New antiarrhythmic drugs in pediatric use: amiodarone

Amiodarone, a class III antiarrhythmic agent, prolongs action potential duration and refractoriness of all cardiac structures. The drug is more rapidly metabolized in pediatric patients than in adults, but its kinetics are still unique compared with other drugs. Due to the unusual pharmacokinetic characteristics of amiodarone, treatment has to be started by administering loading doses, and there is a significant delay both in the achievement of the full anti-arrhythmic effect and in the development of side effects. Amiodarone is a highly effective agent in pediatric patients with automatic and reentrant supraventricular tachycardia as well as in refractory atrial flutter. Efficacy in ventricular tachycardia has been shown to be variable depending on the underlying anatomical substrate. The incidence of side effects is lower than that observed in adult studies with similar duration of therapy but their incidence is still significant. Amiodarone treatment is associated with a significant risk of proarrhythmic effects, requiring hospitalization of the patient during the loading period.

Bronchospasm induced by intravenous adenosine

1. Adenosine is well known to cause bronchoconstriction when inhaled, but to date, there has been only one report following the intravenous route. 2. Adenosine caused bronchoconstriction in two patients (the only two with asthma) out of 26 treated with the drug. In one subject the duration of response was much longer than previously reported following inhalation. 3. We suggest that adenosine may aggravate bronchospasm in some asthmatics and alternative treatments for supraventricular tachycardia should be considered in this group.

Drug therapy of supraventricular tachyarrhythmias--based on efficacy or futility?

The clinical spectrum of supraventricular tachyarrhythmias ranges from infrequent, brief and well tolerated episodes of arrhythmia to attacks resulting in cardiovascular collapse. Many patients have such infrequent episodes that prophylactic or ablative therapy is not indicated. In those with more troublesome symptoms, an initial trial of medical therapy is common unless the arrhythmia has major prognostic or vocational importance. Thus despite the recent advances in catheter ablation techniques, there remains a place for antiarrhythmic drug therapy in supraventricular tachyarrhythmias. Furthermore, ablation therapy in atrial fibrillation is currently unable to control arrhythmias except by destruction of the normal conduction system. In contrast to the therapy goals in ventricular tachyarrhythmias, safety considerations far outweigh those of efficacy in the drug management of supraventricular tachycardias. Many patients with supraventricular tachyarrhythmias are young and have no serious underlying heart disease. Although symptomatic recurrences of arrhythmia are troublesome, these should be regarded as acceptable if the alternative is serious drug-related toxicity. There are relatively few well conducted clinical trials of the efficacy of drug therapy in supraventricular tachycardia. Existing study data and new trial information on the efficacy of propafenone are reviewed.

The cost-effectiveness of treatment of supraventricular arrhythmias related to an accessory atrioventricular pathway: comparison of catheter ablation, surgical division and medical treatment

BACKGROUND

Treatment alternatives for patients with incapacitating supraventricular arrhythmias related to an accessory atrioventricular pathway include transcatheter radiofrequency (RF) ablation, surgical division and long-term antiarrhythmic therapy (medical).

AIM

The aim of this study was to compare in terms of cost and efficacy, transcatheter, surgical and medical treatment of patients with incapacitating supraventricular arrhythmias resulting from an accessory pathway.

METHODS

The study population consisted of 52 patients who underwent transcatheter RF ablation (20 consecutive patients), surgical treatment (20) and medical treatment (12). Two types of economic analysis were used. In all groups, a resource based costing method was used and in the medical and surgical treatment groups, a diagnostic related group (DRG) based costing method was used.

RESULTS

Eighteen out of 20 (90%) patients who underwent catheter ablation remained asymptomatic during 8.4 +/- 1.6 months of follow-up. All surgically treated patients remained asymptomatic during 54 +/- 15 months of follow-up. Only one of the 12 patients in the medical treatment group remained completely free of symptoms during the mean 58 +/- 23 month follow-up period. The mean cost (1992 Australian dollars) per patient, calculated on the basis of actual resources used (with a DRG based costing given in brackets), was $2746 +/- $800 for catheter ablation, $12141 +/- $4465 ($12880 +/- $3998) for surgical treatment and $1713 +/- $748 ($1967 +/- $33) for medical treatment. The total cost of management over 20 years is estimated to be: $2911 for catheter ablation, $17467 for surgery and $4959 for medical treatment.

CONCLUSIONS

In the long term transcatheter RF ablation is the most cost-effective treatment strategy for patients with incapacitating supraventricular arrhythmias related to an accessory pathway.

[Injectable and oral cibenzoline in the treatment of supraventricular tachycardia related to intranodal reentry or accessory atrioventricular conduction pathway]

Cibenzoline, a Vaughan-Williams Class I antiarrhythmic agent, was studied in 26 patients with orthodromic supraventricular tachycardia (SVT) by nodal reentry (n = 10) or an accessory pathway (AP) (n = 16). IV cibenzoline accelerated sinus rhythm, prolonged PR, AH, HV and QT, widened QRS and depressed or blocked anterograde and retrograde conduction in the accessory pathway, significantly, without significantly modifying conduction capacity in the AV node, nor atrial, nodal or ventricular refractory periods. It converted 6/10 of nodal reentries and 9/16 of reentries due to an AP, by a mean dose of 1 mg/kg, in 2 to 3 minutes, in 12 cases out of 16 by blocking retrograde conduction in the reentry circuit. It prevented reinduction of 12 of the 26 cases of SVT, significantly slowing the cycle of induced SVT in other patients. Oral cibenzoline (260 to 390 mg/day) prevented induced SVT in 11 cases out of 25 and spontaneous SVT in 14 cases out of 26, with a follow-up of 11 +/- 4 months (6 to 16), and this regardless of the reentry mechanisms. Intravenous cibenzoline was not associated with any clinical or hemodynamic intolerance but there was facilitation of episodes of SVT in one patient. Oral administration caused only one case of digestive intolerance, leading to lowering of the dose. Plasma levels showed no significant differences between successes and failures, for both the injection and oral formulations of cibenzoline, whether in terms of the conversion or prevention of episodes. Electrophysiological investigations had a 60% positive and 50% negative predictive value, a sensitivity of 64% and a specificity of 50%. Cibenzoline thus appears to be useful for the conversion and prevention of episodes, SVT, regardless of the reentry circuit, and seems justified, in view of its good safety/acceptability, as first line treatment in this diagnostic indication, measurement of plasma levels and electrophysiological investigations being of little apparent value in terms of guiding treatment and predicting its results.

Significance of supraventricular tachyarrhythmias in patients with implanted pacing cardioverter defibrillators

Eighty-six patients were treated with an implantable cardioverter defibrillator (ICD) because of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). In 27 patients an epicardial system was used, in 59 patients a transvenous system with a subcutaneous patch electrode was implanted. During a mean follow-up time of 17 +/- 9 months, inappropriate activations of the ICD due to supraventricular tachycardia were documented by Holter monitoring in 14 patients (16%). In 8 patients paroxysmal atrial fibrillation (AF), in 2 patients chronic AF, in 1 patient atrial flutter, and in 3 patients sinus tachycardia triggered antitachycardia pacing functions (12 patients) or internal defibrillation (2 patients). In 3 patients (5%) VT was induced by inappropriate antitachycardia pacing. In an additional 18 patients (21%) inappropriate activation of antitachycardia functions due to atrial tachyarrhythmias were suspected based on telemetry readouts or the patient's history. Inappropriate activation of ICD therapy triggered by intermittent supraventricular tachyarrhythmias is common. Further improvements of detection algorithms for supraventricular tachycardia are required in future device generations.

Flecainide: its value and danger

Flecainide is an important addition to the therapeutic armamentarium because it is a potent agent for the treatment of paroxysmal supraventricular tachycardia in patients without structural heart disease. Flecainide also may be useful in patients with debilitating nonsustained ventricular arrhythmias in the absence of structural heart disease. It is rarely useful in the management of life-threatening sustained ventricular arrhythmias.

[Efficacy and safety of adenosine triphosphate in the control of supraventricular paroxysmal tachycardia]

Our purpose was to assess the efficacy and safety of intravenous ATP for the acute termination of paroxysmal supraventricular tachycardia. There were 14 women and 10 men, aged 38 +/- 15 years. Three patients had evidence of structural heart disease (Ebstein's anomaly associated to atrial septal defect, operated mitral stenosis with insertion of a mechanical heart valve and CAD respectively). Twelve patients had Wolff-Parkinson-White syndrome and another had undergone surgical ablation of an accessory pathway. At the time of electrophysiologic testing, ATP was administered during episodes of paroxysmal supraventricular tachycardia, via a central vein, in incremental doses of 5, 10 and 20 mg followed by a flush of 10 c.c. of isotonic saline. The mechanism of the arrhythmia was orthodromic AV reentrant tachycardia in 19 (79%), AV nodal reentrant tachycardia in 4 (16.6%) and atrial tachycardia in one patient. The mean frequency of the tachycardia was 174 +/- 33 b.p.m. A dose of 5 mg was effective in 16 patients (66%), 5 required 10 mg and two required 20 mg for termination of the tachycardia. In the patient with atrial tachycardia ATP was not effective. The average time after injection to termination of the arrhythmia was 16 +/- 8 seconds. Orthodromic AV reentrant tachycardia was interrupted in the AV node limb in all but one patient and AV nodal reentry was terminated in the "slow-pathway" in three of the four patients. Nine patients had premature ventricular complexes, isolated or in couplets, after the termination of the SVT. Three patients had immediate recurrence of the SVT.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic effects of intravenous E-4031, a novel class III antiarrhythmic agent, in patients with supraventricular tachyarrhythmias

The electrophysiologic effects of intravenous (i.v.) E-4031, a new class III antiarrhythmic drug, were evaluated in 15 patients with supraventricular tachyarrhythmias [11 men, 4 women; mean age 41 +/- 19 (SD) years]. Eleven patients had accessory atrioventricular (AV) pathways, and 4 patients with no accessory pathway had paroxysmal atrial fibrillation. Electrophysiologic studies were performed before and after E-4031 administration (loading infusion 9 micrograms/kg for 5 min + maintenance infusion 0.15 microgram/kg/min). QT and QTc intervals were significantly prolonged by E-4031 from 0.40 +/- 0.03 (mean +/- SD) to 0.46 +/- 0.03 s (p < 0.0001) and from 0.43 +/- 0.03 to 0.49 +/- 0.04 s (p < 0.0001), respectively. No effect was observed on RR interval, PR interval, QRS duration, or AH and HV intervals. The effective refractory periods (ERPs) of the right atrium and ventricle were significantly prolonged from 219 +/- 27 to 236 +/- 26 ms (p < 0.001) and from 230 +/- 12 to 249 +/- 11 ms (p < 0.001), respectively. The ERP of the AV node did not change significantly after E-4031 administration. In patients with ventricular preexcitation, E-4031 significantly prolonged the ERP of the antegrade accessory pathway conduction from 340 +/- 101 to 362 +/- 106 ms (p < 0.001), but not retrograde accessory pathway conduction. AV reentrant tachycardia was induced in 3 of 11 patients with an accessory pathway, and repetitive atrial firing was induced in 3 of 4 patients with paroxysmal atrial fibrillation. E-4031 could prevent repetitive atrial firing in only 1 patient and could not prevent induction of AV reentrant tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

A consensus report on antiarrhythmic drug use

During the past few years, a number of new antiarrhythmic agents have become available for use in the United States, encainide has been withdrawn from use, and others have had indications for use modified. Therefore, a meeting of arrhythmia specialists was convened in an attempt to develop guidelines for antiarrhythmic therapy. The resultant discussions and guidelines presented in this article address general issues such as the most important antiarrhythmic drug attributes, as well as therapy for particular arrhythmias such as premature ventricular contractions, ventricular tachycardia, ventricular fibrillation, ventricular ectopy, and supraventricular tachyarrhythmias.

Comparative analysis of electrophysiologic effect of metoprolol and disopyramide, acting alone or in combination in patients with supraventricular tachycardia and Wolff-Parkinson-White syndrome

In the aim of determining an electrophysiologic effect of disopyramide and metoprolol at alone therapy and in combination in patients with supraventricular tachycardia on the background of Wolff-Parkinson-White syndrome 23 persons were examined. All patients were subjected to an intracardiac electrophysiological testing; in its process metoprolol in the dosage of 0.2 mg/kg of body weight, disopyramide in the dosage of 2 mg/kg per body weight both separately and in combination were controlled. It was identified that metoprolol and disopyramide are an effective antiarrhythmic preparates applied for arresting and prevention of reciprocating orthodromic tachycardias in patients with Wolff-Parkinson-White syndrome.

Treatment with flecainide for symptomatic and refractory tachyarrhythmias in children

Nine children, aged 2.5 months to 16 years, presenting with tachyarrhythmias were treated with intravenous (i.v.) flecainide, a type 1C antiarrhythmic drug. There were four boys and five girls; seven were supraventricular and two ventricular tachycardias and three had structural cardiac abnormalities. The i.v. dose required to terminate the arrhythmias ranged from 1.0 to 2.4 mg/kg (mean 1.55 mg/kg) although a mean of 1.94 mg/kg per dose was required to maintain sustained sinus rhythm after a single i.v. dose. Eight of the patients--six supraventricular and two ventricular tachyarrhythmias, required maintenance oral flecainide. Oral dosages of 6.7-9.5 mg/kg per day (mean of 7.97 mg/kg per day in three divided doses) were required to effectively prevent the tachyarrhythmias. Intravenous and oral flecainide are safe and effective in terminating supraventricular and ventricular tachyarrhythmias. No evidence of proarrhythmia was found in the patients during follow up of between 5 and 9 months. The present limitation of performing radiofrequency ablation on infants and small children justifies the important place of medical therapy for re-entrant supraventricular tachyarrhythmias.

A new dosing regimen for esmolol to treat supraventricular tachyarrhythmia in Chinese patients

OBJECTIVES

The purpose of this study was to find a safe dosing regimen for esmolol infusion to rapidly control supraventricular tachyarrhythmia after cardiac surgery in Chinese patients.

BACKGROUND

Tachycardia increases cardiac work but reduces myocardial perfusion. Thus, in the critical period immediately after cardiac surgery, tachycardia itself warrants urgent intervention. Esmolol, an ultrashort-acting beta-adrenergic blocking agent, has been reported in western published reports to have good results and few side effects in the treatment of supraventricular tachyarrhythmia. However, its clinical application in Chinese patients has not yet been reported.

METHODS

When supraventricular tachyarrhythmia with a rapid ventricular response (> 110/min) was found early after cardiac surgery, esmolol infusion with a different dosing regimen was used to control the tachyarrhythmia.

RESULTS

With the dosing regimen recommended in western published reports (repeated loading infusion with stepwise increment), acute hypotension with systolic pressure < 80 mm Hg occurred in all six patients after 1 min of loading infusion of esmolol (500 micrograms/kg body weight per min). To avoid the aforementioned complications, a new dosing regimen was constructed. The initial infusion rate of esmolol was set at 150 or 100 micrograms/kg per min, depending on the patient's age and blood pressure. When the desired heart rate was achieved, the initial infusion rate was reduced to the maintenance infusion rate to maintain the therapeutic effect [Maintenance infusion rate = Initial infusion rate x (1 - e-0.077t), where t is the time period in minutes required by the initial infusion of esmolol to achieve the therapeutic effect]. With this new dosing regimen, tachycardia in most patients (9 of 11) could be controlled within 10 min, and no one experienced the side effect of hypotension. The maintenance infusion rate of esmolol needed to control supraventricular tachyarrhythmia in our patients was only 73 +/- 42 micrograms/kg per min (mean +/- SD), much less than that noted in western reports.

CONCLUSIONS

The dosing regimen for esmolol infusion recommended in western studies is not suitable for Chinese patients. In this report we propose a new dosing regimen for esmolol infusion that is both safe and rapid in the treatment of supraventricular tachyarrhythmia in Chinese patients.

Adenosine-induced non-sustained polymorphic ventricular tachycardia

Adenosine has become widely used because of its diagnostic and therapeutic value in the emergency management of arrhythmias. It produces transient heart block by slowing conduction through the AV node and thus terminates supraventricular tachycardias that involve the atrioventricular node. Bradyarrhythmias of short duration are common side effects of the use of this drug. Premature atrial and ventricular beats have also been reported. The very short half-life and lack of serious adverse effects generally lead to the consideration that adenosine is a safe drug. We describe a 56-year-old woman with a supraventricular tachycardia. To terminate this rhythm disorder intravenous adenosine was given. Interruption of the supraventricular tachycardia was followed by non-sustained polymorphic ventricular tachycardia.

Sotalol: a new agent for the treatment of ventricular arrhythmias

Sotalol was developed as a nonselective beta-blocker in the 1960s for the treatment of hypertension and later for cardiac risk management after myocardial infarction. Extensive research has since well described class III type electrophysiologic effects on the repolarization of myocardial fibers. Sotalol prolongs and homogenizes ventricular refractoriness, resulting in good antifibrillatory/antitachycardia protection. The unique combination of beta-blockade and antiarrhythmic effects probably will promote sotalol's use in postmyocardial infarction patients with ventricular tachycardia and sudden death. This article summarizes the pharmacologic and cardiovascular effects of this new drug, outlining its clinical use.

Use of adenosine for diagnosis and treatment of tachyarrhythmias in pediatric patients

This report reviews our experience with the use of adenosine for diagnosis and treatment of narrow QRS complex tachyarrhythmias in children. All electrocardiograms obtained since the introduction of adenosine for clinical use at one pediatric tertiary care institution during an 18-month period were reviewed, and those patients receiving adenosine were included for study. Of the 24 patients who received adenosine, the median age was 4 years; four neonates were included. Adenosine produced atrioventricular block in 21 (88%) of 24 patients. It terminated the tachyarrhythmia in 11 patients and produced atrioventricular block but did not terminate the tachyarrhythmia in 10 patients. The mechanism of the arrhythmia was known in three patients before adenosine administration. Adenosine was useful in establishing the mechanism of the tachyarrhythmia in 17 of the remaining 18 patients but was not useful in one patient, in whom the arrhythmia was successfully terminated because a good-quality electrocardiogram was not obtained during adenosine administration. Therefore the mechanism of the supraventricular tachycardia was ultimately determined for all patients in whom adenosine successfully produced atrioventricular block and had acceptable electrocardiographic tracings. Side effects were limited and transient. We conclude that adenosine was a safe and effective agent for the pharmacologic treatment of narrow QRS complex tachyarrhythmias in our patients, including those less than 1 year of age. If proper electrocardiographic recordings are performed during adenosine administration, it is also helpful in establishing the cause of the tachyarrhythmia.

Postoperative antiarrhythmic effects of diltiazem in patients undergoing coronary bypass grafting

Hemodynamic problems resulting from cardiac arrhythmias often occur in patients undergoing coronary bypass grafting in the early postoperative period. Therefore, in this study the antiarrhythmic effects of the calcium channel antagonist diltiazem were evaluated in coronary bypass grafting. Forty patients were randomly assigned either to a therapy with diltiazem or nitroglycerin. Hemodynamic measurements were established by Swan-Ganz catheter, and long-term ECG analyses were performed preoperatively and 1, 3 and 5 days after operation. There were significantly fewer ventricular arrhythmias (Lown class IV) in the diltiazem groups than in the nitroglycerin groups (p < 0.05). Supraventricular tachycardias were significantly more often observed in the nitroglycerin groups on all 3 days (p < 0.05). As a result, the calcium channel antagonist diltiazem is recommended as a standard adjunct to perioperative medication in cardiac surgery.

Efficacy of adenosine in terminating catecholamine-dependent supraventricular tachycardia

The purpose of this study was to determine if adenosine is equally effective in terminating catecholamine-dependent and independent supraventricular tachycardia (SVT). The effect of adenosine on termination of SVT was studied in 21 patients: 12 with atrioventricular (AV) reciprocating tachycardia, and 9 with AV node reentrant tachycardia. Group 1 comprised 13 patients who had SVT induced in the absence of exogenous catecholamines, whereas group 2 comprised 8 who needed isoproterenol (1.6 +/- 0.4 micrograms/min) for induction. There was no statistical difference between the 2 groups regarding age, weight, mean arterial pressure during sinus rhythm and SVT, cycle length of SVT, or norepinephrine and epinephrine levels during sinus rhythm and SVT. Cycle length during sinus rhythm was significantly decreased in group 2. The mean dose of adenosine needed to terminate SVT was 52 +/- 6 micrograms/kg of body weight in group 1, and 61 +/- 12 micrograms/kg in group 2 (p > 0.05). In addition to isoproterenol not altering the minimal dose of adenosine necessary to terminate SVT, there was also no correlation between the dose of adenosine (mean 55 +/- 6 micrograms/kg) of each patient, and the corresponding endogenous epinephrine (273 +/- 59 pg/ml) (r = -0.19) and norepinephrine (400 +/- 58 pg/ml) (r = 0.01) levels during SVT, or cycle length of SVT (323 +/- 9 ms) (r = -0.35). The results show that adenosine is equally effective in terminating catecholamine-dependent and independent SVT; higher adenosine doses should not be needed to manage catecholamine-dependent SVT.(ABSTRACT TRUNCATED AT 250 WORDS)