Effectiveness of sotalol for therapy of complex ventricular arrhythmias and comparisons with placebo and class I antiarrhythmic drugs

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.

Sotalol: Current Status and Expanding Indications

BACKGROUND: The role of antiarrhythmic drug therapy continues to undergo major changes. The change is necessitated by the advent of invasive interventional procedures, such as catheter ablation of arrhythmias and the use of implantable devices for sensing and terminating life-threatening ventricular arrhythmias and symptomatically traublesome supraventricular arrhythmias. Many conventional and time-honored drugs, such as sodium channel blockers, have been found either to be ineffective or to have the potential to produce serious proarrhythmic reactions. Attention is therefore focused on compounds that prolong repolarization and reduce sympathetic stimulation. Two compounds, amiodarone and sotalol, have emerged as prototypes of drugs of the future. METHODS AND RESULTS: This review focuses on sotalol for controlling supraventricular and ventricular tachyarrhythmias. Sotalol is a major antiarrhythmic agent that combines potent class III action with nonselective beta-blocking properties. The drug's pharmacokinetics is simple. Its elimination half-life is 10-15 hours, the drug being excreted almost exclusively by the kidneys. Sotalol's pharmacokinetics allows development of optimal dosing for initiation of therapy relative to changes in creatinine clearance with further dose adjustment by monitoring the QT interval on the surface electrocardiogram. The compound exerts broad-spectrum antiarrhythmic actions in supraventricular and ventricular arrhythmias. It prevents inducible ventricular tachycardia (VT) and ventricular fibrillation (VF) in approximately 30% of patients with a higher figure for the suppression of spontaneously occurring arrhythmias documented on Holter recordings. CONCLUSIONS: The major role of sotalol is in the management of VT/VF often in conjunction with an implantable cardioverter/defibrillator, in which context it lowere the defibrillation threshold. Sotalol is superior to class I agents, especially in VT/VF and in survivors of cardiac arrest. Sotalol has emerged as a major antifibrillatory compound for the control of life-threatening ventricular arrhythmias as the main indication. Data have indicated its potential for the maintenance of stability of sinus rhythm in patients with atrial fibrillation and flutter after electrical conversion and in preventing their occurrence in a variety of clinical settings.

General principles of antiarrhythmic therapy for ventricular tachyarrhythmias

Sudden cardiac death due to ventricular arrhythmias is a significant cause of mortality in patients with structural heart disease. Over the past several decades, the introduction of new pharmacologic and nonpharmacologic therapy has expanded the treatment options available. This article will focus on the use of antiarrhythmic medication for the treatment of ventricular arrhythmias and will review the following: (1) treatment goals for various clinical populations, (2) the mechanisms of antiarrhythmic and proarrhythmic actions of antiarrhythmic medications, and (3) empiric versus guided pharmacologic therapy.

Sotalol: from "just another beta blocker" to "the prototype of class III antidysrhythmic compound"

Sotalol is a beta-blocking drug devoid of membrane stabilizing properties, as well as intrinsic sympathomimetic actions, or cardioselectivity. In addition, sotalol prolongs atrial and ventricular repolarization (Class III antiarrhythmic activity). It appears to have less myocardial depressant effect than other beta-blocking agents. Given orally, bioavailability of the drug reaches 100%. Sotalol's plasma half-life is 15 hours (range 7-18) and is dependent only on renal function. In clinical practice, it has been found effective in the suppression of nearly all supraventricular and ventricular dysrhythmias except those related to prolonged ventricular repolarization. Most common adverse effects are dyspnea, bradycardia, and fatigue, which results in drug termination in 16% of the cases. Torsades de pointes usually associated with bradycardia and drug induced QTc prolongation has been reported in 1.9%-3.5% of the patients receiving sotalol. This complication may be reduced by limiting the dose (< 640 mg/day) especially in patients with impaired renal function. In addition hypokalemia must be avoided. To sum up, the combination of Class II and Class III effects may carry additional benefits. However, further studies are required to test such hypotheses.

Empiric use of amiodarone and sotalol

Several studies have demonstrated that class I antiarrhythmic drugs do not reduce, and may increase, sudden cardiac death mortality and total cardiac mortality. Because of this, alternative drug choices for antiarrhythmic therapy are necessary. Amiodarone has been demonstrated to be an important and effective antiarrhythmic agent, as has sotalol. The purpose of this article is to review the various indications and possible benefits of the empiric use of these 2 antiarrhythmic agents.

Safety and efficacy of oral sotalol for sustained ventricular tachyarrhythmias refractory to other antiarrhythmic agents

The safety and efficacy of oral sotalol were evaluated in 481 patients with drug-refractory sustained ventricular tachyarrhythmias (VT) in an open-label multicenter study. After drug-free baseline evaluations, therapy was initiated at 80 mg every 12 hours, with upward dose titrations of 160 mg/day being allowed at intervals of 72 hours to a maximum dose of 480 mg every 12 hours. Efficacy determinations were made by either programmed electrical stimulation (PES) or Holter monitoring responses. Of the 481 patients enrolled, 473 underwent acute-phase titration. Of the 269 patients assessable by PES, 94 (34.9%) exhibited complete response (suppression of inducible VT), with an additional 67 patients (24.9%) exhibiting partial response. Of the 109 patients assessable by Holter monitoring, 43 (39.4%) exhibited a complete response. There were no significant differences between responders and nonresponders with regard to left ventricular ejection fraction. Although response rates tended to improve as the sotalol dose was increased to 640 mg/day, efficacy was most commonly achieved at a sotalol dose of 320 mg/day. Sotalol was discontinued because of adverse effects in 42 (8.9%) of the acute-phase patients. The most common adverse effect was proarrhythmia, which was observed in 23 patients (4.9%). Proarrhythmia took the form of torsades de pointes in 12 patients and an increase in VT episodes in 11. In 3 acute-phase patients (0.6%), sotalol was discontinued because of the emergence of congestive heart failure. A total of 286 patients entered the long-term phase. Life-table estimates of the proportion of patients who remained free of recurrence of arrhythmia at 12, 18, and 27 months were 0.76, 0.72, and 0.66, respectively. There were no significant differences in time to recurrence of arrhythmia as related to PES response, Holter monitor response, baseline left ventricular ejection fraction, or history of congestive heart failure. Among the 70 patients (24.5%) in whom there was recurrence of arrhythmia, sudden death occurred in 17 and sustained VT in 41. Sotalol was discontinued owing to presumed adverse effects in 21 (7.3%) of the long-term patients, including 8 with proarrhythmia; proarrhythmia consisted of torsades de pointes in 3 patients and increased episodes of VT in 5. These findings suggest that sotalol is an effective drug for the long-term treatment of patients with drug-refractory sustained VT. Proarrhythmia was observed in only 6.4% of the study population and tended to occur during the acute titration phase. The need to discontinue therapy because of congestive heart failure was uncommon.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrophysiologic basis for the antiarrhythmic actions of sotalol and comparison with other agents

Although synthesized as a nonselective beta-adrenergic blocking compound, sotalol has emerged as the prototype of the so-called class III antiarrhythmic compounds. It delays cardiac repolarization by inhibiting the delayed rectifier potassium current, having a lesser effect on the inward rectifying potassium current with little or no effect on the inward calcium or sodium currents. This property of prolonging repolarization with an accompanying increase in the effective refractory period is not due to blockade of the beta-adrenergic receptors. The major electrophysiologic profile of sotalol constitutes the summed effects of beta blockade and prolonged repolarization. Sotalol exerts a potent antifibrillatory action modulated by its antiadrenergic effects. It suppresses premature ventricular contractions and nonsustained ventricular tachycardia while preventing inducible ventricular tachycardia and fibrillation in patients with advanced structural heart disease. The compound is therefore likely to exert a broad spectrum of antiarrhythmic actions in ventricular arrhythmias.

Sotalol: a novel beta-blocker with class III anti-arrhythmic activity

Initially synthesized in 1960, sotalol is a novel beta-adrenoreceptor blocking agent that also possesses class III anti-arrhythmic properties. The drug's ability to lengthen repolarization and prolong effective refractory periods in all cardiac tissues in addition to its beta-blocking effects make sotalol an attractive agent for use in a variety of supraventricular and ventricular arrhythmias.

Treatment of ventricular arrhythmias after CAST

OBJECTIVE

The primary objective of this article is to review the management of ventricular arrythmias in the light of the unfavourable results reported in the Cardiac Arrhythmia Suppression Trial (CAST).

STUDY SELECTION, DATA EXTRACTION AND SYNTHESIS

CAST tested the hypothesis that suppression of ventricular arrhythmias recorded on a Holter monitor in patients with myocardial infarction would lead to a decrease in subsequent mortality, presumably by preventing sudden death. In the trial, patients with a myocardial infarction which occurred six days to two years previously and with asymptomatic ventricular premature beats which could be suppressed by one of the antiarrhythmic agents flecainide, encainide or moricizine, were randomised to treatment with one of these agents or placebo. Over a mean follow-up period of 10 months, mortality was significantly higher in those patients receiving flecainide or encainide than in those receiving placebo. On the recommendation of the Data and Safety Monitoring Board the trial in these groups was terminated. More recently CAST II in which moricizine was compared to placebo was also terminated, again because of a higher mortality in the patients receiving active treatment. It is likely that much of the excess mortality can be attributed to proarrhythmic effects of the agents.

CONCLUSION

Current management of ventricular arrhythmias are considered in the light of these findings. CAST suggests that specific treatment should be dictated by the presence of associated symptoms and as much by associated structural heart disease as the arrhythmia per se. In particular, specific treatment of ventricular premature beats alone should be avoided. In those with potentially lethal ventricular arrhythmias, referral for appropriate investigation and consideration of non-pharmacological measures is necessary.

Efficacy of intravenous sotalol for suppressing inducibility of supraventricular tachycardias at rest and during isometric exercise

The efficacy of intravenous sotalol (1 mg/kg) for suppressing inducibility of supraventricular tachycardias (SVT) with different electrophysiologic mechanisms was studied in 30 consecutive patients referred for an electrophysiologic study because of paroxysmal SVT. Orthodromic SVT using accessory atrioventricular (AV) connection was inducible in 14 patients, AV nodal reentrant SVT in 8, and intraatrial SVT in 8 before administration of sotalol, Isometric handgrip exercise facilitated the inducibility of SVT in 8 patients who were noninducible at rest. After intravenous sotalol, 7 of 14 patients (50%) with orthodromic SVT, 8 of 8 (100%) with AV nodal reentrant SVT, and 8 of 8 (100%) with intraatrial reentrant SVT became noninducible into sustained SVT, Isometric exercise facilitated the inducibility of only 3 nonsustained SVT runs after sotalol infusion, and exercise did not reverse the prolongation of refractory periods of the atrium, AV node, accessory pathway and ventricle caused by sotalol. During a mean follow-up period of 18 +/- 7 months, none of the 14 patients who remained noninducible into sustained SVT during the stress test after intravenous sotalol and tolerated long-term oral sotalol therapy had recurrence of symptomatic SVT. Thus, sotalol is efficacious for suppressing SVT with AV nodal or intraatrial reentrant mechanism, but less efficacious in patients with accessory AV pathway. The beta-blocking and cellular antiarrhythmic effects of sotalol are not significantly reversed by exercise.

Efficacy and electrophysiologic effects of oral sotalol in patients with sustained ventricular tachycardia caused by coronary artery disease

The efficacy of oral sotalol in preventing sustained ventricular tachycardia induction by invasive electrophysiological testing was assessed in 22 patients (60 +/- 9 years) with prior myocardial infarction. Programmed stimulation consisted of two basic drives followed by up to three extrastimuli at two right ventricular sites. At baseline, sustained monomorphic ventricular tachycardia was inducible in all patients. With sotalol (360 +/- 172 mg/day), it was no longer inducible in 10 patients; in 12 others, it remained inducible and its cycle length was only minimally prolonged (322 +/- 42 to 345 +/- 44 msec, p less than 0.05). Sotalol markedly prolonged sinus cycle length, uncorrected QT interval, and right ventricular effective and functional refractory periods, but had little effect on ventricular conduction time either in sinus rhythm or with right ventricular pacing. There was no significant difference in drug dose or in electrophysiologic effect of drug that related to efficacy, nor was there any correlation between drug-induced prolongation of ventricular tachycardia cycle length and its effects. Six patients received oral sotalol over the long term without spontaneous recurrence of ventricular tachycardia (follow-up: 23 +/- 18 months). These results demonstrate that sotalol is effective (45%) against sustained ventricular tachycardia induction at moderate doses and is well tolerated over a long term in the setting of remote myocardial infarction. However, its electrophysiologic effects as measured at invasive testing are not predictive of efficacy against ventricular tachycardia induction.

Safety and efficacy of sotalol in patients with drug-refractory sustained ventricular tachyarrhythmias

The safety and efficacy of oral sotalol, an investigational beta-adrenergic blocker with class III antiarrhythmic drug properties, were examined in a multicenter study in 236 patients with sustained ventricular tachyarrhythmias. In 104 patients, the index arrhythmia was a cardiac arrest, and all patients had undergone at least 3 previous unsuccessful antiarrhythmic trials (mean = 5 per patient). In the 106 patients assessed by programmed electrical stimulation, sotalol completely suppressed induction of ventricular tachycardia (VT) in 33 (31%) and rendered VT slower (greater than 100 ms prolongation of cycle length) or more difficult to induce in 29 (27%). Using continuous 24-hour ambulatory monitoring methods, sotalol complete- and partial-response rates were 51 and 12%, respectively. Of the 236 acute-phase patients, 151 were discharged receiving long-term sotalol therapy. The median sotalol dose was 480 mg/day. At a mean follow-up of 346 +/- 92 days, 27 patients (18%) had recurrence of sustained arrhythmia; 9, sudden death; 11, sustained VT; 5, automatic defibrillator discharge; and 2, syncope. Adverse effects forced discontinuation of therapy in 10 patients (7%): 6 secondary to symptomatic bradyarrhythmia, 2 due to refractory heart failure, 1 due to torsades de pointes, and 1 from bronchospasm. Life-table analysis of sotalol's overall long-term efficacy at 6, 12 and 18 months were 80, 76 and 72%, respectively. Although mean follow-up was short (less than 1 year), neither acute-phase programmed stimulation nor 24-hour ambulatory monitoring responses were significantly predictive of subsequent arrhythmic outcome. Proarrhythmia was documented in 18 patients (7%), 17 during the acute phase and 1 during long-term follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)