Impact of Right Ventricular Geometry and Left Ventricular Hypertrophy on Right Ventricular Mechanics and Clinical Outcomes in Hypoplastic Left Heart Syndrome

Abstract

Right ventricular (RV) function is a major determinant of survival in hypoplastic left heart syndrome (HLHS). However, the relation of RV geometry to myocardial mechanics and their relation to transplant-free survival are incompletely characterized. We retrospectively studied 48 HLHS patients from the Hospital for Sick Children, Toronto, (median age, 2.2; interquartile range, 3.62years) at different surgical stages. Patients were grouped by the presence (n=23) or absence (n=25) of RV "apical bulging" defined as a sigmoid-shaped septum with the RV leftward apical segment contiguous with the left ventricular (LV) lateral wall. Regional and global RV strain were measured using speckle-tracking echocardiography, and regional strains were analyzed for patterns and peak values. These were compared between HLHS anatomical subtypes and between patients with versus without apical bulging. We further investigated the association between RV geometry and dysfunction with the outcomes of heart failure, death, or transplant. RV global (-7.3%±2.8% vs -11.2%±4.4%; P=.001), basal septal (-3.8%±3.2% vs -11.4%±5.8%; P=.0001) and apicolateral (-5.1%±3.5% vs -8.0%±5.8%, P=.001) longitudinal strain were lower in patients with versus without apical bulging, respectively. Apical bulging was equally prevalent in all HLHS anatomical variants. Twenty of 22 (91%) patients with apical bulging displayed hypertrophy of the LV apical and lateral segments. Death or transplantation were approximately equal in both groups but related to reduced RV global strain in patients with (seven of seven) and not in those without apical bulging (two of eight; P=.022). These results suggest that the finding of apical bulging is related to the presence of a hypertrophied hypoplastic LV, with a negative impact on regional and global RV function. Therefore, analysis of RV and LV geometry and mechanics may aid in the assessment and prognostication of this high-risk population.