Role of spectral measures of heart rate variability as markers of disease progression in patients with chronic congestive heart failure not treated with angiotensin-converting enzyme inhibitors

Measures of heart rate variability in the frequency domain quantify autonomic activity. However, the relation of these measures to the severity of ventricular dysfunction in patients with congestive heart failure remains uncertain. We applied spectral analysis of heart rate variability to 24-hour Hotter monitor recordings obtained from 20 patients with congestive heart failure who were not treated with angiotensin-converting enzyme inhibitors to determine whether significant changes in parameters of heart rate variability reflect the progression of symptoms in patients with ventricular failure. Both total and low-frequency heart rate spectral power were seen to decrease with worsening New York Heart Association (NYHA) functional class. A significantly (p=0.04) higher total power was noted in NYHA class II than in class III patients (3.0 x 10(-3) +/- 3.6 x 10(-4) and 2.5 x 10(-3) +/- 5.9 x 10(-4) [beats/min](2), respectively). Similarly, low-frequency heart rate spectral power was significantly (p=0.008) higher in class II than in class III patients (1.7x10(-3)+/-4.6x10(-4) and 1.1x10(-3)+/-3.5x10(-4) [beats/ min](2), respectively). Only the low-frequency component of the spectrum was directly correlated with left ventricular ejection fraction (LVEF) (r=0.40) with a trend toward statistical significance (p=0.07). Measures of heart rate variability and the changes in autonomic tone that they reflect may therefore serve as markers of the extent of disease progression in patients with congestive heart failure.