Rl. Goldsmith et al., LONG-TERM CARVEDILOL THERAPY INCREASES PARASYMPATHETIC NERVOUS-SYSTEMACTIVITY IN CHRONIC CONGESTIVE-HEART-FAILURE, The American journal of cardiology, 80(8), 1997, pp. 1101
To determine the effect of beta blockade on parasympathetic nervous sy
stem activity, we assessed RR variability during 24-hour Holter monito
ring in 10 patients with congestive heart failure before and after 3 t
o 4 months of treatment with the beta blocker carvedilol. High-frequen
cy-power increased from 26 to 64 ms(2), root-mean-square of successive
differences in RR interval increased from 14.3 to 23.7 ms(2), and per
centage of absolute differences >50 ms between successive normal RR in
tervals increased from 0.8% to 4.7%, all p <0.01, indicating a substan
tial increase in parasympathetic modulation of RR intervals.