Abstract P399: The Relationship Between Heart Rate Variability and Common Carotid Artery Intima-media Thickness. The ELSA-Brasil
Authors: Hoshi Rosangela , LOTUFO Paulo A , Santos Itamar S , Goulart Alessandra C , Mill Jose-Geraldo , Dantas Eduardo , Andreao Rodrigo , Bensenor Isabela M 
Published: March 2020

Background:
Both conditions as a more width common carotid artery intima-media thickness (cIMT), and a low heart rate variability (HRV) have been associated with cardiovascular health-adverse outcomes. Although previous studies have somehow explored the relationship between these markers, they have not credited the influences exerted by factors such as aging, demographics, and lifestyle variables.

Aim:
to investigate whether cardio autonomic alterations are accompanied or not by subclinical atherosclerosis, in apparently healthy men and women aged 35 to 74 years-old examined at the baseline of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

Methods:
The Heart Rate Variability was evaluated on 5-min segments of beat-to-beat heart rate recordings using linear time and frequency domain analyses. The c-IMT images were performed using a Toshiba (Aplio XG™) with a 7.5 MHz linear transducer. The c-IMT was measured in the outer wall during three cardiac cycles. The images were analyzed with specific software (MIA™, Coralville, IA). For this study, c-IMT was defined as the average between the mean left and mean right c-IMT values, and it was analyzed as a continuous and categorized variable (P<75 or P >= 75). Multiple linear models using continuous variables and multivariate logistic regression with categorized cIMT and HRV quartiles were performed.

Results:
Out of 7,201 participants eligible for analyses, 1,685 (23.4%) presented cIM >= 75th percentile. We found significantly reduced HRV variables in subjects with cIMT>=P75 in comparison to those with cIMT<P75: standard deviation of NN interval (SDNN) 33.0 ms
vs.
37.0ms( P< 0.001); root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) 22.0 ms
vs.
26.0ms (P< 0.001); Low-Frequency 191.0ms
2
vs.
260.0ms
2
( P< 0.001); High-Frequency 164.0 ms
2
vs.
238.5ms
2
( P< 0.001). In a crude analysis, an increased Odds Ratio (OR)and 95% Confidence Intervals for cIMT >=P75 was verified within the lowest two quartiles of Low-Frequency:1st quartile, OR = 1.75 (95%CI: 1.39 to 2.19); 2nd quartile, OR= 1.53 (1.25 to 1.87).The same was observed for High-Frequency:1st quartile, OR = 1.94 (1.38 to 2.73); 2nd quartile, OR= 1.60 (1.20 to 2.15). However, those associations did not remain after adjustments for anthropometric and clinical variables for Low-Frequency (1st quartile, OR= 1.08 (0.83 to 1.40); 2nd quartile, OR= 1.22 (0.97 to1.55), and for High Frequency, 1st quartile, OR= 1.16 (0.77 to 1.73); 2nd quartile, OR= 1.17 (0.83 to 1.64).

Conclusions:
Subjects with cIMT greater or equal to 75th percentile presented lower HRV values. However, no independent relationships were detected between cIMT and HRV after multivariate adjustment, suggesting that they may assess different and complementary domains and provide relevant, useful, and non-redundant information of cardiovascular risk.