Analysis of the relationship between each index of low HRV in preoperative patients with the main cardiovascular event followed up to 3 months (table 3.31) showed that ASDNN < 30ms increased the frequency of major cardiovascular events by up to 3 months, 4.16 times at follow-up up to 3 months postop (95% CI: 1.14 - 15.14; p < 0.05).