Estudo da modulação autonômica da freqüência cardíaca de pacientes portadores de doença renal crônica em tratamento conservador

Abstract

Cardiovascular diseases are the leading cause of morbidity and mortality in subjects with chronic kidney disease (CKD). These findings are related to the presence of multiple risk factors for atherosclerosis such as diabetes, dislipidemia, hypertension, and left ventricular hypertrophy, as well as to non traditional risk factors like inflammatory mediators, anemia, and vascular calcification. Furthermore, autonomic nervous system dysfunction has been associated to higher prevalence of cardiac arrhythmias and sudden death in this population. Objectives: In the present study, the heart rate variability (HRV) was evaluated through the spectral analysis using a holter monitoring, both in the supine position and upon passive postural stress in patients with CKD on conservative treatment. Patients and Methods: We evaluated 32 patients with CKD on conservative treatment stages 3, 4 and 5 (CRD group) and 14 healthy volunteers (CON group). All subjects underwent cardiological evaluation including electrocardiogram, and doppler echocardiogram, followed by the analysis of HRV. Heart rate variability was performed by continuous recording of heart rate by holter monitoring system during two periods of 20 minutes in supine position and passive postural tilt of 70° (orthostatic stress). HRV was obtained by spectral analysis of the variables normalized low frequency (LFnu), normalized high frequency (HFnu), indicative of sympathetic and parasympathetic modulation, respectively, as well as the LHnu/HFnu ratio, indicative of sympathovagal balance. Variables were tested for normality using the Kolmogorov-Smirnov test, which showed the condition of non-normality of the data obtained by spectral analysis. Thus, the hypotheses of equality of the values were analyzed with the Mann-Whitney, Wilcoxon, and Kruskal-Wallis non-parametric tests. For normal variables we used unpaired Student´s T test and ANOVA. To assess the correlation between the eGFR and the LFnu/HFnu ratio in patients with CKD, we used Spearman linear correlation coefficient. Results were expressed as the mean (X) ± standard deviation (SD). A p value less than or equal to 0.05 was considered statistically significant. Results: During the pre-inclined period no significant differences among variables in the groups CKD and CON were observed. However, during the inclined period, the variable LFnu was lower (73 ± 13.0 versus 84.5 ± 8, p <0.05), the variable HFnu was higher (26.5 ± 13.0 versus 15.4 ± 8.1, p <0.05), while the LFnu/HFnu ratio was lower (3.3 ± 1.3 versus 7.9 ± 5.6, p <0.05) in the CKD group compared to the CON group. The comparison between patients with CKD in stages 3, 4 and 5, in the pre-inclined period did not show significant differences in the variables LFnu, HFnu and LFnu/HFnu ratio. However, during the inclined period, stage 5 patients showed lower LFnu, higher HFnu and LFnu/HFnu ratio lower than in stage 3 patients (66.9 ± 12.9 versus 78.5 ± 5.2, 33.1 ± 13.0 versus 21.5 ± 5.2 and 2.4 ± 1.2 versus 3.9 ± 1.2, respectively) (p <0.005). Conclusion: Patients with CKD present depressed cardiac autonomic modulation that worsens with decreasing glomerular filtration rate.