SUN-514 Reversal of Catecholamine- induced Electrocardiogram Changes with Alpha-adrenergic Blockade in Pheochromocytoma

Abstract Disclosure: J. Lim Jia Xin: None. S.D. Leungsuwan: None. S. Du Soon: None. A 74-year-old man with a 20-year history of hypertension presented with weight loss over the past few months, associated with more recent onset of abdominal distension and constipation. His medications included losartan 100mg and amlodipine 5mg once daily. Upon admission to the general ward, he was alert and afebrile, had a pulse rate 87 beats/min and blood pressure of 111/64 mmHg. His symptoms raised concerns of possible malignancy. Further workup with computed tomography of the thorax, abdomen and pelvis unexpectedly showed a 3.1 cm x 2.0 cm heterogeneously enhancing lesion in right adrenal gland with enhancement characteristics of portal venous phase 70 HU, delayed phase 49 HU, relative washout 31% which did not favor a lipid-rich nodule. Primary adrenocortical carcinoma and pheochromocytoma were important differentials. He had no adrenergic symptoms. However, 24-hour urine metanephrines showed a markedly elevated urine metanephrine value of 7904 nmol/day [reference range, 400-1500 nmol/day] which was at 5.27 times above upper limit, as well as an elevated plasma metanephrine value of 2.40 [<0.33 nmol/L] which was 7.27 times the upper limit; normetanephrine values were normal for both urine and plasma samples. The diagnosis of pheochromocytoma was made. A 12-lead ECG performed upon admission showed diffuse deep T-wave inversions. The patient did not have chest pain, and a single troponin-T was at 41 ng/L [reference range, <30 ng/L]. Possible differentials to the ECG changes included ischemic heart disease (Wellen’s pattern), hypertrophic cardiomyopathy, stress cardiomyopathy or cerebral T waves such as intracranial haemorrhage. In this given context, the ECG abnormality could also possibly be catecholamine-induced cardiomyopathy. Transthoracic echocardiography showed normal left ventricular ejection fraction of 56 % with regional wall motion abnormalities. Myocardial perfusion imaging showed negative dipyridamole stress-rest perfusion scan for ischemia. Alpha-blockade was initiated shortly after the diagnosis of pheochromocytoma in preparation for right adrenalectomy, aiming for pre-operative blood pressure targets according to Endocrine Society guidelines. Interestingly, at 1 month after alpha-blockade with phenoxybenzamine 10mg twice daily, the ECG showed improvement in T-wave inversions over leads V2-V3. Further normalisation of the T waves was observed on the ECG performed just prior to the operation, 2 months following initiation of alpha-blockade therapy. At 5 weeks post right adrenalectomy, his ECG had largely normalised with only remnant isolated mild T wave inversion in V4. Through serial ECG monitoring, the ischemic-type ECG abnormalities induced by excess catecholamine were demonstrated to undergo resolution following appropriate alpha-blockade even before the surgical resection. Presentation: Sunday, July 13, 2025