Association of Heart Rate Variability with degree of Liver Fibrosis in Non-Alcoholic Fatty Liver Disease Patients

Introduction: Progression of Non-alcoholic fatty liver disease (NAFLD) leads to development of non-alcoholic steatohepatitis (NASH) with increasing grades of fibrosis. NASH fibrosis has also been linked to increased incidence of death due to cardiac causes, usually sudden death. Cardiac autonomic dysfunction is now a known factor for sudden cardiac death. Heart rate variability (HRV) is a standard method of assessing cardiac autonomic function This study was performed to determine the association between HRV parameters and severity of liver fibrosis in NAFLD patients. Methods: We recruited 82 ultrasonography diagnosed NAFLD patients in this cross-sectional study. They underwent transient elastography with FibroScan machine for evaluating the severity of their liver stiffness measure (LSM). On basis of LSM score these NAFLD patients were divided into 3 groups – NAFLD patients with no fibrosis (n=40), with significant fibrosis (n=23) and those with advanced fibrosis(n=19). All patients also underwent a short term 5-minute HRV assessment. Anthropometric tests and certain biochemical parameters were also performed and analysed in all 3 groups. Results: In HRV, a significant increase was found in Heart Rate and a significant decrease in RR interval found to be associated with increase in severity of liver fibrosis. The median values of root mean square of successive differences (RMSSD), NN50 and pNN50%, high frequency (HF) and normalized HF, all measures of cardiac parasympathetic activity were decreased (though not significantly) in patients of NAFLD with significant and advanced fibrosis. However, measures of sympathetic activity like Low frequency (LF) and normalized low frequency (LF norm) as well as LF/HF ratio (marker of sympatho-vagal balance) displayed a rise (though not significant) with increase in severity of liver fibrosis. Anthropometric measures of weight, BMI and waist circumference (WC) were significantly increased with increase in severity of liver fibrosis. Conclusion: We concluded that increased Heart Rate signifying a high sympathetic and low parasympathetic activity was positively associated and RR intervals were negatively associated with increase in severity of liver fibrosis in NAFLD patients. We also concluded that anthropometric measures of weight, BMI and WC were significantly associated with increase in severity of liver fibrosis. Key words: ANS, Autonomic Nervous System; BMI, Body Mass Index; HRV, Heart Rate Variability; HTN, hypertension; IHD, ischemic heart disease; NAFLD, Non-alcoholic fatty liver disease; NASH, Non-Alcoholic Steatohepatitis; WC, Waist Circumference; ANOVA, Analysis of Variance;