Relationship between electrical myocardial instability and postinfarction remodeling in patients with ST-segment elevation myocardial infarction

Abstract

Aim      To study the clinical value of markers for myocardial electrical instability in combination with echocardiographic parameters for predicting the risk of cardiovascular complications (CVC) in the postinfarction period.Material and methods  This study included 118 patients with ST segment elevation myocardial infarction (STEMI) and hemodynamically significant stenosis of one coronary artery. A percutaneous coronary intervention (PCI) with stenting of the infarct-related artery was performed for all patients. On day 7-9 and at 24 and 48 weeks after the treatment, ECG Holter monitoring was performed, which included analyses of ventricular late potentials, dispersion of QT interval duration, heart rate turbulence (HRT) and variability (HRV), and heart chronotropic load (HCL). At baseline and during postinfarction week 12, all patients underwent echocardiography with calculation of indexes of end-diastolic volume (iEDV) and end-systolic volume (iESV) to verify the signs of left ventricular (LV) myocardial remodeling. The criteria for LV pathological remodeling included increases in iEDV >20 % and/or iESV >15 % at 12 weeks after STEMI. The group without remodeling, R(-), consisted of 79 (67 %) patients and the group with signs of LV pathological remodeling, R(+), consisted of 39 (33 %) patients. Quality of life and achieved endpoints were evaluated during 144 weeks.Results By week 48 in group R(-), the stabilization of electrical processes in the myocardium was more pronounced as indicated by a decrease in HFLA by 12 % (р=0.004) and by a fourfold increase in RMS (р=0.047). Only in this group, the baroreflex sensitivity restored; pathological ТРС decreased from 20 to 5% (p=0.002) by the end of the active treatment. Stabilization of the repolarization phase duration in various parts of the myocardium was more active in patients without pathological remodeling as shown by decreases in disp QTa (р=0.009), disp QTe (р=0.03), sd QTa (р=0.006), and sd QTe (р=0.009). This was not observed in the group R(+). The recovery of vagosympathetic balance due to leveling the sympathetic component also was more effective in the group R(-), which was reflected in increased spectral and temporal HRV indexes (р<0.05). Both groups showed reduced HCL values at 24 weeks (р=0.047 and р=0.006); however, the HCL regression remained also at 48 weeks only in the group R(-) (р=0.006). Group R(-) patients reported higher quality of life (р=0.03) than group R(+) patients. Endpoints were achieved more frequently in the group R(+): 87.1 % vs. 27.8 % (odds ratio, 11.8; 95 % confidence interval, 4.6–30.8; р=0.00001).Conclusion      Pathological myocardial remodeling in early postinfarction period is associated with electrophysiological instability of the myocardium, which results in the development of CVC and low quality of life in patients with STEMI.