Use of Right Ventricular Free-Wall Strain in a Multivariable Estimate of Right Ventricular-Arterial Coupling in Pediatric Pulmonary Arterial Hypertension

BACKGROUND: Right ventricular-arterial coupling (RVAC) describes the relationship between right ventricular contractility and pulmonary vascular afterload. Noninvasive surrogates for RVAC using echocardiographic estimates of right ventricular function, such as tricuspid annular plane systolic excursion (TAPSE), have been shown to correlate with invasively measured RVAC and predict clinical outcomes in pediatric pulmonary arterial hypertension. However, given the limitations of TAPSE at accurately estimating right ventricular function in children, we hypothesized that a multivariable estimate of RVAC using right ventricular free-wall longitudinal strain (RVFW-LS) may perform better than those utilizing TAPSE at predicting clinical outcomes. METHODS: In all, 108 children from 2 institutions with pulmonary arterial hypertension underwent hemodynamic catheterization with simultaneous echocardiography. In a retrospective analysis, hybrid (echo and invasive) RVAC metrics included TAPSE/pulmonary vascular resistance (PVRi) and RVFW-LS/PVRi. Noninvasive echocardiographic metrics were TAPSE/echo-derived pulmonary artery systolic pressure (PASP) and RVFW-LS/PASP. RESULTS: RVFW-LS correlated with PVRi (r=0.315, P =0.01), though TAPSE did not (r=0.058, P =0.64). PVRi, PASP, and RVAC metrics declined in patients with worse World Health Organization Functional Class (n=108), while TAPSE and RVFW-LS did not. PVRi, PASP, RVFW-LS/PVRi, TAPSE/PVRi, and RVFW-LS/PASP predicted the outcome variable of transplant or death (area under the curve, 0.771 [ P <0.001], 0.729 [ P =0.004], 0.748 [ P =0.002], 0.732 [ P =0.009], and 0.714 [ P =0.01], respectively), while TAPSE/PASP, RVFW-LS, and TAPSE did not (area under the curve, 0.671, 0.603, and 0.525, respectively). In patients without a history of repaired congenital heart disease (n=88), only RVFW-LS/PASP, PVRi, PASP, and RVFW-LS/PVRi predicted outcomes (area under the curve, 0.738 [ P =0.002], 0.729 [ P =0.01], 0.729 [ P =0.01], and 0.729 [ P =0.015], respectively). CONCLUSIONS: In the pediatric population, baseline PVRi and echo-estimated PASP were strongly associated with adverse clinical outcomes, but TAPSE and RVFW-LS were not. Estimates of RVAC utilizing RVFW-LS were superior to those utilizing TAPSE—however, only marginally additive to PASP and PVRi at predicting the adverse clinical outcome in patients without a history of repaired congenital heart disease.