Study On The Correlation Between Heart Rate Variability And Vascular Calcification In Uremia Patients

Objective: The incidence of uremia is rising year by year, cardiovascular disease is a common complication as well as the leading cause of death in uremia patients.Cardiologists found that the decrease of heart rate variability is closely related to cardiovascular mortality. Nephrologists found that decline of heart rate variability is common in uremic patients. Uremic patients are easily to suffer from vascular calcification and decline of heart rate variability, which are intimately related to cardiovascular disease. The aim of this article is to study the relationship of heart rate variability and vascular calcification in uremia patients, in order to prevent calcification and improve outcomes of this huge group.Methods: We selected 30 uremia patients who were hospitalized from December2013 to February 2015, in Department of Nephrology, First Affiliated Hospital of Dalian Medical University. Inclusion criteria: patients meet the standard definition of CKD from American K/DOQI, and their eGFR which was calculated according to MDRD formula, reached stage 5. All the selected candidates agreed to the study protocol and signed informed consent. Exclusion criteria: cardiac diseases that affect this research, acute myocardial infarction, acute heart failure, primary myocardiopathyand severe arrhythmia; primary osteoporosis and other diseases that affect the metabolism of calcium and phosphate; patients with parathyroidectomy or primary hyperparathyroidism or other diseases that affect the autonomic nervous function;malignant tumor. The clinical data of the candidates were recorded, as well as other biochemical indicators such as serum Cre, BUN, ALB, Ca, P, TG, TC, LDL-C, HDL-C,iPTH and 25 OHD. Using 24-h dynamic electrocardiogram to get the heart rate variability, such as the standard deviation of the Normal to Normal intervals(SDNN),the standard deviation of the average NN intervals calculated over 5 minutes(SDANN),the square root of the mean squared differences of successive NN intervals,(RMSSD).The uremia patients received coronary CT scans to determine coronary arterial calcification score(CACS) and received whole abdominal CT scans to calculate abdominal aortic calcification index(AACI). Statistical analysis: The data was analyzed by SPSS.19.0 software. Differences between mean values of two groups were assessed by t-test; Differences between multiple groups were evaluated by single factor analysis of variance. Pearson’s correlation coefficient was used to test the association between two kinds of parameters. P<0.05 was considered statistically significant.Results: Compared with the normal reference value provided by Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, the SDNN(78.40±24.30 vs 141±39) 、 SDANN(88.94±42.80 vs127±35) of uremia patients are significantly lower(P<0.01), while no difference was found regarding to RMSSD. Coronary arterial calcification was showed in 13 of 27(48%) uremia patients, and with higher CACS, more coronary artery branches are affected. There is no statistical significance in heart rate variability indexes between groups with or without coronary arterial calcification. And no statistical significance was found in the groups with different degree of coronary artery calcification. 81% of the patients who received whole abdominal CT scans were found with positive abdominal aortic calcification. No statistical significance of heart rate variability wasfound in those uremia patients with positive or negative abdominal aortic calcification,or with different degree of abdominal aortic calcification, respectively. Next we studied the correlation of heart rate variability with coronary artery calcification, lower segment and intact abdominal aortic calcification, and no statistical correlation was found. Finally, we detect difference of the heart rate variability indexes in groups with or without diabetes mellitus, and found no statistical significance. We found that the CACS(542.19±1073.34 vs 49.66±118.16) of patients with diabetes mellitus was higher than the other group, with statistical significance.Conclusion: Compared with the normal people, people with uremia have lower heart rate variability. There is no correlation between heart rate variability and vascular calcification in uremia patients.