Heart rate variability and biomarkers of systemic inflammation in patients with stable coronary heart disease: findings from the Heart and Soul Study

Abstract

Background: Chronic low-grade systemic inflammation is a key component in atherogenesis. Decreased heart rate variability (HRV), a strong predictor of cardiovascular events, has been associated with elevations in circulating levels of C-reactive protein (CRP), interleukin (IL)-6, and fibrinogen in apparently healthy individuals. We investigated whether decreased HRV is associated with inflammatory markers in patients with coronary heart disease (CHD).

Methods: We studied the relationship between HRV and CRP, IL-6, and fibrinogen in 862 outpatients with CHD. All participants provided fasting blood samples and underwent 24-h ambulatory monitoring to assess time-domain measures of HRV (MeanNN, SDNN, SDANN, and RMSSD). Regression analyses were adjusted for age, sex, ethnicity, body mass index, smoking, diabetes, beta blocker use, and cardiopulmonary history.

Results: MeanNN, SDNN, and SDANN were significantly and inversely associated with CRP and IL-6 levels in age-adjusted models and after adjustment for all covariates (p ≤ 0.02). MeanNN, SDNN, and SDANN were also inversely associated with fibrinogen levels in age-adjusted models (p < 0.03), but not significantly so in multivariable-adjusted models. Reduced vagal modulation of heart rate (RMSSD) was not significantly associated with any inflammatory measures.

Conclusions: Reduced cardiac autonomic control is associated with increased systemic inflammation in patients with stable CHD. This relationship was largely independent of important covariates.

Figures

Fig. 1

Mean ± SE age-adjusted levels of inflammatory markers in patients with low (SDNN a–c) illustrate the age-adjusted mean ± SEM levels of interleukin-6, fibrinogen, and C-reactive protein levels in patients with SDNN < 100 ms (low heart rate variability, HRV) compared to those with SDNN ≥ 100 ms (normal HRV). Data are given in original units (all p < 0.05)