Neurohumoral variability in left ventricular dysfunction

The immediate and longer term variability of selected vasoactive- and volume-regulating neurohormones were measured in patients entering a substudy of the Studies of Left Ventricular Dysfunction—a randomized clinical trial in patients with left ventricular ejection fraction <35%. The variability of these hormones has not been determined in a large cohort of patients. Immediate (short-term) variability was assessed by systematically comparing levels after 15 and 30 minutes of supine rest at the initial visit, and longer term variability was assessed by comparing 30-minute supine rest values at the initial visit with corresponding values taken at 30 minutes after 16 to 24 days of stable therapy. Initial values obtained at the first visit after 30-minute supine rest for all 209 patients were (mean ± SEM) 512 ± 21 pg/ml for plasma norepinephrine, 1.9 ± 0.2 ng/ml/hr for plasma renin activity, 3.0 ± 0.1 pg/ml for plasma arginine vasopressin, and 129 ± 5.3 pg/ml for plasma atrial natriuretic peptide. All variables were moderately increased relative to established normal values. There was a small but significant decrease from 15- to 30-minute supine posture in all neurohormones, except arginine vasopressin. In the presence of stable background therapy, no significant differences were found between measurements obtained after 30 minutes supine rest at the initial visit and 16 to 24 days later. Spearman correlation coefficients corresponding to immediate and longer term variability were high (range 0.55 to 0.79) (p < 0.0001). We conclude that plasma neurohormone levels are relatively constant over several weeks in patients with chronic left ventricular dysfunction who have received stable background therapy throughout this 3-week period. This suggests that major variations in plasma neurohormone levels may therefore be a possible marker of disease progression or may reflect treatment effects in this population.