Effect of altering conditions of the sequence method on baroreflex sensitivity

Background The sequence method is widely used as a simple, non-invasive mea sure of baroreflex sensitivity (BRS), This technique, originally described in anaesthetized cats, has been transferred virtually unchanged to humans, without evidence that the optimal values in cats are the same as those in p atients with cardiovascular disease. Objective To study the effect of altering the components of the sequence me thod on the measured BRS in patients with chronic heart failure (CHF) and i n normal individuals, Methods Eighty patients with CHF [aged 62 +/- 12 years (mean +/- SD)] and 4 0 normal control individuals [aged 38 +/- 15 years (mean a SD)] underwent m easurement of heart rate and non-invasive blood pressure, Altering only the shift between blood pressure and R-R interval and the required correlation coefficient of the regression line had no effect on the value of SRS, but had a significant effect on the number of valid sequences, Alteration of th e blood pressure or R-R interval thresholds, however, affected not only the number of valid sequences, but also the value of BRS in both groups. In no rmal controls, agreement with the bolus phenylephrine method was improved b y increasing the blood pressure threshold, although this led to a reduction in the number of valid sequences. In patients with CHF, agreement was opti mized by decreasing both the blood pressure and R-R interval thresholds. Th is also had the effect of increasing the number of valid sequences, Conclusion Changes should be made to this technique, to optimize its validi ty in conscious humans, particularly when applied to patients with attenuat ed BRS. (C) 2001 Lippincott Williams & Wilkins.