Supraventricular tachyarrhythmias: drug therapy versus catheter ablation

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

Sustained atrial tachycardia in adult patients. Electrophysiological characteristics, pharmacological response, possible mechanisms, and effects of radiofrequency ablation

BACKGROUND

Mechanisms and electropharmacological characteristics in adult patients with atrial tachycardia (AT) are not well described. We proposed that a combination of electropharmacological characteristics, recording of monophasic action potential, and effects of radiofrequency ablation could further determine the mechanisms and achieve a new classification in adults with various types of AT because they were important in regard to the correlation between mechanisms and pathophysiology, clinical syndrome, and responses to specific pharmacological or nonpharmacological therapies.

METHODS AND RESULTS

Thirty-six patients (11 female, 25 male; mean age, 57 +/- 13 years) with AT were referred for electropharmacological studies and radiofrequency ablation. Resetting response pattern, entrainment phenomenon, recording of monophasic action potential, serial drug test, response to Valsalva maneuver, endocardial mapping technique, and radiofrequency ablation were performed. Seven patients had automatic AT provocable with isoproterenol; neither initiation nor termination was related to programmed electrical stimulation. The other 29 patients had AT initiated or terminated by electrical stimulation and mechanisms related to triggered activity or reentry; nine of them needed isoproterenol to facilitate initiation of AT, associated with delayed afterdepolarization in monophasic action potential. All responded to adenosine (15 to 60 micrograms/kg) and Valsalva maneuver. Dipyridamole terminated AT and decreased the slope of afterdepolarization. Afterdepolarization was not found in the patients with automatic or reentrant AT. In 40 of 41 (98%), AT was ablated successfully, with late recurrence in 2 of 40 (5%) (follow-up, 18 +/- 4 months).

CONCLUSIONS

This study demonstrates the diverse mechanisms and electropharmacological characteristics of AT in adults. Furthermore, radiofrequency ablation of various types of AT could achieve high success and low recurrence rates.

Inpatient versus outpatient initiation of antiarrhythmic drug therapy for patients with supraventricular tachycardia

In-hospital initiation of antiarrhythmic drug therapy is often recommended to observe the effects of the drug and monitor for possible adverse reactions, especially proarrhythmia. However, the actual risk of proarrhythmia in patients undergoing treatment for supraventricular tachyarrhythmias is not well defined. While patients with ventricular tachycardia or ventricular fibrillation most often have underlying structural heart disease, this is not true for many patients with supraventricular tachycardia. It is therefore necessary to define more precisely which patients with supraventricular tachycardia are at risk for ventricular proarrhythmia and sudden cardiac death. An indepth analysis was conducted of 162 patients from 51 published reports of ventricular proarrhythmic events in patients treated for supraventricular tachycardia. Heart disease of various etiologies was present in 96% of patients. Proarrhythmia occurred most commonly with quinidine (72% of cases), and torsade de pointes was the most frequently proarrhythmic event (54%). More than half of all proarrhythmic events occurred within the first 3 days of initiating therapy or soon after increasing the dose of chronic drug therapy. Information was scant regarding the time to occurrence of ventricular proarrhythmia with flecainide and propafenone. With flecainide, nine cases were reported at varying times after initiation of therapy, from in-hospital to 8 months. Two cases of proarrhythmia with propafenone occurred at Day 10 and at 2 years. Because of the low frequency of proarrhythmia, in-hospital initiation of antiarrhythmic drug therapy may not be cost-effective. It is recommended when the effects of the drugs on the arrhythmia must be monitored, or when initiating treatment or increasing the drug dose in patients with structural hear disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug therapy for fetal arrhythmias

Diagnosis of specific types of fetal arrhythmias, especially tachyarrhythmias, is still difficult, often making semi-blind treatment inevitable. Published reports of many experienced clinicians show that digoxin remains a mainstream drug for therapy for fetal SVT and AF; digoxin is used as an initial monotherapy or in combination with other drugs if unresponsive to digoxin alone. It remains to be evaluated whether this treatment strategy offers overall better clinical outcomes than other approaches. Verapamil and propranolol are used in combination with digoxin, although successful control by propranolol seems rare. Quinidine and procainamide reportedly are effective in some cases. Reports on successful outcomes of flecainide therapy have emerged recently, although possible negative inotropic actions are of concern. Amiodarone is effective in some cases with incessant tachycardias, but risks of fetal thyroid dysfunction preclude its use as a firstline drug in uncomplicated fetal SVT cases. Empiric findings still prevail in the area of fetal drug therapy for arrhythmias, especially tachycardias. Heterogeniety of the conditions, lack of comparative studies, and difficulty in monitoring fetal drug level, let alone unbound drug concentrations, further complicate assessment of efficacy of different modes of treatment. Problems identified throughout this review have yet to be solved. Despite all these uncertain factors, however, it is clear that no one can undermine never-ending efforts of many clinicians in this exciting field of medicine.

Adenosine triphosphate treatment for supraventricular tachycardia in infants

Adenosine is an endogenous nucleoside acting on coronary perfusion and myocardial conduction. Although the anti-arrhythmic effects of adenosine have been known for decades, interest in the use of adenosine or adenosine triphosphate (ATP- a precursor of adenosine) in termination of supraventricular tachycardia (SVT) has been renewed. We studied the use of Striadyne (ATP and a mixture of other nucleosides including adenosine) in 22 infants younger than 6 months in order to evaluate efficacy and safety of the drug in this particular age group. Striadyne stopped SVT in 17 cases and was diagnostic in another 4 cases. Ten out of 17 successfully converted infants showed one or more reinitiations of SVT, which were easily controlled. The results support the efficacy of ATP for the termination of re-entry types of tachycardia, as well as its diagnostic value and its lack of serious side-effects.

CONCLUSION

Adenosine or ATP could be the drug of choice for the treatment of junctional tachycardia in infants after vagal manoeuvres have failed. Provided continuous ECG monitoring is performed during injection, adenosine or ATP may be diagnostic in other types of supraventricular tachycardia and even in wide-complex tachycardia. We suggest a bolus injection of 0.5-1.0 mg/kg to be used prior to transport to the paediatric cardiology unit.

Supraventricular tachycardia in a patient receiving ECT, clozapine, and caffeine

A patient receiving electroconvulsive therapy (ECT), clozapine, and intravenous caffeine sodium benzoate developed supraventricular tachycardia. This was rapidly treated with intravenous verapamil. Subsequent maintenance ECT given without caffeine was well tolerated. We believe the combination of clozapine and caffeine at the time of ECT was responsible for the arrhythmia.

Structural heart disease: its importance in association with antiarrhythmic drug therapy

The presence or absence of structural heart disease is an important factor to consider prior to initiating antiarrhythmic drug therapy with a class I or class III antiarrhythmic agent. An appropriate screen for structural heart disease and other associated proarrhythmic risk factors should include a complete history, physical examination, electrocardiogram (ECG), and echocardiogram in all patients; exercise test and Holter monitoring in many/most selected patients; and a signal-averaged ECG, chest x-ray, and invasive procedures only in selected/occasional patients. Whether and when to obtain the tests that are not indicated for all patients must be determined by each individual physician's practice strategy and philosophy, while keeping in mind the likelihood of finding an abnormality in a particular patient, the arrhythmia being treated, the nature of the drug to be used, and cost-effectiveness issues. Given the low incidence of proarrhythmia under most circumstances, screening for clinically unrecognized structural heart disease may appear difficult to justify in the current era of cost containment. However, due to the potential lethality of proarrhythmia, particularly in patients with structural heart disease, pre-drug assessment is prudent.

Single infusion of intravenous cibenzoline in the treatment of supraventricular tachyarrhythmias following heart surgery. A double-blind placebo-controlled parallel study

The efficacy and safety of a single infusion of cibenzoline, a class I antiarrhythmic drug, were assessed in 86 patients presenting with a supraventricular tachyarrhythmia following heart surgery in a placebo-controlled double-blind parallel study. Cibenzoline was effective in 13 patients (30%) vs three patients (6.9%) with placebo (P < 0.05). In the non-converted patients, ventricular rate was significantly slowed by cibenzoline (P < 0.05), which also significantly increased the duration of QRS and QT intervals. Transient adverse events were seen in nine patients receiving cibenzoline: moderate hypotension, sweating, right bundle branch block. One patient with decreased left ventricular function had an increased ventricular rate and QRS duration associated with hypotension. There were no severe adverse events. These results suggest that cibenzoline is effective for the treatment of postoperative supraventricular tachyarrhythmias in patients without impairment of ventricular function.

[The clinical usefulness and efficacy of adenosine triphosphate in an emergency service]

We studied 89 patients diagnosed in our emergency department of paroxysmal supraventricular tachycardia, to describe the efficacy and safety of intravenous adenosine triphosphate (ATP) in their treatment. All received a first bolus of 10 mg of ATP and if no electrical response was observed, a second dose of 20 mg. This treatment was successful in 91% of the patients, lasting of 26.9 seconds to resolve the episode, and in the 53% of the patients with the first dose. In 9% of the patients ATP did not resolve the episode but allowed to diagnose it, which in five patients was atrial flutter, in 2 Wolff-Parkinson-White syndrome and in one atrial fibrillation. Adverse effects appeared in 25.6% of the cases, being in all transitory and banal. ATP is a very effective and safe drug for the treatment of patients with PSVT.

Adenosine for the prehospital treatment of paroxysmal supraventricular tachycardia

STUDY OBJECTIVE

To determine the efficacy and feasibility of adenosine for the treatment of paroxysmal supraventricular tachycardia (PSVT) in the prehospital setting.

DESIGN

Prospective case series.

SETTING

Large, urban, advanced life support emergency medical services system.

PARTICIPANTS

One hundred twenty-nine adult patients with PSVT, as identified by paramedic personnel. Pregnant patients and those taking carbamazepine or dipyridamole were excluded.

INTERVENTIONS

Dose of 12 mg adenosine by rapid i.v. push followed by a 5-mL saline flush and a repeat dose of 12 mg adenosine i.v. push if the patient's rhythm remained unchanged.

MEASUREMENTS AND MAIN RESULTS

Six-second lead II rhythm strips and vital signs were documented before and 2 minutes after the administration of adenosine. Demographic information, past medical history, medications, number of adenosine doses given, and complications were recorded by the paramedic on a case-report form. One hundred six of 129 (82%) of the case-report forms included the rhythm strips from before and after adenosine administration. Actual initial rhythms were determined by a consensus panel. The initial rhythms were PSVT in 79% (84 of 106) of patients, atrial fibrillation in 12% (13 of 106), sinus tachycardia in 5% (five of 106), atrial flutter in 2% (two of 106), and ventricular tachycardia in 2% (two of 106). Eighty-five percent (71 of 84) of patients in PSVT were successfully converted to sinus rhythms; four (5.6%) of these patients required a second 12-mg dose. One patient in atrial fibrillation spontaneously converted to normal sinus rhythm and one patient in ventricular tachycardia converted after adenosine. All other patients not initially in PSVT remained in their initial rhythm. Complications occurred in 12 of 129 patients and included chest pain (five), flushing (three), shortness of breath (two), nausea (one), anxiety (one), dizziness (one), headache (one), and seizure (one). All complications were transient and required no treatment. Prior history of PSVT was the only variable associated with a higher rate of conversion (P = .029).

CONCLUSION

Paramedics are able to accurately identify PSVT using a single lead. Adenosine is safe and effective treatment for PSVT in the prehospital setting. This series is the largest prehospital study of adenosine use to date.

Adenosine in the termination of albuterol-induced supraventricular tachycardia

Five percent of children in the United States have asthma. Status asthmaticus is one of the most common conditions for which children seek care in a pediatric emergency department. beta 2-Agonists such as albuterol are the mainstay of emergency therapy for such children. We present a case of a 4-year-old boy who experienced supraventricular tachycardia (SVT) following albuterol therapy. This is believed to be the first report of adenosine being successfully used to treat a child with albuterol-induced SVT. We also briefly review the recognition and management of SVT in children and the pharmacokinetics of and indications for adenosine.

Fetal hypothyroidism as a complication of amiodarone treatment for persistent fetal supraventricular tachycardia

We present a case of persistent fetal supraventricular tachycardia where transplacental and direct fetal treatment with amiodarone caused an iatrogenic hypothyroidism. This condition was successfully managed with the intra-amniotic instillation of 250 micrograms of L-thyroxine weekly, for 3 weeks. A male infant was delivered at 32 weeks by Caesarean section. The neonatal electrocardiogram showed Wolf-Parkinson-White (WPW) syndrome, which was controlled by digoxin alone. Thyroid function normalized quickly and the baby is developing normally.

Clinical experience with propafenone for cardiac arrhythmias in the young

Seventy-two children were treated with propafenone between 1980 and 1990. The mean age was 34 months (range 0-192). Arrhythmias included atrioventricular re-entry tachycardia in 32 patients (44%), atrial flutter in 16 (22%), atrial or junctional ectopic tachycardia in 10 (14%), atrial re-entry tachycardias in three (4%) and ventricular arrhythmias in 11 patients (16%). The efficacy of oral treatment was good in patients with atrio-ventricular re-entry tachycardia (80%), atrial flutter (71%) and atrial ectopic tachycardia (83%); it was poor in ventricular arrhythmias (40%). The mean oral dose was 13.5 mg.kg-1. day-1. Dosage and serum levels of propafenone did not differ whether the patients were treated successfully or not. No correlation between dosage and serum level was observed. Intravenous propafenone administration was only partially successful in suppressing supraventricular tachycardias (6 of 11 patients). The presence of a congenital heart defect and the time of onset of the arrhythmias had a significant influence on the efficacy of propafenone. Better results were observed in patients with normal hearts and in whom onset of arrhythmia was pre-natal (success 80%) as well as in patients with arrhythmias seen early after surgery for congenital heart defects (success 87%). Success (65%) was also observed in patients without congenital heart defects and postnatal onset of supraventricular arrhythmias. Patients with ventricular or supraventricular arrhythmias late after corrective surgery showed the poorest response (31%).

[Fetal supraventricular tachycardia and nonimmune fetal hydrops]

A case of non-immunitary hydrops fetalis, following supraventricular tachycardia, in a fetus of 29 weeks of a 28-year-old woman at the first pregnancy, who evolved with systemic hypertension and amniorrhexis, being submitted to cesarean deliver. The child needed bilateral thoracic drainage and oro-tracheal intubation for treatment of respiratory failure. Treated with digoxin and diuretic, the newborn went home at the 56th day of life. The authors emphasize the importance of the intrauterine diagnosis of the arrhythmia for the success of the treatment.

[Amiodarone-induced hyperthyroidism causing progression of arrhythmia]

A case of a 38-year-old male with supraventricular paroxysmal tachycardia existing for more than a decade is reported. He has received amiodarone in a daily dose of 800 mg for three years and the tachycardia returned in 1992. New antiarrhythmic drugs were added but no beneficial effect has been achieved and moreover, a case of ventricular fibrillation occurred. The 12-lead ECG performed during tachycardia and the electrophysiological study showed orthodromic AV reentry tachycardia. Laboratory tests performed proved hyperthyreotic state. Attacks of paroxysmal tachycardia were returned and aggravated by the hyperthyreosis induced by amiodarone. Finally, antiarrhythmic drugs were discontinued and methimazol was introduced. Gradually, the patient become asymptomatic within two months. The most important conclusion of the case reported, that the amiodarone induced hyperthyreosis can be subclinical or obscure. Consequently, a regular control of serum thyreoid hormone levels at least twice a year on patients with long term amiodarone administration should be advised.

Sotalol

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

Adenosine for the treatment of supraventricular tachycardia in the ED

To determine the safety and efficacy of intravenous adenosine as used in the emergency department (ED) for the treatment of presumed supraventricular tachycardia, the investigators performed a retrospective chart review in an urban, university-affiliated ED. Seventy-two consecutive patients were treated with intravenous adenosine for presumed supraventricular tachycardia. Of the 72 patients who were treated with adenosine, 46 patients had a confirmed diagnosis of supraventricular tachycardia. Of these, 39 of 46 (84.8%) converted to sinus rhythm after treatment. Of patients who successfully converted to sinus rhythm, none had recurrent tachycardia or required additional pharmacotherapy. Arrhythmias not successfully treated among the initially misdiagnosed patients were atrial fibrillation (n = 11), atrial flutter (n = 7), tachycardia of other origin (n = 5), and ventricular tachycardia (n = 2). No clinically significant adverse effects were noted among the study population. Intravenous adenosine is a safe and efficacious treatment for the emergent treatment of supraventricular tachycardia, including unstable patients (with hypotension and/or chest pain). It is also safe among patients initially presumed to have supraventricular tachycardia, who are later diagnosed with other arrhythmias.

Intraosseous adenosine. As effective as peripheral or central venous administration?

OBJECTIVE

The purpose of this study was to determine if intraosseous administration of adenosine is effective and, if so, to establish therapeutic dosage criteria for the intraosseous route compared with peripheral or central intraosseous route compared with peripheral or central venous routes.

RESEARCH DESIGN

Randomized, unblinded, cross-over, within-animal control study.

SETTING

University hospital in Ohio.

SUBJECTS

Thirty newly weaned piglets.

SELECTION PROCEDURE

Consecutive sample.

INTERVENTIONS

Thirty newly weaned pigs were transesophageally (n = 26) or transvenously (n = 4) paced at a cycle length that was 10% longer than the Wenckebach threshold. The minimum effective dose of adenosine necessary to induce atrioventricular block during pacing was recorded for peripheral venous, central venous, and intraosseous routes.

MEASUREMENTS AND RESULTS

The baseline resting heart rate and Wenckebach thresholds were not statistically different between subjects or between different routes of administration. The intraosseous route required a minimum effective dose of 127 micrograms/kg. Using a log transformation, the difference between central venous and peripheral venous doses was found to be statistically significant. The intraosseous dose was not statistically different from the central venous or peripheral venous doses.

CONCLUSION

The intraosseous route is an effective way of administering adenosine. The peripheral venous dose required to achieve atrioventricular block is higher than the central venous dose and the intraosseous dose is intermediary to the central venous and peripheral venous doses.

The treatment of intractable supraventricular tachycardia after open heart surgery by a continuous infusion of verapamil and ventricular pacing

Four patients who developed intractable supraventricular tachycardia (SVT) after open heart surgery were treated using a new therapeutic method of creating a pharmacological atrioventricular block by the continuous infusion of verapamil with ventricular pacing. Both the initial dose and the effective dose, being the verapamil dose necessary to maintain pharmacological atrioventricular block to prevent the recurrence of SVT, were surveyed with clinical results. The verapamil-induced hemodynamic changes observed 4 h and 8 h after treatment, as indicated by systolic arterial blood pressure, mean arteral blood pressure, heart rate, cardiac index, and urine volume, were compared with the values 1 h before treatment. After an initial low dose infusion of 0.07 +/- 0.02 mg/kg.h had been given, an effective and safe dose of 0.11 +/- 0.05 mg/kg.h was determined. Good hemodynamic and clinical results were achieved in all four patients who are now leading an active life. These results therefore encourage us to apply this therapeutic method for treating patients with intractable and recurrent SVT after open heart surgery.

[Evaluation of the clinical acute electrophysiological effects of propafenone using transesophageal atrial pacing]

The clinical acute electrophysiological effects of propafenone were evaluated using transesophageal atrial pacing (TEAP) in 65 patients with various arrhythmias. The mean age of the patients was 41 years. Incremental pacing and programmed ectopic stimulation were performed on each patient before and during drug administration. Propafenone was given as a bolus injection of 1.5mg.kg-1 body weight followed by drip infusion at a rate of 1 mg.min-1. S-R, P wave, P-R and QRS intervals were prolonged from 194.43 +/- 21.59, 97.49 +/- 10.92, 148.00 +/- 16.20 and 82.21 +/- 7.18ms 223.00 +/- 29.25, 100.22 +/- 10.60, 166.60 +/- 20.10 and 86.54 +/- 7.19ms, respectively (P < 0.005), A-V conduction system effective refractory period (AVCSERP) was prolonged from 316.35 +/- 82.97ms to 360.31 +/- 82.67ms (P < 0.0001) in the treated group. There was no change of atrial ERP and QTc interval (P > 0.05). Fast and slow pathway ERP was prolonged by 13% and 28% of the control value, respectively (P < 0.015), and accessory pathway ERP was prolonged from 278.89 +/- 27.13ms to 305.56 +/- 33.58ms (P < 0.001), in the treated group. Sinus cycle length, corrected sinus nodal recovery time and total sinus-atrial conductive time were significantly prolonged (P < 0.0001). The results can partially explain the antiarrhythmic effects and the side effects of propafenone. TEAP is dependable in evaluating the clinical electrophysiological effects of drugs.

[AV reciprocating tachycardia with intermittent bundle branch block in latent Wolff-Parkinson-White syndrome]

This report deals with a patient with concealed Wolff-Parkinson-White syndrome in whom both narrow and wide QRS tachycardias were observed. The simultaneous occurrence of various QRS morphology during supraventricular tachycardia results in a challenging diagnostic ECG problem. The cycle length during tachycardia with left bundle branch block was longer than the cycle length during narrow QRS supraventricular tachycardia and with functional right bundle-branch block. Electrophysiologic studies revealed fixed V-A conduction time and increased V-A conduction during tachycardia with left bundle branch block. These studies suggested the presence of a concealed left-sided anomalous pathway. Differentiation between intra- and extranodal re-entry and therapeutic modalities are also discussed.

Anaesthesia for caesarean section in a patient receiving high dose amiodarone for fetal supraventricular tachycardia

We report the anaesthetic management of a Caesarean section in a woman treated with high dose amiodarone for fetal supraventricular tachycardia. Most of the interactions between anaesthesia and amiodarone therapy previously reported were observed during general anaesthesia. We therefore chose epidural anaesthesia using incremental doses of lignocaine 2% with adrenaline and fentanyl. This technique appeared to be safe, but since severe refractory vasodilation with hypotension may occur, potent vasopressor agents should be immediately available.