SUN-509 - Walking a Hemodynamic Tightrope: Perioperative Management of Pheochromocytoma in a Patient with Hypertrophic Obstructive Cardiomyopathy

Background: Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by increased ventricular wall thickness predisposing to dynamic left ventricular outflow tract (LVOT) obstruction. Pheochromocytomas are rare catecholamine-secreting neuroendocrine tumors causing systemic vasoconstriction and intravascular volume depletion. Standard preoperative management involves alpha-adrenergic blockade and volume expansion to prevent hemodynamic collapse. However, alpha blockade reduces systemic vascular resistance, which in patients with HOCM can critically worsen the dynamic LVOT gradient and precipitate cardiogenic shock. In addition, volume expansion recommended for preoperative pheochromocytoma management can precipitate congestive heart failure (CHF). The coexistence of these conditions creates a clinical paradox described in this case below.

Case Presentation: A 63-year-old female with known longstanding labile hypertension, HOCM, HFpEF, and mitral insufficiency presented with fatigue and exertional dyspnea. Echocardiogram revealed a hyperdynamic left ventricle and a severely elevated resting LVOT gradient of 144 mmHg. Renal ultrasound for evaluation of AKI incidentally identified a large right suprarenal mass and subsequent CT scan showed a 7.4 x 9.8 x 8.9 cm heterogenous enhancing adrenal tumor. Biochemical workup confirmed catecholamine excess with markedly elevated plasma norepinephrine 9,573 pg/mL (ref: 115-524 pg/mL) and metanephrines 431.9 pg/mL (ref: 0-88 pg/mL) consistent with a pheochromocytoma.

Results: Preoperative management involved a delicate balance of adrenergic blockade and fluid resuscitation. A reversible alpha-1 blocker, doxazosin, was chosen over phenoxybenzamine to allow for a shorter half-life, greater titratability, and a safety window to pause in case of hemodynamic instability. Atenolol was used for beta blockade. To further reduce the catecholamine burden without altering hemodynamics, metyrosine was titrated up to 4g daily over 7 days prior to surgery. Patient was also advised to increase oral volume intake to 2 L/day; however, she developed acute pulmonary edema requiring diuretics. She underwent uneventful robotic-assisted right adrenalectomy. Postoperatively, she required IV fluids, steroids, norepinephrine, and vasopressin to maintain blood pressure. She developed acute decompensated heart failure and required diuretics and BiPAP treatment in the ICU. Once blood pressure was stabilized and rose above 130/80 mmHg, the patient was started on verapamil, the drug of choice for hypertension in HOCM patients.

Conclusion: This case highlights the complex cardiac hemodynamic challenges in the management of pheochromocytoma and the need for a multidisciplinary team of endocrinologists, cardiologists, surgeons, and anesthesiologists to closely coordinate care at Pheo-Para Centers of Excellence.

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