Measuring Flow Hemodynamic Indices and Oxygen Consumption in Children with Pulmonary Hypertension: A Comparison of Catheterization and Phase-Contrast MRI

Abstract

We sought to compare pulmonary flow hemodynamic indices obtained by Fick and thermodilution catheterization techniques with phase-contrast MRI (PC-MRI) in children with diverse etiologies of pulmonary arterial hypertension (PAH). Calculation of pulmonary flow (${\dot{\text{Q}}}_{\text{p}}$) using the Fick principle in most catheter laboratories relies on an estimate of oxygen consumption which may limit its reliability. Flow hemodynamic indices acquired from thirty patients with PAH who underwent successful same-day PC-MRI and catheterization were evaluated for absolute and percent bias. Comparison of ${\dot{\text{Q}}}_{\text{p}}$ between PC-MRI and Fick revealed poor agreement with an absolute bias of 0.96 ± 0.53 L/min/m² and percent bias of 27.7 ± 19.6%. Same analysis between PC-MRI and thermodilution revealed better agreement as demonstrated by absolute bias 0.64 ± 0.47 L/min/m² and percent bias 16.8 ± 12.3%. Retrospectively calculated ${\dot{\text{V}}}_{{{\text{O}}_{2} }}$ from PC-MRI and LaFarge equations revealed poor agreement, with an absolute bias of 33.4 ± 21.6 mL/min/m² and percent bias of 25.8 ± 12.6%. We found that Fick-derived flow hemodynamics dramatically differs from PC-MRI computed metrics in children with PAH. The non-invasive nature of PC-MRI and short acquisition time is ideal for pediatric flow evaluation and may offer a novel route of absolute flow and resistance assessment when combined with cardiac catheterization.