Since the spread of COVID-19, pediatric patients were initially considered less affected by SARS-COV-2, but current literature reported subsets of children with multisystem inflammatory syndrome (MIS-C). This study aims to describe the cardiac manifestation of SARS-COV-2 infection in a large cohort of children admitted to two Italian pediatric referral centers. Between March 2020 and March 2021, we performed a cardiac evaluation in 294 children (mean age 9 ± 5.9 years, male 60%) with active or previous SARS-COV-2 infection. Twenty-six showed ECG abnormalities: 63 repolarization anomalies, 13 Long QTc, five premature ventricular beats, two non-sustained ventricular tachycardia, and one atrial fibrillation. In total, 146 patients underwent cardiac biomarkers: NT-proBNP was elevated in 57, troponin in 34. An echocardiogram was performed in 98, showing 54 cardiac anomalies: 27 left-ventricular dysfunction, 42 pericarditis, 16 coronaritis. MIS-C was documented in 46 patients (mean age 9 ± 4.8 years, male 61%) with cardiac manifestations in 97.8%: 27 ventricular dysfunctions, 32 pericarditis, 15 coronaritis, 3 arrhythmias. All patients recovered, and during follow-up, no cardiac anomalies were recorded. Our experience showed that cardiac involvement is not rare in children with SARS-COV-2, and occurred in almost all patients with MIS-C. However, patients’ recovery is satisfactory and no additional events were reported during FU.

MIS-C is a multisystem inflammatory syndrome that is characterized by multi-organ failure and cardiac involvement. The aim of this study was to describe the long-term cardiovascular outcome in a cohort of MIS-C pediatric patients, who were admitted to two Italian Pediatric Referral Centers. Sixty-seven patients (mean age 8.7 ± 4.7 years, male 60%) were included; 65 (97%) of them showed cardiac involvement. All of the patients completed one month of the follow-up, and 47% completed 1 year of it. ECG abnormalities were present in 65% of them, arrhythmias were present in 9% of them during an acute phase and it disappeared at the point of discharge or later. Pericarditis were detected in 66% of them and disappeared after 6 months. Coronaritis was observed in 35% of the children during an acute phase, and there were no more instances at the 1-year point. An LV dysfunction was present in 65% of the patients at the beginning of the study, with them having a full recovery at the point of discharge and thereafter. Elevated values of the NTproBNP and hsTp were initially detected, which progressively decreased and normalized at the points of discharge and FU. The CMR at the point of FU, there was a presence of long-term myocardial scars in 50% of the patients that were tested. No deaths that were caused by MIS-C during the FU were recorded. Cardiac involvement in MIS-C patients is almost the rule, but the patients’ clinical course was satisfactory, and no additional events or sequelae were observed apart from there being long-term myocardial scars in 50% of the patients that underwent CMR.

Funding Acknowledgements Type of funding sources: None. Background/Introduction Transvenous implantation of pacemaker is performed with fluoroscopy for leads’ insertion and implantation in the heart. This implies radiation exposure for patients and operators. Fluoroscopy allows a two-dimensional view of lead movements, and sometimes it is difficult to implant lead in the complex heart anatomy, or in alternative right ventricular (RV) pacing sites, that often requires higher radiation doses. These alternative pacing sites may prevent pacing-induced ventricular dysfunction. They are his bundle pacing area (HBP), ventricular septum close to the conduction system area (VS), RV outflow tract (RVOT). The use of three-dimensional-electroanatomic mapping system (3D-EAM) may reduce fluoroscopy and guide lead implantation. Published median fluoroscopy data for similar procedure are: 6 mGy (1), 13 mGy and 231 microGy/m2 (2). Purpose of this study is to seek out if a 3D-EAM-guided transvenous implantation into RV alternative sites pacing in paediatric patients can be accomplished with zero or near-zero X-rays. Methods Retrospective analysis of children and adolescents with congenital or acquired (idiopathic) complete atrioventricular block (CAVB) without other congenital heart defects who underwent 3D-EAM-guided pacing in alternative RV sites. The implant procedure was divided in 4 steps: 1-contrast venography; 2- 3D mapping: with a steerable catheter (femoral vein), the 3D-EAM acquired geometric reconstruction of the right heart and a pacing map identified RV sites with narrower paced QRS; 3-axillary vein puncture; 4-lead and pacemaker implantation: 3D-EAM guided stylet-directed screw-in lead implantation toward desired RV sites. Data are reported as median (25th-75th centiles). Results 54 CAVB patients (42 females), underwent 3D EAM-guided pacing (27 VVIR, 27 DDD) at age 11.5 (7.7-14) years, weight 42 (26-54) kg. Pacing sites were: 10 HBP, 4 RVOT, 40 VS (Figure 1). Procedure time was 170 (143-193) min, total fluoroscopy exposure and that of the 4 steps are reported in Table 1. The lowest exposures were: 0.2 mGy, 8 microGy/m2 (VVIR) and 0.6 mGy, 15 microGy/m2 (DDD). Paced QRS was 115 (100-120) ms. Conclusions 3D-EAM-guided alternative RV pacing sites was accomplished with very low fluoroscopic exposure, close to zero in some cases. Therefore, with 3D-EAM we can significantly reduce radiological doses also in difficult pacing procedures in paediatric patients, thus reducing radiological risks and preserving ventricular function. The dream is becoming reality.

Funding Acknowledgements Type of funding sources: None. Background/Introduction One of the main complications of transvenous leads implanted in paediatric patients is the stretching of the lead caused by the somatic growth. It may cause pacing and sensing defects and lead dislodgement or even fracture. Absorbable lead ligature and atrial loop may reduce this risk. However, the loop may induce traction or may unroll too early and therefore impair lead function. Lead extraction and replacement is another solution, although it has some procedural risks in young patients. Lead advancement through pushing it from the pocket may solve growth-induced traction and spare the electrode throughout childhood until post-puberty. Purpose of the study is the retrospective analysis of the outcome of the transvenous lead advancement in children with a pacemaker (PM) in a single tertiary paediatric center. Methods Consecutive patients with a VVIR PM implanted for isolated congenital complete atrioventricular block (no structural heart disease) in alternative right ventricular (RV) pacing sites, with lead stretching underwent a trial of lead advancement during general anaesthesia, cefuroxime antibiotic profilaxis, from 2014 to 2021. After venous angiography showed venous patency, the PM pocket was opened, the lead was released from subcutaneous adherences and with a stylet was gently advanced to create a semi-loop in the atrium without dislodging the tip. Lead data (threshold, sensing, impedance) were compared before and after the procedure. Data are expressed as median (25th-75th centiles) Results: 7 patients underwent PM implantation at 6.9 (5.5-8.0) years of age, 20 (18-21) kg, 116 (106-120) cm, with the lead positioned at parahisian(3)/mid-septum (4 pts) sites. During a follow-up of 3 (1-5) years, advancement procedures were 2 (1-4) per patient. Between procedures, delta age was 15 (12-19) months, height 7 (6-11) cm and weight 4 (2-6) kg. All leads were successfully advanced without any procedural complications. Procedure time (skin to skin) was 91 (69-105) minutes, fluoroscopy was 0.4 (0.2-1.2) mGy, 13 (9-35) microGy/m2. Electrical lead parameters did not showed significant differences between consecutive control times. In one parahisian pacing, chronic threshold increased after 3 years (2 advancement procedures) from 0.7V to 2.6 V/0.4 ms. Conclusion the advancement of transvenous leads in children is a safe and effective procedure, without significant procedural complications and during follow-up, and with low fluoroscopy exposure. This procedure may maintain a good function of transvenous leads until growth has completed.

Funding Acknowledgements Type of funding sources: None. Background/Introduction Before bipolar epicardial leads became widely available and used by heart surgeons, unipolar epicardial leads were frequently implanted in small children requiring permanent pacing. Main complications are lead fractures causing pacing/sensing defect. Therefore, patients should undergo new epicardial or endocardial lead implantation with relevant procedural risks, especially in complex congenital heart disease (CHD). Proximal fractures, close to the generator, may be repaired using a dedicated Unipolar Lead Adapter and Extension, with reduced operative risks. Purpose of the study is the retrospective analysis of the outcome of the repair of unipolar epicardial leads in young patients (pts) in a single tertiary paediatric center. Methods Consecutive patients with proximal fracture underwent a trial of lead repair using the lead adapter/extension, during general anaesthesia, cefuroxime antibiotic profilaxis, from 2004 to 2020. Lead data (threshold, sensing, impedance) were compared before and after the repair procedure. Results 18 patients with CHD (12pts, 10 of whom complex, 6 post-Fontan) or normal structural heart (6pts), who underwent pacemaker implantation at 2.5 (0.7-5.8)years of age for congenital/postoperative atrioventricular block (11pts) and sinus node dysfunction (7pts), showed lead (7 atrial, 11 ventricular) fractures after chronic pacing. At 13 (8-17)years of age, all leads were successfully repaired without any complications. Follow-up was 4 (2-6)years. Four pts (22%) showed again fractures of the repaired lead, after 1 month, 1and 3 years (2pts). Electrical lead parameters are shown in table 1: there were not significant differences between consecutive time of controls, also in the atrial and ventricular lead subgroups. Table 1.-------------------Pre-repair;--intraprocedural;---1 month;----------1 year;-------------4 years. Threshold (V/0.4 ms):--1.1 (0.7-1.4);--1.0 (0.8-1.6);-------1.2 (0.9-1.5);-----1.2 (0.9-2.1);-------1.5 (1.1-1.8). Sensing (mV):--------- 7 (2.4-12);------5.4 (1.3-15);-------4 (1.5-11);----------5 (1.6-12);---------3 (2-10). Impedance (ohm): 343 (289-407);---350 (246-415);--346 (250-432);--374 (250-589);--362 (220-470). Conclusion The repair of fractured unipolar epicardial leads in young patients is a safe and effective procedure, with few complications during follow-up. Effective repair can delay more aggressive procedures.