Characteristics of heart rate variability in patients with acute coronary syndrome without ST segment elevation in comparison with clinical and biochemical parameters

BACKGROUND: The search for rational methods of primary, secondary, and tertiary prevention of coronary heart disease. To date, there are several publications on heart rate variability in ischemic heart disease.

AIM: To study the state of the regulatory systems in the organism of patients with acute coronary syndrome without ST segment elevation based on the heart rhythm, and their relationship with the clinical, biochemical and instrumental parameters of the disease.

MATERIALS AND METHODS: The open comparative study included 76 patients (62 men, 14 women) of mean age, 61.0 ± 0.9 years, who were admitted to the Emergency Cardiology Department diagnosed of acute coronary syndrome without ST segment elevation. On admission, cardiointervalometry was performed using Varicard 2.51 apparatus, and a number of clinical and biochemical parameters were evaluated

RESULTS: Multiple correlations of parameters of heart rate variability and clinical, biochemical and instrumental parameters were observed. From this, a cluster analysis of cardiointervalometry was performed, thereby stratifying patients into five clusters. Two extreme variants of dysregulation of the heart rhythm correlated with instrumental and laboratory parameters. A marked increase in the activity of the subcortical nerve centers (maximal increase of the spectral power in the very low frequency range with the underlying reduction of SDNN) in cluster 1 was associated with reduction of the left ventricular ejection fraction: cluster 1–47.0 [40.0; 49.0], cluster 2–60.0 [58.0; 64.0], cluster 3–60.0 [52.5; 64.5] % (the data are presented in the form of median and interquartile range; Me [Q25; Q75], p < 0,05). Cluster 5 showed significant reduction in SDNN (“monotonous rhythm”), combined with increased level of creatine phosphokinase (CPC): cluster 5–446,0 [186.0; 782.0], cluster 4–141.0 [98.0; 204.0] IU/l; Me [Q25; Q75], p < 0.05) and MВ-fraction of creatine phosphokinase; cluster 5–32.0 [15.0; 45.0], 4 cluster 4–12.0 [9.0; 18.0] IU/l; Me [Q25; Q75], p < 0.05).

CONCLUSIONS: In patients with acute coronary syndrome without ST segment elevation, cluster analysis of parameters of heart rate variability identified different peculiarities of regulation of the heart rhythm. Pronounced strain of the regulatory systems of the body was found to be associated with signs of severe pathology: the predominance of VLF (spectral power of the curve enveloping a dynamic range of cardiointervals in the very low frequency range) in spectral analysis with an underlying reduced SDNN is characteristic of patients with a reduced ejection fraction, and a “monotonous rhythm” is characteristic of patients with an increased level of creatine phosphokinase and MB-fraction of creatine phosphokinase.