The effect of an evening dose of a long-acting beta-blocker on the autonomic tone in patients with congestive heart failure.
BACKGROUND
Heart rate variability (HRV) indices are accepted markers of cardiac autonomic activity and have been used as indicators of beta-blockade effects in congestive heart failure (CHF) patients. In view of the high frequency of sudden cardiac death in the morning, there is a question whether the evening beta-blocker administration would be more efficient than a morning dose.


OBJECTIVE
To compare HRV indices after morning or evening long-acting beta-blocker administration.


METHODS
The study group consisted of 52 CHF patients (NYHA class II/III) in sinus rhythm. Time domain (TD) and frequency domain (FD) HRV analyses were performed for daytime, nighttime and a 24-hour period: first after the morning bisoprolol administration, and then after the same evening dose.


RESULTS
After the evening dose the mean heart rate was significantly lower (p = 0.01), nighttime normal R-R intervals were significantly prolonged (p = 0.008) and the low frequency (LF)/high frequency (HF) ratio was significantly lower for: 24 h (p = 0.0002); daytime (p = 0.003) and nighttime (p = 0.008) with higher HF values in the 24-hour period (p = 0.0007) and in the daytime interval (p = 0.006).


CONCLUSIONS
An evening dose of a beta-blocker is more effective than a morning dose in reversing adverse changes in the autonomic nervous system activity in CHF patients.
Targoński
Ryszard
R
Department of Medical Sciences, Warminsko-Mazurski University, Olsztyn, Poland. rtarg@op.pl
Sadowski
Janusz
J
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000368:Aged; D001341:Autonomic Nervous System / Q000187:drug effects / Q000503:physiopathology; D017298:Bisoprolol / Q000008:administration & dosage*; D048909:Diabetes Complications; D004334:Drug Administration Schedule; D015716:Electrocardiography, Ambulatory; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000188:drug therapy*; D006801:Humans; D008297:Male
D000319:Adrenergic beta-Antagonists; D017298:Bisoprolol