Noninvasive assessment of baroreflex control in borderline hypertension. Comparison with the phenylephrine method.

In this study, we examined the sensitivity of two recently developed noninvasive baroreflex measurement techniques to assess baroreflex control in hypertension. We assessed baroreflex sensitivity noninvasively from covariations of systolic pressure and RR interval using spectral analysis and sequence detection. The noninvasive estimates of baroreflex control were compared with estimates derived from phenylephrine-induced increases in systolic pressure and RR interval in normotensive subjects (n = 27) and borderline hypertensive subjects (n = 15). Baroreflex sensitivity was significantly reduced in the borderline hypertensive group relative to the normotensive group when assessed with the use of either the noninvasive or invasive methods to index baroreflex control. In addition, estimates obtained from the noninvasive methods were significantly correlated with baroreflex sensitivity assessed with the phenylephrine method (spectral: r = .48, P < .001; sequence: r = .50, P < .001). These findings suggest that spectral analysis and the sequence method provide viable alternatives to the pharmacological approach for estimation of baroreflex sensitivity in hypertension.