Sotalol in patients with Wolff-Parkinson-White syndrome

[Historical developments in the diagnosis and treatment of pre-excitation syndromes (WPW)]

In 1930, Wolff, Parkinson and White described the syndrome that bears their names. The mechanisms of supraventricular tachycardias were analyzed by brilliant electrocardiography interpretation by Pick and Langendorf. Wellens and Durrer using electrophysiologic studies analyzed the tachycardia mechanism invasively. In Germany the group by Seipel and Breithardt as well as Neuss and Schlepper studied the tachycardia mechanisms and response to antiarrhythmic drugs invasively by electrophysiological studies. Following the first successful interruption of an accessory pathway by Sealy in 1967, surgeons and electrophysiologists cooperated in Germany. Two centers, Hannover and Düsseldorf were established. Direct current (DC) ablation of accessory pathways was introduced by Morady and Scheinman. Because of side effects induced by barotrauma of DC, alternative strategies were studied. In 1987, radiofrequency ablation was introduced and thereafter established as curative therapy of accessory pathways in all locations.

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.

Antiarrhythmic Drug Therapy of Supraventricular Tachycardia

Pharmacologic therapy is commonly used for the acute treatment and termination of paroxysmal supraventricular tachycardia (SVT) and continues to be an important long-term option for some patients. Drug choice depends on the correct diagnosis of the arrhythmia and an understanding of its mechanism. Pharmacologic agents commonly used in the acute and chronic treatment of SVT are reviewed along with their effect on the various types of SVT. Drugs that are well tolerated with minimal side effects are preferred over agents with perhaps more efficacy but higher risk of toxicity.

Pharmacokinetics/Pharmacodynamics of Antiarrhythmic Drugs

This article describes the pharmacology of antiarrhythmic medications. Although these medications are broadly considered in terms of their blockade of either sodium or potassium channels, they act by a variety of pharmacodynamic mechanisms. Elimination may be via hepatic metabolism or renal mechanisms, or a combination. In particular, interactions between antiarrhythmic medications and other drugs that interfere with hepatic metabolism by P450 enzymes is a source for toxicity.

Sotalol in treatment of pediatric cardiac arrhythmias

BACKGROUND

There is limited experience on sotalol use in the management of childhood arrhythmias. This study reviews the results of our experience with oral sotalol for treatment and prevention of tachyarrhythmias in children.

METHODS

The records of 62 patients (27 female, 35 male, mean age: 8.5+/-5.3 years) treated with sotalol for supraventricular or ventricular arrhythmias from 1994 to 1999 at our institution were reviewed. Demographic, clinical, echocardiographic, electrocardiographic (ECG), ambulatory ECG and electrophysiologic variables were collected.

RESULTS

Forty-two (63.6%) patients had re-entrant supraventricular tachycardia, eight patients (12.9%) had atrial tachycardia, one patient (1.6%) had junctional ectopic tachycardia, four patients (6.5%) had ventricular tachycardia, and seven patients (11.3%) had complex ventricular arrhythmias, as evidenced by surface or ambulatory ECG records; or revealed during the electrophysiological study. The mean sotalol dose was 3.9+/-1.2 mg/kg per day. In 15.5+/-13.9 months of sotalol use 50% (n=31) had complete relief of symptoms and/or arrhythmia and 29% (n=18) had partial relief. Sotalol was ineffective in 20% (n=13). Sotalol was more effective in re-entrant type supraventricular tachycardias (P=0.012). Sotalol was the first choice in 35.5% of patients. The sotalol therapy was initiated in inpatient settings in 40.3% (25 patients). Complications due to sotalol were seen in six patients (five patients developed bradycardia/pauses, and one patient had torsades de pointes) for which the sotalol dose was modified. In patients with sick sinus syndrome, a pacemaker was implanted and in another patient sotalol was stopped.

CONCLUSION

Sotalol, being an effective and safe drug particularly in children, is a good therapeutic alternative for the preventive treatment of childhood tachyarrhythmias.

Supraventricular tachycardia

Supraventricular tachycardias (SVT) comprise those tachycardias that originate above the bifurcation of the bundle of His. They can be classified broadly as AV node dependent and AV node independent. The mechanism and clinical manifestation of SVTs, which is essential to their correct diagnosis, is reviewed. The therapeutic management of SVTs, including acute and chronic drug therapy and catheter ablation, is discussed also.

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.

Current role of pharmacologic therapy for patients with paroxysmal supraventricular tachycardia

Intravenous antiarrhythmic drugs will continue to have an important role in the acute management of SVT. Long-term antiarrhythmic drug therapy is often effective in preventing or reducing frequency and severity of arrhythmic episodes. The cost, adverse effects, and inconvenience of long-term drug therapy will result in the increasing use of curative ablation for most individuals with problematic SVT.

Effect of low dose sotalol on the signal averaged P wave in patients with paroxysmal atrial fibrillation

OBJECTIVE

To investigate the effects of low dose sotalol on the signal averaged surface P wave in patients with paroxysmal atrial fibrillation.

DESIGN

A longitudinal within patient crossover study.

SETTING

Cardiac departments of a regional cardiothoracic centre and a district general hospital.

PATIENTS

Sixteen patients with documented paroxysmal atrial fibrillation. The median (range) age of the patients was 65.5 (36-70) years; 11 were men.

MAIN OUTCOME MEASURES

Analysis of the signal averaged P wave recorded from patients not receiving antiarrhythmic medication and after 4-6 weeks' treatment with sotalol. P wave limits were defined automatically by a computer algorithm. Filtered P wave duration and energies contained in frequency bands from 20, 30, 40, 60, and 80 to 150 Hz of the P wave spectrum expressed as absolute values (P20, P30, etc) and as ratios of high to low frequency energy (PR20, PR30, etc) were measured.

RESULTS

No difference in P wave duration was observed between the groups studied (mean (SEM) 149 (4) without medication and 152 (3) ms with sotalol). Significant decreases in high frequency P wave energy (for example P60: 4.3 (0.4) v 3.3 (0.3) microV2.s, P = 0.003) and energy ratio (PR60: 5.6 (0.5) v 4.7 (0.6), P = 0.03) were observed during sotalol treatment. These changes were independent of heart rate.

CONCLUSIONS

Treatment with low dose sotalol reduces high frequency P wave energy but does not change P wave duration. These results are consistent with the class III effect of the drug and suggest that signal averaging of the surface P wave may be a useful non-invasive measure of drug induced changes in atrial electrophysiology.

Efficacy and proarrhythmia of oral sotalol in pediatric patients

OBJECTIVES

This study sought to assess the efficacy of oral sotalol for various arrhythmias in pediatric patients and to evaluate the incidence of proarrhythmia and systemic side effects.

BACKGROUND

Sotalol is a beta-adrenergic blocking agent with additional class III antiarrhythmic properties. Experience in pediatric patients is limited. Data concerning the incidence of proarrhythmia in children are lacking.

METHODS

Seventy-one pediatric patients (mean age 7.3 years) with various supraventricular and ventricular tachyarrhythmias were treated with oral sotalol. All the patients were admitted to the hospital for initiation of sotalol therapy. Antiarrhythmic and proarrhythmic effects of sotalol were assessed by daily surface electrocardiograms (ECGs) during the in-hospital phase and by serial Holter monitoring.

RESULTS

Sotalol was either completely (27 [66%] of 41 patients) or partially effective (11 [27%] of 41) in 38 (93%) of 41 patients with supraventricular reentrant tachycardias. In patients with atrial flutter predominantly after operation for congenital heart disease, sotalol was effective in 84% of patients (completely in 9 of 19 and partially in 7 of 19). Ventricular tachycardia was completely (3 of 11) or partially (4 of 11) controlled in 64% of children. Proarrhythmia occurred in seven patients (10%) and consisted of symptomatic bradycardia from sinoatrial block and high grade atrioventricular (AV) block, respectively, in two children; asymptomatic high grade AV block in one; torsade de pointes in one; and relevant increased ventricular ectopic activity in three. Proarrhythmia required drug discontinuation in four patients. Mean duration of treatment for all patients was 18 months (range 1 to 40).

CONCLUSIONS

Sotalol was an effective antiarrhythmic drug for a wide range of pediatric tachyarrhythmias. The considerable number of patients with proarrhythmic effects indicates the need for initiation of treatment on an inpatient basis and close monitoring by serial Holter electrocardiography.

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.

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

Sotalol is an antiarrhythmic agent with combined beta-blocking and class III antiarrhythmic properties. This study was designed to assess the safety and efficacy of sotalol in terminating supraventricular tachycardia (SVT), atrial fibrillation (AFib), and atrial flutter (AFl). Ninety-three patients with spontaneous or induced SVT (n = 45) or AF (AFib or AFl; n = 48) with a ventricular rate of > or = 120 beats/min were studied. In the first phase, the double-blind phase, patients were randomly assigned to receive placebo or intravenous (i.v.) sotalol, 1.0 or 1.5 mg/kg. If SVT or AF did not convert to sinus rhythm or if the ventricular rate did not slow to < 100 beats/min within 30 minutes, patients then entered the second phase, the open-label phase, which also lasted 30 minutes, and were given 1.5 mg/kg iv sotalol. In the SVT group, during the double-blind phase conversion to sinus rhythm occurred in 2 (14%) of 14 of patients who received placebo, 10 (67%) of 15 who received sotalol, 1.0 mg/kg (p < 0.05 vs placebo), and 10 (67%) of 15 who received 1.5 mg/kg sotalol (p < 0.05 vs placebo); during the open-label phase, 1.5 mg/kg i.v. sotalol converted 7 (41%) of 17 of patients. In the AF group, during the double-blind phase conversion to sinus rhythm occurred in 2 (14%) of 14 of patients who received placebo, 2 (11%) of 18 who received 1.0 mg/kg sotalol (p not significant [NS] vs placebo), and 2 (13%) of 16 who received 1.5 mg/kg sotalol (p = NS vs placebo); in these groups, a > 20% reduction of ventricular rate without conversion to sinus rhythm occurred in 0 (0%) of 14, 13 (72%) of 18 (p < 0.05 vs placebo), and 12 (75%) of 16 of patients (p < 0.05 vs placebo), respectively; during the open-label phase, 1.5 mg/kg i.v. sotalol converted 7 (30%) of 23 of patients. The most common adverse events were hypotension and dyspnea. During the double-blind phase they occurred in 10% of patients who received placebo, 9% of those who received 1.0 mg/kg i.v. sotalol (p = NS vs placebo), and 10% of those who received 1.5 mg/kg i.v. sotalol (p = NS vs placebo). Most of these events were mild to moderate, but all were transient and clinically manageable.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Supraventricular tachyarrhythmias: drug therapy versus catheter ablation

Until recently, the only options available for treatment of supraventricular arrhythmias involved the use of drug therapy or cardiac surgery. However, over the past several years with the introduction of radiofrequency energy sources as well as steerable catheters, the clinician has a variety of additional nonpharmacologic options. This article reviews the use of pharmacologic therapy versus catheter ablation for the treatment of reentrant supraventricular arrhythmias, involving the atrioventricular junction and/or accessory atrioventricular connection, as well as arrhythmias emanating from the atria such as atrial fibrillation, atrial flutter, and atrial tachycardia.

Sotalol

Sotalol is a novel antiarrhythmic agent combining beta-adrenergic-antagonist actions with the ability to increase cardiac repolarization and refractoriness. The drug's electrophysiologic and clinical profile is different from that of conventional beta-receptor antagonists. As compared with other antiarrhythmic agents, sotalol prevents recurrences of arrhythmia in a higher proportion of patients, particularly among those presenting with ventricular tachycardia and aborted sudden cardiac death. The net hemodynamic effect of sotalol is the result of a balance between the depressant effects due to beta-receptor blockade and an action that tends to increase contractility. Although initially marketed in the United States for treatment of life-threatening ventricular arrhythmias, sotalol also has demonstrated efficacy in many patients with supraventricular arrhythmias. As with all drugs that prolong the QT interval, the syndrome of torsade de pointes is a serious potential adverse effect.

Comparative effects of the combination of digoxin and dl-sotalol therapy versus digoxin monotherapy for control of ventricular response in chronic atrial fibrillation. dl-Sotalol Atrial Fibrillation Study Group

To establish the value of adjuvant dl-sotalol to digoxin for control of the ventricular response in chronic atrial fibrillation, 60 patients were evaluated in a multicenter, randomized, double-blind, parallel, placebo-controlled study. Patients were evaluated with serial ambulatory ECG monitoring and exercise testing during stable digoxin dosing and then with the addition of either a placebo or dl-sotalol, 80 mg/day, or dl-sotalol, 160 mg/day. The combination of digoxin and dl-sotalol, at either 80 or 160 mg/day, resulted in a statistically significant reduction in heart rate at rest and with exercise during both exercise testing and ambulatory monitoring. No significant difference was observed between the two doses of dl-sotalol. There was no significant difference with regard to symptoms or side effects among the three groups. In summary, dl-sotalol was noted to be a safe and effective adjuvant to digoxin for control of the ventricular response in chronic atrial fibrillation.

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.

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.

Sotalol

Sotalol causes noncardioselective beta-adrenergic antagonism and prolongation of repolarization of cardiac tissues (Class III electrophysiologic action). This dual pharmacologic profile confers unprecedented antiarrhythmic properties to the drug. Sotalol is highly bioavailable when administered orally in the fasting state and is mostly cleared unchanged in the urine with an apparent half-life of elimination of 15 to 17 hours. It has been found effective in the suppression of nearly all cardiac arrhythmias, with the exception of those precipitated by prolongation of ventricular repolarization. Its safety and efficacy relative to other antiarrhythmic drugs need to be examined more fully in randomized controlled trials of unselected patients. The adverse effects potentially associated with the use of sotalol are those commonly observed with beta-adrenergic blockade, as well as those resulting from excessive prolongation of the QT interval. The occurrence of torsade de pointes during treatment with sotalol may be minimized by limiting doses to no more than 640 mg/day and by strictly avoiding the development of hypokalemia.

Atrial fibrillation in Wolff-Parkinson-White syndrome: reversal of isoproterenol effects by sotalol

Sotalol has Class II and III antiarrhythmic effects. Its efficacy and safety as a treatment of atrial fibrillation in patients with the Wolff-Parkinson-White (WPW) syndrome is controversial. We evaluated the effects of isoproterenol and IV sotalol (1.5 mg/kg in 10 minutes) given together versus isoproterenol alone on anterograde conduction through the AV node and accessory pathway. Atrial fibrillation was induced in 22 patients with WPW (13 men, 9 women, 36 +/- 16 years old). AV node and accessory pathway conduction were both enhanced by isoproterenol, although the effect was greater on the AV node. The minimum interval between preexcited QRS complexes shortened in all patients. Conversely, sotalol caused a significant prolongation of the shortest preexcited QRS interval as well as of the shortest interval between narrow QRS complexes. In addition, sotalol reversed all the effects of isoproterenol during atrial fibrillation. The percent of preexcited QRS complexes was not significantly modified because variations in ventricular preexcitation results from a balance between the relative effects on refractoriness of the accessory pathway versus of the AV node and in the amount of respective anterograde and retrograde concealed conduction. There were no serious adverse effects. Reversion to sinus rhythm was documented in 12 patients (60%). These short-term observations suggest that sotalol may be safe and effective in the treatment of patients with WPW and atrial fibrillation.

Flecainide in the Wolff-Parkinson-White syndrome

The effects of flecainide on electrophysiologic parameters and arrhythmias in the Wolff-Parkinson-White syndrome were reviewed. Acute administration of flecainide blocks conduction across the accessory pathway in the anterograde direction in 40% and in the retrograde direction in 50% of cases and markedly prolongs refractoriness in the remaining cases. Flecainide has a lesser effect on refractoriness of the His-Purkinje system, atrium, ventricle, and atrioventricular node. Flecainide terminates atrioventricular tachycardia in greater than 80% of cases when given intravenously, and oral therapy prevents clinical recurrences in greater than 60% of cases, but may occasionally result in incessant tachycardia. Long-term efficacy is predicted by abolition of conduction across the accessory pathway or prevention of tachycardia induction at acute electrophysiologic testing. Concomitant administration of a beta-adrenoreceptor blocker results in greater long-term efficacy. Administered during preexcited atrial fibrillation, flecainide consistently slows the ventricular response and converts the majority of cases to sinus rhythm. Serious ventricular proarrhythmia is seen almost exclusively in patients with structural cardiac disease. Flecainide is a useful drug for the acute and chronic control of tachycardia in Wolff-Parkinson-White syndrome.

Effectiveness of oral sotalol for treatment of pediatric arrhythmias

Sotalol is a beta blocker with class III activity. Few investigators have reported its use in pediatric patients. From August 1985 to May 1990, 66 patients (mean age 8.7 years; range 9 days to 24 years), including 14 infants aged less than 3 months, were treated with oral sotalol alone (n = 46) or in association with digoxin (n = 20). Supraventricular reentrant tachycardia was present in 38 patients (20 with documented preexcitation), atrial flutter in 10 and atrial ectopic tachycardia in 7. Three patients had other types of supraventricular tachycardia. Tachycardia was of ventricular origin in 6 patients and both of supraventricular and ventricular origin in the remaining 2. Mean dose of oral sotalol was 135 mg/m2/day given in 2 doses. Congenital heart disease was present in 28 patients, 14 with previous cardiac surgery, mostly at the atrial level. Prior treatment with 1 or more antiarrhythmic agent had been unsuccessful in 83% of patients. Mean duration of treatment was 13.3 months (range 2 months to 5 years). Overall, treatment was successful in 79% of cases. Highest rate of success was observed in patients with supraventricular reentrant tachycardia with or without preexcitation (89%) and in those with atrial ectopic tachycardia (85.5%). Atrial flutter could be controlled in 60% of cases. Sotalol seemed less effective in ventricular tachycardia with a complete control of the arrhythmia being achieved in only 17%; however, it decreased the number of runs of ventricular tachycardia and the number of ventricular premature complexes in 50% of patients. There were no adverse effects in 89% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

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 safety of intravenous sotalol for termination of paroxysmal supraventricular tachycardia. The Sotalol Versus Placebo Multicenter Study Group

A double-blind, placebo-controlled, crossover, multicenter study was conducted to study the efficacy and safety of a single intravenous dose of sotalol (1.5 mg/kg over 10 minutes) in achieving normal sinus rhythm in paroxysmal supraventricular tachycardia (SVT) lasting greater than or equal to 15 minutes. Patients were randomized to either sotalol or placebo as initial treatment, and if the SVT was not terminated a crossover was performed after 20 minutes. A total of 43 patients were enrolled, 38 of whom with spontaneous (n = 14) or induced (n = 24) SVT were analyzed for sotalol efficacy. Most patients (n = 27) had atrioventricular (AV) nodal reentrant tachycardia, and an important subgroup (n = 11) had circus movement tachycardia, using an accessory pathway for retrograde conduction. The number of patients converting to sinus rhythm as a result of the initial treatment was significantly higher in the sotalol group than in the placebo group, for spontaneous (p less than 0.005) as well as for induced tachycardia (p less than 0.001). Sinus rhythm was achieved within 30 minutes in 83% of all patients who received sotalol as the first drug, compared with 16% of the patients first receiving placebo (p less than 0.0001). For sotalol safety analysis, 42 patients were included. A total of 37 patients received sotalol, 19 as the first treatment, and 18 as the second treatment, while 25 patients received placebo. A total of 15 possible adverse effects were reported, occurring in 10 patients with sotalol versus 4 with placebo. The only severe side effect (hypotension) necessitating termination of drug administration occurred with placebo. No proarrhythmic effects were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined sotalol and flecainide given at low dosage in patients with the Wolff-Parkinson-White syndrome

We determined the effects of combined sotalol (160 mg/day) and flecainide (200 mg/day) in 15 patients with the Wolff-Parkinson-White syndrome. After medication given for 3 days, the plasma levels were 0.8 +/- 0.3 micrograms/ml for sotalol and 232 +/- 104 ng/ml for flecainide. Electrophysiologic testing showed complete blockade of the accessory pathway in 4 patients and a decrease in the anterograde conduction capacity by 27% in the remainder. The effect on the accessory pathway was unrelated to the resting conduction properties. Initiation of circus movement tachycardia was prevented in 5 of 11 patients. During a median period of 28 months of follow-up, 87% of patients were either free of tachycardia or satisfactorily improved. No proarrhythmic or adverse drug effects were observed.

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.

Usefulness of sotalol in suppressing ventricular tachycardia or ventricular fibrillation in patients with healed myocardial infarcts

The electrophysiologic effects and antiarrhythmic efficacy of oral sotalol were investigated in 42 patients with coronary artery disease and prior myocardial infarction who presented with ventricular tachycardia (VT), ventricular fibrillation (VF) or syncope. The mean left ventricular ejection fraction was 36 +/- 9%. Baseline programmed cardiac stimulation initiated sustained VT (26 patients) or VF (16). The induced arrhythmia was not suppressed by conventional antiarrhythmic drugs in any patient (3 +/- 2 trials/patient). The mean daily dosage of sotalol was 221 +/- 84 mg. The right ventricular effective refractory period increased from 247 +/- 25 to 273 +/- 26 ms with sotalol (p = 0.0001) and the corrected QT interval increased from 431 +/- 35 to 456 +/- 62 ms (p = 0.02). Arrhythmia suppression was defined as no sustained VT or VF in response to programmed cardiac stimulation using up to 3 extrastimuli. Induced VT or VF was suppressed by sotalol therapy in 10 (24%) patients (group 1). Group 1 patients had faster induced arrhythmias at the baseline study than patients whose induced ventricular arrhythmia was not suppressed (group 2). The mean left ventricular ejection fraction tended to be higher in group 1 patients (p = 0.07). Fourteen patients (including 9 group 1 patients) continued receiving sotalol after discharge. In 2 group 2 patients, sotalol was combined with a class IA antiarrhythmic drug. During a mean follow-up period of 7.9 +/- 4.9 months, 2 patients had recurrent VT and in 2 others sotalol was discontinued due to side effects.

Diprafenone for treatment of Wolff-Parkinson-White syndrome

The effect of intravenous (1.5 to 2.0 mg/kg body weight) and oral (300 to 375 mg/d) diprafenone was studied in 15 patients with the Wolff-Parkinson-White syndrome and symptomatic supraventricular tachycardia. Intravenous application of diprafenone significantly increased atrioventricular nodal conduction time as well as the effective refractory periods of the right ventricle and the accessory pathway in both the antegrade and retrograde directions. Antegrade conduction block in the accessory pathway occurred in two patients after the dose was increased to 2.0 mg/kg body weight. Intravenous diprafenone suppressed the inducibility of supraventricular tachycardia in two patients, but the tachycardia cycle length was significantly increased in all other patients. Fourteen patients were treated with oral diprafenone, and 11 were asymptomatic during a 17-month follow-up, two of these after the dose had been increased to 375 mg/d. Oral therapy had to be withdrawn in two patients because of adverse gastrointestinal side effects and in one because of recurring bronchospasm.

Clinical experience with sotalol in patients with drug-refractory ventricular arrhythmias

Sixty-five patients with symptomatic, drug-refractory, sustained ventricular tachycardia or fibrillation were treated with oral sotalol (80 to 480 mg twice daily). Sotalol was withdrawn in 11 patients because of continued inducibility of ventricular tachycardia at the time of follow-up electrophysiologic study. Therefore, the clinical effectiveness of sotalol could be evaluated in 54 patients followed up for 11.5 +/- 6 months (range 0.2 to 25). The actuarial incidence of successful sotalol therapy was 54 +/- 13% at 6 months and 47 +/- 13% at 12 months. In 39 patients who underwent electrophysiologic testing while receiving oral sotalol, the drug prevented the reinduction of ventricular tachycardia/fibrillation in 8 (20%). During follow-up study, arrhythmia recurred in 1 (17%) of 6 patients whose ventricular tachycardia was noninducible with oral sotalol and in 8 (44%) of 18 with inducible tachycardia but who were continued on oral sotalol therapy. Adverse effects were noted in 28 patients (42%), requiring drug withdrawal in 13 (22%) and dose reduction after hospital discharge in 10 (15%). Exacerbation of ventricular arrhythmia occurred in six patients (9%), one of whom had associated hypokalemia. Sotalol is frequently useful in the control of intractable, life-threatening ventricular arrhythmias, and its efficacy appears to be predicted by programmed stimulation. However, there is a high rate of limiting side effects, which precludes its use in a large number of patients, and a substantial risk of arrhythmia exacerbation.

Use of intracardiac recordings to determine the site of drug action in paroxysmal supraventricular tachycardia

Paroxysmal supraventricular tachycardia most often results from atrioventricular (AV) reentry using an accessory AV pathway (Wolff-Parkinson-White syndrome) or reentry within the region of the AV node. In AV reentry, using an accessory pathway, suppression of the tachycardia may be achieved by depressing either anterograde AV nodal conduction or retrograde accessory pathway conduction. Intracardiac recordings and programmed electrical stimulation have established that beta-adrenergic antagonists and calcium channel blockers principally affect AV nodal conduction (anterograde limb of the reentrant circuit), whereas class IA and IC agents principally affect the accessory AV pathway (retrograde limb). Pharmacologic therapy has been more effective when directed at the limb in which conduction is most marginal at the tachycardia rate (weak limb). In individual patients, intracardiac recordings and programmed electrical stimulation can be used to identify the weak limb, indicating the class of agents most likely to be effective. Specialized techniques allowing direct recording of accessory pathway activation suggest that limitations in accessory pathway conduction may be explained by anatomic impediments. Conduction is most limited at the atrial interface of the accessory pathway in some patients, whereas in others the ventricular interface may be the limiting factor. Class IA and IC agents appear to have the greatest effect at sites where conduction is most tenuous, i.e., at the anatomic impediments. Similar considerations apply to AV nodal reentry. Anterograde slow AV nodal pathway conduction is most often depressed by digitalis preparations, beta-adrenergic antagonists, and calcium channel blockers, whereas retrograde fast AV nodal pathway conduction is more often depressed by class IA and IC agents. Intracardiac recordings and programmed electrical stimulation can also be used in these patients to identify the weak limb and direct pharmacologic therapy. Direct catheter recordings of AV nodal conduction remain elusive, limiting knowledge of the different conduction properties of the anterograde and retrograde limbs and the site(s) of drug action. Studies in progress, comparing the retrograde AV nodal conduction time during tachycardia with that during ventricular pacing at the same rate, suggest that the His bundle may be incorporated in the reentrant circuit in some patients. It appears that verapamil more readily depresses retrograde fast pathway conduction in these patients than in those in whom the His bundle does not form part of the reentrant circuit, but the reasons for this are unknown.

Sotalol for refractory sustained ventricular tachycardia and nonfatal cardiac arrest

The efficacy and safety of sotalol were assessed by electrophysiologic testing and ambulatory recordings in 16 patients with recurrent sustained ventricular tachycardia (VT) or nonfatal cardiac arrest who were refractory to an average of 4.8 conventional antiarrhythmic agents. Twenty-four-hour ambulatory recordings were performed before and after sotalol therapy. Fourteen patients underwent baseline electrophysiologic study and sustained VT was inducible in 12. Oral sotalol (320 to 960 mg/day) completely suppressed inducible sustained VT in 7 patients (58%), with modification in 3 (25%). Ventricular premature complexes were suppressed from baseline (mean +/- standard deviation) 431 +/- 616 to 60 +/- 110/hr (p less than 0.03). After a mean follow-up of 19 +/- 7 months, 12 of 14 patients receiving sotalol treatment had successful suppression of ventricular premature complexes (60 +/- 85/hr) and remained clinically free of sustained VT, except 2 who needed additional antiarrhythmic drugs to suppress the recurrent sustained VT. One patient died suddenly after 25 months of sotalol treatment. No severe side effects were noted during sotalol therapy. This study demonstrates that sotalol is a well-tolerated, effective antiarrhythmic agent in patients at high-risk for sudden death. It appears to be beneficial in patients who did not benefit from multiple drug treatment.