Methods to increase clinical applicability of heart rate variability analysis for noninvasive detecting severity of coronary lesions in patients with coronary heart disease

Recently, Feng et al. (1) published an article entitled “Altered heart rate variability depends on the characteristics of coronary lesions instable angina pectoris” in Anatol J Cardiol, where they have shown that the parameters of heart rate variability (HRV) are associated with the severity of coronary lesions in patients with stable angina pectoris. Noninvasive detecting the severity of coronary lesions in patients with coronary heart disease (CHD) including stable angina pectoris is a very important problem. The authors have used time domain parameters and have not used frequency-domain indices in their study (1). However, the time and frequency domain indices of HRV complement each other for heart autonomic control assessment (2). The absence of analysis of frequency domain indices restricts the interpretation of results of the study. In addition, the authors have not provided any information on duration and other parameters of electrocardiogram (ECG) recording used in their analysis of HRV. Feng et al. (1) revealed statistically significant differences between the patients with different severity of coronary lesions. However, despite statistical significance of these differences, the group distributions of HRV parameters in their tables 3-5 substantially overlap with each other. This reduces the clinical applicability of the study results. The clinical applicability can be improved by using various autonomic parameters and different functional tests (load test, breathing test, etc.). In our study (3), we studied the frequency estimates of HRV in the low and high frequency spectral bands in CHD patients with different severity of coronary lesion during bicycle exercise test. We have revealed the static differences between the patients with different coronary lesion that agree in general with Feng et al. (1) and have shown the adaptation potential of heart autonomic control in these patients (3). Similar approach can be used to improve the clinical reliability of load test (4), which is often used in patients with coronary lesions (5).