The Road Less Traveled: Evaluating Hypoxemia in Pulmonary Hypertension

Abstract

<h3>Introduction</h3> There is a broad differential diagnosis for hypoxemia in patients with pulmonary arterial hypertension (PAH). We present an update to a previously-presented case of PAH due to Takayasu arteritis (TA), with a complex subsequent course including PAH therapies and multiple structural interventions. <h3>Case Report</h3> A 59-year-old woman with a history of thyroid cancer, PAH due to TA, and severe symptomatic aortic stenosis with recent transcatheter aortic valve replacement presented with hypoxemic respiratory failure and volume overload. The prior diagnostic work-up for vasculitis was presented previously. Her TA was in remission on immunosuppressive therapy and PAH was managed with tadalafil, ambrisentan, selexipag, and warfarin. At the time of presentation with hypoxemic respiratory failure, she required 35L of supplemental oxygen and chest CT showed pulmonary edema. An echocardiogram showed signs of elevated cardiac output and early passage of saline bubbles, consistent with a patent foramen ovale (PFO). The dose of selexipag was decreased to address high-output heart failure from its action as a prostacyclin receptor agonist. After diuresis, a cardiac catheterization revealed normal filling pressures, mean PA pressure of 27mmHg, normal cardiac output, pulmonary vascular resistance of 4-5 W.U., pulmonary vein saturation of 97%, and left atrial saturation of 87%, consistent with right-to-left shunting (Qp:Qs of 0.8). She was diuresed to euvolemia and discharged on home oxygen. Two months later, she underwent planned percutaneous PFO closure. There was no evidence of residual shunting on post-procedure echocardiogram. Management of high-output heart failure and the right-to-left shunt resulted in improved hypoxemia and stability on triple therapy for PAH. <h3>Summary</h3> This case demonstrates the challenges in diagnosing and treating the underlying etiologies of hypoxemia in patients with PAH. Keeping a broad differential diagnosis and avoiding diagnostic anchoring in this patient population may uncover unexpected but treatable causes of hypoxemia.