(136) Precipitous Discovery of Pheochromocytoma After Cardiac Catheterization in Adolescent Fontan Patient

Introduction: Pheochromocytoma is a rare catecholamine-secreting neuroendocrine tumor and an uncommon cause of secondary hypertension in children. Recent evidence has shown an association between chronic hypoxia due to cyanotic congenital heart disease (CCHD) and the development of pheochromocytoma. We present the case of an undiagnosed pheochromocytoma in an adolescent Fontan patient that was discovered after a cardiac catheterization.

Description: A fourteen-year-old female with history of hypoplastic left heart syndrome status post fenestrated Fontan operation with failing Fontan physiology requiring multiple heart failure therapies and budesonide presented for a surveillance cardiac catheterization. After induction, she developed tachycardia (141 bpm), hypertension (142/ 91 mmHg), hypoxemia (SaO2 30-50%), and fever (38.4°C.) Her cardiac function was depressed with an elevated Fontan pressure of 23 mmHg. The initial post-procedural course was complicated with blood pressure lability prompting further evaluation of her Fontan circuit with a CT angiogram which revealed a left sided retroperitoneal mass suspicious for a neuroendocrine tumor. Diagnosis of pheochromocytoma was confirmed by 24-hr urine and plasma free metanephrines. Alpha blockade with phenoxybenzamine was initiated with improvement of her hypertension.

Discussion: Managing a patient with Fontan physiology in the setting of an elevated catecholamine response provides unique intensive care challenges. In the Fontan circulation, blood flow from the systemic venous circulation through the lungs is entirely passive, requiring an adequate transpulmonary gradient and low pulmonary vascular resistance. In our patient, catecholamine induced vasoconstriction led to an increase in systemic vascular resistance and central venous pressure, worsening pulmonary blood flow. It is important to consider that treatment with alpha blockade can improve systemic afterload and impair passive pulmonary blood flow. Given the increasing evidence linking chronic hypoxia and neuroendocrine tumors in patients with CCHD, and the life-threatening consequences if left untreated, clinicians should consider pheochromocytoma as a cause of unexplained clinical deterioration in this unique patient population.