Electrophysiologic effects of intravenous and oral sotalol for sustained ventricular tachycardia secondary to coronary artery disease

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.

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.

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.

Infarct related artery patency: relation to serial electropharmacological studies and outcome in patients with previous myocardial infarction and ventricular tachyarrhythmias

Evidence suggests that infarct related artery (IRA) patency may improve survival after acute myocardial infarction, which is thought to be partially due to a lower incidence of malignant ventricular tachyarrhythmias. However, little is known about the effect of IRA patency on antiarrhythmic drug response and long-term outcome in patients with previous infarction who already experienced sustained ventricular tachyarrhythmias. A total of 152 patients with remote myocardial infarction and documented ventricular tachycardia (VT) or ventricular fibrillation (VF) underwent coronary angiography and programmed ventricular stimulation before and after oral administration of d,l-sotalol (240-640 mg/day). D,l-sotalol suppressed inducibility of VT/VF in 37 (25.2%) patients. The IRA was patent in 38.1% of all patients. There was no significant difference in the frequency of drug response between patients with patent or occluded IRAs (26.8% vs 24.2%, P = 0.87). In patients with a patent IRA, d,l-sotalol tended to be more effective in the absence of a left ventricular aneurysm, although this difference did not reach statistical significance (P = 0.38). Ejection fraction and collateral blood flow had no effect on drug response in the presence or absence of IRA patency. During follow-up (13.0 +/- 19.9 months) of 29 patients discharged on oral d,l-sotalol, 3 patients experienced symptomatic VT and 4 sudden death. Arrhythmia recurrence and death of all cause (n = 6) and cardiac death (n = 4) were independent of IRA patency status. IRA patency had no effect on short-term drug response to d,l-sotalol in patients with remote myocardial infarction and documented VT/VF. Long-term outcome of patients with sustained ventricular tachyarrhythmias is independent of IRA patency status. In contrast to a previous report, outcome of electropharmacological testing was not predicted by the patency of the IRA.

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.

Parenteral antiarrhythmics for life-threatening ventricular arrhythmias

The acute management of life-threatening ventricular tachyarrhythmias often includes the use of parenteral antiarrhythmics. There are a number of agents currently available for this purpose. They are used to suppress inducible monomorphic ventricular tachycardia during programmed electrical stimulation, they terminate spontaneous sustained ventricular tachycardia, and prevent ventricular fibrillation in the setting of an acute myocardial infarction. Serious adverse reactions include proarrhythmia, hypotension, severe bradyarrhythmias, and precipitation of congestive heart failure. A comparative evaluation of intravenous antiarrhythmics is difficult due to inherent differences in the choice of agents for study, protocol design, patient population, defined endpoint, and serum drug levels. Likewise, the reported adverse reaction rates vary from 0.4% to 75%. To understand the difficulties in clinical decision-making in this problem area, particularly drug selection, we present here a review of pertinent clinical trials evaluating parenteral drug efficacy and adverse effects.

Long-term antiarrhythmic efficacy and safety of d-sotalol in patients with ventricular tachycardia and a low ejection fraction

Since in patients with ventricular tachycardia (VT) and compromised left ventricular function, antiarrhythmic therapy poses a particular problem, an open-label safety study of d-sotalol, a new class III antiarrhythmic agent, was performed. Thirteen patients with defined VT and a low left ventricular ejection fraction (LVEF) were treated with orally administered d-sotalol, 100 mg bid, and in a few patients 100 mg tid, in an open study. Patients were followed up for 35 +/- 11 months, with the longest follow-up amounting to 51 months. The data obtained suggest that d-sotalol was moderately effective as an antiarrhythmic agent, in particular with respect to premature ventricular contractions (PVCs) and coupled and repetitive PVCs. The beneficial effect appeared to persist on long-term treatment. d-Sotalol was well tolerated and no subjective or objective adverse reactions were observed. There were no signs of worsening of congestive heart failure, proarrhythmogenic activity, or torsades de pointes, although QT-prolongation was observed. There were no dropouts in the study. Two patients died: One patient with idiopathic dilated cardiomyopathy (with LVEF = 11%) died suddenly after 38 months of follow-up and one patient after 17 months from recurrent myocardial infarction. Neither of these had shown recurrence of VT on 24 hour ambulatory ECG recordings. In conclusion, in this small group of patients d-sotalol appeared to be safe and well tolerated during long-term treatment of patients with VT and poor left ventricular function. There were clear suggestions of antiarrhythmic activity, reflected by the suppression of complex ventricular arrhythmias and by the absence of recurrent VT on long-term follow-up in the majority of patients.(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.

Multicenter trial of sotalol compared with procainamide in the suppression of inducible ventricular tachycardia: a double-blind, randomized parallel evaluation. Sotalol Multicenter Study Group

Sotalol is the prototype class III agent that combines beta-blocking properties with the propensity to prolong the effective refractory period by lengthening the action potential duration. Its precise effect on the prevention of ventricular tachycardia-ventricular fibrillation (VTVF) compared to class I agents has not been evaluated in a blinded study. In a double-blind parallel-design multicenter study, the electrophysiologic and antiarrhythmic effects of intravenous and oral sotalol (n = 55) and procainamide (n = 55) were therefore compared in patients with VTVF inducible by programmed electric stimulation. Sotalol produced a greater effect on lengthening the ventricular effective refractory period (VERP). It prevented the inducibility of VTVF in 30% versus 20% for procainamide, but this was not significantly different. In an alternate therapy group (n = 41) of similar patients previously refractory to or intolerant of procainamide, intravenous sotalol prevented inducibility in 32%. The pooled overall sotalol efficacy rate was 31%. There was a significant relation between the increase in the VERP and the prevention of inducibility of VTVF (n = 56; p < 0.02). VERP of > or = 300 msec was critical for the prevention of VTVF inducibility. Thirteen sotalol and 6 procainamide responders from the randomized group and 30 from the nonrandomized groups completed 1 year of oral sotalol therapy follow-up. Life-table analysis of these patient in each group showed a trend in favor of sotalol; however, statistical analysis was not possible because of the small numbers of patients. Both sotalol and procainamide were well tolerated. In the randomized group there was one case of sudden death during treatment with sotalol and two cases of nonfatal torsades de pointes in the procainamide group and two in the sotalol group; in the nonrandomized alternate therapy group, there were 6 cases of nonfatal torsades de pointes. The data support the emerging role of sotalol in the control of symptomatic ventricular tachycardia and fibrillation.

Comparative haemodynamic effects of verapamil, flecainide, amiodarone and sotalol in the conscious rabbit

1. The effect of intravenous boluses of verapamil (0.15 mg/kg), flecainide (2 mg/kg), amiodarone (5 mg/kg), and sotalol (1.5 mg/kg) on mean arterial pressure, heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), and peak rate of change of left ventricular pressure (LV dP/dt) were assessed in the conscious rabbit. 2. All four drugs had negative inotropic effects: verapamil reduced peak LV dP/dt by 19 +/- 4% (mean +/- s.e.m.; P < 0.01), flecainide by 27 +/- 9% (P < 0.001), amiodarone by 11 +/- 2% (P < 0.01) and sotalol by 13 +/- 3% (P < 0.01). 3. The drugs had different effects on CO as a result of differences in their actions on peripheral blood vessels: verapamil and amiodarone produced, respectively, a 12 +/- 4% (P < 0.03) and 16 +/- 6% (P < 0.01) increase in CO associated with a substantial vasodilatory effect (TPR reduced 15 +/- 7% [P < 0.05] and 20 +/- 5% [P < 0.01], respectively). Flecainide caused only a small (6 +/- 1%; P < 0.01) increase in CO and sotalol had no effect on either CO or TPR. 4. Bolus intravenous injections of verapamil, flecainide and amiodarone produced an increase in HR, while sotalol reduced HR by 10 +/- 2% (P < 0.01). The increase in HR and cardiac output seen with verapamil, flecainide and amiodarone was in part secondary to reflex increase in sympathetic tone and these changes were abolished after total cardiac autonomic blockade. 5. The modest reduction in cardiac performance associated with sotalol was abolished by cardiac autonomic blockade, suggesting that the predominant effect of sotalol on contractility was mediated through its beta-adrenoceptor blocking effect.

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.

Comparative mechanisms of antiarrhythmic drug action in experimental atrial fibrillation. Importance of use-dependent effects on refractoriness

BACKGROUND

Antiarrhythmic drugs are considered to terminate atrial fibrillation by prolonging refractoriness, but direct experimental evaluation of this concept has been limited. The atria are activated rapidly during atrial fibrillation, and antiarrhythmic drugs are known to have important rate-dependent actions. The potential role of such properties in determining drug effects during atrial fibrillation has not been evaluated.

METHODS AND RESULTS

We evaluated the effects of representative class Ia (procainamide), Ic (propafenone), and III (sotalol) antiarrhythmic drugs on sustained cholinergic atrial fibrillation and atrial electrophysiological properties in anesthetized, open-chest dogs. Loading and maintenance doses were used to produce stable plasma concentrations, and computer-based 112-electrode epicardial mapping was used to study atrial conduction and activation during atrial fibrillation. Clinically used doses of procainamide and propafenone terminated atrial fibrillation in 13 of 13 (100%) and 7 of 10 (70%) dogs, respectively, but a dose of sotalol (2 mg/kg IV) in the clinical range terminated atrial fibrillation in only 2 of 8 (25%) dogs (P = .0005 vs procainamide, P = .08 vs propafenone). Procainamide and propafenone prevented atrial fibrillation induction in 13 of 13 (100%) and 7 of 10 (70%) dogs, respectively, compared with none of 8 dogs for 2 mg/kg sotalol (P < .0001 vs procainamide, P = .004 vs propafenone). A larger dose of sotalol (cumulative dose, 8 mg/kg) was uniformly effective in terminating atrial fibrillation and preventing its induction. All drugs significantly increased atrial refractory period, with effects that were use dependent for propafenone but reverse use dependent for sotalol. Effective doses of all drugs significantly increased the wavelength for reentry at rapid atrial rates in the presence of vagal stimulation into the range observed under drug-free conditions in the absence of vagal input. The inefficacy of clinical doses of sotalol was explained by the reverse use dependence of its effects on refractoriness, which resulted in reduced effects on wavelength at rapid rates. The effects of propafenone on refractoriness were significantly increased at rapid rates, contributing to its ability to increase wavelength and terminate atrial fibrillation. Activation mapping showed that drugs terminated atrial fibrillation by reducing the number and increasing the size of reentry circuits, leading to termination by mechanisms related to block in the remaining circuit(s).

CONCLUSIONS

We conclude that antiarrhythmic drugs terminate experimental atrial fibrillation by increasing the wavelength for reentry at rapid rates, leading to a reduction in the number of functional reentry circuits and, eventually, failure of reentrant excitation. Use-dependent effects on refractoriness can limit (in the case of the reverse use dependence of sotalol) or contribute (in the case of propafenone) to antiarrhythmic drug efficacy against atrial fibrillation by determining drug-induced changes in wavelength at rapid atrial rates.

Comparative hemodynamic effects of amiodarone, sotalol, and d-sotalol

The effects of intravenous boluses of amiodarone (5 mg/kg), racemic sotalol (enantiomeric ratio d/l-sotalol 1:1;1.5 mg/kg), and d-sotalol (0.75 mg/kg) on mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), left ventricular end-diastolic pressure (LVEDP), and peak rate of change of left ventricular pressure (LV dp/dt) were assessed in conscious rabbits. Amiodarone and sotalol had a modest negative inotropic effect: amiodarone reduced peak LV dp/dt by 8 +/ 2% (mean +/- SEM) (p < 0.05) and sotalol by 6 +/- 2% (p < 0.05). These two drugs had quite different effects on CO as a result of differences in their actions on peripheral blood vessels: amiodarone caused a 13 +/- 3% (p < 0.05) increase in CO associated with a substantial vasodilatory effect (TPR reduced 25 +/- 3%; p < 0.01); sotalol did not produce any substantial change in either CO or TPR. Bolus intravenous injection of amiodarone was associated with a significant increase in HR (12 +/- 3%; p < 0.01), whereas sotalol reduced HR by 7 +/- 1% (p < 0.05). In contrast, administration of the dextro-rotatory optical isomer, d-sotalol, produced no significant change in peak LV dp/dt, LVEDP, CO, TPR, or HR. These results confirm that amiodarone and racemic sotalol have a comparatively weak cardiodepressant action. The experiments also show that the reduction in cardiac performance associated with racemic sotalol is mediated predominantly through the beta-adrenoreceptor blocking action of the levo-rotatory isomer (l-sotalol) rather than any substantial cardiodepressant effect of the dextro-rotatory isomer.

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.

Effects of sotalol on the signal-averaged electrocardiogram in patients with sustained ventricular tachycardia: relation to suppression of inducibility and changes in tachycardia cycle length

OBJECTIVES

This study examines the effects of sotalol on the signal-averaged electrocardiogram (ECG) in patients with spontaneous and inducible sustained ventricular tachycardia and correlates these findings with the effect of sotalol on tachycardia inducibility and tachycardia rate.

BACKGROUND

Standard electrocardiography generally does not detect any change in the duration of the QRS complex resulting from sotalol therapy. However, the signal-averaged ECG is more sensitive than the standard ECG for detecting changes in QRS duration induced by antiarrhythmic drugs and can also detect changes in late potential duration.

METHODS

Signal-averaged electrocardiography was performed before therapy in 30 patients with spontaneous and inducible ventricular tachycardia, and both electrophysiologic study and a signal-averaged ECG were repeated during therapy with d,l-sotalol.

RESULTS

During sotalol therapy the signal-averaged QRS duration decreased by 2.6 +/- 6.6 ms in the 11 patients with no inducible tachycardia during therapy, whereas it increased by 3.8 +/- 5.8 ms (p = 0.01) in the 19 patients with inducible tachycardia during therapy. In the latter group there was a significant positive correlation between prolongation of tachycardia cycle length and prolongation of late potential duration by sotalol (r = 0.56, p = 0.01).

CONCLUSIONS

Sotalol can alter QRS and late potential duration as measured by the signal-averaged ECG. Prolongation of QRS duration or late potential duration may reflect a slowing of conduction by sotalol that may interfere with this agent's antiarrhythmic efficacy and slow ventricular tachycardia.

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.

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

In new antiarrhythmic drug development, key comparisons include those with placebo, standard (class I) agents and other beta blockers. This review will cover the first 2 comparisons. The effectiveness of 2 doses of sotalol for complex ventricular arrhythmias has been compared with placebo in a 6-week, multicenter study (parallel, double-blind design) in 102 patients. The frequency of ventricular premature complexes (VPCs) was reduced only 10% with placebo, 75% with low-dose sotalol (160 mg administered twice daily) and 88% with high-dose sotalol (320 mg administered twice daily) (both p less than 0.05 vs placebo). The defined efficacy criterion (greater than or equal to 75% VPC suppression) was achieved by 6% of patients taking placebo, 34% of patients taking low- and 71% of patients taking high-dose sotalol. Sotalol was generally well tolerated, especially with the lower dose. Heart rate decreased, and PR and QTc intervals increased modestly. An open, randomized, crossover study compared sotalol with procainamide in 33 patients. A reduction in VPCs of greater than or equal to 75% was achieved in 22 patients (67%) with sotalol and in 13 patients (39%) with procainamide. Quinidine and sotalol have also been compared in a multicenter study in patients with chronic, complex VPCs, with results to be presented in the near future. Thus, sotalol's antiarrhythmic efficacy is well demonstrated by comparisons with placebo, and its effectiveness and tolerance are likely to compare favorably with standard class I drugs, suggesting its potential as a first-line antiarrhythmic agent.

Concentration/response relations for the multiple antiarrhythmic actions of sotalol

Sotalol, one of the first beta-receptor antagonists synthesized, is a promising investigational agent with remarkable efficacy for treatment of patients with ventricular and supraventricular arrhythmias. Unlike other beta blockers, sotalol also possesses class III antiarrhythmic action, evidenced by prolongation of the myocardial action potential duration. This additional action probably accounts for the greater antiarrhythmic efficacy of sotalol compared with other beta blockers. Sotalol's class III antiarrhythmic action becomes apparent at concentrations higher than those necessary for significant beta-receptor antagonism, both in vitro and in human subjects. In a study correlating dosage and antiarrhythmic response with prolongation of rate-corrected QT (QTc) (a measure of class III action) and the degree of beta-receptor blockade (assessed by the reduction of the maximal exercise-induced heart rate), 11 of 17 patients had an antiarrhythmic response. Eight of these 11 responders had been unresponsive to conventional beta-receptor antagonists. The plasma concentration associated with significant QTc prolongation (2.55 micrograms/ml) was found to be much greater than that associated with 50% reduction in maximal slowing of heart rate (0.8 micrograms/ml). As with other beta-receptor antagonists, the activities of sotalol's 2 stereoisomers differ, with the I-isomer having far more beta-blocking activity. However, both isomers have equal class III antiarrhythmic activity. When increasing doses of the d-isomer of sotalol (50 to 400 mg every 12 hours) were evaluated in patients with chronic ventricular arrhythmias, arrhythmia frequency was suppressed greater than 80% in 3 patients and 50% in 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiarrhythmic efficacy, clinical electrophysiology, and pharmacokinetics of 3-methoxy-O-desmethyl encainide (MODE) in patients with inducible ventricular tachycardia or fibrillation

In most patients, the clinical effects of therapy with encainide are mediated by the generation of the active metabolites O-desmethyl encainide and 3-methoxy-O-desmethyl encainide (MODE). Data from in vitro and animal studies have indicated that MODE has electrophysiologic and pharmacokinetic features that make its further evaluation desirable; in earlier studies, we found that MODE suppressed chronic high-frequency nonsustained ventricular arrhythmias at plasma concentrations of 50-160 ng/ml. We now report the clinical electrophysiology, antiarrhythmic activity, and pharmacokinetics of MODE in 17 patients with inducible ventricular tachyarrhythmias (VTs) in whom programmed electrical stimulation was performed before drug administration and after one or two sequences of loading and maintenance infusions of MODE. Because the relation between plasma concentration and effect had been incompletely defined, a dose-titration approach was adopted: available pharmacokinetic data were used to construct loading and maintenance infusion regimens that were predicted to attain low plasma concentrations in initial patients while higher infusion rates were evaluated in subsequent patients. MODE prevented VT induction in three of 17 patients and VT cycle length was increased by greater than or equal to 100 msec in a further seven of 17; most responses to MODE occurred at plasma concentrations greater than 556 ng/ml (greater than 1 SD above mean plasma MODE during encainide therapy). Response to MODE did not predict subsequent response to oral therapy with encainide. MODE increased intracardiac conduction times, QT intervals during atrial and ventricular pacing, and right ventricular effective refractory periods (RVERP); changes in RVERP were most prominent at rapid pacing rates, while changes in intracardiac conduction were rate-independent at cycle lengths between 400 and 600 msec. Plasma MODE concentrations measured during electrophysiology study correlated well with those predicted by the pharmacokinetic simulations (r = 0.91, p less than 0.001). Serial plasma sampling after programmed electrical stimulation indicated a minimum MODE elimination half-life of 8.2 +/- 5.4 hours. Side effects were confined to three instances of asymptomatic conduction system depression in subjects with latent conduction system disturbances. We conclude that MODE slows intracardiac conduction, delays repolarization, and can suppress or substantially modify inducible VT. Moreover, it was only with the adoption of the dose-titration strategy that we were able to safely demonstrate that plasma MODE concentrations higher than those routinely observed during encainide therapy were required to substantially alter cardiac electrophysiology.

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.

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)