In 1918, an investigation1 was reported in which an electrocardiographic study was made on the dog following the ligation of the coronary arteries. The changes in the T-deflection subsequent to the closure of branches of the left coronary artery were the most constant findings. Immediately following the ligation, this deflection became more prominent, and the height that it assumed apparently depended on the degree to which the circulation to the left ventricle was disturbed. After the closure of the descending or circumflex branches the amplitude of the T-wave occasionally approached and in a few instances even exceeded that of the R-deflection. The increase in the amplitude of the T-wave has repeatedly been observed in later work in which it was necessary to ligate branches of the left coronary artery.
Within twenty-four hours the T-deflection became sharply negative. The extent to which this wave became a negative phase and the duration