Thyrotoxicosis, unstable angina and normal coronary angiogram.

It is well known that thyrotoxicosis may elicit acute myocardial ischemia even in patients with angiographically normal coronary vessels. The involved mechanisms are not clearly defined although some hypothesis have been suggested. We report a case of a 54-year-old woman affected by Graves' disease with thyrotoxicosis which was referred to our Institute because of unstable angina. During hospitalization a two dimensional echocardiogram, performed during chest discomfort, showed left ventricular apical akinesis and impaired global systolic function. A subsequent coronary angiography revealed normal epicardial vessels. She was successfully treated with high-dose methimazole and propranolol and a repeat echocardiogram evaluation showed normalization of left ventricular systolic function. Six months later, because of the appearance of paroxysmal atrial fibrillation, the patient underwent total thyroidectomy and a substitutive therapy with L-T4 (100 micrograms/die) was started. The authors review the possible mechanisms involved in the pathogenesis of myocardial ischemia during thyrotoxicosis.