Systolic time intervals during isometric exercise in supine position should be corrected also for arterial pressure

In this paper we have studied the relationship between the systolic time intervals (STI) and the heart rate (HR) and systolic arterial pressure (SAP) in a group of 24 healthy subjects at three different effort levels during an isometric exercise in supine position and in basal conditions. We observed a decrease of the non corrected STI values during the exercise. Then we corrected STI using the regression equations obtained by plotting STI values versus the corresponding HR values at rest and during the exercise. We showed an increase of corrected left ventricular ejection time (LVET) during the whole exercise, and an increase of corrected total electromechanical systole (QS2c) at 50% effort level and then a return to the basal values. We also derived the multiple regression equations correlating QS2 and LVET with HR and SAP. Notwithstanding these equations show a significant positive correlation between the two STI considered and SAP only at the maximum effort, we corrected LVET and QS2 values by these equations assuming that the relationship between these parameters exists also in basal conditions and during the remaining stages of the exercise. By this correction we found a decrease of LVETc and QS2c in accordance with hemodynamic data reported by other authors. We may conclude that it seems useful to correct the STI obtained during isometric exercise in supine position both for HR and SAP.