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Aims In congenitally corrected transposition of the great arteries (CCTGA) the right ventricle (RV) is systemic. Atrioventricular block (AVB) and systolic dysfunction are frequently observed. Permanent pacing of the subpulmonary left ventricle (LV) may worsen RV dysfunction. The aim of this study was to seek out if LV conduction system pacing (LVCSP) guided by three-dimensional-electroanatomic mapping systems (3D-EAMs) can preserve RV systolic function in paediatric CCTGA patients with AVB. Methods and results Retrospective analysis of CCTGA patients who underwent 3D-EAM-guided LVCSP. Three-dimensional-pacing map guided lead implantation towards septal sites with narrower paced QRS. Electrocardiograms (ECGs), echocardiograms, and lead parameters (threshold, sensing, and impedance) were compared at baseline (pre-implantation) and at 1-year follow-up. Right ventricle function was evaluated by 3D ejection fraction (EF), fractional area change (FAC), RV global longitudinal strain (GLS). Data are reported as median (25th–75th centiles). Seven CCTGA patients aged 15 (9–17) years, with complete/advanced AVB (4 with prior epicardial pacing), underwent 3D-guided LVCSP (5 DDD, 2 VVIR). Baseline echocardiographic parameters were impaired in most patients. No acute/chronic complications occurred. Ventricular pacing was >90%. At 1-year follow-up QRS duration showed no significant changes compared with baseline; however, QRS duration shortened in comparison with prior epicardial pacing. Lead parameters remained acceptable despite ventricular threshold increased. Systemic RV function was preserved: FAC and GLS improved significantly, and all patients showed normal RV EF (>45%). Conclusion Three-dimensional-EAM-guided LVCSP preserved RV systolic function in paediatric patients with CCTGA and AVB after short-term follow-up.

Background Pacemakers (PMKs) and implantable cardioverter-defibrillators (ICDs) are frequently utilized in patients with specific cardiac rhythm disorders. The downfalls of these devices are several but no data exist regarding leads thrombosis. Aim of the study the analysis of pacing lead thrombosis occurrence in paediatric PMK-ICD patients. Methods single Centre retrospective study of a series of paediatric/young adult patients showing pacing lead thrombosis. Data are reported as median (interquartile range). Results from 2015 to 2021 five patients (2 males), aged 16 (12-22) years, showed transthoracic echocardiographic evidence of lead vegetations during routine follow-up after 5 (1-16) years from lead's initial implantation. Age at device implantation was 9 (5-12) years. Two patients had dual-chamber ICD, 3 had PMKs (2 DDD, 1 VVI). No patient had any early wound complications after implantation. At the time of thrombosis detection, no patient reported any recent fever or symptoms of clinical illness. Devices and leads were normally functioning in all patients. Blood examination revealed absence of infectious or inflammatory signs, and all patients had negative hemocultures for aerobic, anaerobic bacteria and fungi. Therefore, lead thrombosis was diagnosed. Transesophageal echocardiogram (TEE) confirmed the echo finding. Thrombophilia testing revealed that 4 out of 5 patients had methylenetetrahydrofolate reductase (MTHFR) mutation, homozygous and heterozygous (2 each). Patients received oral anticoagulation therapy (OAT) and TEE showed complete recovery in 4 patients after 6-12 months; one adult patient is followed-up elsewhere. Conclusions pacing lead thrombosis is a rare complication in paediatric/young adult patients with PMK/ICD, well treated with OAT. MTHFR mutation is a risk factor for this complication.

Background 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. Objective 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 8 patients underwent PM implantation at 6.8 (5.8-8.0) years of age, 20 (18-21) kg, 116 (106-120) cm, with the lead positioned at parahisian(3)/mid-septum (5 pts) sites. During a follow-up of 3 (1-5) years, advancement procedures were 1.5 (1.0-4.3) per patient. Between procedures, delta age was 16 (12-20) months, height 8 (7-11) cm and weight 5 (3-7) kg. All leads were successfully advanced without any procedural complications. Procedure time (skin to skin) was 96 (73-108) minutes, fluoroscopy was 0.5 (0.2-1.4) mGy, 16 (10-46) microGy/m2. Electrical lead parameters did not showed significant differences between consecutive control times. Conclusion the advancement of transvenous leads in children is a safe and effective procedure, with low fluoroscopy exposure, without significant acute and chronic complications. This procedure seems to preserve transvenous leads until growth has completed.

Aims Different authors have described three-dimensional (3D) voltage mapping of the Koch’s triangle (KT) in order to find low-voltage bridges (LVBs) as targets for a successful transcatheter ablation (TCA) of the slow pathway (SP) in children. Recently, the advisor high density (HD) Grid™ mapping catheter was introduced as new multipolar catheter for HD mapping. The aim of the study was to describe our preliminary experience with the use of HD Grid™ catheter in LVB and electrophysiologically guided cryoablation of SP in children. Methods and results Twenty-one children (mean age 13 ± 3 years) with atrioventricular nodal re-entrant tachycardia (AVNRT) underwent cryoablation of SP guided by voltage HD mapping of the KT using HD Grid™ catheter. In order to better highlight the differences with conventional mapping, point collection was performed in each patient with this new multipolar catheter and with a quadripolar catheter. The conventional mapping collected 871 ± 262 points and used 211 ± 80 points in 887 ± 275 s, whereas HD mapping collected 7468 ± 2947 points, using 604 ± 165 points in 513 ± 181 s (P Conclusions Our preliminary experience shows that HD mapping is faster and offers higher spatial resolution and definition. Procedural time can be reduced maintaining the TCA safe, with reduced fluoroscopy use, and successful.