Effects of intravenous sotalol in patients with atrioventricular accessory pathways

Supraventricular Tachycardia

The term paroxysmal supraventricular tachycardia encompasses a heterogeneous group of arrhythmias with different electrophysiologic characteristics. Knowledge of the mechanism of each supraventricular tachycardia is important in determining management in the office, at the bedside, and in the electrophysiology laboratory. Paroxysmal supraventricular tachycardias have an abrupt onset and offset, typically initiating and terminating with premature atrial ectopic beats. In the acute setting, both vagal maneuvers and pharmacologic therapy can be effective in arrhythmia termination. Catheter ablation has revolutionized therapy for many supraventricular tachycardias, and newer techniques have significantly improved ablation efficacy and decreased periprocedural complications and procedure times.

The Use of Intravenous Sotalol in Cardiac Arrhythmias

Sotalol is a non-selective beta-adrenergic blocking agent without intrinsic sympathomimetic activity. It has the additional unique property of producing pronounced prolongation of the cardiac action potential duration. Sotalol therapy has been indicated for the management of supraventricular arrhythmias, refractory life threatening ventricular arrhythmias and atrial fibrillation/flutter. Until recently, sotalol was only available in the oral form, however, it was approved for intravenous administration by the US Food & Drug Administration (FDA). The current recommendations are for sotalol 75-150mg to be administered intravenously over 5hours. This rate of administration does not reflect the majority of the research that has been performed with regards to intravenous sotalol. Also, the safety of intravenous bolus dosing of 100mg over 1 and 5minutes has previously been demonstrated. The antiarrhythmic action of sotalol depends on its ability to prolong refractoriness in the nodal and extra nodal tissue. Hence, by giving a lower dose over a long duration, patients may not necessarily benefit from its anti-arrhythmic potential. The purpose of this article is to review the research that has been conducted with regards to dosage and safety of intravenous sotalol, its electrophysiological effects and finally the spectrum of arrhythmias in which it has been used to date.

Meta-analysis of the Risk of Torsades de Pointes in patients treated with intravenous racemic sotalol

OBJECTIVE

Intravenous (IV) racemic sotalol is useful for the treatment of multiple tachydysrhythmias. The authors hypothesized that the risk of torsades de pointes (TdP) in patients treated with a single IV infusion of sotalol is lower than the 2-4% risk associated with chronic oral sotalol therapy.

METHODS

A MEDLINE search under the subject heading "sotalol" was made of all publications involving humans written in English or German from 1966 to October 1, 2000. A meta-analysis of all original reports including patients who were given a single infusion of at least 1.5 mg/kg or 100 mg of IV sotalol over 30 minutes or less was performed. Potential variables predictive of TdP were assessed. The primary outcome was the observation of TdP associated with IV sotalol infusion. Secondary measurements included hypotension, bradycardia, and worsening of congestive heart failure. All excluded studies and case reports were also examined for evidence of TdP associated with IV sotalol treatment.

RESULTS

The search included 1,005 publications. There were 37 reports in which 962 patients received IV sotalol and met the inclusion criteria. There was one report of self-terminating TdP lasting 10 seconds among the 962 patients included in the study. There was no report of TdP associated with only IV racemic sotalol administration in any of the excluded studies. If it is assumed that the risk of TdP is homogeneous in the population of patients treated with IV sotalol, then based on the 962 included patients, the rate of TdP is 0.1% (95% CI = 0.003% to 0.6%).

CONCLUSIONS

The overall risk of TdP in patients treated with a single infusion of IV sotalol is low compared with that in patients given chronic oral sotalol therapy.

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.

Short-term myocardial uptake of d- and l-sotalol in humans: relation to hemodynamic and electrophysiologic effects

The myocardial concentration of many cardioactive drugs has been identified as an important determinant of their short-term effects in previous studies. Although sotalol is frequently administered via short-term intravenous injection, no previous studies had sought to correlate its uptake by the heart with its various effects. We determined the time course of short-term uptake of d,l-sotalol by human myocardium in vivo and investigated the relation between myocardial content of sotalol and the short-term hemodynamic, electrocardiographic, and electrophysiologic effects of the drug. Sixteen patients received a 20-mg intravenous bolus of sotalol at the time of diagnostic cardiac catheterization. Myocardial content of d- and l-sotalol (by using a paired transcoronary sampling technique) and the short-term hemodynamic and electrophysiologic effects of the drug were determined < or = 20 min after injection. Myocardial accumulation of sotalol was not enantioselective, proceeded very rapidly (maximal at 0.74 +/- 0.10 min, representing 2.05 +/- 0.45% of the total injected dose), and was not significantly influenced by left ventricular systolic function or the extent of coronary artery disease. Approximately one third of peak myocardial content was still present 17.5 min after sotalol administration. Maximal effects of the drug (reduction in spontaneous heart rate, p < 0.005; reduction in maximal rate of LV pressure increase (LV+dP/dtmax, p < 0.005); and prolongation of PR intervals, p < 0.02) were delayed by approximately 10 min relative to maximal myocardial sotalol content. The significant prolongation of AH intervals (p < 0.01) and atrioventricular nodal effective refractory periods (p < 0.0002) that was observed was also maximal 10 min after administration of sotalol. Thus a consistent delay between myocardial sotalol content and the short-term effects of the drug was observed. In conclusion, the accumulation of both d- and l-sotalol by the human myocardium is more rapid than that of any other agent studied to date, with considerable hysteresis between myocardial drug uptake and subsequent cardiac effects.

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.

Sotalol: a breakthrough antiarrhythmic?

OBJECTIVE

To review the pharmacology, pharmacokinetic, dosing, adverse effects, and therapeutic uses of sotalol.

DATA IDENTIFICATION

Articles were identified with an English-language literature computer search via Knowledge Finder, using the term sotalol, and with an extensive search of bibliographies of identified articles.

STUDY SELECTION

Relevant or representative animal studies, human trials, and case reports were selected for evaluation.

DATA EXTRACTION

The literature was assessed for quality, methodology, and outcome information.

DATA SYNTHESIS

Sotalol is a racemic compound with Class II (beta-blocking properties) and Class III (prolonged action potential) antiarrhythmic activity. It has been suggested that the plasma concentration associated with QTc prolongation (a measure of the Class III action) is much greater than that associated with beta-blockade. Therefore, sotalol is categorized as a Class III antiarrhythmic agent. The 1-isomer is responsible for the beta-blocking activity, whereas both isomers have Class III properties. After oral dosing in fasting patients with normal renal function, sotalol is > 90 percent absorbed, achieves peak serum concentrations in 2-4 h, is excreted unchanged 80-90 percent in the urine, has a volume of distribution of 1-2 L/kg, and has an elimination half-life of about 12 h. Sotalol is effective in patients with life-threatening ventricular arrhythmias that have been refractory to other conventional antiarrhythmic drugs. In general, sotalol appears to be well tolerated, with many of its adverse effects caused by beta-blocking activity. As with other antiarrhythmic agents, the possibility of proarrhythmia (frequently torsade de pointes) exists.

CONCLUSIONS

Racemic sotalol is an effective Class III antiarrhythmic agent approved by the Food and Drug Administration for the treatment of documented life-threatening ventricular arrhythmias. Investigations continue with racemic sotalol in the management of supraventricular arrhythmias. Trials with the d-isomer are also ongoing.

Sotalol. An updated review of its pharmacological properties and therapeutic use in cardiac arrhythmias

Sotalol is a nonselective beta-adrenoceptor antagonist which prolongs cardiac repolarisation independently of its antiadrenergic action (class III antiarrhythmic properties). The antiarrhythmic action of sotalol appears to arise predominantly from its class III properties, and the drug exhibits a broader antiarrhythmic profile than the conventional beta-blockers. Sotalol is effective in controlling paroxysmal supraventricular tachycardias and the ventricular response to atrial fibrillation/flutter in Wolff-Parkinson-White syndrome, in maintaining sinus rhythm after cardioversion of atrial fibrillation/flutter, and in preventing initiation of supraventricular tachyarrhythmias following coronary artery bypass surgery. Sotalol shows promise in the control of nonmalignant and life-threatening ventricular arrhythmias, particularly those associated with ischaemic heart disease. It is effective in suppressing complex forms of ventricular ectopy, displaying superior antiectopic activity to propranolol and metoprolol. The acute efficacy of sotalol in preventing reinduction of sustained ventricular tachyarrhythmias and suppressing spontaneous episodes of these arrhythmias on Holter monitoring is translated into long term prophylactic efficacy against arrhythmia recurrence in approximately 55 to 85% of patients with refractory life-threatening ventricular arrhythmias. In addition, sotalol offers the advantage over the class I agents of reducing cardiac and all-cause mortality in the high risk population with life-threatening ventricular arrhythmias. The adverse effects of sotalol are primarily related to its beta-blocking activity and its class III property of prolonging cardiac repolarisation. Sotalol is devoid of overt cardiodepressant activity in patients with mild or moderate left ventricular dysfunction. The overall arrhythmogenic potential is moderately low, but torsade de pointes may develop in conjunction with excessive prolongation of the QT interval due to bradycardia, hypokalaemia or high plasma concentrations of the drug. In summary, sotalol displays a broad spectrum of antiarrhythmic activity, is haemodynamically well tolerated, and confers a relatively low proarrhythmic risk. It is likely to prove particularly appropriate in the treatment and prophylaxis of life-threatening ventricular tachyarrhythmias.

Short- and long-term antiarrhythmic and hemodynamic effects of d,l-sotalol in patients with symptomatic ventricular arrhythmias

The antiarrhythmic and hemodynamic effects of sotalol (160 to 480 mg/day), a beta-blocking agent that prolongs ventricular repolarization, were examined in 38 patients with complex symptomatic ventricular ectopic activity. During ambulatory monitoring, 24 patients (63%) exhibited a reduction of greater than 75% in single ventricular premature beats (VPBs) and greater than 90% reduction in repetitive arrhythmia. In contrast to the effects of other agents, left ventricular ejection fraction as determined by radionuclide angiography was not impaired, increasing slightly from 45 +/- 14% to 47 +/- 14% during therapy (p less than 0.05). Antiarrhythmic drug efficacy did not correlate with baseline ejection fraction or sotalol-induced changes in ventricular function. Late follow-up studies disclosed that antiarrhythmic efficacy and tolerance were maintained in the majority of patients. Repeat radionuclide angiography at 6 months revealed no late drug-induced depression of left ventricular function. Sotalol appears to be an effective and well tolerated agent for treatment of complex ventricular ectopic activity, even in the setting of compromised cardiac function.

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.

Electrophysiologic evaluation of antiarrhythmic drugs

Electrophysiologic techniques are used to assess the properties of antiarrhythmic drugs and also to provide support for the selection of antiarrhythmic therapy for individual patients. Assessment of the antiarrhythmic efficacy of drugs requires that the arrhythmia can be induced by programmed electrical stimulation and is critically dependent on the stimulation protocol. Continued inducibility on drug therapy appears to be a strong predictor of recurrences and sudden death, although the predictive value of electrophysiologic testing remains controversial for some drugs. These techniques may also be useful for determining the proarrhythmic potential of antiarrhythmic agents, but the aggravation of tachycardia that occurs in 10-30% of patients during electrophysiologic testing is unpredictable and its significance is unknown. The electrophysiologic approach to drug therapy has limitations, but, nevertheless, it is useful and should maintain a prominent place in the evaluation of antiarrhythmic therapy.

Sotalol for paroxysmal supraventricular tachycardias

Used in adequate dosages, sotalol is efficacious in the conversion of acute supraventricular arrhythmias, an effect that is predictable on the basis of the drug's known electropharmacologic actions. Electrophysiologic studies have shown that both oral and intravenous sotalol are effective in preventing the induction of sustained arrhythmias and that the success of acute suppression is indicative of subsequent clinical control. Interim results of a recent trial of prophylaxis against recurrence of paroxysmal supraventricular tachycardia are reported, demonstrating a high efficacy with an acceptably low profile of adverse effects.

Efficacy, safety, and tolerance of d-sotalol in patients with refractory supraventricular tachyarrhythmias

The efficacy, safety, and electrophysiologic effects of intravenous and oral d-sotalol, an investigational class III antiarrhythmic agent, are not yet well characterized. We evaluated the electrophysiologic, antiarrhythmic, and hemodynamic effects of d-sotalol infusion (1.5 to 2.75 mg/kg) and of chronic oral therapy (200 to 400 mg bid) in 10 patients with chronic, paroxysmal supraventricular tachyarrhythmias refractory to 5 +/- 2 standard agents. Four patients had paroxysmal supraventricular tachycardia (PSVT), four had paroxysmal atrial fibrillation, two had atrial flutter, and one had nonparoxysmal reciprocating junctional tachycardia (NPRJT). PSVT was inducible or spontaneously present in 4 of 4 before d-sotalol. After intravenous d-sotalol PSVT was noninducible in three patients and slowed by 40% in one. Atrial fibrillation was inducible or spontaneously present in 4 of 4 before therapy. After intravenous d-sotalol, one became noninducible, and three achieved rate-slowing (the mean falling from 69 to 61 bpm). In one patient, atrial flutter became noninducible; in another, d-sotalol slowed the rate of atrial flutter by 28%. D-sotalol restored sinus rhythm in the patient with NPRJT. Intravenous d-sotalol increased the sinus cycle length; the QTc, PR, and AH intervals; and the AV nodal functional refractory period, the AV nodal effective refractory period; and the right ventricular effective refractory period significantly. The atrial effective refractory period, sinoatrial conduction time, and corrected sinus recovery time tended to increase, but did not reach statistical significance. The QRS, PA, and HV intervals did not change. Mean BP fell 13.4 +/- 9.2% after intravenous d-sotalol, but no adverse symptoms developed.(ABSTRACT TRUNCATED AT 250 WORDS)