SAT484 High Degree AV Block And Sinus Arrest: Cardiovascular Manifestations Of Myxedema Coma

Disclosure: J. Bosques-Lorenzo: None. P. Rivera: None. J. Colon-Castellano: None. Y. Otero-Dominguez: None. Bosques-Lorenzo Jaymilitte, Rivera-Cariño Patricia, Colon-Castellano Janet, Otero-Dominguez Yomaira. Background: Myxedema coma is a rare and life-threatening complication of severe hypothyroidism. The most common presenting symptoms are altered mentation, hypothermia, edema, and respiratory depression. The cardiovascular system is often involved, in the form of sick sinus syndrome, bradycardia, low voltage QRS complex, QT prolongation, and rarely cardiac arrest. Here we present a case of myxedema coma complicated with high degree AV block and sinus arrest. Clinical Case: A 84 year-old man with history of hypothyroidism on levothyroxine 125 mcg, presented to the ER due to disorientation, bilateral leg edema, and abdominal discomfort for 3 days. Vital signs revealed a temperature of 97.5 F, HR of 60bpm, BP 174/88 mmHg, and oxygen saturation of 100% at room air. Physical exam was pertinent for bilateral lower extremity edema, facial puffiness, macroglossia, slow mentation, and scattered rales on lung auscultation. Laboratories showed an elevated TSH (296.8 uIU/mL), with low total T3 and free T4 (45.03 ng/dL and 0.228 ng/dL respectively) with a myxedema score of 45. Altered renal parameters as per BUN and creatinine levels (83.4 mg/dL and 5.75 mg/dL) without electrolytes disturbances and elevated CPK (1250 U/L). Infectious process was ruled out. Chest X-ray showed vascular congestion. Echocardiogram showed a small pericardial effusion. Patient was admitted to ICU and started on IV Levothyroxine, along with hydrocortisone. Liothyronine was initially not available. On second admission day, the patient developed hypothermia (94.3 F) which was managed with passive warming. Telemetry monitoring recorded multiple episodes of bradycardia raging from 30 to 50 bpm, high-degree AV block, and one episode of sinus arrest of 15 seconds with self-resolution. Altered mentation persisted for which endotracheal intubation was performed to secure airway. A temporary transvenous pacing was placed emergently. Levothyroxine dose was further adjusted and liothyronine was initiated. After a few days of treatment, patient demonstrated clinical improvement that was supported with follow up thyroid function test. Patient was extubated and transitioned to oral levothyroxine. Nevertheless, he remained dependent of transvenous pacing for which permanent pacemaker placement was coordinated. Conclusion: Cardiovascular complications in myxedema coma are associated with poor prognosis with a mortality approaching 80%. Few cases of sinus or cardiac arrest associated to Myxedema coma have been reported in the literature. In this case, the patient developed high-degree AV block with concomitant sinus arrest despite prompt initiation of intravenous thyroid hormone. Prompt identification of cardiovascular involvement can prevent cardiovascular morbidity and mortality in myxedema coma. Presentation Date: Saturday, June 17, 2023