New developments in catheter ablation for patients with congenital heart disease.

Introduction: There are numerous challenges to catheter ablation in patients with congenital heart disease (CHD), including access to cardiac chambers, distorted anatomies, displaced conduction systems, multiple and/or complex arrhythmia substrates, and excessively thickened walls, or interposed material. Areas covered: Herein, we review recent developments in catheter ablation strategies for patients with CHD that are helpful in addressing these challenges. Expert opinion: Remote magnetic navigation overcomes many challenges associated with vascular obstructions, chamber access, and catheter contact. Patients with CHD may benefit from a range of ablation catheter technologies, including irrigated-tip and contact-force radiofrequency ablation and focal and balloon cryoablation. High-density mapping, along with advances in multipolar catheters and interpolation algorithms, is contributing to new mechanistic insights into complex arrhythmias. Ripple mapping allows the activation wave front to be tracked visually without prior assignment of local activation times or window of interest, and without interpolations of unmapped regions. There is growing interest in measuring conduction velocities to identify arrhythmogenic substrates. Noninvasive mapping with a multielectrode-embedded vest allows prolonged bedside monitoring, which is of particular interest in those with non-sustained or multiple arrhythmias. Further studies are required to assess the role of radiofrequency needle catheters and stereotactic radiotherapy in patients with CHD.

Cryoablation for Perinodal Arrhythmia Substrates in Patients With Congenital Heart Disease and Displaced Atrioventricular Conduction Systems.

OBJECTIVES: The purpose of this study was to assess the safety and efficacy of cryoablation for perinodal substrates in patients with congenital heart disease (CHD) and a displaced atrioventricular (AV) conduction system or an AV conduction system location that was difficult to predict. BACKGROUND: Catheter ablation for perinodal arrhythmias in patients with CHD may incur higher risks due to unconventional or difficult to predict locations of the AV conduction system. Cryoablation carries theoretical advantages for such patients but has not been studied in this setting. METHODS: A total of 35 patients with CHD underwent cryoablation for perinodal substrates at the Montreal Heart Institute between 2006 and 2016. Ten of these patients, age 33 ± 13 years, 60% male, had AV conduction systems that were displaced or of uncertain location and underwent cryoablation (6-mm electrode-tip catheter) for 12 perinodal arrhythmias: AV nodal re-entrant tachycardia (n = 4), non-automatic focal atrial tachycardia (n = 4), septal intra-atrial re-entrant tachycardia (n = 3), and para-Hisian automatic focal atrial tachycardia (n = 1). Four patients had single-ventricle physiology and had undergone Fontan palliation (3 atriopulmonary and 1 intracardiac total cavopulmonary connection), 4 underwent repair of AV septal defects, 1 had congenitally corrected transposition of the great arteries (TGA), and 1 had TGA with a Mustard baffle. RESULTS: Cryoablation was acutely successful in 9 of 12 targeted arrhythmias (75%) with no procedural complication. Crossover to radiofrequency ablation successfully eliminated the remaining 3 arrhythmias at sites deemed safe by cryoablation, with no complication. Over a follow-up period of 26 (interquartile range: 15 to 64) months, 1 of 9 successfully cryoablated arrhythmias recurred. CONCLUSIONS: Cryoablation is feasible, safe, and moderately effective for perinodal arrhythmia substrates in patients with various forms of CHD associated with AV conduction systems that are displaced or in locations that cannot be reliably predicted.

Atrial fibrillation in young patients.

INTRODUCTION: Atrial fibrillation (AF) is the most frequent arrhythmia worldwide. While mostly seen in elderly, it can also affect young adults (≤ 45 years of age), older adolescent, and children. Areas covered: The aim of this review is to provide an overview of the current management of AF in young patients. Specific issues arise over diagnostic workup as well as antiarrhythmic and anticoagulation therapies. The future management and diagnostic strategies are also discussed. Expert commentary: Management of AF in the young adult is largely extrapolated from adult studies and guidelines. In this population, AF could reveal a genetic pathology (e.g. Brugada, Long QT or Short QT syndromes) or be the initial presentation of a cardiomyopathy. Therefore, thorough workup in the young population to eliminate potential malignant pathology.

Risk stratification for sudden death in arrhythmogenic right ventricular cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC) is an uncommon but increasingly recognized inherited cardiomyopathy that is associated with malignant ventricular arrhythmias and sudden cardiac death, particularly in young individuals. The implantable cardioverter-defibrillator (ICD) is widely regarded as the only treatment modality with evidence to support improved survival in patients with ARVC and secondary prevention indications. In contrast, there is no universally accepted risk stratification scheme to guide ICD therapy for primary prevention against sudden cardiac death. Potential benefits must be weighed against the considerable risks of complications and inappropriate shocks in this young patient population. This article tackles the challenges of risk stratification for sudden cardiac death in ARVC and critically appraises available evidence for various proposed risk factors. The authors' over-arching objective is to provide the clinician with evidence-based guidance to inform decisions regarding the selection of appropriate candidates with ARVC for ICD therapy.

Significant persistent ductus arteriosus in infants less or equal to 6 kg: percutaneous closure or surgery?

BACKGROUND: Percutaneous closure of large persistent ductus arteriosus using the Amplatzer duct occluder is an alternative to surgery. However, this device is not recommended in infants weighing less than 6 kg. AIM: To evaluate the safety and effectiveness of this procedure in low-body-weight infants. METHODS: We reviewed retrospectively data for infants weighing less or equal to 6 kg who underwent percutaneous closure of significant persistent ductus arteriosus using the Amplatzer duct occluder in France between 1998 and 2007. RESULTS: Data for 58 patients (mean weight: 5 kg, range: 3.4-6; mean age: 5.5 months, range: 2.1-15.3) were reviewed. Mean angiographic persistent ductus arteriosus minimal diameter was 3.7 mm (range: 1-7.5). Implantation of the Amplatzer duct occluder was successful in 89.7% of cases. In six (10.3%) patients, the device was not implanted because it would have led to significant aortic obstruction. One procedure-related death occurred in a 4 kg infant (1.7%). Major and minor complications occurred in 6.9 and 31.0% of patients, respectively. Persistent ductus arteriosus diameter greater than 3.7 mm, type C (tubular shape) and diameter/patient weight ratio greater than 0.91 were significantly associated with an unsuccessful procedure and/or major complications. During a median 10-month follow-up, no late device embolization occurred. CONCLUSIONS: Although percutaneous closure of significant persistent ductus arteriosus with the Amplatzer duct occluder is effective in low-body-weight infants, the level and severity of complications indicate surgery as first-line treatment, at least until further studies are done to assess the safety and effectiveness of the new Amplatzer duct occluder II in low-body-weight infants.

Advances in paediatric interventional cardiology since 2000.

Interventional paediatric and congenital cardiology is expanding at a rapid pace. Validated techniques (such as aortic or pulmonary valve dilatations and occlusion of persistent ductus arteriosus and atrial septal defects) are improving thanks to the use of smaller introducers and sheaths, low-profile balloons and novel devices. Moreover, catheter-based interventions have emerged as an attractive alternative to surgery in other fields: pulmonary valve replacement, balloon and stent implantation for native and recurrent coarctation, and percutaneous closure of ventricular septal defects. On the other hand, percutaneous interventions in the paediatric population may be limited by patient size or the anatomy of the defect. Hybrid approaches involving both cardiac interventionists and surgeons are being developed to overcome these limitations. Based on a better understanding of cardiac development, fetal cardiac interventions are being attempted in order to alter the history of severe obstructive lesions. Finally, some interventional procedures still carry a low success rate-for example, pulmonary vein stenosis, even with the use of conventional stents. Biodegradable stents and devices are being developed and may find an application in this setting as well as in others. The purpose of this review is to highlight the advances in paediatric interventional cardiology since the beginning of the third millennium.

Isolated cleft of the mitral valve: distinctive features and surgical management.

BACKGROUND: Controversy remains as to whether isolated cleft of the mitral valve and cleft of the atrioventricular septal defect are different entities. Our objectives were to provide a precise description of isolated cleft of the mitral valve and to clarify its surgical management and outcome. METHODS: Patients with surgical repair of isolated cleft of the mitral valve were included. RESULTS: Ten patients (9 female) underwent repair at a mean age of 12.1 +/- 10.5 years and mean weight of 32.1 +/- 17.8 kg. Preoperative echocardiography showed mild or less than mild mitral regurgitation in 6 cases and moderate to severe regurgitation in 4. Intraoperative examination confirmed in all cases a cleft dividing the anterior leaflet of an otherwise normal mitral valve. Attachment of the cleft to the ventricular septum by accessory chordae was found in 3 cases whereas preoperative echocardiography found such attachments in 5. Direct suture of the cleft was performed in 9 cases, associated with repair of tricuspid valve straddling (n = 1), subaortic stenosis (n = 1), and ventricular septal defect (n = 1). One patient with thickened cleft's edges required an Alfieri-type repair. After a mean follow-up of 4.9 years (range, 1.3 to 11.9), all patients are asymptomatic without significant mitral regurgitation. CONCLUSIONS: Echocardiographic description of isolated cleft of the mitral valve is not always as accurate as intraoperative analysis. This is a distinct morphologic entity from the cleft of the left-sided valve of atrioventricular septal defect, and seems associated with a strong female predominance, with various cardiac and extracardiac features. Surgical repair is successful with excellent midterm results.

Asymptomatic congenital atresia of the left inferior pulmonary vein: a case report.

We present an unusual fortuitously discovered case of atresia of the left inferior pulmonary vein with drainage via anastomosis to the left upper pulmonary vein and the left atrium. Atresia of the pulmonary veins is a very rare anomaly that results from defective incorporation of the pulmonary venous system into the left atrium. The initial diagnosis, drawn from plain radiographs, was confirmed by cardiac catheterization and pulmonary angiography. The appearance of clinical signs, prognosis, and the need for treatment depend on how well substitute drainage is performed.

Transcatheter perforation followed by pulmonary valvuloplasty in neonates with pulmonary atresia and ventricular septal defect.

BACKGROUND: The classic management of neonates with pulmonary atresia with ventricular septal defect (PAVSD) and moderately hypoplastic pulmonary arteries is usually a systemic to pulmonary artery shunt or ductus arteriosus stenting. We report our experience of transcatheter treatment of PAVSD by perforation followed by balloon dilation of the valve, as it is performed in pulmonary atresia - intact ventricular septum. PATIENTS AND METHOD: Three patients were treated at a mean age and weight of 7.5 days (range 7-8) and 2.9kg (range 2.5-3.3), respectively. Two newborns were prenatally diagnosed, with micro deletion 22q11 in one case. The three patients had no other pulmonary blood flow support than the ductus arteriosus and were on prostaglandin E1 infusion. The pulmonary atresia was predominantly valvular without significant muscular obstruction. By echocardiography, the mean size of the pulmonary annulus was 6.5mm (range 6-7). In all cases, the valvular perforation was performed with a 0.014 coronary guidewire, followed by balloon dilation when successfully. RESULTS: The procedure succeeded in two cases but failed in the third newborn in whom a long subvalvar muscular stenosis was found at surgery. In the two successful cases, the mean postprocedural transpulmonary doppler gradient was 33.5mmHg (range 17-50). One patient experienced a femoral venous thrombosis that was successfully treated by heparin and a transient right bundle branch block occurred in another one. In the two successful cases, the prostaglandin E1 infusion was weaned and the surgical repair was performed at 4 and 12 months, respectively. CONCLUSION: In selected cases with PAVSD, perforation followed by balloon dilation of the pulmonary valve offers an interesting alternative to other surgical or transcatheter palliative therapies.

Ebstein's anomaly assessed by real-time 3-D echocardiography.

The outcome of patients with Ebstein's malformation depends mainly on the severity of the tricuspid valve malformation. Accurate description of the tricuspid anatomy by two-dimensional echocardiography remains difficult. We applied real-time three-dimensional echocardiography to 3 patients with Ebstein's anomaly. Preoperative and postoperative descriptions of the tricuspid valve were obtained from views taken inside the right ventricle. Surface of the leaflets as well as the commissures were obtained by three-dimensional echocardiography. Real time three-dimensional echocardiography is a promising tool, providing new views that will help to evaluate the ability and efficiency of surgical valve repair in patient with Ebstein's malformation.

Off-label use of an adjustable gastric banding system for pulmonary artery banding.

BACKGROUND: Pulmonary artery banding is proposed as a first palliation in infants with complex congenital heart disease and high pulmonary blood flow. In addition, it may be used to retrain the left ventricle. Optimal tightening may be difficult to obtain, leading to reoperation. An implantable device for pulmonary artery banding with telemetric control was recently developed allowing for repeated adjustments, but it is presently limited to patients weighing less than 20 kg. In large animals, we tested an off-label adjustable gastric banding system for pulmonary artery banding. METHODS AND RESULTS: Fourteen ewes weighing 50 to 75 kg underwent implantation of the Lap-Band device (BioEnterics Corp, Santa Barbara, Calif) around the main pulmonary artery through a left thoracotomy. All had functional evaluation with progressive occlusion and opening of the device at implantation and every 2 weeks until sacrifice immediately after implantation (group 1, n = 8), at 1 month (group 2, n = 3), at 3 months (group 3, n = 3), or death. Invasive pressure measurements in the right ventricle and aorta were carried out each time. Devices were easily implanted in all animals. Progressive occlusion and reopening were possible in all animals during each time point. Two animals died of right heart failure related to excessive tightening of the band. Retrieval of the device without any major damage was possible in 12 of 14 animals. CONCLUSION: With this implantable device, we were able to adjust the pulmonary artery diameter in animals. Patients requiring left ventricle retraining and weighing more than 30 kg would benefit from the device's use in humans.

Real-time three-dimensional fetal echocardiography using matrix probe.

OBJECTIVE: To investigate the feasibility of using real-time three-dimensional echocardiography (3DE) to evaluate the fetal heart. METHODS: Sixty fetuses were studied with gestational age between 22 and 34 weeks. The fetal heart was normal in 44 fetuses. In 16 fetuses, the fetal heart had morphologic abnormalities (hypoplastic left ventricle in 4, tetralogy of Fallot in 2, Ebstein anomaly in 2, rhabdomyomes in 2, hypoplastic right ventricle in 1) or myocardial dysfunction (in 5 fetuses). Real-time 3DE was performed with a cardiac matrix probe (2-4 MHz). Two modalities of 3D imaging were performed: Biplane and Live 3D imaging. RESULTS: Real-time 3DE was performed successfully in 93%. Biplane imaging allowed a multiplanar scanning of the fetal heart. Using rotation, lateral and vertical tilts, the normal cardiac structures were identified from a unique reference image plane: atria and ventricles, atrioventricular valves, aorta and pulmonary artery. Live 3D imaging allowed surface imaging of the fetal heart. 'En face' view of the foramen ovale from the right atrium was obtained, showing the shape of the orifice. By cropping the pyramidal imaging volume, ascending aorta, aortic arch and ductus arteriosus were depicted from a single dataset. In pathologic fetal hearts, 3DE was helpful for (1) localizing multiple cardiac tumors; (2) estimating size and function of the right and left ventricles; (3) evaluating mechanism of valvular regurgitation and pulmonary obstruction. CONCLUSION: Real-time 3DE is a feasible and non-time-consuming method, allowing a multiplanar scanning and new inside 3D views of the fetal heart.