Exercise stress testing and systolic time intervals.

Changes in ET/PEP in normal subjects are characterized by initial increase associated with the increase in the heart rate, stroke volume and cardiac contractility and are subsequently followed by plateuing or slightly decrease after exceeding the 70% heart rate level of the age predicted maximal heart rate. The decrease in ET/PEP is thought to be mainly due to decrease in stroke volume. After exceeding the predicted maximal heart rate ET/PEP reveals remarkable decrease that may reflect decreased cardiac function (CF). Some patients with ischemic heart diseases revealed decrease of ET/PEP at the heart rate less than the 60% level of the age predicted maximal heart rate. This may indicate decreased cardiac contractility associated with decreased stroke volume (Fig. 10). Since transient left ventricular failure is thought to take place in anginal attack, decreased ET/PEP at the heart rate below the 60% of age predicted maximal heart rate may indicate decreased cardiac function, although invasive evaluation of the cardiac function was not performed in the present study.