Right Ventricular Systolic Function Parameters in Hypoplastic Left Heart Syndrome

Assessment of the systolic function of the right ventricle (RV) in patients with hypoplastic left heart syndrome (HLHS) is important. The asymmetric shape and heavy trabeculations make accurate assessment of RV systolic function challenging. Novel measures of RV function could be helpful in distinguishing reduced versus preserved function in HLHS and may also be worse in HLHS with preserved function compared to normal controls. These novel methods offer promise, but research and clinical applicability is hindered as no cut-off values for normal function have been established. We performed a retrospective comparison of functional assessments from echocardiograms of HLHS patients with preserved and reduced RV function along with a control group of normal patients. Measures of function included fractional area change (FAC), tissue motion annular displacement of the tricuspid (TMAD-TV) and pulmonary valves (TMAD-PV), myocardial performance index (MPI), tricuspid tissue Doppler S' velocity, and RV global longitudinal strain (RVGLS). Comparisons were made between three groups: normal patients, HLHS with preserved function, and HLHS with reduced function defined as FAC < 35%. FAC was chosen as the reference as it is a historical standard. 41 HLHS patients were studied. Of these patients, 20 had HLHS with reduced function, and 21 had preserved function. They were compared with 27 age-matched, normal, controls. Comparison between HLHS and normal controls: in HLHS with preserved RV systolic function, compared to normal controls, tissue Doppler S', MPI, and TMAD-TV were all abnormal (all p < 0.05). RVGLS was not statistically different (20.5 ± 3.6% for normal vs. 17.9 ± 2.6% for HLHS with preserved function). TMAD-PV was similar between groups (16.1 ± 4.6% vs. 16.7 ± 5.1%). All measures were significantly worse (all p < 0.05) in the HLHS with reduced function group compared to normal controls. Comparison between HLHS preserved vs reduced function: in HLHS with reduced function defined by FAC < 35%, all measures were significantly worse compared to HLHS with preserved function (all p < 0.05). The cut-off values that correspond to a FAC of > 35% were 14.5% for TMAD-TV and 16% for RVGLS. All measures except RVGLS and TMAD-PV estimated worse function than controls even for HLHS with preserved function. Each of the functional measures was able to identify preserved vs reduced function in HLHS with FAC as the reference standard. Cut-off values between preserved and reduced function in HLHS were estimated for TMAD-TV and RVGLS based on a relatively small cohort. These cut-off values will aid in the research design of future studies.