Abstract 13225: In vivo Sino-Atrial Node Mapping in Children and Adults With Congenital Heart Disease

Abstract

Introduction: Sinus node dysfunction (SND) is a common sequel in patients with congenital heart disease (CHD) and encompasses disturbances in sino-atrial node (SAN) impulse generation and/or its propagation from SAN exit sites towards the atrial myocardium. At present, the underlying pathophysiological mechanisms of SND in patients with CHD are incompletely understood. Therefore, we performed epicardial mapping of SAN activity in pediatric and adult patients with CHD undergoing primary surgical correction. Methods: Intra-operative epicardial mapping (interelectrode distance 2 mm) of the right atrium (RA) was performed during SR in 12 pediatric patients (0.6 [0.4-2.4] years) and 15 adults (46±14 years) to compare potential characteristics of SAN activation. Results: In all pediatrics, SAN activity was solely observed near the junction of the superior caval vein and RA, while SAN activity in adults was observed even up to the middle part of the RA. Within a radius of 8 mm from the SAN exit site, more conduction disorders (11 [8-13] % vs 6 [5-8] %, p=0.011) were seen in adults compared to pediatric patients, while there was no difference in conduction velocity (71 [64-75] cm/s vs 67 [62-75] cm/s, p=0.258). However, within 2 mm of the SAN exit site conduction was significantly slower in adult patients (47 [30-56] cm/s vs 25 [9-50] cm/s, p=0.010). Potential morphology recorded from pediatric patients consisted of a broad monophasic S-wave with high amplitude (4.9 [3.4-6.0] mV) and an R/S ratio close to 1 (0.98 [0.96-1.00]), while the potentials in adults contained smaller S-wave amplitudes (2.6 [1.9-4.2] mV, p=0.014), larger R-wave amplitudes (0.2 [0.1-0.5] mV, p=0.036) and smaller R/S ratio (0.92 [0.87-0.96], p<0.001). In adults, potential duration was substantially longer (45 [37-50] ms vs 66 [60-70] ms, p<0.001) and was more often fractionated. Conclusions: For the first time we characterized electrophysiological properties of SAN activation in pediatric and adult patients with CHD. Solely in adults, SAN activation was observed at the middle part of the RA, which may indicate changes in preferential SAN exit site. These novel insights into SAN activation in patients with CHD may partly explain why this population is prone to develop SND relatively early in life.