Correlation of T-wave changes occurring during exercise ECG with the hemodynamic changes that govern myocardial O2 balance.

Over 200 healthy males 16 to 60 yr of age were examined with the submaximal exercise test (SMET). ECG, heart rate and blood pressure were measured during rest, immediately after exercise and after 5 min of recovery. Relationships were examined between the percentage change of T-wave amplitude (delta T%) on transition from one phase of the test to the other and the percentage changes of five hemodynamic indices which are known to determine myocardial O2 balance. These indices were heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), myocardial tension index (MTI) and cardiovascular effort index (CVEI). Two new indices of myocardial O2 balance, namely, coronary perfusion index (Formula: see text) and demand supply index (Formula: see text) are also presented. All of these correlations were examined in the group as a whole and in various subgroups, according to age an physical fitness. In the highly fit group, there was a negative correlation between delta T% and delta HR% (P less than 0.001), delta MTI% (P less than 0.007) and delta DSI% (P less than 0.003), and a positive correlation between delta T% and delta CPI% (P less than 0.004). In the young, highly fit subgroup, there was a negative correlation between delta T% and delta HR% (P less than 0.001), delta MTI% (P less than 0.01), delta CVEI% (P less than 0.05) and delta DSI% (P less than 0.004), and a positive correlation between delta T% and delta CPI% (P less than 0.01). These correlations were mainly found during the transition from rest to effort. The results indicate that during the SMET, T-wave depression might be a manifestation of negative O2 balance in the subendocardial layer, even in subjects who most probably do not suffer from organic coronary disease.