Radiofrequency catheter ablation of ventricular tachycardia in children and young adults with congenital heart disease

[Interventional treatment of tachyarrhythmia in children with congenital heart disease]

In children and adolescents with congenital heart disease (CHD) tachyarrhythmia occurs more frequently compared to patients with otherwise normal hearts. Arrhythmia substrates may be a natural part of certain congenital cardiac malformations or may result from long lasting myocardial deterioration as a result of CHD and/or cardiac surgery. Treatment of tachycardia is more frequently required even in early childhood, as the impact on quality of life, morbidity and mortality is higher due to an often reduced hemodynamic tolerance. Over the past 20 years interventional electrophysiology has been established as the therapy of choice for the majority of chronic or chronically recurrent tachycardia even in children with CHD. The success and risks of treatment are predominantly influenced by the individual expression of the cardiac anomaly and, if surgery has been performed, the highly variant postoperative anatomy. Introduction of 3D electroanatomical mapping systems together with modern cardiac imaging tools have significantly contributed to an improved understanding, particularly in postoperative tachycardia. Despite such progress, success rates are lower and recurrences are more frequent compared to patients without CHD. Complex and often multiple tachycardia courses account for the still limited performance as well as a frequently insufficient lesion formation with the use of radiofrequency current in the hypertrophic and fibrotic myocardium. Electrophysiology in children and adolescents, particularly if CHD is present, represents a highly specialized discipline requiring a high expertise in CHD, CHD surgery and cardiac electrophysiology and is ideally imbedded within an interdisciplinary cardiological and cardiosurgical setting.

Tachyarrhythmias and catheter ablation in adult congenital heart disease

Advances in surgical technique have had an immense impact on longevity and quality of life in patients with congenital heart disease. However, an inevitable consequence of these surgical successes is the creation of a unique patient population whose anatomy, surgical history and haemodynamics result in the development of a challenging and complex arrhythmia substrate. Furthermore, this patient group remains susceptible to the arrhythmias seen in the general adult population. It is through a thorough appreciation of the cardiac structural defect, the surgical corrective approach, and haemodynamic impact that the most effective arrhythmia care can be delivered. Catheter ablation techniques offer a highly effective management option but require a meticulous attention to the real-time integration of anatomical and electrophysiological information to identify and eliminate the culprit arrhythmia substrate. This review describes the current approach to the interventional management of patients with tachyarrhythmias in the context of congenital heart disease.

Electrophysiological interventions for treatment of congestive heart failure in pediatrics and congenital heart disease

Heart failure therapy, while well tested in the adult population, therapeutic interventions are less well defined in the pediatric population. Several treatment strategies are available for the adult patient with heart failure, thought few of these therapies have been proven in children. Morbidity and mortality in the pediatric population with a failing heart is significant, and rhythm management as well as strategies to improve hemodynamics are important in the care of these children. This review will address issues of rhythm management and resynchronization therapy in pediatric and congenital heart disease patients with heart failure.

Characterization of Anatomic Ventricular Tachycardia Isthmus Pathology After Surgical Repair of Tetralogy of Fallot

Background—

Although catheter ablation has been used to target the critical isthmuses for re-entrant monomorphic ventricular tachycardia in tetralogy of Fallot, the anatomy and histology of these regions have not been fully characterized. Autopsy hearts with tetralogy of Fallot were evaluated to clarify the pathological substrate.

Methods and Results—

Twenty-seven hearts with the diagnosis of tetralogy of Fallot were examined. Anatomically defined isthmuses included (1A) ventriculotomy-to-tricuspid annulus, (1B) ventriculotomy-to-ventricular septal defect patch, (2) ventriculotomy-to-pulmonary annulus, (3) pulmonary annulus-to-ventricular septal defect patch, and (4) ventricular septal defect patch-to-tricuspid annulus. Length and wall thickness were measured for all specimens, and light microscopy was performed for those surviving surgery. For subjects ≥5 years at death, isthmuses 1A and 1B were present in 88%, isthmus 2 in 25%, isthmus 3 in 94%, and isthmus 4 in 13%. Isthmus 1A had the greatest dimensions (mean length, 3.9±1.08; thickness, 1.5±0.3 cm), isthmus 1B intermediate dimensions (mean length, 2.4±0.8; thickness, 1.1±0.4 cm), and isthmuses 2, 3, and 4 the smallest dimensions (mean length, 1.5±0.5, 1.4±0.8, and 0.6±0.4 cm; thickness, 0.5±0.2, 0.6±0.2, and 0.3±0.04 cm, respectively). Histological examination (n=7) revealed increased fibrosis in anatomic isthmuses relative to nonisthmus controls.

Conclusions—

Consistencies in isthmus dimensions and histology are found among patients with repaired tetralogy of Fallot. Isthmus 1A is associated with the largest morphological dimensions, whereas the nearby newly described isthmus 1B is significantly smaller. Of isthmuses with the smallest dimensions, isthmus 3 is the most common.

Radiofrequency catheter ablation of intractable ventricular tachycardia in an infant following arterial switch operation

A full-term male neonate presented with cyanosis upon delivery and was subsequently diagnosed with d-transposition of the great arteries, ventricular septal defect, and restrictive atrial septal defect. Following initiation of intravenous prostaglandins and balloon atrial septostomy, an arterial switch operation was performed on day 3 of life. The postoperative course was complicated by intractable ventricular tachycardia that was refractory to lidocaine, amiodarone, esmolol, fosphenytoin, and mexiletine drug therapy. Ventricular tachycardia was suppressed with overdrive atrial pacing but recurred upon discontinuation. Seven weeks postoperatively, radiofrequency catheter ablation was performed due to hemodynamically compromising persistent ventricular tachycardia refractory to medical therapy. The ventricular tachycardia was localized to the inferior-lateral right ventricular outlet septum. The procedure was successful without complications or recurrence. Antiarrhythmics were discontinued after the ablation procedure. Seven days after the ablation, a different, slower fascicular rhythm was noted to compete with the infant's sinus rhythm. This was consistent with the preablation amiodarone having reached subtherapeutic levels given its very long half-life. The patient was restarted on oral beta blockers and amiodarone. The patient was subsequently discharged home in predominantly sinus rhythm with intermittent fascicular rhythm.

Rising charges and costs for pediatric catheter ablation

INTRODUCTION

Catheter ablation has been shown to be effective for pediatric tachyarrhythmias, but the associated charges and costs have not been described in the recent era. Understanding such contemporary trends may identify ways to keep an effective therapy affordable while optimizing clinical outcomes.

METHODS

We used the 1997-2009 Kids' Inpatient Databases to examine trends in charges and costs for pediatric catheter ablation and identify determinants of temporal changes.

RESULTS

There were 7,130 discharges for catheter ablation in the sample. Mean age at ablation was 12.1 ± 0.2 years. Patients with congenital heart disease (CHD) made up 10% of the sample. Complications occurred in 8% of discharges. Mean total charges rose 219% above inflation (from $23,798 ± 1,072 in 1997 to $75,831 ± 2,065 in 2009). From 2003 to 2009, costs rose 25% (from $20,459 ± 780 in 2003 to $25,628 ± 992 in 2009). Charges for ablation increased markedly relative to surgical procedures, but with a similar slope to other catheter-based interventions. Multivariable analysis revealed that year (P < 0.0001), payer (P = 0.0002), CHD (P < 0.0001), valvular heart disease (P = 0.0004), cardiomyopathy (P = 0.0009), hospital region (P < 0.0001), length of stay (P < 0.0001), and complications (P < 0.0001) predicted increased charges. The same factors also predicted increased costs. Charges and costs varied considerably by region, particularly for high-volume centers (P < 0.0001).

CONCLUSIONS

Charges and costs for pediatric catheter ablation increased relative to other procedures and significantly outstripped inflation. Further study of complications, length of stay, and regional differences may help control rising costs while maintaining quality of care.

[Arrhythmias in patients with surgically corrected tetralogy of Fallot]

The population of adults with surgically corrected tetralogy of Fallot (TOF) is increasing. Atrial and ventricular arrhythmias are prevalent, and therapeutical approaches including implantable cardioverter-defibrillators and radiofrequency catheter ablation need to be considered carefully for the prevention of hemodynamic deterioration and sudden cardiac death. Complex anatomy, myocardial hypertrophy, and broad channels of slow conduction may in part explain some challenges regarding risk stratification, and identification/modification of the arrhythmogenic substrate in these patients. The aim of this brief review is 2-fold: (1.) To present insights into characteristics of typical TOF related arrhythmias and (2.) to reflect therapeutical concepts targeting tachyarrhythmias in these patients by focusing on catheter ablation.

Reversed polarity of bipolar electrograms for predicting a successful ablation site in focal idiopathic right ventricular outflow tract arrhythmias

BACKGROUND

Radiofrequency catheter ablation (RFCA) for idiopathic right ventricular outflow tract (RVOT) arrhythmias is typically guided by local activation time (LAT) mapping and unipolar electrogram morphology (QS configuration). However, LAT mapping is limited by the large variation among patients, and the area demonstrating a QS configuration of the unipolar electrogram may be larger than the focal source. Reversed polarity has been proposed as a criterion for guiding RFCA.

OBJECTIVE

The purpose of this study was to investigate the value of reversed polarity of adjacent bipolar electrograms for predicting a successful ablation site in idiopathic RVOT arrhythmias.

METHODS

Twenty-five consecutive patients (12 men [48%], age 43 ± 15 years) undergoing RFCA for RVOT arrhythmia were studied. Electrograms of ablation sites and of points within a 15-mm radius to the successful site were evaluated for LAT, unipolar electrogram morphology, and the presence of reversed polarity of adjacent bipolar electrograms. Electrogram characteristics of successful ablation sites were compared to those of nonsuccessful ablation sites. The spatial distribution of each electrogram characteristic was studied.

RESULTS

Successful ablation sites more often demonstrated reversed polarity and had an earlier LAT than nonsuccessful sites. A wide spatial distribution was observed for unipolar electrograms with a QS configuration around the successful ablation site. Mapping based on LAT and reversed polarity had a higher predictive value for a successful ablation site than mapping based on LAT and QS configuration.

CONCLUSION

The presence of reversed polarity has a high predictive value for successful ablation sites in focal idiopathic RVOT arrhythmias and is likely to reduce the number of RFCA applications.

Arrhythmogenic causes of chest pain in children

Although cardiac causes of chest pain in children are infrequent, arrhythmias are implicated in most cardiac related cases. The most common arrhythmias associated with chest pain are supraventricular tachycardias, but more ominous rhythms, such as ventricular tachycardia or bradycardias, can manifest as chest pain. Investigation of all children with chest pain suspected of arrhythmia should include detailed history and physical examination and a 12- or 15-lead electrocardiogram. In some cases echocardiogram, 24-hour Holter monitoring, exercise stress testing, or other cardiac evaluations may be indicated. Children with a history of cardiac disease or cardiac surgery are particularly at risk for arrhythmias and may experience chest pain in association with their arrhythmias.

[Catheter ablation of tachyarrhythmias in children and adolescents]

BACKGROUND

Catheter ablation has been increasingly applied in children and adolescents with tachyarrhythmias. The aim of this article is to assess the results of ablation therapy of tachycardias in patients below 18 years of age at Haukeland University Hospital.

MATERIAL AND METHODS

141 patients (70 boys and 71 girls, aged 5-17 (13.5 +/- 3.5 ) years with tachyarrhythmias underwent an electrophysiologic study and catheter ablation in the period 1992-2007.

RESULTS

Ablation was successfully performed in 138/141 (98%) patients., The procedure was repeated (3 patients twice) until the arrhythmia substrate disappeared in 16 of 138 patients. 81/141 (57%) patients had accessory pathways; 52 (37%) had double atrioventricular nodal pathways, 48 had concealed and 33 patients had overt (classical Wolff-Parkinson-White-syndrome) atrioventricular pathways. 8 (6%) patients had other atrial or ventricular tachyarrhythmias and 4 (3%) had organic heart disease. Use of a 3D mapping system was decisive for success for ablation in patients with complex cardiac diseases. Procedure-related complications were observed in 2/141 (1.4%) patients of whom one had a temporary third degree and one had a permanent first-degree atrioventricular block which did not entail further treatment.

CONCLUSION

Catheter ablation of tachycardia in children and adolescents is a safe treatment method with a high success rate and few complications and should be preferred before drug therapy.

Postoperative ventricular tachycardia in patients with congenital heart disease: diagnosis and management

Ventricular tachycardia (VT) after palliative repair of congenital heart disease is relatively rare. Despite this rarity, VT is a known cause of early, intermediate and late morbidity and mortality in these patients. A number of factors have been linked to the development of VT in this unique patient population. The purpose of this article is to provide a concise overview regarding the etiology, diagnosis and treatment of VT in patients with congenital heart disease. In-depth information will be provided to aid diagnosis and the treatment of early postoperative VT. The use of additional diagnostic methods such as echocardiography, cardiac catheterization and electrophysiology studies to risk assess patients with postoperative VT will also be discussed. In addition, I examine the long-term management strategies for VT in these patients, from medical management and cardiovascular surgery to implantation of cardioverter-defibrillators.

Practical aspects of implantable defibrillator therapy in patients with congenital heart disease

Improved awareness of the risk for malignant ventricular arrhythmias in patients with congenital heart disease (CHD), together with dramatic advances in implantable cardioverter-defibrillator (ICD) technology, have led to a rapid increase in device therapy for this population. Clinical challenges remain surrounding patient selection and difficulties with lead positioning that arise in response to the anatomic and physiologic complexities of CHD. This article will attempt to review contemporary data on ICD use in the CHD population with particular attention to the novel implant methodology required for many of these patients.

Frequency of spontaneous ventricular tachycardia in a pediatric population

Few data exist on the incidence of spontaneously occurring ventricular tachycardia (VT) in an unselected pediatric population. The aim of this study was to define the incidence and outcomes of VT in a general pediatric population. A retrospective analysis was performed of all documented episodes of VT in children referred to a single center during a 10-year study period ending in December 2005. The study center drains a stable referral area with 252,000 children aged <16 years, with no other pediatric cardiologic or pediatric intensive care services available. Twenty-seven patients with spontaneously occurring episodes of VT were observed, accounting for a VT incidence of 1.1 episodes/100,000 childhood years. Thirteen patients had VT in the absence of structural heart disease, and 14 had VT in the presence of a wide range of underlying cardiac disease. Overall mortality was 5 of 27 patients (19%), but mortality was seen exclusively in patients with underlying heart disease; for this subgroup of patients, mortality was 36%. Idiopathic VT in children with structurally normal hearts carried a good prognosis, and treatment was required in a minority (20%) of these patients. In conclusion, this study highlights that VT in childhood is rare, and outcomes are highly dependent on the underlying pathologic substrate.

Noncontact mapping and radiofrequency catheter ablation of fast and hemodynamically unstable ventricular tachycardia after surgical repair of tetralogy of Fallot

OBJECTIVES

The goal of this work was to assess efficacy of radiofrequency (RF) ablation of fast ventricular tachycardia (VT) in patients after surgical repair of tetralogy of Fallot (TOF) guided by noncontact mapping.

BACKGROUND

Ventricular tachycardias after repair of TOF are associated with significant morbidity and mortality.

METHODS

Ten patients after surgical repair of TOF underwent electrophysiological study for hemodynamically unstable VT using the noncontact mapping system. Dynamic substrate mapping was performed and activation was recorded during basic rhythm and induced VT (mean cycle length 269 ms) using color-coded isopotential maps and reconstructed unipolar electrograms.

RESULTS

A total of 13 VTs were induced in the 10 patients. In 11 of 13 VTs, a macro-re-entrant mechanism was identified; 2 had a focal origin. For macro-re-entrant VT, RF current lesion lines were created between areas of residual conduction; in 2 patients, no RF current was delivered due to high risk of atrioventricular block. Focal applications were performed for the focal VTs. Ventricular tachycardia was not inducible after RF application in the 8 patients in whom ablation was attempted (100%, 80% of all patients). An internal cardioverter-defibrillator had already been implanted in 2 patients and was recommended to the rest of the group. During follow-up (mean 35.4 months), 6 of 8 patients with a successful procedure were still free of VT, and 2 patients had recurrence of VT with a different cycle length.

CONCLUSIONS

In patients with fast and unstable VT after surgical repair of TOF, noncontact mapping helped to identify the tachycardia substrate and allowed for effective and safe treatment by RF ablation.

Catheter Ablation of Ventricular Tachycardia After Repair of Congenital Heart Disease

Background— Catheter ablation of ventricular tachycardia (VT) after repair of congenital heart disease can be difficult because of nonmappable VTs and complex anatomy. Insights into the relation between anatomic isthmuses identified by delineating unexcitable tissue using substrate mapping techniques and critical reentry circuit isthmuses might facilitate ablation.

Methods and Results— Sinus rhythm voltage mapping of the right ventricle was performed in 11 patients with sustained VT after repair of congenital heart disease. Unexcitable tissue from patch material, valve annulus, or dense fibrosis, identified from bipolar voltage (<0.5 mV) and pacing threshold (>10 mA), was defined as an anatomic isthmus boundary bordering 4 isthmuses between (1) the tricuspid annulus and scar/patch in the anterior right ventricular outflow, (2) the pulmonary annulus and right ventricular free wall scar/patch, (3) the pulmonary annulus and septal scar/patch, and (4) the septal scar/patch and tricuspid annulus. The reentry circuit isthmuses of all induced 15 VTs (mean cycle length, 276±78 ms; 73% poorly tolerated), identified by activation, entrainment, and/or pace mapping, were located in an anatomic isthmus (11 of 15 VTs in anatomic isthmus 1). Transecting the anatomic isthmuses by ablation lesions abolished all VTs. During 30.4±29.3 months of follow-up, 91% of patients remained free of VT.

Conclusions— Reentry circuit isthmuses in VT late after repair of congenital heart disease are located within anatomically defined isthmuses bordered by unexcitable tissue. The boundaries can be identified with 3-dimensional substrate mapping and connected by ablation lines during sinus rhythm. These findings should facilitate catheter and surgical ablation of stable and unstable VTs.

Outcomes After Late Reoperation in Patients With Repaired Tetralogy of Fallot: The Impact of Arrhythmia and Arrhythmia Surgery

BACKGROUND

We evaluated outcomes in patients requiring late reoperation after tetralogy of Fallot (ToF) repair to identify risk factors for arrhythmia and determine whether arrhythmia surgery decreased the risk of subsequent death or recurrent arrhythmia.

METHODS

Review was performed of all ToF patients from 1969 to 2005 undergoing reoperation late (> 1 year) after repair. Patients with associated lesions, except pulmonary atresia, were included. A total of 249 patients had 278 reoperations. Procedures at initial reoperation included pulmonary valve replacement (PVR) in 217, ablation in 63, and tricuspid valve repair/replacement in 46. Pre-reoperative arrhythmias were present in 75, including supraventricular tachycardia (SVT) in 31, ventricular tachycardia (VT) in 34, and SVT+VT in 10 patients.

RESULTS

Median age at reoperation was 23 years (range, 1 to 63). Ten-year survival after reoperation was 93%, and was independent of arrhythmia status (p = 0.86). Arrhythmia patients were characterized by older age at initial repair and at late reoperation, tricuspid and pulmonary regurgitation, and longer QRS duration (p < 0.001 for all). Risk factors for post-reoperative recurrent arrhythmia were longer QRS duration and not having PVR. Longer QRS duration, with a cut-point of more than 160 msec, was associated with recurrent SVT (p = 0.004). Supraventricular tachycardia ablation improved arrhythmia-free survival (75% versus 33%, p < 0.001) but VT ablation did not (96% versus 95%, p = 0.50). However, recurrent VT occurred in only 3 patients (10%).

CONCLUSIONS

Late mortality in patients undergoing reoperation after ToF repair is not impacted by pre-reoperative arrhythmia. Prolongation of QRS identifies patients at risk for recurrent VT and SVT, but recurrent VT is uncommon. Early PVR, and surgical ablation in patients with SVT, decreases arrhythmic risk.

[Electrical heart diseases--therapy during childhood and adolescence]

With increasing experience, radiofrequency catheter ablation of tachyarrhythmia substrates has become first choice therapy for children >4 years of age with recurrent tachyarrhythmia. In younger patients, the risks associated with the procedure (typically procedure-related AV block or possible coronary artery damage) have to be weighed against the natural history of the tachyarrhythmia substrate, and the degree of control achieved with pharmacologic agents. Ablation for postoperative arrhythmias is more complicated, and associated with lower success rates and a higher rate of recurrence (of the same or a new tachyarrhythmia) despite acute procedural success. In this setting, catheter ablation has to be considered in conjunction with further surgery or the use of a defibrillator as a backup device to prevent arrhythmia-related sudden death. Also in inherited arrhythmias as in long QT syndrome and Brugada syndrome, implantable defibrillators have to be considered as a possible therapeutic option for patients with a higher risk for sudden cardiac death, irrespective of age.