Reproducibility of methods for assessing baroreflex sensitivity in normal controls and in patients with chronic heart failure

Baroreflex sensitivity (BRS) conveys useful prognostic information in patie nts with heart disease, yet methods for its quantification suffer from poor reproducibility and test failure in some patients with heart failure. We s et out to compare the short-term reproducibility and success rate of four d ifferent methods of assessing BRS in normal subjects and patients with chro nic heart failure (CHF). A total of 31 patients with CHF and 18 normal cont rols underwent BRS testing using four techniques: (1) bolus phenylephrine ( BRSPhe), (2) alpha-index in both low- and high- frequency bands (BRSalpha L F and BRSalpha HF respectively), (3) the sequence method (BRSSeq), and (4) a new 0.1 Hz controlled-breathing, time-domain analysis method (BRSCbr). Ea ch subject underwent two test episodes with each method on the same day. Th e average values for BRS in patients and controls respectively were: BRSPhe , 4.4 (+/-4.4) ms/mmHg and 19.8 (+/-11.5) ms/mmHg; BRSalpha LF, 5.6 (+/- 4. 1) ms/mmHg and 15.4 (+/- 5.0) ms/mmHg; BRSalpha HF, 7.1 (+/- 7.0) ms/mmHg and 25.1 (+/-8.3) ms/mmHg; BRSSeq, 7.7 (+/-6.3) ms/mmHg and 22.5 (+/-8.4) m s/mmHg; BRSCbr, 6.6 (+/-5.9) ms/mmHg and 22.8 (+/-10.8) ms/mmHg. The coeffi cients of variation (S.D. of the difference in repeated values divided by m ean) in patients and controls respectively were: BRSPhe, 85.6% and 52.2%; B RSalpha LF, 65.9% and 33.7%; BRSalpha HF, 99.7% and 52.1%; BRSSeq, 30.7% an d 40.4%; BRSCbr, 30.7% and 19.6%. The numbers of test failures in patients were: BRSPhen, 15; BRS alpha LF, 7; BRSalpha HF, 5; BRSSeq, 14; BRSCbr, 1. Of the four techniques assessed for measuring BRS, the controlled breathing time-domain method yielded the best reproducibility and lowest failure rat e in controls and in patients with CHF.