Acute myocardial infarction as the first presentation of thyrotoxicosis in a 31-year old woman - case report

A 31-year old woman, previously fit & well was admitted with pressing retrosternal chest pain and palpitations of sudden onset. Her body weight was normal (BMI 20.5 kg/m²) and there was no significant family history of cardiac disease. She smoked, however, about 15 cigarettes a day and she had been taking combined oral contraceptive pill (Cilest^®) for about three years. On admission she appeared sweaty and in pain, blood pressure 130/70 mmHg, heart rate about 110/min, mild lid-lag sign. Heart sounds were normal and chest was clear. ECG revealed 2-3 mm ST segment elevations in II, III, aVF as well as V2 to V5. Troponin I was raised and she was qualified to an emergency coronary angiography. This revealed a massive spasm of left anterior descending (LAD) coronary artery that responded to intracoronary glyceryl trinitrite administration, however, with the presence of critical narrowing of the LAD apical segment with possible superimposed thrombus. Cardiac ultrasound revealed akinesis of 1/2 of apical area consistent with myocardial infarction

She was started on Aspirin, Simvastatin, and Diltiazem, but continued to have persistent tachycardia and tremor. Thyroid function tests were ordered and showed thyrotoxicosis [free T4-46.9 pmol/l (ref. range 9-25), free T3-11.9 pmol/l (2-5), TSH - 0.02 mIU/l (0.27-4.2)]. She was referred for an endocrine opinion and started on Thiamazole. Other investigations revealed elevated anti-TPO and anti-TSH receptor antibodies consistent with Graves' disease. Thrombophilia screen was negative. She had remained euthyroid on a "block & replace" regimen (Thiamazole plus L-Thyroxine) that was discontinued after 18 months. She denies any anginal symptoms, but continues to smoke against medical advice.

Our case highlights the possibility of development of an acute myocardial infarction in a young subject with thyrotoxicosis. We speculate that patient's smoking habit combined with subtle thyrotoxicosis-induced prothrombotic state and/or coronary-artery spasm had lead to the above-mentioned acute coronary event.