Thyrotoxicosis and lactate-producing angina pectoris with normal coronary arteries.

Three patients with thyrotoxicosis are described, in whom the presenting symptom was severe cardiac pain at rest or on effort and who were admitted to hospital with suspected or proven myocardial infarction. All patients were studied by selective coronary arteriography and left ventriculography after thyroid function tests which confirmed thyrotoxicosis. There was no demonstrable disease of the major coronary arteries in any of the patients, yet myocardial infarction and left ventricular aneurysm were shown to be present in 1, and there was definite electrocardiographic evidence of ischaemia in all 3. In addition, under stress the myocardium of all 3 patients produced lactate. It is recommended that thyrotoxicosis be seriously considered in the differential diagnosis of cardiac pain, particularly in younger women. The cause of the pain seems related to the cellular effects of thyrotoxicosis on the myocardium and current views of these effects are summarised. Of the 3 patients, 1 died suddenly 6 months after becoming euthyroid, indicating that the disease may not be as benign as expected. A guarded prognosis and continued medical follow-up are recommended when thyrotoxicosis presents with angina pectoris even when normal coronary arteries have been demonstrated.