Valsalva maneuver in the assessment of baroreflex responsiveness in borderline hypertensives

Baroreceptor function was assessed by (1) the reflex response during Valsalva maneuver, (2) phenylephrine injection, and (3) increase in neck tissue pressure by a neck-chamber in 15 borderline hypertensives (B) and in 15 age-matched normotensives (N). B responded to the fall in blood pressure, occurring in phase II of Valsalva maneuver, with an increase in blood pressure and a decrease in the R-R interval of comparable extent to those observed in normals. On the contrary, in phase IV B showed a depressed heart rate reflex response whether evaluated by the slope of the regression line obtained by plotting the R-R interval versus the systolic blood pressure (slope: B = 6.1 ± 3.3; N = 35.6 ± 7, p < 0.005) or by the change in R-R interval (ΔR-R interval: B = 67.5 ± 37 ms; N = 319 ± 55ms, p < 0.005). On the other hand, both phenylephrine injection and neck-chamber procedure showed an impaired baroreflex responsiveness in B. A linear positive correlation was found between the individual values of the slopes obtained during phase IV of Valsalva maneuver and after phenylephrine injection both in N (r = 0.944, p < 0.001) and in B (r = 0.84, p < 0.001). Finally, a linear positive correlation was found between the individual values of the slopes obtained by the phenylephrine technique and the corresponding maximum percent change in R-R interval during phase IV of the Valsalva maneuver both in normals and in hypertensives. In conclusion, overshoot bradycardia during Valsalva maneuver seems to show enough specificity in the evaluation of baroreflex responsiveness to be employed in epidemiological studies in this area.