Flecainide and amiodarone: combined therapy for refractory tachyarrhythmias in infancy

Multiple recurrent supraventricular tachycardia in infantile tuberous sclerosis complex: management requiring triple-drug therapy

We report the case of a female neonate admitted to the neonatal ICU with a rapid, narrow-complex tachyarrhythmia determined to be supraventricular tachycardia. Multimodality imaging and genetic testing confirmed a diagnosis of tuberous sclerosis complex with multiple cardiac rhabdomyomas. At 13 days of age, the patient was readmitted, exhibiting recurrent supraventricular tachycardia non-responsive to first-line treatment. Management required triple-drug therapy, whereafter the patient remained stable without recurrences. This is a rare report of supraventricular tachycardia in a functionally normal heart with the occurrence of supraventricular tachycardia due to structural abnormalities, with the possibility of multiple concealed accessory pathways.

Triple Antiarrhythmic Therapy in Newborns with Refractory Atrioventricular Reentrant Tachycardia

Atrioventricular reentrant tachycardia (AVRT) is the most common form of supraventricular tachycardia in newborns. AVRT is sometimes refractory to conventional antiarrhythmic therapy. We describe our experience about the use of the triple combination of flecainide + propranolol + amiodarone as third-line regimen for refractory and recurrent AVRT in newborns. We considered a series of 14 patients who had failed both first-line and second-line therapy and were treated using the combination of flecainide + propranolol + amiodarone. Transoesophageal electrophysiologic study (TES) was performed to test the effectiveness of medical therapy during hospitalization and to try to reduce the amount of therapy, after amiodarone wash-out, before 1 year of age. TES was repeated at 1 year of age to test the spontaneous resolution of the arrhythmia after treatment discontinuation. Rhythm control was achieved in all 14 patients. At a mean age of 9.3 ± 2 months, AVRT was not inducible by TES in 11/12 amiodarone-free patients. At a mean age of 14.1 ± 3 months, AVRT was still inducible in 7/12 patients after interrupting the entire antiarrhythmic therapy (58.3%). Triple combination was effective as third-line option to suppress AVRT refractory to single and double antiarrhythmic therapy, with no significant adverse events. Our experience suggests that triple therapy could be maintained for a short-term treatment, discontinuing amiodarone before 1 year of age to avoid long-term side effects. Newborns who needed triple therapy appear to have a lower chance of accessory pathway disappearance at 1 year of age. TES could be useful for risk stratification of recurrences at the time of drug discontinuation in infants considered to be at higher risk of recurrent AVRT.

Ivabradine-Flecainide as Breakthrough Drug Combination for Congenital Junctional Ectopic Tachycardia: A Case Report and Literature Review

Congenital junctional ectopic tachycardia (CJET) is a rare tachyarrhythmia that remains difficult to manage, with suboptimal control in most cases. Here, we report literature research on the use of ivabradine in the treatment of pediatric junctional ectopic tachycardia (JET), both congenital and postoperative, and describe the successful use of ivabradine-flecainide association for CJET therapy resistant to other antiarrhythmic agents. This new drug combination was effective in completely suppressing JET. Ivabradine-flecainide combination may be considered a new therapeutic strategy of CJET with a satisfactory efficacy/tolerability ratio in patients resistant to conventional drug combinations.

Supraventricular tachyarrhythmias during the intrauterine, neonatal, and infant period: A 10-year population-based study

BACKGROUND

We aimed to evaluate the incidence, type, and management of supraventricular tachyarrhythmias (SVT) during the first year of life in a retrospective, population-based, single-center study during a 10-year period.

METHODS

The analyzed patient cohort is based on data from the only specialized center managing all cases of neonatal and infant SVTs between 2009 and 2018 in the Slovak Republic (5.5 million population). A total of 116 consecutive patients <366 days old were included in the study.

RESULTS

Calculated SVT incidence ratio was 1:4500 in the first year of life. AV reentry tachycardia was the leading arrhythmia (49%). SVT in this specific population was frequently a transient problem with spontaneous resolution in 87% of patients during a median 3-year follow up. Congenital heart disease was common (16%). Intrauterine treatment by drugs administered to mother was safe and effective in preventing unnecessary cesarean deliveries. In arrhythmia termination, amiodarone and propafenone were equally safe and effective, with possible more favorable pharmacodynamics of the former. For prophylactic treatment, sotalol and propafenone were equally safe and effective and became the preferred basis of long-term drug therapy in our center. However, this therapy requires intensive monitoring during its initiation.

CONCLUSION

The prognosis of SVT in the first year of life is good: with optimized pharmacological treatment, the need for early catheter ablation and mortality rate are low (<1%) and there is a high rate of spontaneous arrhythmia resolution. Heart failure is a possible predictor of arrhythmia persistence with need for ablation in later life.

Management of Supraventricular Tachycardia in Infants

Supraventricular tachycardia is the most common tachyarrhythmia encountered in infants. In older children and adults, definitive treatment of the supraventricular tachycardia substrate with catheter ablation is a common approach to management. However, in infants, the risks of catheter ablation are significantly higher, and the patients often outgrow the potential to experience episodes. Therefore, antiarrhythmic medications are often utilized to minimize the likelihood of experiencing episodes. This article reviews the common arrhythmia mechanisms encountered in infants and the medications used to treat these patients.

Neonatal arrhythmias: diagnosis, treatment, and clinical outcome

Arrhythmias in the neonatal period are not uncommon, and may occur in neonates with a normal heart or in those with structural heart disease. Neonatal arrhythmias are classified as either benign or nonbenign. Benign arrhythmias include sinus arrhythmia, premature atrial contraction, premature ventricular contraction, and junctional rhythm; these arrhythmias have no clinical significance and do not need therapy. Supraventricular tachycardia, ventricular tachycardia, atrioventricular conduction abnormalities, and genetic arrhythmia such as congenital long-QT syndrome are classified as nonbenign arrhythmias. Although most neonatal arrhythmias are asymptomatic and rarely life-threatening, the prognosis depends on the early recognition and proper management of the condition in some serious cases. Precise diagnosis with risk stratification of patients with nonbenign neonatal arrhythmia is needed to reduce morbidity and mortality. In this article, I review the current understanding of the common clinical presentation, etiology, natural history, and management of neonatal arrhythmias in the absence of an underlying congenital heart disease.

Drug-drug interactions and QT prolongation as a commonly assessed cardiac effect - comprehensive overview of clinical trials

Background

Proarrhythmia assessment is one of the major concerns for regulatory bodies and pharmaceutical industry. ICH guidelines recommending preclinical tests have been established in attempt to eliminate the risk of drug-induced arrhythmias. However, in the clinic, arrhythmia occurrence is determined not only by the inherent property of a drug to block ion currents and disturb electrophysiological activity of cardiac myocytes, but also by many other factors modifying individual risk of QT prolongation and subsequent proarrhythmia propensity. One of those is drug-drug interactions. Since polypharmacy is a common practice in clinical settings, it can be anticipated that there is a relatively high risk that the patient will receive at least two drugs mutually modifying their proarrhythmic potential and resulting either in triggering the occurrence or mitigating the clinical symptoms. The mechanism can be observed either directly at the pharmacodynamic level by competing for the molecular targets, or indirectly by modifying the physiological parameters, or at the pharmacokinetic level by alteration of the active concentration of the victim drug.

Methods

This publication provides an overview of published clinical studies on pharmacokinetic and/or pharmacodynamic drug-drug interactions in humans and their electrophysiological consequences (QT interval modification). Databases of PubMed and Scopus were searched and combinations of the following keywords were used for Title, Abstract and Keywords fields: interaction, coadministration, combination, DDI and electrocardiographic, QTc interval, ECG. Only human studies were included. Over 4500 publications were retrieved and underwent preliminary assessment to identify papers accordant with the topic of this review. 76 papers reporting results for 96 drug combinations were found and analyzed.

Results

The results show the tremendous variability of drug-drug interaction effects, which makes one aware of complexity of the problem, and suggests the need for assessment of an additional risk factors and careful ECG monitoring before administration of drugs with anticipated QT prolongation.

Conclusions

DDIs can play significant roles in drugs’ cardiac safety, as evidenced by the provided examples. Assessment of the pharmacodynamic effects of the drug interactions is more challenging as compared to the pharmacokinetic due to the significant diversity in the endpoints which should be analyzed specifically for various clinical effects. Nevertheless, PD components of DDIs should be accounted for as PK changes alone do not allow to fully explain the electrophysiological effects in clinic situations.

Electronic supplementary material

The online version of this article (doi:10.1186/s40360-016-0053-1) contains supplementary material, which is available to authorized users.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antiarrhythmics

OBJECTIVE

Arrhythmias are a common occurrence in critically ill pediatric patients. Pharmacotherapy is a usual modality for treatment and prevention of arrhythmias in this patient population. This review will highlight particular arrhythmias in the pediatric critical care population and discuss salient points of pharmacotherapy of these arrhythmias. The mechanisms of action for the various agents, potential adverse events, place in therapy, and evidence for their use will be summarized.

DATA SOURCES

The literature was searched for articles related to the topic. Expertise of the authors and a consensus of the editors were additional sources of data in the article.

DATA SYNTHESIS

The author team synthesized the current pharmacology and recommendations and present them in this review. Tables were generated to summarize the state of the art evidence-based practice.

CONCLUSION

Specialized knowledge as to the safe and effective use of the antiarrhythmic pharmacotherapy in the intensive care setting can lead to safe and effective rhythm management in patients with complex heart disease.

Combination of flecainide and propranolol for congenital junctional ectopic tachycardia

Congenital junctional ectopic tachycardia is a rare tachyarrhythmia with high mortality. A pharmacological approach in early infancy is regarded as the first-line therapeutic option. Pharmacologically, amiodarone alone or in combination with other drugs is the most commonly reported effective agent for congenital junctional ectopic tachycardia, but it has many adverse effects. Here we report the case of a 40-day-old infant. The clinical course suggests that combined oral flecainide and propranolol is an effective alternative therapy for early infants. Esophageal lead electrocardiography may give a clear diagnosis of junctional ectopic tachycardia.

Oral flecainide is effective in management of refractory tachycardia in infants

BACKGROUND

Propranolol and digoxin have been used as first line drugs for treatment of supraventricular tachycardia (SVT) in infants. Flecainide and other drugs have been effective as a second line treatment for controlling refractory SVT.

MATERIAL AND METHODS

This is a prospective study without randomization and control. The inclusion criteria were: infants (≤12 months) with tachyarrhythmia who failed to respond to first line drugs. Patients having post-surgical arrhythmias were excluded from the study.

RESULTS

A total of 8 infants were treated with flecainide for refractory tachyarrhythmia's. Diagnosis on electrocardiogram (ECG) was atrioventricular reentry tachycardia (AVRT) in 5, atrial ectopic tachycardia (AET) in 2, a combination of AVRT and atrioventricular nodal reentry tachycardia (AVNRT) in 1. All patients had failed trial of antiarrhythmic drugs prior to presentation: digoxin and propranolol in 7, amiodarone in 3, cardioversion in 1. Flecainide (80-130 mg/m(2) orally) resulted in termination of the tachycardia in all 8 patients. Acute pharmacological termination of arrhythmia occurred with oral flecainide loading in 1 and temporarily with intravenous esmolol loading in 1 patient. Adjuvant therapy in form of propranolol was used in 5 and digoxin in 2. There were no side effects noted. Four episodes of recurrence were noted in 3 patients over 2 years, all of which responded to dose increase. Mean follow up time is 24.75 months.

CONCLUSION

This small case series indicates that flecainide is an effective antiarrhythmic agent, free of side effects and when used orally is capable of terminating and controlling relatively resistant supraventricular tachycardia in children.

Outcomes of interventional electrophysiology in children under 2 years of age

BACKGROUND

Despite the increasing utilisation of interventional electrophysiology in adults and older children with arrhythmias, there are few data reflecting the safety and efficacy of this procedure in the age group under 2 years.

AIM

We describe our experience in assessing the efficacy and safety with this group of children.

METHODS

We undertook a retrospective review of all infants under 2 years of age who underwent an interventional electrophysiology procedure between 1995 and 2009 to determine indications, procedural details, short- and long-term success, and complication rate.

RESULTS

A total of 23 interventional electrophysiology procedures were performed in 17 patients initially under 2 years of age. Of these, three patients had congenital heart disease. The most common indication was arrhythmia resistant to pharmacological agents (59%), with the remaining cases being arrhythmia complicated by cardiovascular instability (41%). There was initial success in 15 patients after the first procedure, with early recurrence in four. Following six repeat procedures, there was long-term success in 15 patients (88%), with three repeat procedures being performed after 2 years of age. There was one non-procedural death related to persisting arrhythmia. There were three minor complications. In one patient, cryotherapy was used successfully.

CONCLUSIONS

The interventional electrophysiology procedure is a viable therapeutic option in infants under 2 years with arrhythmia resistant to other conventional medical management.

Fetal cardiac arrhythmia detection and in utero therapy

The human fetal heart develops arrhythmias and conduction disturbances in response to ischemia, inflammation, electrolyte disturbances, altered load states, structural defects, inherited genetic conditions, and many other causes. Yet sinus rhythm is present without altered rate or rhythm in some of the most serious electrophysiological diseases, which makes detection of diseases of the fetal conduction system challenging in the absence of magnetocardiographic or electrocardiographic recording techniques. Life-threatening changes in QRS or QT intervals can be completely unrecognized if heart rate is the only feature to be altered. For many fetal arrhythmias, echocardiography alone can assess important clinical parameters for diagnosis. Appropriate treatment of the fetus requires awareness of arrhythmia characteristics, mechanisms, and potential associations. Criteria to define fetal bradycardia specific to gestational age are now available and may allow detection of ion channelopathies, which are associated with fetal and neonatal bradycardia. Ectopic beats, once thought to be entirely benign, are now recognized to have important pathologic associations. Fetal tachyarrhythmias can now be defined precisely for mechanism-specific therapy and for subsequent monitoring of response. This article reviews the current and future diagnostic techniques and pharmacologic treatments for fetal arrhythmia.

Intravenous amiodarone used alone or in combination with digoxin for life-threatening supraventricular tachyarrhythmia in neonates and small infants

OBJECTIVES

The purpose of this study was to report the efficacy of intravenous amiodarone alone or in combination with digoxin in neonates and small infants with life-threatening supraventricular tachyarrhythmia (SVT).

METHODS

We retrospectively analyzed 9 neonates and small infants with life-threatening or resistant SVT who were treated with intravenous amiodarone alone or in combination with digoxin.

RESULTS

This report consists of 8 patients with reentrant SVT and 1 with atrial flutter. On admission, 7 patients had a congestive heart failure and 3 of whom had cardiovascular collapse. Intravenous rapid bolus of adenosine caused a sustained sinus rhythm in 4 patients. These patients were given digoxin initially, but recurrence of persistent tachyarrhythmia necessitated the use of intravenous amiodarone in all these patients. Amiodarone was given initially to the other 4 patients in whom adenosine caused only temporary conversion to the sinus rhythm. It was effective in 2 patients. In the other 2, digoxin was added to therapy for tachycardia control. Amiodarone alone or in combination with digoxin effectively controlled reentrant SVT in all patients. This combined treatment caused ventricular rate control in patient with atrial flutter, and conversion to the stable sinus rhythm was achieved at approximately 8 months.

CONCLUSIONS

Intravenous amiodarone alone or in combination with digoxin was found to be safe and effective in controlling refractory and life-threatening SVT in neonates and small infants.

Implantable cardioverter defibrillator as a bridge to recovery in an infant with cardiac rhabdomyoma

Multiple cardiac rhabdomyomas in an infant presented with recurrent life-threatening ventricular arrhythmias refractory to medical treatment and necessitating the placement of an implantable cardioverter defibrillator (ICD). The device functioned effectively as a bridge to recovery during a 2-year follow-up period, when the tumor showed spontaneous regression, along with an almost complete resolution of the ventricular arrhythmias. We conclude that childhood cardiac rhabdomyomas causing severe drug-refractory ventricular arrhythmias can be managed by ICD therapy.

Detection and management of life threatening arrhythmias in the perinatal period

The management of tachyarrhythmias and bradyarrythmias in the fetus requires a team approach with careful monitoring of fetal well-being as well as care in establishing a precise diagnosis with use of m-mode and Doppler echocardiography to determine the atrial and ventricular rate. A persistent fetal heart rate less than 80 beats per minute (bpm) suggests complete atrioventricular block. A persistent fetal heart rate over 180 bpm suggests pathological tachycardia, most of which are a supraventricular tachycardia mediated via an accessory pathway. However, around 20% are due to atrial flutter, and this review highlights why medical management should be different for these cases, and for those with hydrops or cardiac failure. It also illustrates which fetus or infant may be at particular risk, and illustrates key features in their management before and after birth.

Case report: an infant with congenital junctional ectopic tachycardia requiring extracorporeal mechanical oxygenation

PURPOSE OF REVIEW

A case report of an infant with hemodynamic compromise and impending collapse due to congenital junctional ectopic tachycardia. Medical therapy was maximized and he required the rapid initiation of extracorporeal life support, in order to achieve hemodynamic stability.

RECENT FINDINGS

This case report briefly reviews the presentation and treatment options for congenital junctional ectopic tachycardia, as well as the indications for initiation of mechanical support for this potentially lethal condition.

SUMMARY

Congenital junctional ectopic tachycardia is a rare though often fatal arrhythmia of the newborn or infant. Medical treatment options may be limited, or may require time to attain efficacy. Despite aggressive escalation of antiarrhythmic therapy, mechanical support in the form of extracorporeal mechanical oxygenation is a viable option, until the arrhythmia is well controlled and the myocardium recovers function.

Combined use of 1C and III agents for highly symptomatic, refractory atrial fibrillation

BACKGROUND

Despite advances in non-pharmacologic therapy for atrial fibrillation (AF), some patients remain highly refractory.

OBJECTIVE

We report our experience with the unique combined use of 1C and III agents in patients with highly refractory paroxysmal atrial fibrillation.

MATERIALS AND METHODS

Six patients with symptomatic AF (three persistent) were selected after failing multiple antiarrhythmic medications and radiofrequency ablation. They were started on flecainide or propafenone and sotalol or dofetilide during three days of inpatient monitoring. No patient had coronary artery disease. All patients had loop recorder follow-up and ECG recordings during clinic visits for a mean follow-up of 9 +/- 11 months.

RESULTS

After therapy, all patients had complete, sustained control of their symptoms with no evidence of AF or proarrhythmia on monitoring. One patient had recurrence of AF after stopping sotalol and was started back on the drug with complete control.

CONCLUSIONS

Combined therapy with a 1C and III agent may be an effective alternative for the treatment of selective, highly refractory AF. Careful patient selection and hospitalization for initiation is necessary to minimize potential proarrhythmic effects. As this is a short-term therapy, further study is needed to assess the extent of efficacy in a larger number of patients.

Neonatal tachycardias: an update

This review provides an updated framework for the diagnosis and management of neonatal tachycardias.

Cardiovascular drugs for the newborn

This article reviews the various cardiovascular drugs for newborns, including antiarrhythmics, antihypertensives, inotropes, and pulmonary vasodilators. Antiarrhythmic drugs are classified according to their mechanisms of action, such as effects on ion channels, duration of repolarization, and receptor interaction, which help with understanding the effects of individual antiarrhythmic drugs and selection of drugs for specific arrhythmias. Drug treatment for hypertension should start with a single drug from one of the following classes: ACE inhibitors, angiotensin-receptor antagonists, beta-receptor antagonists, calcium channel blockers, or diuretics. The inotropic drug should be selected according to its specific pharmacologic properties and the specific cardiovascular abnormality to be corrected. An effective pulmonary vasodilator must dilate the pulmonary vasculature more than the systemic vasculature.

Successful use of an intravenous infusion of flecainide and amiodarone for a refractory combination of postoperative junctional and ectopic tachycardias

After repair of an atrioventricular septal defect with common atrioventricular junction in a 2-month-old girl, rapid atrial tachycardia, in combination with junctional ectopic tachycardia, led to severe postoperative cardiovascular compromise. Intercurrent runs of ectopic atrial tachycardia made atrial pacing impossible, despite high doses of intravenous amiodarone. Following the addition of flecainide to the infusion, we were able to control the rhythm, and when combined with atrial pacing, this led to an immediate haemodynamic improvement. Treatment of refractory supraventricular tachycardias with amiodarone combined with flecainide can be very effective in the setting of postoperative cardiac intensive care.

Automatic atrial tachycardia in an infant following general anesthesia

Automatic atrial tachycardia (AAT) is a rare supraventricular tachyarrhythmia (<10% of all supraventricular tachycardias), which can present in infants or young children. There are no published reports of AAT occurring in an infant or child following noncardiac surgery and general anesthesia. This report describes the management of a previously healthy 5-month-old infant, who developed AAT in the postanesthesia care unit following an uneventful circumcision under general anesthesia.

Radiofrequency Catheter Ablation in Small Children:. Relationship of Complications to Application Dose

Little data exists to support the use of procedural modifications during radiofrequency catheter ablation (RFCA) in small children. A single institution database was reviewed for patients under 15 kg undergoing RFCA from January 1998 to August 2001. Of 268 RFCA procedures, 18 were done in 14 patients under 15 kg (median weight 5.7 kg, 3.5-13.7; age 5.8 months, 1.2-19.8). Six patients had normal hearts, 4 had congenital heart disease, and 4 patients had cardiomyopathy. Diagnoses were orthodromic reciprocating tachycardia (ORT) in nine patients/nine studies, chaotic atrial tachycardia (CAT) in one patient/two studies, and VT in four patients/seven studies. RFCA variables included maximum temperature (69 degrees C, 50-78), total applications (10, 2-21), applications > 20 seconds (5, 0-15), and total application time (331 s, 26-1,006 s). Complications were pericardial effusion in 1 patient, mild mitral regurgitation in 1, and myocardial infarction in 1 patient. When indexed for weight, the number of applications with a duration > 20 seconds in the ORT group was significantly greater in complicated versus uncomplicated procedures (0.7 applications/kg vs 0.16 applications/kg, P = 0.05). In addition, for the ORT subgroup, the indexed total application time trended higher in complicated versus uncomplicated procedures (40.6 s/kg, vs 6.6 s/kg, P = 0.1). RFCA success was 9/9 in ORT, 6/7 in VT, and 0/2 in CAT. RFCA can be successful in small children; however, complications appear to be related to RF dose indexed for body size. Thus, the decision to proceed with RFCA, and the application duration and number should be guided by patient size, balanced against the risks of the arrhythmia, and reserved for dire circumstances.

Flecainide and sotalol: a new combination therapy for refractory supraventricular tachycardia in children <1 year of age

OBJECTIVES

The goal of this study was to assess the efficacy and safety of the combination therapy of flecainide and sotalol for the treatment of refractory supraventricular tachycardia (SVT) in children <1 year of age.

BACKGROUND

Supraventricular tachycardia in infants can be refractory to single-drug as well as standard combination medical therapy. Radiofrequency ablation (RFA) is the definitive treatment of refractory SVT; however, interventional therapy poses a high risk of morbidity and mortality in this age group.

METHODS

A retrospective review was performed identifying infants who required flecainide and sotalol to control refractory SVT. Patient age, previous drug therapy, duration of treatment, flecainide levels and corrected QT intervals were recorded; 24 h Holter monitoring was utilized to gauge efficacy of treatment. Efficacy was defined as suppression of SVT to no more than rare nonsustained episodes or slowing of SVT to a clinically tolerable rate.

RESULTS

Ten patients (median age: 29 days, range: 1 to 241 days) failed at least two antiarrhythmic agents including either flecainide or sotalol as single agents before initiating combination therapy. Efficacy was achieved in all patients. The failure rate for therapy was reduced from 100% to 0% (95% confidence interval: 0% to 26%). The median doses used were: flecainide 100 mg/m(2)/day (range: 40 to 150 mg/m(2)/day) and sotalol 175 mg/m(2)/day (range: 100 to 250 mg/m(2)/day). Median duration of therapy was 16 months (range: 5 to 35 months). No proarrhythmia occurred.

CONCLUSIONS

The combination of flecainide and sotalol can safely and effectively control refractory SVT and may obviate the need for RFA in children <1 year.

Amiodarone -- waxed and waned and waxed again

Amiodarone has been used as an anti-arrhythmic drug since the 1970s and has an established role in the treatment of ventricular tachyarrhythmias. Although considered to be a class III anti-arrhythmic, amiodarone also has class I, II and IV actions, which gives it a unique pharmacological and anti-arrhythmic profile. Amiodarone is a structural analogue of thyroid hormone and some of its anti-arrhythmic properties and toxicity may be attributable to interactions with nuclear thyroid hormone receptors. The lipid solubility of amiodarone gives it an exceptionally long half-life. Oral amiodarone takes days to work in ventricular tachyarrhythmias, but iv. amiodarone has immediate effect and can be used in life threatening ventricular arrhythmias. Intravenous amiodarone administered after out-of-hospital cardiac arrest due to ventricular fibrillation improves survival to hospital admission. Many survivors of myocardial infarction (MI) die during the subsequent year, probably due to ventricular arrhythmia. Amiodarone reduces sudden death after MI and this benefit is predominantly observed in patients with preserved cardiac function. Sudden cardiac death, predominantly due to ventricular arrhythmias, is also commonly seen in patients with heart failure. The Grupo de Estudio de la Sobrevida en lsuficiencia Cardiaca en Argentina (GESICA) and Estudio Piloto Argentino de Muerte Subita y Amiodarona (EPAMSA) trials showed survival benefit of amiodarone in heart failure, whereas Congestive Heart Failure-Survival Trial of Anti-arrhythmic Therapy (CHF-STAT) did not. Subsequent meta-analysis established a survival benefit of amiodarone in heart failure. Implanted Cardioverter Def ibrillators (ICDs) also give survival benefit to patients at risk of sudden death. In patients with a history of ventricular fibrillation or haemodynamically-compromising ventricular tachycardia, ICDs have been shown to be superior to anti-arrhythmic drugs, principally amiodarone. Further analysis has been undertaken to ascertain which patients are most likely to benefit from ICDs, as these are more expensive than treatment with amiodarone. Patients with severely depressed ejection fractions should be the first to be considered for ICDs. A new indication for amiodarone is atrial fibrillation or flutter. Amiodarone is effective in chronic and recent onset atrial fibrillation and orally or iv. for atrial fibrillation after heart surgery. In atrial fibrillation amiodarone is more than or equi-effective with flecainide, quinidine, racemic sotalol, propafenone and diltiazem and therefore should be considered for first line therapy. Amiodarone is also safe and effective in controlling refractory tachyarrhythmias in infants and is safe after cardiac surgery.

Pharmacologic management of arrhythmias in patients with congenital heart disease

The management of cardiac arrhythmias has evolved rapidly over the past decade. This includes the development of more effective antiarrhythmic medications as well as catheter- and device-based therapies. Antiarrhythmic medications remain the primary treatment modality for most acute arrhythmias; however, the long term use of these medications may be accompanied by severe adverse effects. For this reason, antiarrhythmic medications are increasingly used in conjunction with other forms of therapy, such as catheter ablation or pacemaker implantation. Patients with congenital heart disease often have an increased propensity for cardiac arrhythmias due to both inherent conduction system abnormalities and impaired ventricular function. The purpose of this review is to examine the currently available antiarrhythmic drugs and assess their role in the treatment of arrhythmias in patients with congenital heart disease. It is important to emphasize that patients with congenital heart disease often have hemodynamic limitations and may be at an increased risk for developing adverse effects with antiarrhythmic agents. An awareness of the arrhythmias associated with congenital heart disease, the natural history of these arrhythmias, and the potential benefit of treatment with antiarrhythmic medications versus other forms of therapy provides a rational basis for therapy in this challenging population of patients.

Antiarrhythmic agents: drug interactions of clinical significance

The management of cardiac arrhythmias has grown more complex in recent years. Despite the recent focus on nonpharmacological therapy, most clinical arrhythmias are treated with existing antiarrhythmics. Because of the narrow therapeutic index of antiarrhythmic agents, potential drug interactions with other medications are of major clinical importance. As most antiarrhythmics are metabolised via the cytochrome P450 enzyme system, pharmacokinetic interactions constitute the majority of clinically significant interactions seen with these agents. Antiarrhythmics may be substrates, inducers or inhibitors of cytochrome P450 enzymes, and many of these metabolic interactions have been characterised. However, many potential interactions have not, and knowledge of how antiarrhythmic agents are metabolised by the cytochrome P450 enzyme system may allow clinicians to predict potential interactions. Drug interactions with Vaughn-Williams Class II (beta-blockers) and Class IV (calcium antagonists) agents have previously been reviewed and are not discussed here. Class I agents, which primarily block fast sodium channels and slow conduction velocity, include quinidine, procainamide, disopyramide, lidocaine (lignocaine), mexiletine, flecainide and propafenone. All of these agents except procainamide are metabolised via the cytochrome P450 system and are involved in a number of drug-drug interactions, including over 20 different interactions with quinidine. Quinidine has been observed to inhibit the metabolism of digoxin, tricyclic antidepressants and codeine. Furthermore, cimetidine, azole antifungals and calcium antagonists can significantly inhibit the metabolism of quinidine. Procainamide is excreted via active tubular secretion, which may be inhibited by cimetidine and trimethoprim. Other Class I agents may affect the disposition of warfarin, theophylline and tricyclic antidepressants. Many of these interactions can significantly affect efficacy and/or toxicity. Of the Class III antiarrhythmics, amiodarone is involved in a significant number of interactions since it is a potent inhibitor of several cytochrome P450 enzymes. It can significantly impair the metabolism of digoxin, theophylline and warfarin. Dosages of digoxin and warfarin should empirically be decreased by one-half when amiodarone therapy is added. In addition to pharmacokinetic interactions, many reports describe the use of antiarrhythmic drug combinations for the treatment of arrhythmias. By combining antiarrhythmic drugs and utilising additive electrophysiological/pharmacodynamic effects, antiarrhythmic efficacy may be improved and toxicity reduced. As medication regimens grow more complex with the aging population, knowledge of existing and potential drug-drug interactions becomes vital for clinicians to optimise drug therapy for every patient.

Supraventricular tachycardia in the neonate and infant

Supraventricular tachycardia (SVT) is the most common sustained arrhythmia to present in the neonatal and infancy age group. Predisposing factors (congenital heart disease, drug administration, illness and fever) occur only in 15% of infants. The presentation of SVT in the neonate is frequently subtle, and may include pallor, cyanosis, restlessness, irritability, feeding difficulty, tachypnea, diaphoresis and grunting. Congestive heart failure is more common in infants under 4 months of age (35% incidence). Age-related differences in the distribution of SVT mechanisms occur in different age groups. In infants under 1 year of age, the mechanisms underlying SVT are atrial tachycardia (15%), AV nodal re-entry tachycardia (5%), and AV reciprocating tachycardia (80%). Options for acute management include: use of the diving reflex, intravenous adenosine, transesophageal pacing, and cardioversion. Intravenous administration of verapamil should be avoided. Data regarding freedom from recurrence of untreated SVT in the first year of life are limited, and may be in the range of 25-60%. Chronic therapy with digoxin, beta-blockers, flecainide, sotalol and amiodarone has proved effective in controlling recurrent episodes of SVT. Radiofrequency ablation can be employed successfully in medically refractory cases, but should be avoided in this age group (increased complication rate).

Successful radiofrequency catheter ablation of congenital junctional ectopic tachycardia with preservation of atrioventricular conduction in a 9-month-old infant

An infant with congenital junctional ectopic tachyardia required frequent hospitalizations due to tachycardia acceleration despite multiple antiarrhythmic medications. At 9 months of age, he underwent successful radiofrequency catheter ablation of the tachycardia with preservation of AV conduction.

Standards of laboratory practice: cardiac drug monitoring

In this Standard of Laboratory Practice we recommend guidelines for therapeutic monitoring of cardiac drugs. Cardiac drugs are primarily used for treatment of angina, arrhythmias, and congestive heart failure. Digoxin, used in congestive heart failure, is widely prescribed and therapeutically monitored. Monitoring and use of antiarrhythmics such as disopyramide and lidocaine have been steadily declining. Immunoassay techniques are currently the most popular methods for measuring cardiac drugs. Several reasons make measurement of cardiac drugs in serum important: their narrow therapeutic index, similarity in clinical complications and presentation of under- and overmedicated patients, need for dosage adjustments, and confirmation of patient compliance. Monitoring may also be necessary in other circumstances, such as assessment of acetylator phenotypes. We present recommendations for measuring digoxin, quinidine, procainamide (and N-acetylprocainamide), lidocaine, and flecainide. We discuss guidelines for measuring unbound digoxin in the presence of an antidote (Fab fragments), for characterizing the impact of digoxin-like immunoreactive factor (DLIF) and other cross-reactants on immunoassays, and for monitoring the unbound (free fraction) of drugs that bind to α1-acid glycoprotein. We also discuss logistic, clinical, hospital, and laboratory practice guidelines needed for implementation of a successful therapeutic drug monitoring service for cardiac drugs.

Pharmacologic management of supraventricular tachycardias in children. Part 2: Atrial flutter, atrial fibrillation, and junctional and atrial ectopic tachycardia

OBJECTIVE

To review the literature regarding the use of antiarrhythmic agents in the management of atrial flutter (AF), atrial fibrillation (Afib), junctional ectopic tachycardia (JET), and atrial ectopic tachycardia (AET) in infants and children. To discuss the advantages and disadvantages of specific agents in each type of arrhythmia in an effort to develop treatment guidelines.

DATA SOURCE

A MEDLINE search encompassing the years 1966-1996 was used to identify pertinent literature for discussion. Additional references were found in the articles, which were retrieved via MEDLINE.

STUDY SELECTION

Clinical trials that address the use of antiarrhythmic agents for the treatment of supraventricular tachycardia, AF, Afib, JET, and AET in children were selected. Literature pertaining to dosage, pharmacokinetics, efficacy, and toxicity of antiarrhythmic agents in children were considered for possible inclusion in the review; information judged to be pertinent by the authors was included in the discussion.

DATA EXTRACTION

Although there are numerous reports of antiarrhythmic use in children, there are very few large studies designed that evaluate the use of specific antiarrhythmic agents in the treatment of AF, Afib, JET, or AET. Ideally, controlled clinical trials are used to develop clinical guidelines; however, in this situation, most data and information must be obtained from case series of children treated. Although the results from these types of studies may be useful in developing guidelines for the optimal use of these agents for the treatment of AF, Afib, JET, and AET, controlled trials are required for establishing standard treatment guidelines for all patients.

DATA SYNTHESIS

Despite limited scientific evaluation of conventional agents in the treatment of AF, Afib, JET, or AET in children, they continue to be the standards of care. Most information regarding the use of conventional agents in children has been extrapolated from the adult literature. Little justification for the use of the agents or dosing in children is available. Controlled trials regarding the use of newer antiarrhythmic agents (propafenone, amiodarone, flecainide) are available; however, the variance in dosing schemes, presence of structural heart disease, and patient age may confound the results.

CONCLUSIONS

Because of greater clinical experience, conventional antiarrhythmic agents generally remain as first-line therapy in the management of most supraventricular tachycardias in children. Atrial pacing or cardioversion to reestablish sinus rhythm is indicated for initial episodes of AF in infants, followed by chronic prophylactic therapy in those with significant structural heart disease or in infants in whom AF recurs. Attempts to eliminate AF in children outside the neonatal or infancy period should begin with trials of traditional agents such as digoxin or procainamide, and if unsuccessful, subsequent trials of amiodarone. Digoxin and beta-blockers remain the mainstay of therapy for children with Afib, followed by procainamide for treatment failures. Intravenous amiodarone, the newest addition to our antiarrhythmic armamentarium, is the most promising agent in the treatment of postoperative JET. This arrhythmia has been traditionally managed with corporal cooling and/or digoxin therapy; however, intravenous amiodarone may now be a valuable option. Although relatively unsuccessful in the management of congenital JET and AET, conventional agents are typically used prior to the initiation of long-term therapy with potentially more toxic agents such as amiodarone or propafenone. Additional well-designed, controlled trials are needed to further evaluate the comparative efficacy of agents such as flecainide, sotalol, moricizine, propafenone, and amiodarone in the management of AF, Afib, JET, and AET in children, as well as to evaluate the dosing and toxicity in various age groups.

Ventricular tachycardia in neonates

Infant VT can be a devastating arrhythmia, with high mortality for those presenting with myocarditis, long QT syndrome, or cardiovascular collapse with rapid VT due to tumors. While management of these patients can be challenging and discouraging, other infants with wide QRS rhythms tend to follow a more benign course. These latter patients have accelerated idiopathic ventricular rhythm or aberrant forms of infant supraventricular tachycardia. Distinguishing these forms of wide QRS tachycardia from the more lethal forms is paramount to institution of appropriate therapies.

Management of infants, children, and adolescents with paroxysmal supraventricular tachycardia

Several acceptable options are available for the successful management of children either with an acute PSVT episode or with ongoing episodes. These options include the "no treatment" management approach. Although an example of an algorithm used in one center is provided for this Medical Progress article, other algorithms also are successfully practiced among pediatric cardiologists together with primary care pediatricians. Current and ongoing updated data related to the important factors of presenting symptoms, natural history, results of the treatment options, and the risk/ benefit ratios of the treatment options are essential when one is choosing the specific management approach.