The effect of ventricular conduction velocity on ST-segment level in acute myocardial ischemia

The ECG changes in acute myocardial ischemia was studied with ST segment map pattern. Three isolated coronary perfused and isovolumetric contracting canine heart preparations were used. In each preparation, large and small sized acute ischemia was induced by 5 min occlusion of proximal and distal portion of left circumflex coronary artery. Single exponential relationship was seen between R wave amplitude and ventricular activation time (VAT) in normal and in coronary occlusion. The marked degree of delayed VAT induced lowering in R-wave amplitude. Prolongation of VAT, increasing in R-wave amplitude and ST segment elevation was shown at ischemic area. The maximum change in VAT and in R-wave amplitude was seen at center of ischemic zone. The ST segment map pattern was similar with solid angle distribution pattern, despite the slight disturbance of conduction velocity, however, marked delay over 45 msec VAT induced extremely difference of ST map from solid angle distribution map.