Subcutaneous implantable cardioverter-defibrillator: is it ready for use in children and young adults? A single-centre study.

Aims: Use of the subcutaneous implantable cardioverter-defibrillator (S-ICD) to prevent sudden cardiac death is increasing. Few data exist on S-ICD in young patients. We reviewed our single-centre experience in order to assess the effectiveness and safety of S-ICD implantation, and to identify potential factors associated with complications. Methods and results: Observational, non-randomized, standard-of-care study on S-ICD implantation/follow-up in young patients with inherited arrhythmias (IA), cardiomyopathies, and congenital heart defects (CHD). Fifteen patients (6 CHD, 8 cardiomyopathies, and 1 IA), median age 15 years (25th-75th centiles, 14-28), 10 of them <18 years, with body mass index (BMI) 22.6 ± 3.4, underwent S-ICD implantation (primary prevention 93%). The first six patients underwent a standard implantation procedure (three surgical incisions), the following nine a two-incision procedure. No intraoperative complications occurred. Over 12 (7-24) months follow-up, two patients received appropriate shocks and one (7%) inappropriate shock. Four patients had device-related complications requiring surgical intervention: three skin erosions at the superior parasternal incision, one pocket infection. A higher risk of complications was seen in patients who underwent standard procedures [hazard ratio (HR) 4.98, 95% confidence interval (CI) 1.53-47.36; P = 0.0482] and those with BMI <20 (HR 9.44, 95% CI 0.95-93.23; P = 0.0169). Conclusion: S-ICD implantation was safe and effective in young patients with low rates of inappropriate shock. However, the risk of device-related complications during follow-up remains substantial in patients with low BMI. To prevent possible complications, a two-incision technique should be preferred.

Physiological pacing in young patients with complex congenital heart defects.

AIM: Young patients with operated complex congenital heart defects (CHD) often develop sinus node dysfunction (SND) requiring permanent pacing with rate-responsive function. Activity-driven sensors cannot account for nonmovement stress and cannot modulate heart rate physiologically. Closed Loop Stimulation (CLS, Biotronik, Berlin, Germany) is a physiological rate-responsive pacemaker based on the indirect measure of ventricular contractility. No data are available on the effects of such pacing strategy in young patients. METHODS: We report a series of nine patients with CHD and SND who underwent single-chamber CLS-atrial pacing with endocardial or epicardial lead. During the first 30 days, the pacemaker was programmed in AAI pacing mode and then was switched to CLS-atrial pacing mode. An in-hospital control was scheduled 1-2 months later to evaluate the CLS response to neurovegetative stresses (i.e., nonmovement stress [Stroop color test, handgrip] and exercise stress test) and Holter monitor. CLS pacing was compared with rate-responsive accelerometer-driven pacing (AAIR). RESULTS: At telemetric interrogation, CLS pacing showed a more physiological pattern of 24-h heart rate trends than accelerometer sensors. The data obtained during nonmovement/exercise stress demonstrated a physiological increase in the pacing rate with CLS, in synergy with spontaneous events. The accelerometer sensor histogram, during nonmovement stress, showed a "nonresponse" behavior (only lower rate events), and during exercise test showed most events in lower rate range. Holter monitoring showed increase of average and maximum heart rate compared with AAIR. CONCLUSION: In young CHD patients, endocardial/epicardial CLS-atrial pacing demonstrated a physiological response of heart rate to neurovegetative and physical stresses.

What endocardial right ventricular pacing site shows better contractility and synchrony in children and adolescents?

AIMS: Right ventricular (RV) apical (RVA) pacing can induce left ventricular (LV) dyssynchrony, remodeling, and dysfunction in children with complete atrioventricular block (CAVB). We compared the functional outcome of RVA with RV alternative pacing sites (RVAPS), including para-Hisian, septal, and outflow tract sites. METHODS: This is a single-center, retrospective study. Data were collected before pacemaker implantation (transvenous leads), postoperatively, at 6 months, and at 1-2-3-4 years. Electrocardiogram evaluation included QRS duration, axis, QTc/JTc, and QTc dispersion. Echocardiographic evaluation included 2-D/3-D assessment of ventricular dimensions (Z-score of LV end-diastolic dimension), function (ejection fraction), and synchrony. RESULTS: From 2009 to 2015, 55 patients with CAVB, aged 3-17 years, with or without other congenital heart defects, underwent RVAPS (30 patients, median age 11 years) or RVA (25 patients, median 12 years). All leads were positioned into the septum. Before implantation, no significant differences in parameters were observed, except for higher Z-score in RVAPS than in RVA. After implantation, at a median follow-up of 2.5 (range 1-6) years, the two groups showed no significant differences in LV dimensions, contractility, and synchrony. QRS intervals of RVAPS were significantly shorter than RVA. Clinical status was good and contractility/synchrony indexes were normal or adequate in all patients. CONCLUSIONS: In pediatric patients, RVAPS and RVA showed no significant differences in LV dimensions, contractility, and synchrony. Preimplantation dilated patients showed LV reverse remodeling. RVAPS demonstrated shorter QRS intervals. Therefore, septal pacing sites, either RVA or RVAPS, seem to determine good contractility and synchrony at a mid-term follow-up.

Miniaturized Implantable Loop Recorder in Small Patients: An Effective Approach to the Evaluation of Subjects at Risk of Sudden Death.

BACKGROUND: The etiological diagnosis of syncope and/or palpitations in children is often challenging. However, when noninvasive conventional examinations are inconclusive, the subcutaneous miniaturized implantable loop recorder (ILR) is recommended. The aim of our study was to evaluate the efficacy of miniaturized cardiac implantable devices in the early diagnosis of arrhythmias in children ≤6 years. METHODS: From March 2014 to May 2015, 21 patients (median age 5 years) underwent implantation of miniaturized ILR at our Institution after a complete cardiac work up. Median follow-up was 10 months. RESULTS: One patient underwent device removal for pocket infection and one needed a pocket revision. Eleven (52%) patients did not show any symptom and/or arrhythmia. Eight patients experienced symptoms during ILR monitoring: six had no electrocardiographic abnormalities, two had significant sinus pauses. Two patients had significant arrhythmias without symptoms and in one of these a pacemaker was implanted. The overall diagnostic yield was 47%. CONCLUSIONS: Miniaturized ILR could be very useful to make a diagnosis and to decide future management strategies in small patients with undefined symptoms or severe cardiac diseases. Considering its characteristics, miniaturized ILR could start a new era in the diagnosis and follow-up of young patients with symptomatic and/or malignant arrhythmias.

Recent advances in three-dimensional electroanatomical mapping guidance for the ablation of complex atrial and ventricular arrhythmias.

PURPOSE: To provide a brief overview of some relevant technological advances in the field of three-dimensional electroanatomical mapping (3D-EAM) that have recently entered the clinical arena and their role in guiding catheter ablation (CA) of complex atrial and ventricular arrhythmias. METHODS: In this technical report, we describe the general features of three novel algorithms featured in the updated CARTO PRIME™ mapping module for CARTO®3 version 7 3D-EAM system (Biosense Webster Inc., Diamond Bar, CA, USA): local activation time (LAT) hybrid, coherent mapping and map replay modules. We also report three challenging arrhythmia cases in which CA was successfully guided by these softwares. RESULTS: The LAT hybrid module was used in a case of premature ventricular complex originating from the right coronary cusp. This algorithm facilitated safe positioning of the ablation catheter away from the right coronary ostium, avoiding potential harm to this vital structure. The coherent mapping module helped to identify the critical as well as a bystander isthmus of an atrial macro-re-entrant tachycardia in a grown-up patient with congenital heart disease. The map replay module allowed rapid retrospective activation mapping of two unstable ventricular tachycardias in a case of nonischemic cocaine-associated cardiomyopathy. CONCLUSION: 3D-EAM systems offer significant advantages in the management of challenging arrhythmias, and the introduction of novel algorithms underpins improvements in patients' outcomes. Given the increasing sophistication of these systems, however, a close collaboration among cardiac electrophysiologists, engineers and technicians is highly needed in order to get the best from the available technology.