SAT-623 Acute Bradycardia Secondary to Worsening of Hypothyroidism Post-Iodine Contrast

Abstract

Abstract BACKGROUNDPatient with history or risk of developing thyroid disorder can develop worsening of overt hypothyroidism after exposure to iodine containing contrast. We report a case of bradycardia requiring CCU treatment due to worsening of hypothyroidism due to iodine contrast.CASE DETAILSA 68 years old female with history of heart failure, coronary artery disease, hypertension, diabetes mellitus and hypothyroidism presented to ED for chest pain and dyspnea. She was taking L-thyroxine 100mcg with other medications at home. CT angiography was negative and coronary angiogram was unremarkable. Her symptoms were alleviated and she was discharged home next day. Her discharge vitals included heart rate within normal limit. After 3 days she presented to ED for dizziness and weakness. Her vitals included heart rate of 51 and BP of 105/50. EKG showed sinus bradycardia. She was not taking medications that could potentially cause bradycardia, including beta-blockers. She was discharged next day without change in medications. She again presented to the hospital next day due to dizziness, fatigue and bradycardia. Vitals signs showed BP of 91/48 with heart rate of 37. She was admitted to CCU and treated with dopamine drip. Her TSH was 11.90(0.35-5.5 uIU/ml) and free T4 0.69(0.76-1.46ng/dl). She was started on 125mcg of L-thyroxine and was discharged home on this dose. After 2 days of discharge patient again presented to ED for the 4th time for dizziness and bradycardia. EMS details regarding vitals and EKG were not available but document did include atropine given en route, suggesting likely bradycardia of <40. On arrival to ED, Heart rate was 52 with BP 120/59. TSH done this visit was reported 26.40. Patient confided not taking 125mcg of L-thyroxine but continuing 100mcg, the dose she was on before first admission. Patient was again started on 125mcg of levothyroxine in hospital and observed for 3 days. Patient’s symptoms were resolved, and her heart rate was >60/min on the day of discharge.DISCUSSION Association of iodine contrast with hypothyroidism has been less studied compared to that with hyperthyroidism. Risk factors such as pre-existing sub-clinical hypothyroidism and hashimoto thyroiditis has been identified in some studies. It is postulated that in presence of excess iodine, iodine internalization into the thyrocyte and iodine organification is suppressed, also known as Wolff-Chaikoff effect. In most of the reported cases and studies, transient changes in thyroid function after exposure to iodine contrast rarely resulted change in management. Our case is unique in the sense that patient needed treatment in cardiac critical care including chronotropic agent. As use of iodine contrast in acute care setting has been on rise since last few decades, a hospital clinician needs to be vigilant about this phenomenon.