| Abstract: | Of ten healthy women, 43 to 61 years of age, four exhibited 1 mm. or more of upsloping ST-segment depression after maximal exercise, using the Bruce multistage treadmill protocol; the other six did not. Cardiac output (direct Fick) was not different in the two groups, wither at rest or during exercise. The women with ST-positive responses were older (56 vs. 51 years) and heavier (relative weights 109 per cent vs. 102 per cent), and their resting mean systemic pressures were higher. Their systemic and pulmonary mean arterial pressures during the last five minutes of upright exercise were significantly higher (P less than 0.001) than those in the ST-negative group. Although the ratio of systemic to pulmonary mean arterial pressures was higher at rest, it progressively fell during exercise in the ST-positive group. Polarcardiographic display of the Frank ECG during the first 3 minutes of recovery after maximal exercise showed significant differences between the ST and T of the two groups. At initial recovery, MS-phi greatly exceeded 10.6 mV. which is sensitive PCG ischemic exercise criterion in the ST-positive group. Although the number of observations is limited, it is concluded that greater hemodynamic stress imposed on the subendocardium by elevated pressures, rather than by any significant functional evidence of restriction in coronary blood flow, probably explains much of the postexertional ST-segment depression after maximal exercise. |
