Resynchronisation therapy width in Group I, p = 0.042. Final values of the QRSst and QRSno-st width were lower in Group I, p = 0.015 and p = 0.001 respectively. There are no significant differences in baseline QRS and QRSst between the groups. End-systolic and end-diastolic LV volume significantly decreased in both groups; reduction in the end-systolic volume was greater in Group I compared to Group II, p = 0.039. EF increased in both groups; percentage increase in EF was significantly higher

more »

... Group I, p = 0.048. Functional class (FC) of HF decreased in both groups; the final FC value was significantly lower in Group I, 2.12 versus 2.64 in Group II, p = 0.001. Conclusions: VVD optimization in CRT devices using ECG influences on hemodynamic parameters in the long-term period. The narrowest QRS can be the sign of optimal cardiac synchronization. This safe and reproducible method improves the electrical systole of the myocardium and can adjust the conduction system of ventricles that leads subsequently to a decrease in FC of HF.