Two addition situations that may be associated with elevation of the ST segment simulating acute transmural ischemia are listed here. Both a rapid elevation in extracellular potassium and acute myocarditis are uncommon causes of such ST segment changes but should be kept in mind. Acute myocarditis is of particular importance because if may also be associated with abnormal T waves and Q waves, i.e. all of the ECG changes typical of an acute infarction. In addition, myocarditis may be associated with sinoatrial, atrioventricular and intraventricular conduction disturbances.