The Systolic to Diastolic Duration Ratio in Children with Hypoplastic Left Heart Syndrome: A Novel Doppler Index of Right Ventricular Function

Abstract

Right ventricular (RV) function is an important determinant of clinical status in children with hypoplastic left heart syndrome (HLHS). However, assessment of RV function remains challenging because of its complex morphology. We investigated the S/D duration ratio in children with HLHS as a novel index of global RV function. We measured systolic (S) and diastolic (D) duration using tricuspid regurgitation duration from Doppler flow, to calculate the S/D ratio in 33 children with HLHS and 33 control subjects matched for age and sex. We compared the S/D ratio between patients with HLHS and control subjects, between patients with HLHS and normal and abnormal RV function, and between patients with HLHS at different stages of palliation. We further correlated the S/D ratio with catheterization data. Patients and control subjects were well matched for age (3.12 +/- 4.5 vs 3 +/- 4.5 years, not significant) sex, and heart rate (cycle length 524 +/- 179 vs 575 +/- 162 milliseconds, not significant). Patients with HLHS had a significantly higher S/D ratio than control subjects (1.65 +/- 0.85 vs 0.85 +/- 0.2, P < .0001). The S/D ratio became increasingly elevated in HLHS at higher heart rates, but not in control subjects. The S/D ratio was significantly higher in patients with HLHS and decreased RV function as compared with patients with HLHS and normal RV function (2.2 +/- 0.7 vs 1.5 +/- 0.47, P = .006), and significantly increased in patients with Norwood stage 1 versus patients with Norwood stages 2 and 3 HLHS (2.16 vs 1.4 and 1.32, respectively, P < .01 and P < .001, respectively). The S/D ratio did not correlate with catheterization-derived RV end-D pressure or cardiac index. Patients with HLHS have an increased S/D ratio as a result of a shortened D and prolonged S. Measurement of the S/D duration ratio using Doppler flow is a novel method to augment assessment of global RV function in HLHS.