MON-462 Pheochromocytoma as a Reversible Cause of Decompensated Heart Failure in a Patient With Pre-existing Cyanotic Heart Disease

Abstract Disclosure: A.S. Xiang: None. R.J. Clifton-Bligh: None. S.M. De Sousa: None. E. Boehm: None. M.G. Burt: None. C.A. Muir: None. D.J. Topliss: None. A.W. Russell: None. Background: Cyanotic heart disease is associated with a 5-fold increased risk of developing pheochromocytoma and paraganglioma (PPGL) via unique pathogenic mechanisms related to hypoxemia-driven somatic EPAS1 (encoding hypoxia-inducible transcription factor 2-alpha, HIF2α) gain-of-function variants. Herein, we report an individual with acute decompensated heart failure on a background of complex cyanotic heart disease precipitated by hypercatecholaminemia from a pheochromocytoma. Clinical Case: A 58-year-old man was referred for heart transplantation after developing acute decompensated heart failure on a background of complex cyanotic congenital heart disease with Eisenmenger’s syndrome. He was noted to have had a 20mm heterogeneous left adrenal lesion incidentally detected 2 years prior that was lost to follow-up. Repeat CT showed tumor enlargement to 34mm, and 68Ga DOTATATE PET demonstrated Krenning 4 (high) SSTR expression without metastasis. Plasma normetanephrine was 20782pmol/L (normal <900pmol/L) with a normal plasma metanephrine, consistent with suspected HIF2α-mediated pathogenesis. Following extensive MDT discussion regarding the timing and sequence of adrenalectomy and heart transplantation, he proceeded with adrenalectomy first. Prazosin was prescribed for pre-operative alpha-blockade, with a maximum tolerated dose of 0.5mg BD. Beta-blockade and proactive hydration were not used due to concern for worsening hemodynamic instability and fluid overload. He underwent a successful left posterior retroperitoneoscopic adrenalectomy, showing a now 62mm pheochromocytoma with intact SDHB and SDHA IHC. The postoperative period was complicated by profound vasoplegia and hypoxia (SpO2 30%, versus baseline SpO2 70%), presumed secondary to reduced pulmonary circulation. He required concurrent high-dose noradrenaline, vasopressin, fludrocortisone, midodrine and high flow nasal oxygen to maintain adequate blood pressure and oxygen saturation. Heart rate and rhythm remained at baseline throughout (30-40bpm, junctional escape rhythm). After one week without hemodynamic improvement, a single chamber pacemaker dramatically improved his hemodynamic state, allowing all supports to be weaned along with resolution of hypoxia to baseline saturation. The patient has since demonstrated complete resolution of heart failure symptoms back to NYHA Class I. He walks 10,000 steps daily without limitation. Germline PPGL gene panel testing was negative, and there is no family history of PPGL. Sanger sequencing of tumour DNA for EPAS1 gain-of-function variants is underway. Conclusion: PPGLs are an important differential for cardiac decompensation in patients with cyanotic heart disease, who have an increased risk of these rare tumors due to activation of hypoxia-induced tumorigenesis. We show that surgical cure of PPGL can offer complete symptom resolution. Presentation: Monday, July 14, 2025