Impedance Cardiography and Heart Rate Variability for Long-Term Cardiovascular Outcome Prediction After Myocardial Infarction

Abstract

Background and Objective. The objective of our study was to evaluate the predictive power of a combined assessment of heart rate variability (HRV) and impedance cardiography (ICG) measures in order to better identify the patients at risk of serious adverse events after ST-segment elevation myocardial infarction (STEMI): all-cause or cardiac mortality (primary outcomes) and in-hospital recurrent ischemia, recurrent nonfatal MI, and need for revascularization (secondary outcomes). Material and Methods. A total of 213 study patients underwent 24-hour electrocardiogram (used for HRV analysis) and thoracic bioimpedance monitoring (used for calculation of hemodynamic measures) immediately after admission. The patients were examined on discharge and contacted after 1 and 5 years. Cox regression analysis was used to determine the predictors of selected outcomes. Results. The standard deviation of all normal-to-normal intervals (SDNN) and cardiac power output (CPO) were found to be the significant determinants of 5-year all-cause mortality (SDNN ≤100.42 ms and CPO ≤1.43 W vs. others: hazard ratio [HR], 11.1; 95% CI, 4.48–27.51; P<0.001). The standard deviation of the averages of NN intervals (SDANN) and CPO were the significant predictors of 5-year cardiac mortality (SDANN ≤85.41 ms and CPO ≤1.43 W vs. others: HR, 11.05; 95% CI, 3.75–32.56; P<0.001). None of the ICG measures was significant in predicting any secondary outcome. Conclusions. The patients with both impaired autonomic heart regulation and systolic function demonstrated by decreased heart rate variability and impedance hemodynamic measures were found to be at greater risk of all-cause and cardiac death within a 5-year period after STEMI. An integrated analysis of electrocardiogram and impedance cardiogram helps estimate patient’s risk of adverse outcomes after STEMI.