It has been rarely reported intermittent changing axis deviation also occurs during atrial fibrillation. Intermittent changing axis deviation during acute myocardial infarction and changing axis deviation associated with atrial fibrillation and acute myocardial infarction too have been also rarely reported. It has also been reported acute myocardial infarction during l-thyroxine substitution therapy in a patient with elevated levels of free triiodothyronine and without significant coronary artery stenoses. An acute myocardial infarction due to coronary spasm associated with l-thyroxine therapy has also been reported too. We present a case of changing axis deviation during acute myocardial infarction in a 56-year-old Italian woman with permanent atrial fibrillation and l-thyroxine therapy and without significant coronary stenoses. Also this case focuses attention on changing axis deviation in the presence of atrial fibrillation during acute myocardial infarction and on the possible development of acute myocardial infarction without significant coronary stenoses associated with l-thyroxine therapy.