5-Year Results of Atrioventricular and Interventricular Delay Optimization in CRT Devices by ECG

Purpose: To assess the impact of atrioventricular (AVD) and interventricular delay (VVD) optimization in CRT based on changes in PR interval and the width of QRS using ECG on hemodynamic parameters in the five-year period.

Materials and methods: The sub-analysis of 54 patients (pts) in sinus rhythm after CRT implantation with AVD and VVD optimization in the long-term period. Pts were randomized into 2 groups: 1) AVD and VVD optimization, 2) only AVD optimization. Standard follow-up protocol, echocardiography and optimization of AVD, VVD were carried out every 6 months. The sub-analysis inclusion criteria: CRT implantation period ≥5 years, absence of electrode dislocations, stable device sensitivity and stimulation. According to criteria there were 26 pts in Group I, 28 pts in Group II. The optimal sensed/paced AV interval was assumed to the finished symmetrical intrinsic/stimulated P wave respectively, without isoline before biventricular QRS (bivQRS). VVD optimization was implemented by gradual change of stimulation delay time of the right/left ventricle (from zero to 40 ms) and simultaneous measurement of bivQRS on ECG. The final VVD result was assumed to the narrowest bivQRS.

Results: There was no differences in baseline QRS and bivQRS as well as etiology of cardiomyopathy. The mean observation period was 6.3±1.1 years. There has been significant reduction in the bivQRS width in all 54 pts, p=0.037. Final values of the bivQRS and the intrinsic QRS width were lower in Group I, p=0.026 and p=0.048 respectively. Echocardiography parameters significantly decreased only in Group I. LV end-systolic volume was less in the Group I than the Group II, p=0.045. EF increased in both groups; the degree of EF increase was higher in Group I, p=0.029.

Conclusions: AVD and VVD optimization both influence on hemodynamic parameters in the long-term period. VVD optimization makes a contribution in response to CRT. The narrowest QRS complex can be the sign of optimal cardiac synchronization.