1638: Hemodynamic Reconsideration in Resistant Pulmonary Hypertension: Case of an Undiagnosed Shunt

Introduction: Partial anomalous pulmonary venous return (PAPVR) is a rare congenital anomaly wherein pulmonary veins drain into systemic circulation. Long-standing pulmonary overcirculation can lead to pulmonary hypertension (PH). We report a patient with refractory PH where PAPVR was identified upon reevaluation. Description: A 43-year-old male with a 12-year history of difficult to treat PH and patent foramen ovale (PFO) presented for second opinion. Medical history is significant for asthma and remote methamphetamine use. Initial PH diagnosis occurred in his early 30s after acute hypoxic respiratory failure requiring ventilation. Transesophageal echocardiogram revealed PFO. Initial right heart catheterization showed mPAP of 47 mmHg, pulmonary vascular resistance 4.3 Wood Units, with no hemodynamic improvement during trial of PFO occlusion, thus no closure. Despite triple therapy (selexipag, tadalafil, ambrisentan) and diuresis, his symptoms and hemodynamics remained unchanged. Repeat catheterization at our center revealed a significant oxygen saturation step-up between high (52%) and low superior vena cava (SVC, 83%) indicating a left-to-right shunt. Additionally, saturation dropped from pulmonary veins (99%) to left atrium (94%). Contrast angiography confirmed PAPVR, with right upper and middle pulmonary veins draining into the SVC. Due to elevated PVR and right-to-left shunting, multidisciplinary consensus recommended optimizing PH therapy before shunt closure. Discussion: PAPVR prevalence is approximately 0.2%-0.7%, frequently coexisting with sinus venosus atrial septal defects. Significant PAPVR may cause pulmonary overcirculation, vascular remodeling, and PH in up to 37% of cases. Symptoms are nonspecific. PAPVR suspicion should increase in idiopathic PH with disproportionate right ventricular dilation or preserved DLCO. Often, imaging misses this anomaly; thus, RHC with shunt run is essential to detect step-up in saturation. Surgical correction, indicated by right ventricular dilation and shunt fraction (Qp/Qs) >1.5, requires normalized PVR. Elevated PVR necessitates prior targeted PH therapy to optimize operability. Surgical correction significantly improves symptoms and can reverse PH progression.