Autonomic influences on ventricular repolarization in congestive heart failure

We studied the QT interval rate-dependence in patients with congestive hear t failure (CHF). The long-term autonomic nervous function was investigated by separate analysis of diurnal and nocturnal periods. For this purpose, QT m rate-dependence was determined from Holter recordings. Twelve patients wi th stable CHF (mean age 63 +/- 2 years) and 15 healthy subjects (mean age 5 9 +/- 4 years) were included in the study. CHF patients showed an increased nocturnal QTm rate-dependence when compared to normal subjects (0.150 [95% confidence interval (CI) 0.114 to 0.186] versus 0.106 [95% CI 0.080 to 0.1 33], P <.05). Ln contrast, QTm rate-dependence was not significantly differ ent between the 2 groups during the day (0.177 [95% CI 0.149 to 0.210] in t he CHF group versus 0.194 [95% CI 0.158 to 0.231] in the control group). It was also not significantly different between day and night for the CHF gro up, thus showing a loss of the circadian modulation in these patients. Thus , ventricular myocardial properties are altered by changes in the autonomic nervous system in CHF, as observed at the atrial level. These modification s may be related to the increased susceptibility to ventricular arrhythmias .