Sympathetic Predominance Followed by Functional Denervation in the Progression of Chronic Heart Failure

Using spectral analysis of heart rate and systolic arterial pressure variabilities, the study was set up to evaluate cardiovascular efferent autonomic modulation in patients with different degrees of chronic heart failure. We studied 30 patients with stable chronic heart failure and 15 controls of similar age. ECG, arterial blood pressure and respiratory signal were recorded at rest, during controlled respiration and during passive head-up tilting. R-R interval periods of 256-512 were analysed. Routine 2D echocardiogram and Doppler studies were also carried out. As expected, we found a decrease in the mean and variance of R-R intervals in patients with sever heart failure. In New York Heart Association (NYHA) class II patients, the power spectral pattern of R-R variability was characterized by the predominance of the low frequency component (72 +/- 3 nu), considered a marker of sympathetic activity, and by its unresponsiveness to tilting. Patients in NYHA class III also presented blunted changes in spectral components during tilting. A drastic decrease in the variance of R-R intervals (191 +/- 58 vs 1056 +/- 149 ms2 in controls) and an almost complete absence of the low frequency spectral component (8 +/- 3 nu) were present in patients in NYHA class IV. Controlled respiration, which in normal subjects decreased the low frequency component, induced changes that blunted progressively as heart failure increased. These data suggest that autonomic neural modulation and cardiovascular response to neural activity differ at different stages of the disease.