Coronary Artery Bypass Grafting in the Presence of Severe Hyperthyroidism: A Case Report

BACKGROUND In coronary artery bypass grafting, hyperthyroidism with autoantibodies, as seen in Basedow disease, is uncommon and rarely leads to severe thyrotoxicosis. However, surgery can trigger this condition, and documented cases have resulted in poor outcomes. We describe the case of an incidental hyperthyroidism finding on preoperative evaluation for coronary artery bypass grafting for triple-vessel coronary artery disease. CASE REPORT A 58-year-old man presented with exertional dyspnea, chest pain, and postprandial vomiting. Coronary angiography revealed severe triple-vessel disease. After admission, he experienced additional episodes of chest pain, which required continuous infusion of coronary vasodilators and strict bed rest. Preoperative screening showed severe hyperthyroidism. Thiamazole 80 mg/day and potassium iodide 50 mg/day were initiated but discontinued after 2 weeks because of leukopenia (white blood cell count, 2800×10⁹/L). Although thyroidectomy was considered, coronary artery bypass grafting was prioritized owing to cardiac risk concerns. Perioperative management included continuous hemodiafiltration dialysis, methylprednisolone (1000 mg/day), and slow plasma exchange, starting with surgery to prevent thyroid storm. Intravenous gamma globulin was administered 3 days before and after surgery. Free triiodothyronine and free thyroxine were normalized on postoperative days 3 and 7, respectively. The postoperative course was uneventful, and the patient remained symptom-free at 1-year follow-up. CONCLUSIONS Coronary artery bypass grafting with uncontrolled hyperthyroidism is prone to complications, and a thyroid storm can be fatal. Although surgery should be avoided in cases of uncontrolled hyperthyroidism, in rare cases in which urgent treatment is not feasible, a critical intervention as described in this report may prevent thyroid crisis.