APPRAISAL OF THE STATE OF THE AUTONOMIC N ERVOUS-SYSTEM IN HYPERTROPHIC CARDIOMYOPATHY ANALYZING HEART-RATE-VARIABILITY

Introduction. The analysis of heart rate variability has been accepted as a non-invasive method to evaluate the influence of the autonomic n ervous system over the heart. Although heart rate variability has been used during the last decade in several illnesses the studies in hyper trophic cardiomyophathy are scarce. Objectives. We report the activity of the autonomic nervous system in patients with hypertrophic cardiom yophathy using the analysis of heart rate variability. Patients and me thods. Heart rate variability was evaluate by the analyzing 24-h ambul atory electrocardiograms (Bolter) in 20 patients with hypertrophic car diomyopathy and in 15 controls. This method has been used to measure h eart rate variability. Spectral analysis of the frequencies were calcu lated using fast Fourier transformation. Spectral heart rate variabili ty was computed as high (0.15 to 0.40 Hz) low (0.04 to 0.15 Hz) and to tal (0.01 to 1.0 Hz). We compared the relation between low/high freque ncy as an index of the sympathic/parasympathic balance. All data are e xpressed as mean value +/- SD. The unpaired Student t-test was used. A two tailed p valued < 0.05 was considered statistically significant. Results. There were no differences in the mean heart rates among the p atients with hypertrophic cardiomyophathy and normal subjects (mean +/ - SD: 71 +/- 9 versus 74 +/- 11 beats/minute; p = NS) while there was a significant decline in total spectral (mean +/- SD: 7.14 +/- 1.1 ver sus 7.57 +/- 0.6 In [ms(2)]; p = 0.02) and high (mean +/- SD: 5,22 +/- 0.8 versus 5.63 +/- 1.3 In [ms(2)]; p = 0.04) as well as in low spect ral frequency of heart rate variability (mean +/- SD: 22 +/- 0.8 versu s 5.63 +/- 1.3 In [ms(2)]; p = 0.04) in patients with hypertrophic car diomyopathy. There were no differences in the low/high frequency compo nent ratio in these patients (mean +/- SD: 1.1 +/- 0.1 versus 1.2 +/- 0.1 In [ms(2)]; p = NS). Conclusions. These facts suggest that the pat ients with hypertrophic cardiomyopathy have an alteration in the auton omic nervous system: sympathic (low spectral frequencies) and parasymp athic activity thigh spectral frequencies), although this does not ref lect an imbalance between sympathic: and parasympathic activities (rel ation of low to high spectral frequencies).