Beta-adrenergic blockade by nadolol in control of ventricular tachyarrhythmias

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.

Efficacy of sotalol guided by programmed electrical stimulation for sustained ventricular arrhythmias secondary to coronary artery disease

Sotalol is a class III antiarrhythmic drug with additional beta-blocker activity that has been shown to be effective in supraventricular and ventricular arrhythmias. Its long-term efficacy for ventricular arrhythmias is not as well described. Patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) who had their clinical arrhythmia inducible at baseline electrophysiologic study received sotalol 320 to 640 mg/day. Repeat programmed stimulation was performed after a minimum of 72 hours while receiving the final dose. Of 28 patients (25 men and 3 women) whose arrhythmias were inducible at baseline, 15 had their arrhythmias suppressed with sotalol. Sotalol had greater success in suppressing arrhythmias in those with VF (8 of 9, 89%) than in those with VT (7 of 19, 37%, p < 0.01). In patients with a history of coronary artery disease but no history of myocardial infarction the arrhythmia was suppressed in 7 of 8 (88%) compared with 8 of 20 (40%, p < 0.05) patients with a history of myocardial infarction. All 15 patients in whom ventricular arrhythmias were suppressed continued to take long-term sotalol, and at a follow-up of 10.3 +/- 6.4 months none has had arrhythmia recurrence. Thus, sotalol is an effective drug for the suppression of ventricular arrhythmias as judged by programmed electrical stimulation. It appears to be more effective in patients in whom the clinical arrhythmia is VF rather than VT.

Efficacy and safety of intravenous and oral nadolol for supraventricular tachycardia in children

The efficacy and safety of oral nadolol in supraventricular tachycardia were evaluated prospectively in 27 children (median age 5.5 years). Fifteen patients had an unsuccessful trial of digoxin therapy. Intravenous nadolol was given to seven patients during electrophysiologic study; five of these had an excellent response and two had a partial response (25% decrease in tachycardia rate). Six of these patients had a similar response to oral nadolol. Twelve patients received both propranolol and nadolol. Among six patients, intravenous propranolol was successful in four and unsuccessful in two; all six had a similar response to oral nadolol. With oral propranolol, tachycardia was well controlled in four patients and persistent in two; five of five patients had a similar response to oral nadolol. Twenty-six patients were treated with oral nadolol; the arrhythmia was well controlled in 23, 2 had recurrent tachycardia and 1 patient had tachycardia at a 25% slower rate. The effective dose of nadolol ranged between 0.5 and 2.5 mg/kg body weight once daily (median dose 1 mg/kg per day). During follow-up (3 to 36 months), compliance and tolerance were excellent; excluding 2 patients with reactive airway disease who developed wheezing, only 3 (12%) of 24 had side effects necessitating a change in drug therapy. Once a day nadolol is a safe and effective agent in the management of supraventricular tachycardia in children. Its long-term efficacy can be predicted by the short-term response to intravenous nadolol or propranolol during programmed electrophysiologic study.

Suppressant effects of conventional beta blockers and sotalol on complex and repetitive ventricular premature complexes

Beta-blocking drugs have been shown to reduce the overall mortality and risk of sudden cardiac death in survivors of acute myocardial infarction. It is not known whether such an effect is mediated by suppression of ventricular premature complexes (VPCs). The circadian rhythmicity of ventricular arrhythmia can also be suppressed by beta-blocking drugs, and this may help reduce the risk of sudden cardiac death during the morning hours. Recent studies have also shown that beta blockers can provide a safe and effective combination with class IA antiarrhythmic agents when arrhythmias cannot be controlled with class IA agents alone. Sotalol, a nonselective beta antagonist, has unique electrophysiologic properties, and several studies have shown it to be more effective than conventional beta blockers in suppressing ventricular arrhythmias. However, direct comparative studies of the suppression of VPCs are lacking. In a recent double-blind, placebo-controlled, parallel study, the antiarrhythmic effects of sotalol and propranolol were compared in 172 patients with greater than 30 VPCs/hour. After the initial 1-week washout and 1-week placebo period, patients were randomly assigned to either 160 mg of sotalol administered twice daily (76 patients) or 40 mg of propranolol administered 3 times daily (91 patients). Those responding to therapy (decreases greater than 75% VPCs) continued to take these doses, but nonresponders were given higher doses, 320 mg of sotalol twice daily or 80 mg of propranolol 3 times daily, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of nadolol alone or in combination with a type IA antiarrhythmic drug in sustained ventricular tachycardia: a prospective study

We examined the clinical efficacy and safety of intravenous nadolol acutely, as well as chronic nadolol alone or combined with a type IA antiarrhythmic drug in 19 patients with sustained ventricular tachycardia and heart disease, mean age 62 +/- 15 years, and mean left ventricular ejection fraction 39 +/- 8%. Patients underwent electrophysiological studies in the drug-free state (control), after intravenous nadolol (dose = 0.05 mg/kg), and oral nadolol (dose = 80 mg/day) for 5 days alone or in combination with a type IA antiarrhythmic drug. Electrocardiographic and electrophysiological effects as well as ventricular tachycardia induction at electrophysiological study were analyzed. Long-term therapy with oral nadolol alone or in combination with a type IA antiarrhythmic drug was evaluated in responders. Intravenous nadolol prolonged RR and QRS intervals but had no effect on PR and QTc intervals. Oral nadolol alone tended to prolong RR intervals (P = 0.08). Oral nadolol with type IA antiarrhythmic drug prolonged RR and QTc intervals (P less than 0.001). The mean right ventricular effective refractory period tended to prolong after intravenous nadolol alone (from 251 +/- 29 to 263 +/- 25 msec, P = 0.08). Oral nadolol and type IA antiarrhythmic drugs did not prolong right ventricular effective refractory period (P = 0.3). Eighteen patients had inducible sustained ventricular tachycardia at control electrophysiological study. After intravenous nadolol, ventricular tachycardia was no longer inducible in seven patients. Ventricular tachycardia did not recur and remained noninducible in two of six patients who tolerated oral nadolol alone. Mean right ventricular effective refractory period prolonged from baseline values (from 249 +/- 30 to 271 +/- 30 msec, P less than 0.02) in patients who became noninducible on intravenous nadolol. In patients who remained inducible, mean right ventricular effective refractory period remained unchanged (from 253 +/- 29 to 258 +/- 22 msec, P greater than 0.2). In nonresponders to intravenous or oral nadolol, oral nadolol, and type IA antiarrhythmic drug suppressed ventricular tachycardia induction in two of ten patients. During follow-up, three patients continued on oral nadolol alone (one patient) or oral nadolol and type IA antiarrhythmic drug (two patients). Adverse effects resulting in nadolol discontinuation occurred in five patients. Therefore, we concluded that intravenous nadolol is effective in acute suppression of inducible ventricular tachycardia in selected patients. Oral nadolol alone or in combination with type IA antiarrhythmic drug is infrequently effective and poorly tolerated by this patient population. In addition, electrophysiological studies on intravenous nadolol do not predict the outcome of oral nadolol therapy.

Effects of propafenone on ventricular arrhythmias: double-blind, parallel, randomized, placebo-controlled dose-ranging study

Propafenone is a new class Ic antiarrhythmic compound with a broad pharmacologic profile. In this study, its dose-response relationship was examined in a double-blind, randomized, placebo-controlled five treatment parallel design protocol. Patients enrolled had heart disease with Lown grade 2 premature ventricular contractions (PVCs) (greater than or equal to 30/hr) documented on 24-hour Holter recordings. Propafenone was compared in four doses (337.5, 450, 675, and 900 mg/day) to placebo. The double-blind phase lasted 2 weeks. Two hundred twenty-six patients were enrolled, of whom 171 were men and 55 were women; their mean age was 59.8 years and 85% were Caucasian and 4% were black. The arrhythmias were symptomatic in 173. Twenty (8.8%) withdrew from the study before completion: 15 had adverse reactions, two had intercurrent illnesses, and three withdrew for administrative reasons. In one patient, the density of arrhythmia appeared to increase with propafenone. Side effects were of central nervous system or gastrointestinal origin; less than 5% of patients developed first-degree atrioventricular block or intraventricular conduction defect. There were no deaths in the study. The occurrence of side effects was not related to dose. Propafenone had no effect on heart rate. It increased the PR interval at all doses (9% to 22% compared to placebo at baseline; p less than 0.01) at 450 to 900 mg/day after 2 weeks of therapy. The drug increased the QRS duration at all doses, highly significantly at 675 mg/day (8.5 msec; p less than 0.01) and at 900 mg/day (15.7 msec; p less than 0.01) after 2 weeks of therapy. Only at the highest dose was the QTc slightly but significantly (14.3 msec; p less than 0.01) increased. Propafenone exerted a dose-dependent effect on PVCs recorded on serial 24-hour Holter recordings: compared to placebo, at 2 weeks 337.5 mg/day reduced PVCs by 70.8% (p less than 0.05), 450 mg/day reduced PVCs by 82.0% (p less than 0.01), 675 mg/day reduced PVCs by 90.2% (p less than 0.01) and 900 mg/day reduced PVCs by 95.3% (p less than 0.01). The effects of the two highest doses of propafenone were significantly greater than those of 337.5 mg/day. In 68% of the patients receiving 900 mg/day, 80% or greater reduction in total PVCs was found. In addition, there was a greater than 90% decrease in ventricular couplets, and 96% decrease in ventricular tachycardia (VT) beats. Propafenone eliminated PVCs in 8% of all patients, ventricular couplets in 58%, and VT beats in 91%.(ABSTRACT TRUNCATED AT 400 WORDS)

Beta blockers in combination with class I antiarrhythmic agents

The hemodynamic and antiarrhythmic interactions between nadolol and a commonly used class I antiarrhythmic agent, quinidine or procainamide, were evaluated in 18 patients with ventricular arrhythmias in a double-blind, parallel study. Patients qualified for entry into the study if their ventricular arrhythmias remained poorly controlled (greater than or equal to 10 ventricular premature complexes/hr) with the class I agent alone and they had a left ventricular ejection fraction greater than 30%. Patients received their usual therapeutic doses of quinidine or procainamide throughout the study, which consisted of 3 treatment periods; a 2-week placebo treatment period, a 2-week open-label oral nadolol dose titration period, during which the dosages of nadolol were gradually increased from 40 mg daily to a maximum tolerated dose up to 120 mg daily, and a 4-week randomized, parallel comparison period during which patients were treated with either a class I agent alone or a combination of a class I agent and nadolol. Left ventricular ejection fractions by radionuclide ventriculography and 24-hour ambulatory electrocardiographic (Holter) recordings were obtained at the end of each treatment period. A positive treatment response was defined as greater than or equal to 75% reduction in ventricular premature complex frequency. During the dose titration phase, combination therapy with nadolol (mean dose 94 mg daily) and class I agents produced a mean decrease in ventricular premature complexes of 79% (p less than 0.01), and a mean decrease in ventricular couplets of 95% (p less than 0.01). A positive response was observed in 57% of patients treated with nadolol plus a class I agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic effects of beta blockers in ventricular arrhythmias

Beta-adrenergic receptor blocking agents are effective antiarrhythmic drugs in patients with ventricular arrhythmias. However, these agents exert little or no measurable electrophysiologic effect on normal Purkinje and ventricular muscle fibers when administered acutely. They prevent catecholamine-induced increases in Purkinje fiber automaticity and may interfere with catecholamine-dependent slow responses. beta-adrenergic blocking drugs also prevent the decrease in ventricular fibrillation threshold induced by catecholamines. In the acutely ischemic ventricle, some beta blockers selectively depress conduction within the ischemic zone. The long-term administration of some beta blockers has, in contrast to their short-term effects, been shown to prolong action potential duration and effective refractory period in the ventricle. Which of these observed electrophysiologic effects, either alone or in combination, contributes to the ventricular antiarrhythmic effects of beta-blocking drugs in man is at present unknown.

Antiarrhythmic effects of beta-adrenergic blocking agents in benign or potentially lethal ventricular arrhythmias

Classification of ventricular arrhythmias into those that are benign, potentially lethal and lethal is based on their associated risk for producing sudden cardiac death. This classification system is useful in defining indications for the treatment of ventricular arrhythmias and predicting differential rates of antiarrhythmic drug efficacy and toxicity. Whether the reduction of potentially lethal ventricular arrhythmias will prevent sudden cardiac death remains to be determined. The class II antiarrhythmic agents--the beta-adrenergic blocking drugs--have been shown to reduce sudden cardiac death in postmyocardial infarction patients, but the precise mechanism of their effect has not been defined. beta blockers are efficacious in approximately 50% of patients with benign or potentially lethal ventricular arrhythmias. This response is comparable to that seen with the class IA agent disopyramide or the class IB agents tocainide and mexiletine. beta blockers have favorable side-effect profiles including a low incidence of proarrhythmia and a lack of organ toxicity such as hepatitis, pulmonary fibrosis or agranulocytosis, which are concerns with class I and class III antiarrhythmic drugs. The proper dosage of the beta blocker is critical in limiting adverse effects. In a study of 23 patients with benign or potentially lethal ventricular arrhythmias, 11 (48%) of the patients responded to nadolol with a reduction of greater than 75% in arrhythmia frequency, and several patients responded at nadolol dosages as low as 10 mg daily. Thus, it is plausible to consider beta blockers as first-choice antiarrhythmic therapy, even in patients with left ventricular dysfunction when sympathetic tone is not required to maintain cardiac compensation.

Electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol in refractory supraventricular tachyarrhythmias

The electrocardiographic and electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol therapy were examined in 34 patients with recurrent supraventricular tachyarrhythmias (SVT) undergoing electrophysiologic evaluation. Programmed electrical stimulation was performed in the control (drug-free) state, after infusion of intravenous nadolol (mean dose 0.09 +/- 0.03 mg/kg) and after chronic oral nadolol therapy in patients who responded to intravenous nadolol (mean dose 83 +/- 12 mg for 5 days). Intravenous nadolol administration prolonged mean sinus cycle length (p = 0.009), mean PR interval (p = 0.001) and mean AH interval (p = 0.001), with no significant electrophysiologic effects in the atrium, ventricle or accessory bypass tracts. Oral nadolol had similar electrocardiographic and electrophysiologic effects, but of lesser magnitude. Intravenous nadolol resulted in complete suppression of induced SVT in 78% of patients with sinus and atrioventricular nodal reentrant tachycardia and 11% of patients with atrioventricular (AV) reentrant tachycardia (p less than 0.001). Partial responses were frequent in intraatrial or AV reentrant tachycardia (37%). Oral nadolol suppressed induction of SVT in patients who responded to intravenous nadolol. Adverse reactions to intravenous and oral nadolol were infrequent--6% and 8%, respectively--and usually did not require drug withdrawal. Intravenous nadolol is highly effective in sinus and AV nodal reentrant tachycardia, and a successful electrophysiologic response to it predicts efficacy of long-term oral nadolol therapy. It has limited efficacy alone in AV reentrant tachycardia and should be considered in combination with other antiarrhythmic therapy in this type of SVT.

Effectiveness of low-dose nadolol for ventricular arrhythmias

To determine the minimal effective dose of nadolol to suppress frequent ventricular premature complexes (VPCs), 23 patients with at least 30 VPCs/hour on 2 baseline 24-hour Holter recordings were studied. The initial dose of nadolol was 10 mg/day orally, and this dose was doubled at weekly intervals until arrhythmia suppression was achieved, adverse effects appeared, or a maximal dose of 160 mg/day was reached. After each dose level a 24-hour ambulatory Holter monitor was recorded. A pharmacokinetic trial was conducted in patients who responded to nadolol treatment. Frequent VPCs were suppressed at least 75% by nadolol in 11 of 23 patients (48%) and the minimal effective dose was 10 mg/day in 3 patients, 20 mg/day in 4, 40 mg/day in 3 and 80 mg/day in 1 patient. At these doses, minimal steady-state levels of nadolol in serum (Cmin) ranged from 3.9 to 47.0 ng/ml, and these serum concentrations were proportional to the oral dose of nadolol (r = 0.753, p less than 0.001). No relation, however, was observed between Cmin levels and percent reduction of VPCs. Cmin and heart rate changes were comparable between responders and nonresponders, suggesting that the degree of beta blockade was similar between these 2 groups. Adverse reactions were noted in 6 patients, and 2 had an asymptomatic increase in the frequency of VPCs and 1 patient an increase in beats of ventricular tachycardia. This study details the importance of selecting an individualized dose for nadolol for control of ventricular arrhythmias; in more than half of the patients doses of 20 mg/day or less were effective.