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

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.