PERINATAL CARDIAC FUNCTIONAL ADAPTATION IN HYPOPLASTIC LEFT HEART SYNDROME: A LONGITUDINAL ANALYSIS

Abstract

The perinatal transition is characterized by acute changes in cardiac loading. Compared to normal newborn combined cardiac output (CCO), single right ventricular (RV) output of neonates with hypoplastic left heart syndrome (HLHS) is markedly greater. We sought to examine the mechanisms of cardiac adaptation which facilitate this perinatal transition from late fetal to early neonatal life in HLHS. Prospectively recruited pregnancies complicated by fetal HLHS (n=35) and health controls (Ctrl, n=17) underwent serial echocardiography in late gestation (38±1weeks) and 6, 24 and 48 hours after birth. Cardiac function was assessed using conventional, tissue Doppler and speckle tracking echocardiography. Term HLHS fetuses had an RV output (RVCO) comparable to Ctrl CCO via higher stroke volume (SV). Compared to both left ventricular (LV) and RV indices of Ctrls, they exhibited a globular and dilated RV with reduced relative wall thickness (RWT) [RWT: 0.40±0.08 vs. 0.49±0.10, p<0.01], increased Tei index' [HLHS vs. Ctrl LV/Ctrl RV: sphericity index (SI): 0.9±0.25 vs. 0.5±0.10/0.6±0.11, RV area index: 28±6cm2/m2 vs. 15±3cm2/m2/17±5cm2/m2, Tei index': 0.65±0.11 vs. 0.43±0.07/0.45±0.09, all p<0.0001]. HLHS neonates generated elevated RVCO compared to Ctrl CCO via higher heart rate and SV, with further RV dilatation, increased longitudinal systolic strain at 48h [-17±4% vs. -14±3%/-14±5%] with reduced circumferential and rotational myocardial deformation and altered diastolic function. HLHS neonates also demonstrated right atrial (RA) enlargement with increased longitudinal strain: 6h (33±12% vs. 26±6%), 24h (37±15% vs. 26±13%), 48h (38±11% vs. 24±13%), p<0.0001. Term HLHS fetuses exhibit altered RV geometry and RV systolic and diastolic functional parameters. After birth, further alterations in these cardiac parameters likely reflect adaptation to acutely altered RV loading from increasing cardiac output and pulmonary artery flow demands.