Acute myocardial infarction due to coronary spasm associated with L-thyroxine therapy

A 63-year-old man with hypothyroidism is described. He had been receiving L-thyroxine therapy following mitral valve surgery. About three weeks into the therapy regimen, he complained of severe retrosternal chest oppression. Electrocardiographic findings and laboratory data indicated a diagnosis of acute myocardial infarction due to the L-thyroxine therapy. Emergency selective coronary angiography was performed. Comparing his coronary angiograms with those obtained before surgery indicated a severely spastic left coronary artery. We believe this is the first report of myocardial infarction due to coronary spasm, demonstrated by angiography associated with L-thyroxine therapy.