The peculiarities of changes in myocardial electrical activity and heart rate variability in patients with coronary artery disease depending on the stage of concomitant iron deficiency

Abstract

The aim of the study: to assess changes in myocardial electrical activity and heart rate variability (HRV) in patients with coronary artery disease (CAD) depending on the stage of iron deficiency (ID) and identify their relationship with ferrokinetic parameters. Materials and methods. In total, 90 patients with CAD, stable angina II–III FC were examined (men – 35, women – 55, age – 69 (61; 72) years). The patients were divided into 4 groups: the 1st group (n = 16) consisted of patients with concomitant ID anemia (IDA) of mild and moderate severity, the 2nd (n = 15) – with latent ID, the 3rd (n = 14) – with functional ID, the 4th (n = 45) – patients with CAD without iron metabolism disorders. The HRV features during 24 hours, daytime and nighttime as well as their relationships with ferrokinetic and hematological parameters were analyzed. The data analysis was performed using Statistica 13.0. Results. CAD patients with concomitant IDA demonstrated a tendency to have a higher average daytime heart rate value (U = 14.0; p ≈ 0.08), a longer duration of tachycardia (U = 20.0; p ≈ 0.06), and a significantly greater number (2.4 times) of ventricular extrasystoles (VE) (U = 7.0; p < 0.05) compared to patients without iron metabolism disorders. There were no statistically significant differences in heart rate, episodes of tachycardia, and the number of arrhythmic events in CAD patients with different stages of ID. During the temporal analysis of HRV indicators, patients with different stages of concomitant ID demonstrated a decrease in overall HRV due to SDNN-index, rMSSD (%) and HRVT triangular index both in active and passive periods as compared to patients without iron metabolism disorders. Spectral analysis of HRV has revealed reduced parasympathetic activity of the autonomic nervous system due to HF indicator in patients of the 1st–3rd groups. The presence of concomitant IDA was characterized by maximum changes in HRV indicators and the predominance of central mechanisms of HRV regulation over autonomic ones, which was confirmed by a significant increase in the centralization index (IC) and stress index (SI). For CAD patients with concomitant IDA and latent ID, a number of relationships between ferrokinetic and HRV parameters was found. There were no statistically significant correlations between indicators of iron metabolism and HRV in patients with CAD and functional ID. Conclusions. The decrease in iron stores in the body due to its tissue and transport reserves is accompanied by changes in the myocardial electrical activity, a progressive reduction in heart rate variability, autonomic dysfunction towards a suppression of the parasympathetic domain activity, confirming the relevant correlations with the ferrokinetic parameters.