STI usefulness during isometric exercise in labile hypertensive patients.

Measurement of the left ventricular systolic time intervals (STI) was considered a valid method in demonstrating the presence of a state of beta-drenergic hyperstimulation. The authors used this method during isometric exercise to differentiate between a group of 16 normal subjects (N) and 16 random labile hypertensives (LH), and between the N and 16 fixed hypertensives (FH). Exercise resulted in a general shortening (p less than 0.01) of the STI, an increase (p less than 0.01) in the systolic arterial pressure (SAP), and an increase (p less than 0.01) in the heart rate (HR) in all the groups studied. The study also demonstrated that the state of blood pressure (diagnosis) alone does not significantly influence the course of the exercise test, and that the interaction diagnosis-exercise gives quantitatively different results in the three groups, to the extent that it is possible to recognize a specific polygraphic pattern for the LH. In this group there is a greater shortening of the Q--S2 and the non-corrected LVET (p less than 0.01) than for the N. The behaviour for the FH falls between the other groups, but it is not possible to distinguish clearly between this group and its neighbour on either side. We conclude that the measurement of the STI during isometric exercise could be useful in determining a diagnostic pattern for subjects who show a lability in their blood pressure.