Abstract 10367: An Unusual Vasodilator Response: Recognizing a Rare Subtype of Pulmonary Arterial Hypertension

Abstract

Introduction: Pulmonary veno-occlusive disease (PVOD) is a rare subtype of pulmonary arterial hypertension (PAH) caused by intimal fibrosis of the pulmonary venules and septal veins. While the hemodynamic profile is suggestive of pre-capillary pulmonary hypertension, vascular obstruction distal to the pulmonary capillary beds distinguishes PVOD from other forms of PAH. Case: A 29-year-old woman presented with progressive dyspnea and fatigue. She was tachycardic, hypotensive, and volume overloaded on exam. ECG was notable for right-axis deviation. TTE showed a dilated, hypokinetic RV and small LV with mild global hypokinesis and septal flattening throughout the cardiac cycle. A CTA chest excluded pulmonary embolism but showed diffuse centrilobular ground-glass opacities and lymphadenopathy which raised suspicion for PVOD. She underwent right heart catheterization with the following measurements (mmHg): RA 14, PA 99/56 (mean 71), PCWP 12, and CI 1.1 L/min/m 2 with PVR 28.1 WU. Following initiation of an epoprostenol infusion, she became increasingly hypoxemic with repeat CT chest demonstrating dramatic worsening of ground-glass opacities and vascular congestion. This response to a vasodilator challenge led to a clinical diagnosis of PVOD. She was urgently listed for and underwent bilateral lung transplantation. Explanted lung tissue subsequently confirmed the diagnosis. Conclusion: In most forms of PAH, vasodilators mitigate arteriolar narrowing and improve pulmonary blood flow, while in PVOD they exacerbate pulmonary capillary congestion due to increased arteriolar blood flow relative to the venous outflow due to fixed narrowing of the pulmonary venule network. Because lung biopsy is contraindicated in severe pulmonary hypertension, the clinician must recognize that worsening pulmonary edema in response to vasodilator challenge with normal PCWP is a critical clue pointing towards PVOD. Timely diagnosis is essential given the poor prognosis for this condition for which lung transplantation is the definitive treatment.