Diurnal variation in plasma norepinephrine in patients with heart failure.

Diurnal variation in plasma norepinephrine (PNE) levels is well documented in healthy individuals but not in patients with heart failure. Therefore, we attempted to determine variations in PNE levels over 24 hours, measured hourly, in six patients with an ejection fraction below 40% and a history of heart failure of longer than 3 months. Three controls without a history of heart failure also were evaluated. Both patients and controls had diurnal variations in PNE, with highest levels occurring during the day and lowest at night. When data in patients were evaluated by 6-hour time intervals the mean value for 6:00 A.M.-12:00 noon was approximately twice as high as 12:00 midnight-6:00 A.M. (689+/-329 vs 338+/-166 pg/ml, p<0.05, respectively). Patients also had significant peak to trough variation in PNE levels compared with controls (959+/-396 vs 386+/-84 pg/ml, p<0.02, respectively). These results suggest that significant intrapatient variations in PNE occur over 24 hours in patients with heart failure. These variations may have to be accounted for when evaluating and treating patients with heart failure.