Background and objective: The objective of our study was to investigate whether the combination of markers of heart rate variability (HRV) and impedance cardiography (ICG) help evaluate the risk of in-hospital death, ventricular arrhythmia, or complicated course secondary to myocardial infarction (STEMI) and to clarify whether combined analysis of HRV and ICG improve prognosis of STEMI, comparing 3 groups: 1) diabetic, 2) nondiabetic, and 3) diabetes-unselected patients.
Material and methods: The parameters reflecting heart rate variability and central hemodynamics were estimated from a 24-hour synchronic electrocardiogram and thoracic impedance signal recordings in 232 patients (67 diabetic) on the third day after myocardial infarction. Logistic regression analysis was used to determine the predictors of selected outcomes. Different prognostic models were compared with the receiver operating characteristic curve analysis.
Results: The model consisting of low- and high-frequency power ratio (LF/HF) and cardiac output (CO) was elaborated for the prognosis of in-hospital death in the group 3 (odds ratios [ORs] were 9.74 and 4.85, respectively). Very low-frequency power (VLF), cardiac index (CIN), and cardiac power output (CPO) were the predictors of ventricular arrhythmia in the group 2 (ORs of 1.005, 5.09, and 66.7, respectively) and the group 3 (ORs of 1.004, 3.84, and 37.04, respectively). The predictors of the complicated in-hospital course in the group 1 were the baseline width of the minimum square difference triangular interpolation of the highest peak of the histogram of all NN intervals (TINN) and stroke volume (SV) (ORs of 1.006, and 1.009, respectively); in the group 2, the mean of the standard deviations of all NN intervals for all 5-minute segments of the recording (SDNN index) and CPO (ORs of 1.06 and 2.44, respectively); and in the group 3, SDNN index, VLF, LF/HF, CIN (ORs of 1.04, 1.004, 2.3, and 3.49, respectively).
Conclusions: The patients with decreased HRV and low estimates of central hemodynamics evaluated by ICG are at an increased risk of the adverse in-hospital course of STEMI. The combined analysis of HRV and ICG hemodynamic estimates contributes to the risk assessment of the complicated in-hospital course of STEMI, in-hospital hemodynamically significant ventricular arrhythmia, and in-hospital death secondary to STEMI. The in-hospital prognostic value of the combined estimates of HRV and ICG is lower in the STEMI patients with diabetes mellitus as compared with the nondiabetic patients.