Non-invasive determination by cardiovascular magnetic resonance of right ventricular-vascular coupling in children and adolescents with pulmonary hypertension

Background: Pediatric pulmonary hypertension (PH) remains a disease with high morbidity and mortality in children. Understanding ventricular-vascular coupling, a measure of how well matched the ventricular and vascular function are, may elucidate pathway leading to right heart failure. Ventricular vascular coupling ratio (VVCR), comprised of effective elastance (E_a, index of arterial load) and right ventricular maximal end-systolic elastance (E_es, index of contractility), is conventionally determined by catheterization. Here, we apply a non-invasive approach to determining VVCR in pediatric subjects with PH. Methods: This retrospective study included PH subjects who had a cardiovascular magnetic resonance (CMR) study within 14 days of cardiac catheterization. PH was defined as mean pulmonary artery pressure (mPAP)∈≥∈25 mmHg on prior or current catheterization. A non-invasive measure of VVCR was derived from CMR-only (VVCR_m) and compared to VVCR estimated by catheterization-derived single beat estimation (VVCR_s). Indexed pulmonary vascular resistance (PVRi) and pulmonary vascular reactivity were determined during the catheterization procedure. Pearson correlation coefficients were calculated between PVRi and VVCR_m. Receiver operating characteristic (ROC) curve analysis determined the diagnostic value of VVCR_m in predicting vascular reactivity. Results: Seventeen subjects (3 months-23 years; mean 11.3∈±∈7.4 years) were identified between January 2009-August 2013 for inclusion with equal gender distributions. Mean mPAP was 35 mmHg∈±∈15 and PVRi was 8.5 Woods unit x m2∈±∈7.8. VVCR_m (range 0.43-2.82) increased with increasing severity as defined by PVRi (p∈<∈0.001), and was highly correlated with PVRi (r∈=∈0.92, 95 % CI 0.79-0.97, p∈<∈0.0001). Regression of VVCR_m and PVRi demonstrated differing lines when separated by reactivity. VVCR_m was significantly correlated with VVCR_s (r∈=∈0.79, CI 0.48-0.99, p <0.0001). ROC curve analysis showed high accuracy of VVCR_m in determining vascular reactivity (VVCR∈=∈0.85 had a sensitivity of 100 % and a specificity of 80 %) with an area under the curve of 0.89 (p∈=∈0.008). Conclusion: Measurement of VVCR_m in pediatrics is feasible. Pulmonary vascular non-reactivity may be contribute to ventricular-vascular decoupling in severe PH. Therapeutic intervention to maintain a low vascular afterload in reactive patients may preserve right ventricular functional reserve and delay the onset of RV-PA decoupling. Use of VVCR_m may have significant prognostic implication.