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

Abstract

: 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(R)) 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 TREATMENT AND PROGRESS: 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.

Conclusions: 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.

Figure 1

Admission ECG of the presented patient with an acute myocardial infarction and thyrotoxicosis. The tracing demonstrates 2-3 mm ST segment elevations in II, III, aVF as well as V2 to V5.

Figure 2

Critical narrowing of left anterior descending artery in the presented patient close to the apical region with flow cessation possibly with residual thrombus, no evidence of significant narrowing in other vessels.

Figure 3

Echocardiographic image showing left ventricular wall motion abnormalities of the apex in systole (arrows): apical two chamber view (left upper panel), four chamber view (right upper panel) and three chamber view (left lower panel). Matching bulls eye display of left ventricular segments strain quantitative analysis (right lower panel). Reduced myocardial contraction within the region of myocardial infarction is clearly visible (blue and pink colour).