The Influence of Cardiovascular and Metabolic Variables on Autonomic Nervous System Activity

Abstract

Multiple factors influence the balance of parasympathetic (PS) and sympathetic (SY) drive in the autonomic nervous system (ANS). Root mean square of successive differences of R-R intervals (RMSSD), is a linear metric obtained during the assessment of heart rate variability (HRV) and represents PS input to the heart. Systolic time intervals (STI) assessed via pre-ejection period (PEP, the time from the start of the QRS complex to the opening of the aortic valve), are a non-invasive measure that reflects SY activity at rest. PURPOSE:To investigate the effects of biological variables typically associated with metabolic syndrome on ANS activity as measured by RMSSD and PEP. METHODS: Utilizing the Atherosclerosis Risk in Communities (ARIC) dataset, 1,216 subjects (62.8% female, 74±4.8yrs) free from known cardiovascular disease, hypertension, myocardial infraction, and diabetes, not currently taking beta-blockers, and non-smokers were evaluated for fasting glucose (FBG) and insulin (FI) concentrations, waist circumference (WC), blood pressure (BP), RMSSD and PEP. Simultaneous 5-minute recordings of resting ECG, carotid arterial pulse, and phonocardiogram were used to assess PEP and RMSSD. FBG, FI, and WC inferred a latent variable termed glucose management (GM), where pulse and diastolic BP inferred a latent variable termed cardiac control (CC). Path analysis assessed the relationship between latent variables and RMSSD and PEP, after controlling for age, race, and sex. RESULTS: The model fit was acceptable (root mean square error of approximation = 0.108 [90% CI = .098, .118], comparative fit index = .649, and standardized root mean square residual = .07), with CC positively associated with PEP (β = .27, p <.01), but negatively associated with RMSSD (β = -.41, p <.01). Contrary to CC, GM was negatively associated with PEP (β = -.18, p <.01), but positively associated with RMSSD (β = .20, p <.01). CONCLUSIONS:Latent variables (CC and GM) in this model show opposing associations with RMSSD and PEP, suggesting that the metabolic syndrome risk factors included influence HRV and STI.This Abstract was prepared using ARIC Research Materials obtained from the NHLBI Biologic Specimen and Data Repository Information Coordinating Center and does not necessarily reflect the opinions or views of the ARIC or the NHLBI.