Effect Of Intra-abdominal Fat On Autonomic Nervous Function In Patients With Hypertension

The clinical study confirmed that obesity and hypertension are closely related, In1948World Health Organization, obesity was included in the ranks of diseases, and considered as the risk factors for hypertension, diabetes and coronary heart disease. Currently the prevalence of hypertension also increased dramatically, among patients with obesity and hypertension, this two factors influence each other, leading to the cardiovascular system damage aggravated. Therefore, prevention of obesity hypertension appearance has clinical significance. The traditional diagnostic indicators of obesity are including waist circumference, body mass index, waist to hip ratio, et al. In recent years, ultrasound technology has been applied to the detection of abdominal fat, which can be diagnosed according to the thickness of abdominal fat. As a measure of cardiac autonomic nervous system function indicators, heart rate variability can be used to predict the risk of long-term cardiovascular events for patients. There is seldom report about use of heart rate variability as the cardiovascular system damage indicators. This study mainly explored the impact of obesity hypertension on cardiac autonomic nervous system.Objective:To investigate the relationship between waist circumference, intra-abdominal fat and cardiac autonomic nerve function in patients with hypertension The object of study: Select patients in our department from May2009to May2010,353cases of hypertensive patients, including197cases of male and female156cases; mean age55±13years of age. Diagnosis of hypertension is in accordance with the standards of the1999WHO/ISH guidelines; intra-abdominal fat accumulation is judged based on the ultrasound measurements of intra-abdominal fat thickness. Exclusion criteria: hyperthyroidism, secondary hypertension, infection, myocardial infarction, NYHA class II and above, heart failure, arrhythmia, Diabetes Mellitus.Methods:1. measurement of hypertension and waist circumference:according to2005chinese hypertension guide:The mercury sphygmomanometer measured sitting right arm blood pressure. there is a personal determination of body mass index, waist circumference. According to waist circumference value divided into abdominal fat groups and normal group.(waist circumference of men≥90cm, waist circumference of female≥85cm).2. measurement of biochemical indicator:All patients, after eight hours fasting, take the vein blood check at8-9containing total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL)-cholesterol, low density lipoprotein (LDL)-cholesterol and blood sugar.3. measurement of Intra-Abdominal Fat:In our own laboratory for examination rooms, HY260L ultrasound B-ultrasound determination of the B value of intra-abdominal fat thickness (peritoneum lines the middle to the abdominal aorta anterior wall distance), and A-value of abdominal fat. According to the intra-abdominal fat ultrasonic thickness males≥38.5mm, women≥34.7mm, divided into intra-abdominal fat accumulation group and normal group of intra-abdominal fat; quartile (15.6mm,27.1mm,38mm) method in accordance with the thickness of the intra-abdominal fat is divided into four groups to compare heart rate variability differences between the groups.4. measurement of heart rate variability:Using CB type dynamic ECG analysis system to monitor the24-hour ECG, calculating heart rate variability (standard deviation of all sinus RR interval (SDNN, reflecting the total nervous tension), standard deviation of the average RR interval every5min (SDANN, reflecting sympathetic tone), difference between adjacent RR interval root-mean-square (RMSSD, reflecting vagal tone), percentage of differences between successive RR intervals that are greater than50msec (PNN50) and the standard deviation of NN between the average (SDNN index)) as a reflection of the patients with cardiac autonomic function indicators.5.Statistical method:all measurement data indication by mean±standard deviation, Compared of measurement data in obese group with normal group,and intra-abdominal fat accumulation group with normal intra-abdominal fat group used independent sample T-test. quartile grouping according to the Intra-abdominal fat thickness, Compared of interclass with heart rate variability used one-factor analysis of variance (ANOVA). influencing factors analysis with heart rate variability used Linear regression analysis. P<0.05indicated statistical significance.Results:1、In all patients with hypertension the SDNN and SDANN in the obese group was significantly lower (P<0.05) compared with the normal group. Compared male obesity group with normal group, there were not statistically difference of the heart rate variability time domain indexes. The SDNN and SDANN of the female obese group was significantly lower than the normal group (P<0.05).2、In all hypertensive patients, the SDNN, SDANN, RMSSD and SDNN in intra-abdominal fat accumulation group was significantly lower (P<0.05) when compared with normal intra-abdominal fat group. In male intra-abdominal fat accumulation group, the RMSSD and SDANN were lower than the intra-abdominal fat normal group, and this was statistically significant (P <0.05). The SDANN and SDNN of female intra-abdominal fat accumulation group was significantly lower (P<0.05) than the intra-abdominal fat normal group.3、quartile grouping analysis according to the Intra-abdominal fat thickness shows that with the increase of intra-abdominal fat thickness, the heart rate variability was significantly lower:the pNN50, SDNN, SDANN, RMSSD, SDNN index of intra-abdominal fat thickness38mm～group was significantly decreased than the～15.5mm group (P<0.05); the pNN50, SDNN, SDANN, RMSSD of group38mm was significantly lower (P<0.05) when compared with15.6～27.0mm group. The SDNN and SDNN index was significantly lower in27.1～38mm and15.5mm groups (P<0.05); the SDNN was significantly lower in27.1～38mm group and15.6～27.0mm group (P<0.05).4、Linear regression analysis showed that:B value of intra-abdominal fat thickness, fasting plasma glucose (FPG), gender seemed as the independent influencing factors of SDNN. B value of intra-abdominal fat thickness and gender seemed as the independent influencing factors of SDANN. B value of intra-abdominal fat thickness, fasting glucose and diastolic blood pressure seemed as independent influencing factors of SDNN index.Conclusion:1、Abdominal obesity significantly reduced heart rate variability in patients with hypertension; the abdominal obesity influence for heart rate variability on female is more than that on male.2、Abdominal fat accumulation was significantly lower the heart rate variability in hypertensive patients; this effect was no significant difference in patients with different sexes.3、Intra-abdominal fat accumulation is an independent risk factor of the key indicators of heart rate variability in hypertensive patients.