State of nonspecific adaptive mechanisms

of the body, assessed by heart rate variability,

in patients with acute coronary syndrome

depending on its type and outcome

Girivenko A.I., Smirnova E.A., Nizov A.A., Lapkin M.M., Trutneva E.A., Yunevich D.S.

The problem of acute coronary syndrome (ACS) remains relevant. Despite obvious progress in treatment, the medium and longterm prognosis remains unfavorable.

Patients with ACS belong to the veryhighrisk category for complications, which necessitates the search for additional markers of adverse longterm outcomes.

Aim — to study the state of nonspecific adaptive mechanisms (NAM) of the body using heart rate variability (HRV) parameters in patients with ACS and to compare these data with disease outcomes.

Materials and methods. This open prospective study included 151 patients with ACS (122 men, 29 women), median age 62.0 [55.0; 69.0] years, divided into 3 groups:

Group 1 — ACS with persistent STsegment elevation;

Group 2 — ACS without STsegment elevation who underwent percutaneous coronary intervention; Group 3 — ACS without STsegment elevation managed conservatively.

The state of NAM was assessed by HRV parameters on admission. Longterm outcomes were evaluated by telephone interview 1 year after hospitalization. The primary endpoint was hospitalization for any form of ACS and/or allcause death within 1 year.

Results. In patients with ACS without STsegment elevation who received only conservative treatment and in patients with unstable angina, heart rate was lower compared to patients with ACS without STsegment elevation who underwent percutaneous coronary intervention. No statistically significant relationship was found between HRV parameters and ACS outcome. Cluster analysis identified 4 clusters with different regulatory features: Cluster 1 was characterized by maximal reduction in HRV; Cluster

2 — pronounced centralization of heart rate regulation; Cluster 3 — predominance of autonomic loop regulation over central; Cluster 4 — predominance of vasomotor center activity. In Clusters 1 and 2, with the greatest strain on NAM, a higher number of hospitalizations for ACS and

deaths were observed during the 1 year followup.

Conclusion. Cluster analysis allows identification of ACS patients with different degrees of NAM strain. Greater NAM strain is characteristic of patients with myocardial infarction and is associated with an unfavorable prognosis during 1 year followup, while the association of patient status in the identified clusters with prognosis is stronger than that of individual HRV parameters.

Keywords: heart rate variability, state of nonspecific adaptive mechanisms of the body, acute coronary syndrome,

cluster analysis, prognosis.

For citation: Girivenko AI, Smirnova EA., Nizov AA et al. The state of the body’s nonspecific adaptive mechanisms, assessed by heart rate variability, in patients with acute coronary syndrome, depending on its type and outcome. International Heart and Vascular Diseases Journal. 2026; 14(51):19-25. DOI: 10.24412/2311-1623-2026-51-25-33