Quick Fire Session
SCMR 22nd Annual Scientific Sessions
Steven Abman, MD
Professor of Pediatric Pulmonology; Director, Pediatric Heart Lung Center; Director, Ventilator Care Program; Co-Director, Pediatric Pulmonary Hypertension Program
University of Colorado Denver; Children's Hospital Colorado
Acute vasoreactivity testing (AVT) is critical for diagnostic and therapeutic evaluation of pulmonary arterial hypertension (PAH). This is conventionally done by cardiac catheterization. Flow hemodynamics and stiffness parameters derived by phase-contrast MRI (PC-MRI) have recently been demonstrated to correlate with catheterization-derived parameters, including pulmonary vascular resistance index (PVRi) and mean pulmonary artery pressure (mPAP). The objective of this study was to compare wave intensity analysis (WIA) indices by MRI, obtained pre and post inhaled nitric oxide (iNO), to conventional hemodynamic parameters recorded during catheterization.
Per convention, 8 pediatric patients (6 female, mean age 13.6 years, SD 3.6 years) underwent cardiac catheterization with iNO challenge as part of standard of care. Within 24 hours, these patients also underwent two-dimensional PC-MRI to analyze hemodynamic and stiffness parameters in the main pulmonary artery at baseline and at 10 minutes following iNO 40ppm + FiO2 1.0. MRI-derived flow and area waveforms required for WIA were sampled from PC images. Maximum area (Amax), minimum area (Amin), relative area change (RAC), pulse wave velocity (PWV), forward compression wave (FCW), and backward compression wave (BCW) were obtained from PC images for pre and post iNO in each subject. All compression waveforms were indexed to ejected stroke volume.
Comparison of WIA indices with PVRi and mPAP revealed strong positive correlations between BCW and mPAP both pre and post iNO administration (Table 1). BCW also demonstrated positive correlation with PVRi post but not pre iNO administration. Additionally, Amax correlated positively with mPAP under both conditions. There was no significant difference in WIA or hemodynamic parameters pre and post iNO administration. While there was also no significant correlation between ∆ WIA indices and ∆PVRi or ∆mPAP pre and post iNO, the data suggested a trend toward positive correlation between ∆BCW and ∆PVRI (Fig 3).
In this preliminary study, backward compression wave was strongly associated with the gold standard parameter of mPAP obtained via cardiac catheterization in pediatric pulmonary arterial hypertension patients. Ongoing enrollment is occurring and will provide better understanding of the relationship between WIA and invasive hemodynamic measurements. Non-invasive iNO challenge using PC-MRI suggests that BCW, a WIA marker of stiffness, may be a good predictor of acute vasodilator testing in pediatric pulmonary arterial hypertension.