Delayed effect of blood pressure fluctuations on heart rate in patients with end-stage kidney disease.

The time delay of the baroreflex may be affected by decreased autonomic activity in uremia. To assess the magnitude and the time delay of heart rate response in patients with end-stage renal disease, continuous beat-to-beat intervals (IBI) and systolic blood pressure (SBP) recordings were monitored in hemodialysis (HD) patients (n = 72), in patients after renal transplantation (TX) (n = 41) and in age-matched controls (C) (n = 34). A 2-term prediction model was computed, in which each IBI change was represented as a function of SBP difference values of two immediately preceding beats. Baroreflex slope and the frequency domain variables low frequency (LF) α index, phase shift, and lag time were also calculated. b₁ coefficient, representing the dependence of IBI difference with the first previous SBP difference was lower in HD than in Cs, but increased after TX. b₁ correlated with age, baroreflex slope, and LF α, and b₂ (the 2nd term), with both the phase shift between SBP and IBI and lag time. The latter was lower in Cs than in HD or transplanted patients. These findings show that the time delay of the heart rate response to SBP variations is increased in renal insufficiency. The prolonged delay may contribute to the circulatory instability in uremic patients.