Flow versus resistance: hemodynamic phenotyping of pulmonary hypertension in infants with shunts and concurrent lung disease

Neonatal pulmonary hypertension (PH) can be categorized into three distinct physiologies: resistance-driven precapillary pulmonary arterial hypertension (PAH), flow-driven precapillary PH, and postcapillary PH. We present eight patients, divided into three groups: premature infants with BPD, infants with chronic respiratory failure secondary to CDH or genetic syndrome, and an infant with a multilevel shunt. In each case, echocardiography was an important, non-invasive tool for screening risk of PAH. However, many of the common echocardiographic parameters used to assess PAH are confounded by volume and pressure loading due to cardiac shunts. These factors may lead to inaccurate assessments of patient hemodynamics and inappropriate treatment decisions. This series highlights challenging clinical cases of at-risk neonates wherein echocardiographic data was initially suggestive of PAH physiology, but subsequent invasive hemodynamic testing revealed significant flow from cardiac shunts, specifically atrial septal defects, ventricular septal defects, and/or patent ductus arteriosus, were main contributors to their clinical presentation.