A study on myocardial ischemia in the left ventricular wall with special reference to electrographic and metabolic changes.

Ischemic changes in the left ventricular wall were investigated during graded coronary constriction in 9 dogs. Epicardial and intramyocardial electrograms were recorded and changes in ST-segment voltage were correlated with the changes in intramyocardial gas tensions in outer and inner layers of the myocardium measured using a mass spectrometer. Electrographic and metabolic changes appeared first in inner layer and proceeded to outer layer with increasing severity of coronary constriction. In both layers intramyocardial ST-segment elevation was closely related with the increase in carbon dioxide tension (r = 0.78 in inner layer and r = 0.67 in outer layer). Epicardial electrogram, however, reflected the regional ischemia less sensitively than intramyocardial electrograms and has a limited function to detect myocardial ischemia.