The electrophysiologic effects of intravenous propranolol in the Wolff-Parkinson-White syndrome

Landiolol, an intravenous β1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node

Introduction

During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site.

Objective

We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation.

Methods

We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020.

Results

Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence.

Conclusion

Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

Pre-excited RR intervals during atrial fibrillation in the Wolff-Parkinson-White syndrome: influence of the atrioventricular node refractory period

The ventricular rate and percent of pre-excited QRS complexes during atrial fibrillation were compared in two groups of patients with the Wolff-Parkinson-White syndrome. Group A consisted of 22 patients whose anterograde effective refractory period of the accessory pathway was longer than that of the atrioventricular (AV) node. Group B consisted of 23 patients in whom this relation was reversed. No patient had organic heart disease. Both groups had a similar effective refractory period of the accessory pathway (288 +/- 37 vs. 280 +/- 26 ms), whereas that of the AV node was shorter in group A than group B (242 +/- 25 vs. 285 +/- 27 ms, p = 0.0001). Patients in group A had a lower percent of pre-excited QRS complexes during atrial fibrillation (39 +/- 43% vs. 93 +/- 20%, p = 0.0001). In the 21 patients whose refractory period was measured, the difference was plotted against the percent of pre-excited QRS complexes; there was a significant correlation between the two (r = -0.83, p less than 0.001). In patients in whom pre-excited RR intervals were present, the pre-excited RR intervals were compared between the two groups. Both groups had similar effective refractory periods of the accessory pathway (265 +/- 22 vs. 280 +/- 27 ms) and ventricle (200 +/- 17 vs. 211 +/- 26 ms). The effective refractory period of the AV node was shorter in group A (248 +/- 22 vs. 285 +/- 28 ms, p = 0.0005). The shortest pre-excited RR interval did not show any difference (244 +/- 37 vs. 265 +/- 41 ms). However, both the average (328 +/- 39 vs. 397 +/- 56 ms, p = 0.001) and longest (495 +/- 109 vs. 666 +/- 205 ms, p = 0.02) pre-excited RR intervals were shorter in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intravenous propranolol or verapamil on infant orthodromic reciprocating tachycardia

The effects of intravenous verapamil (0.15 mg/kg) and propranolol (0.2 mg/kg) with regard to atrioventricular (AV) conduction and tachycardia termination during paroxysmal atrial tachycardia were compared in 2 groups of infants (verapamil n = 14, propranolol n = 18, mean age 80 +/- 21 days, range 1 to 364). Using transesophageal recording techniques, tachycardia cycle length, AV intervals and ventriculoatrial intervals were measured before and after drug administration. Both intravenous propranolol and verapamil significantly prolonged tachycardia cycle length and AV interval (cycle length--propranolol 230 +/- 30 to 262 +/- 33 ms, p less than 0.05, verapamil 223 +/- 38 to 245 +/- 32 ms, p less than 0.05; AV interval--propranolol 98 +/- 26 to 126 +/- 38 ms, p less than 0.05, verapamil 96 +/- 19 to 109 +/- 24 ms, p less than 0.05). Neither drug prolonged the ventriculoatrial interval. Tachycardia terminated after intravenous verapamil in 11 of 14 infants (79% efficacy rate). Tachycardia terminated in 0 of 18 after intravenous propranolol (0% efficacy rate). In 8 infants an atrial deflection was recorded on the esophageal electrocardiogram at the time of tachycardia termination after intravenous verapamil, which suggested that tachycardia terminated by block occurring in the AV node. In 2 infants a ventricular deflection was recorded at the time of tachycardia termination after verapamil, which suggested that block occurred in the accessory connection. Both drugs prolonged tachycardia cycle length by prolonging AV conduction to a similar degree.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of flestolol on ventricular rate during atrial fibrillation in Wolff-Parkinson-White syndrome

The ultrashort-acting beta blocker flestolol was studied during atrial pacing and atrial fibrillation (AF) in 10 patients with Wolff-Parkinson-White syndrome. Flestolol was given as a 100-micrograms/kg bolus followed by a 10-micrograms/kg/min infusion for 15 minutes. The drug did not alter the antegrade effective refractory period of the accessory pathway or the atrial paced cycle length at which block occurred in the accessory pathway. After flestolol, the percent of preexcited QRS complexes during AF increased (60 +/- 10 vs 87 +/- 5%, p = 0.01). Despite this, the ventricular rate slowed, with increases in mean RR interval (382 +/- 20 vs 416 +/- 22 ms, p = 0.02) and in the shortest interval between preexcited QRS complexes (251 +/- 18 vs 270 +/- 17 ms, p less than 0.01). The effect of isoproterenol 3 to 5 micrograms/min was studied in 5 patients. During atrial pacing, isoproterenol decreased the antegrade refractory period and the atrial paced cycle length of block in the accessory pathway (p less than or equal to 0.05). During AF, it decreased the percent of preexcited QRS complexes, mean RR interval and shortest interval between preexcited QRS complexes (p less than 0.05). Flestolol reversed the effects of isoproterenol both during atrial pacing and AF. Thus, flestolol does not alter conduction over the accessory pathway during atrial pacing, but during AF it slows conduction over the accessory pathway and prevents isoproterenol-mediated increases in ventricular rate. This suggests that in patients with Wolff-Parkinson-White syndrome sympathetic stimulation after the onset of AF enhances conduction over the accessory pathway and is an important determinant of ventricular rate.

Electropharmacology of flestolol for supraventricular tachycardia without associated structural heart disease

Flestolol is an ultrashort-acting beta-blocking drug with a half-life of 6.9 minutes. Its antiarrhythmic efficacy was studied in 21 patients with spontaneous and inducible supraventricular tachycardia: atrioventricular (AV) nodal tachycardia in 6 patients and orthodromic AV reciprocating tachycardia in 15. It increased the effective refractory period of the AV node in all patients with AV nodal tachycardia (fast pathway, p less than 0.02; slow pathway, p less than 0.01), but did not alter the anterograde (n = 8) or retrograde (n = 9) refractory periods of accessory pathways. Flestolol prevented initiation of tachycardia by causing block in anterograde AV nodal conduction. It was more effective in patients with AV nodal tachycardia (5 of 6) than in those with AV reciprocating tachycardia (4 of 15, p less than 0.03). In patients in whom it was ineffective, the mean tachycardia cycle length increased by 54 ms because of an increase in AH interval (p less than 0.0001, n = 11). The cycle length of tachycardia induced 30 minutes after infusion was similar to the cycle length in the control state (354 vs 355 ms, n = 16). Flestolol's kinetics permitted clinically indicated electropharmacologic testing of a second antiarrhythmic drug in 8 patients and control of ventricular rate until arrhythmia surgery in 1 patient with incessant tachycardia. No hypotension or toxicity occurred. Our findings indicate that flestolol's principal antiarrhythmic effects are on the AV node, similar to the effects of other beta-blocking drugs. Its ultrashort duration of action is an advantage during electropharmacologic testing.

Electropharmacology of sotalol in patients with Wolff-Parkinson-White syndrome

The beta-adrenoceptor-blocking and class III effects of sotalol were assessed in 11 patients with inducible orthodromic reciprocating tachycardia. Serum sotalol concentration, maximum exercise heart rate, and electrophysiologic study data were obtained at control, at the beta-adrenoceptor-blocking dosage (407 +/- 149 mg/day, 1.4 +/- 0.5 micrograms/ml), and at the maximum well-tolerated dosage (924 +/- 337 mg/day, 3.2 +/- 1.3 micrograms/ml). Class III effects (increases in anterograde and retrograde accessory connection effective refractory periods, ventricular effective refractory period, and the QT interval during fixed-rate atrial pacing) were evident at the beta-adrenoceptor-blocking dosage of sotalol and became more marked at the maximum well-tolerated dosage. For example, the mean anterograde accessory connection effective refractory period was significantly increased over control (272 +/- 41 msec) by the beta-adrenoceptor blocker (324 +/- 52 msec) and was further significantly increased by the maximum well-tolerated dose (364 +/- 37 msec). Similarly, the minimum preexcited RR interval during atrial fibrillation was increased in all patients at each dosage tested. Antiarrhythmic efficacy, defined by the absence of inducible, sustained, orthodromic reciprocating tachycardia and a minimum preexcited RR interval during atrial fibrillation of 300 msec or greater, was achieved in four patients at the beta-adrenoceptor-blocking dosage and in another four patients at the maximum well-tolerated dosage. These eight patients received long-term sotalol therapy and none has had recurrent, sustained reciprocating tachycardia during 15 +/- 12 months of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-blocker therapy for the Wolff-Parkinson-White syndrome

Two types of arrhythmias are associated with the Wolff-Parkinson-White syndrome: those in which the accessory pathway is a required part of the reentrant circuit, e.g., orthodromic atrioventricular reciprocating tachycardia, and those that conduct over the accessory pathway but do not require its activation for maintenance of tachycardia, e.g., atrial flutter/fibrillation. Increased sympathetic tone shortens the refractoriness of atrial and ventricular tissue; however, conduction in the atrium and ventricle is not considered the limiting factor for maintenance of atrioventricular reciprocating tachycardia or conduction over the accessory pathway in atrial arrhythmias. Intravenous beta-adrenergic blockers given to patients in the resting state have a minimal to moderate effect in depressing atrioventricular nodal conduction, but have little or no effect on accessory pathway refractoriness or conduction in most patients. In patients presenting with atrioventricular reentry, intravenous administration of beta-adrenergic blocking drugs often is not effective to terminate tachycardia. However, long-term oral therapy with these agents may be beneficial, especially in patients in whom enhanced sympathetic tone is responsible for the initiation or maintenance of tachycardia.

Effective termination of reentrant supraventricular tachycardia by single dose oral combination therapy with pindolol and verapamil

We evaluated the efficacy of single oral dose combining 20 mg pindolol and 120 mg verapamil in termination of paroxysmal supraventricular tachycardia (SVT) in 12 patients with recurrent symptomatic tachycardia. All had electrically inducible SVT lasting longer than 30 minutes. Patients were administered placebo or crushed pindolol and verapamil on 2 consecutive days after tachycardia was electrically induced and allowed to sustain for 30 minutes. With placebo, SVT lasted 186 +/- 18 minutes (mean +/- SEM); five patients converted spontaneously within 121 to 180 minutes. With pindolol and verapamil, 9 of 12 patients (responders) converted to sinus rhythm within 8 to 74 minutes. The mean duration of SVT in the nine responders was 28 +/- 8 minutes compared with 168 +/- 20 minutes on placebo (p less than 0.001). Before termination, tachycardia rate on pindolol and verapamil slowed significantly from 182 +/- 5 to 164 +/- 7/min (p less than 0.05) compared with no significant change in the rate of SVT on placebo. The mean systolic blood pressure during tachycardia was 97 +/- 5 mm Hg with placebo and 101 +/- 7 mm Hg with pindolol and verapamil. Serum levels of pindolol and verapamil obtained in seven patients at time of spontaneous termination of tachycardia were 66 +/- 13 and 56 +/- 14 ng/ml, respectively. The side effects with pindolol and verapamil included lightheadedness in one patient and symptoms of rapid palpitations in three. A single oral dose of pindolol and verapamil is safe and effective in termination of acute paroxysmal SVT and may be the initial therapy of choice in selected patients.

Intravenous esmolol for the treatment of supraventricular tachyarrhythmia: results of a multicenter, baseline-controlled safety and efficacy study in 160 patients. The Esmolol Research Group

Efficacy and safety of esmolol in the treatment of supraventricular tachyarrhythmias (SVT) was evaluated in this open-label, baseline-controlled, multicenter study. One hundred sixty patients with SVT received an intravenous infusion of esmolol in doses ranging from 25 to 300 micrograms/kg/min for up to 24 hours. All of the 160 patients were evaluated for safety, and 147 of them were eligible for evaluation of therapeutic response. Therapeutic response was defined as greater than or equal to 15% reduction in the average baseline heart rate of conversion to normal sinus rhythm. Seventy-nine percent (116 of 147) of the patients exhibited a therapeutic response. The cumulative percentage response increased significantly with increasing esmolol doses up to 200 micrograms/kg/min. The mean (+/- SEM) dose of esmolol producing a therapeutic response was 97.2 +/- 5.5 micrograms/kg/min. Among all patients (n = 160), 39% exhibited hypotension. In 58% of these patients, hypotension resolved with or without adjustment of the esmolol dose while the infusion continued; among almost all of the remaining patients, hypotension resolved within 30 minutes after esmolol was discontinued. Most patients at risk for adverse effects during beta blockade (i.e., those with diabetes mellitus, congestive heart failure, asthma, etc.) tolerated esmolol therapy, and there were no clinically important trends among the reported changes in laboratory variables. The results of the study indicate that esmolol is effective and well tolerated for the treatment of SVT.

Intrinsic electrophysiologic properties of reentrant supraventricular tachycardia involving bypass tracts

This study evaluates the effects of autonomic blockade (propranolol, 0.2 mg/kg, and atropine, 0.04 mg/kg) in 20 patients with paroxysmal supraventricular tachycardia (SVT). In 8 patients the SVT circuit involved a concealed atrioventricular bypass for retrograde conduction (group I) and in 12 a concealed atrio-His pathway (group II). Autonomic blockade did not significantly change atrial and ventricular refractory periods, whereas it prolonged atrioventricular nodal refractoriness without varying AH interval. The ventriculoatrial interval did not change in any patient. The H2A2 interval was unchanged in all but 2 group II patients. In both groups, the effective refractory period of the concealed bypass was prolonged by autonomic blockade. In the basal state, SVT was induced in all patients; after autonomic blockade, SVT was induced in 7 patients in group I (87%) and in 7 in group II (58%) (p less than 0.05). Cycle length of SVT was prolonged after autonomic blockade in 11 of these 14 patients. The variations were observed only in the anterograde conduction (Ae-H interval), whereas retrograde conduction (H-Ae interval) was unchanged in all patients. These data indicate that the autonomic system appears to facilitate induction of SVT in patients with concealed atrio-His bypass as well as shorten the cycle length of SVT in both groups of patients.

Termination of paroxysmal supraventricular tachycardia with a single oral dose of diltiazem and propranolol

The efficacy of a single oral dose combination of 120 mg diltiazem and 160 mg propranolol in terminating paroxysmal supraventricular tachycardia (PSVT) was evaluated in 15 patients. All 15 patients underwent electrical induction of PSVT that lasted longer than 15 min, and all underwent randomized crossover placebo and diltiazem and propranolol studies on 2 consecutive days. On each day PSVT was induced and placebo or diltiazem and propranolol was administered 15 min later. Electrical conversion of PSVT was performed when severe symptoms occurred or at the end of 240 min. With placebo PSVT lasted 164 +/- 89 (mean +/- SD) min; four patients had spontaneous conversion. With diltiazem and propranolol PSVT lasted 39 +/- 49 min (p less than .001); 14 patients had spontaneous conversion in an average of 27 +/- 15 min. None of the 14 patients had electrical reinduction of sustained PSVT after conversion. The sinus nodal recovery time during spontaneous or electrical conversion of PSVT was 911 +/- 459 msec with placebo and 1076 +/- 270 msec with diltiazem and propranolol (NS). Two patients developed transient second-degree atrioventricular block and junctional rhythm while on diltiazem and propranolol. Serum diltiazem and propranolol levels (ng/ml) after diltiazem and propranolol in five patients were, respectively, 49 +/- 26 and 108 +/- 101 at 15 min, 232 +/- 147 and 228 +/- 148 at 30 min, 254 +/- 169 and 370 +/- 393 at 45 min, 280 +/- 115 and 209 +/- 189 at 60 min, 188 +/- 72 and 268 +/- 264 at 120 min, and 118 +/- 57 and 265 +/- 148 at 240 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Preexcitation syndromes. Mechanisms and management

Ventricular preexcitation occurs when, in relation to atrial events, some or all of the ventricular muscle is activated earlier by the atrial impulse than would be expected if conduction of the impulse activated the ventricles by way of the normal atrioventricular conduction system. The purpose of this article is to review the pathophysiology of the variants of preexcitation and to discuss the therapeutic approach to patients who have tachyarrhythmias.

Safety and efficacy of esmolol (ASL-8052: an ultrashort-acting beta-adrenergic blocking agent) for control of ventricular rate in supraventricular tachycardias

Esmolol (ASL-8052) is a new intravenous beta-adrenergic blocking agent that has exhibited both cardiac selectivity and an extremely short half-life in animal studies. To assess its clinical efficacy, 16 patients were studied with a rapid ventricular rate associated with atrial flutter (n = 2), atrial fibrillation (n = 10), atrial tachycardia (n = 2) and multifocal atrial tachycardia (n = 2). During a 30 minute control period of observation, the ventricular rate ranged from 121 to 150 beats/min (mean 133.2 +/- 10.6). Using a double blind crossover method, esmolol was infused intravenously for a maximum of 60 minutes. Infusions of 50, 100, 150, 200, 250 and 300 micrograms/kg per min were given in consecutive 5 minute periods (during the first minute of each period, a loading dose of 500 micrograms/kg was given). Not all patients received the maximal dose. A response was defined as conversion to sinus rhythm or a 20% reduction in ventricular rate. One patient with atrial fibrillation associated with the Wolff-Parkinson-White syndrome did not respond. In the remaining 15 patients, their highest esmolol infusion rate was maintained for an additional 30 minutes. This resulted in a reduction in ventricular rate to a mean of 97.8 +/- 12.9 beats/min (range 72 to 119) (p less than 0.001). Conversion from flutter/fibrillation to sinus rhythm occurred in two patients. During the infusion, six had transient asymptomatic hypotension that was mild and manageable. After infusion, ventricular rate and blood pressure returned rapidly toward control values within 25 minutes in patients without conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Nadolol and supraventricular tachycardia: an electrophysiologic study

To assess antiarrhythmic efficacy of oral nadolol, 15 patients with recurrent supraventricular tachycardia were studied. Eight patients had atrioventricular (AV) nodal reentrant tachycardia and seven had AV reciprocating tachycardia involving an accessory AV pathway. Electrophysiologic studies were performed before and after intravenous infusion of propranolol (0.20 mg/kg), and were repeated 5 to 8 days after oral nadolol therapy at a daily dose of 80 to 160 mg. Both intravenous propranolol and oral nadolol induced significant prolongation of the sinus cycle length from 741 +/- 73 ms to 834 +/- 97 and 1,029 +/- 95 ms, respectively (p less than 0.001 and p less than 0.0001, respectively). Both intravenous propranolol and oral nadolol depressed AV nodal but not accessory AV pathway conduction, and shifted the dual AV nodal pathway conduction curves (A1A2, A2H2; A1A2, H1H2) upward and to the right by prolonging the conduction time and increasing the refractory period. Ten patients (seven with AV nodal reentry and three with AV reciprocation) who responded to intravenous propranolol also responded to oral nadolol with loss of the inducibility of sustained tachycardia; the remaining five patients (one with AV nodal reentry and four with AV reciprocation) who did not respond to intravenous propranolol also failed to respond to oral nadolol with persistence of the inducibility of sustained tachycardia. Thus, in conclusion, intravenous propranolol testing predicts the therapeutic efficacy of oral nadolol therapy and oral nadolol in once-daily doses may be used for long-term prophylaxis of recurrent supraventricular tachycardia.

Effects of acebutolol on paroxysmal atrioventricular reentrant tachycardia in patients with manifest or concealed accessory pathways

Electrophysiologic studies before and after administration of 50 mg of intravenous (IV) acebutolol were performed in 20 patients. Four of the 20 had persistent preexcitation, two had intermittent preexcitation, and 14 had a concealed retrogradely conducting accessory pathway (AP). Acebutolol depressed anterograde AP conduction with loss of preexcitation in one patient and increased the effective refractory period of AP in the remaining three; in most, it depressed anterograde normal pathway conduction. The longest atrial paced cycle length producing atrioventricular (AV) nodal block increased from 290 +/- 7 to 39 +/- 6 msec (mean +/- SEM) after acebutolol (p less than 0.01). Acebutolol had no significant effect on retrograde AP conduction. Sustained AV reentrant tachycardia was inducible in all 20 patients before acebutolol and in 19 after acebutolol. The cycle length of tachycardia increased from 323 +/- 8 to 352 +/- 8 msec after acebutolol (p less than 0.01), reflecting an increment of A-H interval from 148 +/- 8 to 174 +/- 9 msec (p less than 0.01). Electrophysiologic studies were reported after 800 mg of oral acebutolol given in four divided doses at six-hour intervals in eight patients. The results were comparable to those of IV acebutolol. Thus, acebutolol depresses AV nodal conduction and slows the rate of AV reentrant tachycardia, but is generally ineffective in inhibiting the induction of sustained tachycardia. It occasionally depresses anterograde AP conduction.

Verapamil in the treatment of PSVT

Verapamil is considered by many investigators to be the drug of choice for the acute management of uncomplicated PSVT. Several clinical investigators have demonstrated termination of PSVT in more than 90% of their patients within minutes following IV drug administration. The incidence of reported severe adverse reactions has been less than 1%. PSVT may be complicated by underlying heart disease, or by antegrade accessory pathway conduction in individuals with pre-excitation syndrome. Such conditions, or the prior use of beta-blocking agents, may contraindicate the use of verapamil. However, the history of recent myocardial ischemia or the prior use of digitalis does not appear to contraindicate verapamil therapy. Guidelines for the emergency management of the patient in PSVT are presented.

The electrophysiologic effects of intravenous lidocaine in the Wolff-Parkinson-White syndrome

Twelve patients with the Wolff-Parkinson-White syndrome underwent electrophysiologic study, before and after the bolus intravenous administration of lidocaine, 1 mg./kg. There was no significant increase in the effective refractory period of the anterograde AV node pathway, the anterograde or retrograde accessory pathway, or the atrial or ventricular muscle; intravenous bolus administration of lidocaine is unlikely to terminate the re-entry tachycardias, or decrease the rate of the ventricular response in atrial fibrillation, in the WPW syndrome. There was no significant increase in the anterograde or retrograde AV conduction times; bolus administration of lidocaine is unlikely to decrease the rates of the re-entry tachycardias. In addition, lidocaine failed to alter significantly features related to tachycardia initiation. Except in isolated, unpredictable cases, intravenous bolus administration of lidocaine is not likely to be of benefit in the supraventricular tachyarrhythmias of the WPW syndrome.