Relationship between ST-segment elevation and local tissue flow during myocardial ischaemia in dogs.

The relationship between electrocardiographic ST-segment changes and local tissue flow recorded from idential sites in the myocardium was determined by inserting platinum electrodes into the left ventricular wall of anaesthetized dogs. Local myocardial blood flow was measured during graded coronary constriction by recording tissue hydrogen desaturation rate. In the detection of ischaemic ST-segment elevation, intramural recordings proved to be more sensitive than corresponding epicardial recordings. Significant ST-segment elevation could only be detected by reducing local myocardial flow below 50% of control; by further reduction ST-segment elevation increased in proportion to the reduction in myocardial flow. Thus, significant myocardial ischaemia might exist without electrocardiographic alterations.