectifier current blockade), which leads to increases in action potential duration and refractory period throughout the heart and in QT interval on the surface electrocardiogram. Its better hemodynamic tolerance than other beta-blockers may be a result of enhanced inotropy associated with class III activity. Sotalol's ability to suppress ventricular ectopy is similar to that of class I agents and better than that of standard beta-blockers. Unlike class I agents, its use in a postinfarction trial was not associated with increased mortality rate. Therapeutically, it has shown superior efficacy for prevention of recurrent ventricular tachycardia and ventricular fibrillation, which was the basis for its approval. In a randomized study, the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial, sotalol was associated with an increased in-hospital efficacy prediction rate (by Holter monitor or electrophysiologic study), reduced long-term arrhythmic recurrence rate with superior tolerance, and lower mortality rate than class I ("standard") antiarrhythmic drugs. Sotalol was 1 of 2 drugs selected for comparison with implantable defibrillators in the recent National Institutes of Health Antiarrhythmics versus Implantable Defibrillator (AVID) study. Sotalol appears to be a preferred drug for use with implantable defibrillators; unlike some other agents (eg, amiodarone) it does not elevate and, indeed, may lower defibrillation threshold. Although unapproved for this use, sotalol is active against atrial arrhythmias. It has shown efficacy equivalent to propafenone and quinidine in preventing atrial fibrillation recurrence, but it is better tolerated than quinidine and provides excellent rate control during recurrence. Sotalol's major side effects are related to beta-blockade and the risk of torsades de pointes (acceptably small if appropriate precautions are taken). Unlike several other antiarrhythmics (eg, amiodarone), it has no pharmacokinetic drug-drug interactions, is not metabolized, and is entirely renally excreted. Initial dose is 80 mg twice daily, with gradual titration to 240 to 360 mg/day as needed. The daily dose must be reduced in renal failure. On the basis of favorable clinical trials and practice experience, sotalol has shown a steadily growing impact on the treatment of arrhythmias during its 5 years of market availability, a trend that is likely to continue.

Comparison between propafenone and digoxin administered intravenously to patients with acute atrial fibrillation. PAFIT-3 Investigators. The Propafenone in Atrial Fibrillation Italian Trial

In recent-onset atrial fibrillation, intravenous propafenone has been shown to effectively restore sinus rhythm, whereas the efficacy of intravenous digoxin has been questioned. We directly compared these 2 drugs and placebo in acute atrial fibrillation. One hundred twenty-three patients with atrial fibrillation lasting <72 hours were randomized to a 10-minute intravenous infusion of either propafenone (2 mg/kg, 41 patients) or digoxin (0.007 mg/kg, 40 patients) or placebo (42 patients). After 1 hour, nonconverted propafenone or digoxin patients were switched to the alternative drug, while nonconverted placebo patients were randomized to either propafenone or digoxin. The observation time ended 1 hour later. By 1 hour, conversion rates were 49% in the propafenone group, 32% in the digoxin group (p = 0.12), and 14% in placebo group (p <0.001 vs propafenone, p = 0.08 vs digoxin). After crossover, digoxin converted 5% of propafenone patients, while propafenone converted 48% of digoxin patients (p <0.05). In the 36 nonconverted placebo patients, sinus rhythm was obtained in 53% of cases with propafenone, and in 5% with digoxin (p < 0.05). Globally, among the 116 patients who received a drug as first treatment, 30 of 60 patients (50%) were converted by propafenone versus 14 of 56 (25%) by digoxin (p <0.01) (odds ratio 2.0, 95% confidence interval 1.19 to 3.36). In nonconverters, the ventricular rate reduction was faster (15 vs 45 minutes) and more prominent (-24% vs -14%) with propafenone than with digoxin. In conclusion, intravenous propafenone terminates atrial fibrillation more effectively than either placebo or intravenous digoxin. In addition, in nonconverted patients, it obtains a more rapid and marked control of the ventricular rate.

The peri-operative management of atrial fibrillation

Atrial fibrillation is a common arrhythmia frequently seen in surgical patients. The onset of new atrial fibrillation during the peri-operative period is less common. There are many possible precipitating factors, although volatile agents themselves may have an antifibrillatory action. The management of atrial fibrillation includes removal of any precipitating factors and treatment of the arrhythmia itself. Immediate management of acute-onset atrial fibrillation is usually direct current cardioversion. Alternatively, anti-arrhythmic drugs can be used to achieve cardioversion. In patients with rapid, chronic atrial fibrillation or those refractory to cardioversion, priority is given to control of the ventricular rate. Thrombo-embolism is a significant risk if atrial fibrillation is paroxysmal or persists for more than 48 h.

Prospective comparison of flecainide versus sotalol for immediate cardioversion of atrial fibrillation

This study sought to compare the efficacy and safety of intravenous flecainide and sotalol for immediate cardioversion of atrial fibrillation. We performed a prospective, randomized, single-blind, multicenter trial, including 106 hemodynamically stable patients with atrial fibrillation, stratified according to duration of the arrhythmia. Exclusion criteria included severely reduced left ventricular systolic function, recent antiarrhythmic therapy, and hypokalemia. Patients were randomly assigned to receive either intravenous flecainide or intravenous sotalol. Trial medication was given at a dose of 1.5 mg/kg body weight (maximum 150 mg). Overall, 28 of 54 patients (52%) given flecainide and 12 of 52 patients (23%) given sotalol converted to sinus rhythm during the first 2 hours after start of the infusion (p = 0.003). Multivariate analysis confirmed that treatment allocation to flecainide, an arrhythmia duration of < or = 24 hours, higher plasma magnesium level at baseline, higher age for men, and lower age for women independently increases the probability of conversion. The frequency of adverse effects was not significantly different in the 2 treatment groups.

Superiority of ibutilide (a new class III agent) over DL-sotalol in converting atrial flutter and atrial fibrillation. The Ibutilide/Sotalol Comparator Study Group

OBJECTIVE

To compare the efficacy and safety of a single dose of ibutilide, a new class III antiarrhythmic drug, with that of DL-sotalol in terminating chronic atrial fibrillation or flutter in haemodynamically stable patients.

DESIGN

Double blind, randomised study.

SETTING

43 European hospitals.

PATIENTS

308 patients (mean age 60 years, 70% men, 48% with heart disease) with sustained atrial fibrillation (n = 251) or atrial flutter (n = 57) (duration three hours to 45 days) were randomised to three groups to receive a 10 minute infusion of 1 mg ibutilide (n = 99), 2 mg ibutilide (n = 106), or 1.5 mg/kg DL-sotalol (n = 103). Infusion was discontinued at termination of the arrhythmia.

MAIN OUTCOME MEASURE

Successful conversion of atrial fibrillation or flutter, defined as termination of arrhythmia within one hour of treatment.

RESULTS

Both drugs were more effective against atrial flutter than against atrial fibrillation. Ibutilide was superior to DL-sotalol for treating atrial flutter (70% and 56% v 19%), while the high dose of ibutilide was more effective for treating atrial fibrillation than DL-sotalol (44% v 11%) and the lower dose of ibutilide (44% v 20%, p < 0.01). The mean (SD) time to arrhythmia termination was 13 (7) minutes with 2 mg ibutilide, 19 (15) minutes with 1 mg ibutilide, and 25 (17) minutes with DL-sotalol. In all patients, the duration of arrhythmia before treatment was a predictor of arrhythmia termination, although this was less obvious in the group that received 2 mg ibutilide. This dose converted almost 48% of atrial fibrillation that was present for more than 30 days. Concomitant use of digitalis or nifedipine and prolongation of the QTc interval were not predictive of arrhythmia termination. Bradycardia (6.5%) and hypotension (3.7%) were more common side effects with DL-sotalol. Of 211 patients given ibutilide, two (0.9%) who received the higher dose developed polymorphic ventricular tachycardia, one of whom required direct current cardioversion.

CONCLUSION

Ibutilide (given in 1 or 2 mg doses over 10 minutes) is highly effective for rapidly terminating persistent atrial fibrillation or atrial flutter. This new class III drug, under monitored conditions, is a potential alternative to currently available cardioversion options.

Absorption kinetics of oral sotalol combined with cisapride and sublingual sotalol in healthy subjects

AIMS

To study the absorption kinetics of sotalol following administration of different formulations. A formulation which results in fast absorption might be useful in the episodic treatment of paroxysmal supraventricular tachycardia (SVT), atrial fibrillation (Afib) or atrial flutter (Afl).

METHODS

In an open randomized crossover study seven healthy male volunteers were given an intravenous infusion of 20 mg sotalol, for assessing the absolute bioavailability, an oral solution containing 80 mg sotalol, an oral solution containing both 80 mg sotalol and 20 mg cisapride and an 80 mg sotalol tablet, which was taken sublingually.

RESULTS

The addition of cisapride decreased the time at which maximum serum concentrations were reached (tmax) from 2.79 (1.85-4.34) h to 1.16 (0.68-2.30) h (P=0.009) [95% CI: -2.59, -0.55] and increased the absorption rate constant (ka) from 0.49 (0.31-0.69) h(-1) to 1.26 (0.52-5.61) h(-1) (P=0.017). The absolute bioavailability of sotalol was reduced by cisapride from 1.00+/-0.15 to 0.70+/-0.26 (P=0.006), while maximum serum concentrations of both oral solutions were not significantly different. Compared with the sublingually administered tablet with a median tmax of 2.12 (0.89-3.28) h, the sotalol/cisapride oral solution gave a smaller tmax (p=0.009) [95% CI: -1.64, -0.36]. The ka of the sotalol/cisapride solution was significantly (P=0.010) larger than the ka of 0.56 (0.33-0.75) h(-1) found after sublingual administration of the tablet.

CONCLUSIONS

The sotalol/cisapride oral solution might be suitable for the episodic treatment of SVT, Afib or Afl.

Temporary atrial electrode for the treatment of supraventricular tachycardia after cardiac operations

BACKGROUND

Supraventricular tachycardia is a common postoperative complication early after cardiac operations. A temporary atrial patch electrode for low-energy atrial defibrillation was developed in 1992 and subsequently tested.

METHODS

The electrode first was tested and removed intraoperatively during open heart operations in 10 patients (phase I). After the intraoperative testing, the temporary atrial patch electrode was implanted in 20 patients for postoperative termination of spontaneous episodes of supraventricular tachycardia (phase II). When supraventricular tachycardia occurred, biphasic shocks (1.2 to 5 J) were applied and the atrial defibrillation thresholds were measured.

RESULTS

In phase I, the mean intraoperative atrial defibrillation threshold was 1.6 +/- 1.4 J, with a mean shock impedance of 64 +/- 7.3 omega. In phase II, 6 of 20 patients (30%) had 7 episodes of atrial fibrillation (n = 6) and atrial flutter (n = 1) after operation. In 5 patients, the supraventricular tachycardia could be converted to a sinus (n = 5) or normofrequent atrioventricular rhythm (n = 1). The mean postoperative defibrillation threshold was 2.7 +/- 2.1 J, with a mean shock impedance of 50.2 +/- 6.8 omega.

CONCLUSIONS

The temporary atrial patch electrode allows low-energy defibrillation of episodes of atrial fibrillation. It may serve as an alternative therapeutic option for the treatment of supraventricular tachycardia.

Treatment strategies for atrial fibrillation

Atrial fibrillation is the most common arrhythmia observed in clinical practice, occurring in 0.4% of the general population and in up to 4% of people greater than 60 years old. It is often associated with other cardiovascular disorders, such as hypertension, coronary artery disease, or cardiomyopathy. Critical evaluation and management of patients with atrial fibrillation requires knowledge of etiology, prognosis, and treatment options of this arrhythmia. On initial presentation, emergency electrical cardioversion should be performed if the patient is hemodynamically unstable. If the patient is stable, initial rate control is recommended, using atrioventricular nodal blocking agents. Further treatment mainly depends upon the duration of the episode. Patients who are in atrial fibrillation <48 hours can be safely cardioverted. Patients who are in atrial fibrillation for >48 hours are commonly anticoagulated for 3 to 4 weeks before and after cardioversion because of the risk of thromboembolism formation in the left atrial appendage. An alternate strategy, which is especially attractive when immediate cardioversion is desired, is transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. After cardioversion, sinus rhythm can be maintained with class I and III drugs, such as flecainide and propafenone or amiodarone and sotalol. New treatment options, such as atrial defibrillation, atrioventricular junctional ablation, or modification of atrial pacing to prevent atrial fibrillation, are currently under investigation. Although atrial fibrillation is so common in clinical practice, it still remains difficult to treat. Conversion and maintenance to sinus rhythm with antiarrhythmic drug therapy has not shown any improvement in mortality, and some patients may benefit more from ventricular rate control. This review article discusses different treatment strategies for patients with atrial fibrillation.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Characterization of low right atrial isthmus as the slow conduction zone and pharmacological target in typical atrial flutter

BACKGROUND

Previous electrophysiological studies in patients with typical atrial flutter suggested that the slow conduction zone might be located in the low right atrial isthmus, which is a path formed by orifice of inferior vena cava, eustachian valve/ridge, coronary sinus ostium, and tricuspid annulus. The conduction characteristics during atrial pacing and responses to antiarrhythmic drugs of this anatomic isthmus were unknown.

METHODS AND RESULTS

Forty-four patients, 20 patients with paroxysmal supraventricular tachycardia (group 1) and 24 patients with clinically documented paroxysmal typical atrial flutter (group 2), were studied. A 20-pole halo catheter was situated around the tricuspid annulus. Incremental pacing from the low right atrium and coronary sinus ostium was performed to measure the conduction time and velocity along the isthmus and lateral wall in the baseline state and after intravenous infusion of procainamide or sotalol. In both groups, conduction velocity in the isthmus during incremental pacing was significantly lower than that in the lateral wall before and after infusion of antiarrhythmic drugs. Furthermore, gradual conduction delay with unidirectional block in the isthmus was relevant to initiation of typical atrial flutter. Compared with group 1, group 2 had a lower conduction velocity in the isthmus and shorter right atrial refractory period. Procainamide significantly decreased the conduction velocity, but sotalol did not change it. In contrast, sotalol significantly prolonged the atrial refractory period with a higher extent than procainamide. After infusion of procainamide, the increase of conduction time in the isthmus accounted for 52+/-19% of the increase in flutter cycle length, and 5 of 12 patients (42%) had spontaneous termination of typical flutter. After infusion of sotalol, typical flutter was induced in only 6 of 12 patients (50%) without significant prolongation of flutter cycle length.

CONCLUSIONS

The low right atrial isthmus with rate-dependent slow conduction properties is critical to initiation of typical human atrial flutter. It may be the potentially pharmacological target of antiarrhythmic drugs in the future.

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.

Efficacy of intravenous propafenone in termination of atrial flutter by overdrive transesophageal pacing previously ineffective

Fifty patients with symptomatic type I atrial flutter in whom termination of the arrhythmia with transesophageal stimulation was unsuccessful were randomized to undergo a repeat procedure after intravenous propafenone (n = 25) or placebo (n = 25). Immediate sinus rhythm recovery rate was 36% in the propafenone group and 4% in the placebo group (p = 0.005), indicating that intravenous propafenone increases the rate of successful transesophageal stimulation and can be used when a first attempt at conversion is ineffective.

Antiarrhythmic drug therapy in the treatment of atrial fibrillation

Treatment of atrial fibrillation is often unsatisfactory because no available drug has been shown to be clearly superior for maintaining patients in sinus rhythm, and all agents have significant potential for toxicity. Selection of an antiarrhythmic drug is more likely to be based on the drug's potential for toxicity, rather than its demonstrated superior efficacy in the treatment of atrial fibrillation. Careful assessment of each patient for contraindications to individual agents and the likelihood of treatment success needs to be done before initiating antiarrhythmic therapy.

Efficacy and safety of repeated intravenous doses of ibutilide for rapid conversion of atrial flutter or fibrillation. Ibutilide Repeat Dose Study Investigators

BACKGROUND

Currently available antiarrhythmic drugs have limited efficacy for acute termination of atrial fibrillation and flutter, especially if the arrhythmia is not of recent onset. The purpose of this multicenter study was to determine the efficacy and safety of repeated doses of intravenous ibutilide, a class III antiarrhythmic drug, in terminating atrial fibrillation or flutter.

METHODS AND RESULTS

Two hundred sixty-six patients with sustained atrial fibrillation (n = 133) or flutter (n = 133), with an arrhythmia duration of 3 hours to 45 days, were randomized to receive up to two 10-minute infusions, separated by 10 minutes, of ibutilide (1.0 and 0.5 mg or 1.0 and 1.0 mg) or placebo. The conversion rate was 47% after ibutilide and 2% after placebo (P < .0001). The two ibutilide dosing regimens did not differ in conversion efficacy (44% versus 49%). Efficacy was higher in atrial flutter than fibrillation (63% versus 31%, P < .0001). In atrial fibrillation but not flutter, conversion rates were higher in patients with a shorter arrhythmia duration or a normal left atrial size. Arrhythmia termination occurred a mean of 27 minutes after start of the infusion. Of 180 ibutilide-treated patients, 15 (8.3%) developed polymorphic ventricular tachycardia during or soon after the infusion. The arrhythmia required cardioversion in 3 patients (1.7%) and was nonsustained in 12 patients (6.7%).

CONCLUSIONS

Intravenous ibutilide given in repeated doses is effective in rapidly terminating atrial fibrillation and flutter and under monitored conditions is an alternative to current cardioversion options.

Comparison of sotalol with digoxin-quinidine for conversion of acute atrial fibrillation to sinus rhythm (the Sotalol-Digoxin-Quinidine Trial)

We randomized 61 patients with paroxysmal atrial fibrillation (AF) ( < 48 hours from onset) to either sotalol or quinidine treatment. Conversion of rhythm was recorded by Holter monitoring. The starting 80 mg dose of sotalol was repeated at 2, 6, and 10 hours if AF persisted (heart rate > 80 beats/min), and if systolic blood was > or = 120 mm Hg. In the quinidine group, if heart rate > 100 beats/min, it was decreased with intravenous digoxin, whereafter 200 mg of oral quinidine sulfate was given maximally 3 times, each dose 2 hours apart. Conversion of AF to sinus rhythm occurred in 17 or 33 patients (52%) taking sotalol, and in 24 of 28 patients (86%) taking quinidine (p < 0.0001). Electric cardioversion was necessary in 39% of the former and in 14% of the latter group. The mean delay from first trial drug to sinus rhythm with the trial medication was 10.2 +/- 7.6 hours in the sotalol group and 4.0 +/- 2.9 hours in the quinidine group (p < 0.01). Treatment was discontinued in 16 patients taking sotalol (48%) because of asymptomatic bradycardia or hypotension, and in 20 taking quinidine (71%) because of rhythm conversion. Asymptomatic wide complex tachycardia (QRS > 0.12 second) was found in 13% and 27% of patients taking sotalol and quinidine, respectively. The longest RR intervals were 6.4 and 3.8 seconds in the sotalol and quinidine groups, respectively. Oral sotalol did not appear as effective as quinidine sulfate treatment in conversion of paroxysmal AF.(ABSTRACT TRUNCATED AT 250 WORDS)

Sotalol: a new beta-adrenergic blocker for ventricular arrhythmias

Sotalol is a water-soluble, nonselective, beta-adrenergic blocker that was recently approved in oral form in the United States for the treatment of ventricular arrhythmias that are judged to be life-threatening. As a beta-blocker, sotalol is unique in having additional class-III antiarrhythmic activity. It is still not resolved whether sotalol is more effective than other beta-blockers in managing arrhythmias, but there are suggestions that it might possess greater antiarrhythmic and life-protecting activities than other types of antiarrhythmic drugs. The drug is well tolerated, but, because of its electrophysiologic activity, there is a small risk of proarrhythmia, specifically the development of polymorphic ventricular tachycardia and torsade de pointes.