SIMULTANEOUS INVASIVE AND NONINVASIVE EVALUATIONS OF BAROREFLEX SENSITIVITY WITH BOLUS PHENYLEPHRINE TECHNIQUE

Estimation of baroreflex sensitivity (BRS) is receiving increasing att ention in clinical and experimental cardiology. Until recently, in mos t studies BRS has been assessed on the basis of invasive blood pressur e measurement, which limits its use in large-scale studies and in clin ical practice. The development of continuous noninvasive blood pressur e monitoring has made it possible to assess BRS noninvasively. We comp ared central invasive and peripheral noninvasive techniques in the ass essment of BRS during cardiac catheterization in 40 patients with poss ible coronary artery disease. The correlation between noninvasive and invasive BRS was high (r = 0.92; p < 0.001). However, the noninvasive method resulted in significantly higher BRS values than did the invasi ve method (7.1 +/- 6.5 msec/mm Hg vs 5.1 +/- 4.3 msec/mm Hg, respectiv ely; p < 0.001) because of the smaller increase in systolic blood pres sure after phenylephrine injection by the noninvasive technique than b y the invasive technique (18.9 +/- 6.8 mm Hg vs 25.2 +/- 7.8 mm Hg, re spectively; p < 0.01). The difference between noninvasive and invasive BRS correlated positively with invasive BRS (r = 0.54; p < 0.001) and inversely with age (r = -0.39; p < 0.01) and resting systolic blood p ressure (r = -0.30, p < 0.05). A noninvasive BRS value of <4.0 ms/mm H g showed a sensitivity of 94%, a specificity of 91%, and an accuracy o f 93% in identifying cases of reduced invasive BRS (<3.0 msec/mm Hg). Our findings encourage the use of finger-cuff method in the assessment of BRS. However, noninvasive BRS values were slightly but significant ly higher than invasive BRS values, a difference that should be taken into account when BRS is measured by the noninvasive approach.