Tall upright T waves in the precordial leads.

One hundred ten cases of T waves more than 10 mm in height in the precordial leads were studied. The T waves were wide in ischemic heart disease and thin and peaked in uremia. Marked changes in the ventricular gradient were obselved in ischemic heart disease and in uremia with hyperkalemia. In other conditions, the changes in the ventricular gradient were of a lesser degree. In cases of left ventricular hypertrophv, the T waves were tall from V1 to V4 in systolic (pressure) overloading, from V4 to V3⁄4 in diastolic (volume) overloading, and from V2 to V6 in combined types of overloading. The appearance of tall T waves was the earliest electrocardiographic sign encountered in clinical and experimental cases of acute myocardial infarction. In anterior myocardial infarction they disappeared within 24 hours indicating initial transient ischemia, while in angina pectoris and posterior myocardial infarction they lasted for a longer time probably due to persistent subendocardial ischemia.