Autonomic function in chronic liver disease assessed by Heart Rate Variability Study.

BACKGROUND: Chronic liver disease is associated with cardiovascular changes, including hyperdynamic circulation with increased blood volume and cardiac output, and with reduced peripheral vascular resistance. Autonomic dysfunction is a common finding in these patients, being involved in the pathogenesis of the hyperdynamic condition. The aim of our study was to evaluate autonomic function in cirrhotic patients by using the 24 hour Heart Rate Variability study. We also sought to relate the degree of autonomic dysfunction with the severity of the liver disease.
MATERIAL AND METHODS: We studied 22 cirrhotic patients, 50% of whom were male, mean age 44.14 +/- 11.32 years. The etiology was alcohol related in 12 (54.6%), virus hepatitis in 6 (27.2%), autoimmune related in two (9.1%) and other in the remaining two (9.1%). In terms of severity liver disease 6 patients were in Child-Pugh's class A (27.3%), 9 in Child-Pugh's class B (40.9%) and 7 in Child-Pugh's class C (31.8%). Thirteen patients (59%) had ascites. Both patients and 20 age-sex matched healthy volunteers underwent 24 hour ECG Holter study with assessment of Heart Rate Variability (time and frequency domains).
RESULTS: The cirrhotic patients showed severe decrease in Heart Rate Variability when compared to healthy volunteers: SDNN (84.14 +/- 35.78 ms vs 148.9 +/- 33.97 ms; p < 0.0001), pNN50 (3.54 +/- 4.61 vs 11.17 +/- 9.88; p = 0.004). The spectral analysis revealed markedly decrease of average total power, with reduction of all components (VLF, LF, HF), in the absence of significant difference in LF/HF ratio (2.52 +/- 1.40 vs 2.98 +/- 1.57; p = NS). Ascites had relationship with more pronounced autonomic impairment: SDNN (70.31 +/- 30.32 ms vs 104.11 +/- 34.97 ms; p = 0.03). On the other hand, alcohol related etiology did not influence Heart Rate Variability parameters. Moreover, we found significant positive correlations between SDNN (dependent variable) and Prothrombin activity (r = 0.64; p = 0.001), as well as with Serum Albumin (r = 0.40; p = 0.05), but not with Total Bilirubin (r = -0.14; p = 0.51). Prothrombin activity was the only independent predictor of autonomic dysfunction.
CONCLUSION: Chronic liver disease is accompanied by a significant Heart Rate Variability decrease. Alcohol related etiology does not indicate further autonomic dysfunction. The greater the hepatopathy severity, the greater the Heart Rate Variability impairment. Hepatocellular dysfunction indicators have more accuracy to demonstrate autonomic disturbances than cholestasis indicators.