The Association Between Residual Myocardial Ischemia and Heart Rate Variability Early After Acute Myocardial Infarction

Background Residual myocardial ischemia and decreased heart rate variability (HRV) are common findings during the acute phase of acute myocardial infarction. Both signs have been associated with a poor prognosis. The present study investigated the association between residual myocardial ischemia and HRV in the early phase after AMI. Patients and Methods Seventy‐four patients were monitored with ambulatory electrocardiography during 23 ± 1 hours, 4 ± 1 days after AMI. In addition, 24 healthy individuals (controls) with similar age and gender were also monitored. HRV was computed in time and frequency domains. Residual myocardial ischemia was defined as the presence of ST‐segment depression during ambulatory electrocardiography, defined as a 0.1 mV horizontal or downsloping ST‐segment deviation from the reference level, elapsing 1 minute or longer, measured 80 ms after the J point. Results Residual myocardial ischemia was found in 22 (30%) patients. Some time‐domain and all frequency‐domain measures of HRV were lower in patients showing residual myocardial ischemia compared with those without residual myocardial ischemia. All time‐ and frequency‐domain measures of HRV were higher in controls compared with patients with residual myocardial ischemia. Only SDNN and low frequency band values were lower in patients without residual myocardial ischemia compared with healthy controls. Both residual myocardial ischemia and a decreased HRV were associated with poor in‐hospital outcome. Conclusions Patients showing residual myocardial ischemia during ambulatory electrocardiography performed early after AMI had lower values of HRV compared with those without residual myocardial ischemia. The causality between these findings are not still defined and deserve further research.