Optimization of cardiac resynchronization therapy according to the surface ECG

Abstract

Background: Atrioventricular and interventricular delay (VVD) optimization is an important part of CRT correction. The lack of this procedure or incorrect performance may reduce the positive effect of cardiac resynchronization and enhance Heart Failure (HF). Widely used selection of VVD methods with different ways of echocardiography requires special skills and time-consuming. Aim: To assess the impact of VVD optimization in CRT devices based on changes in the width of the QRS complex using ECG on intracardiac hemodynamic parameters in the long-term period. Materials and methods: 96 patients after CRT implantation were divided into 2 groups (I - with selection of VVD, n=48, II - without selection of VVD, n=48) with sinus rhythm, complete left bundle branch block, ejection fraction (EF) ≤35%.QRS complex was measured before CRT implantation (QRSown), then every 6 months: QRS measurement in the temporary device suppression mode (QRSno-st), measuring the width of the stimulated QRS complex (QRSst) during the VVD optimization process. VVD selection was implemented by gradual change the delay time of stimulation of the right/left ventricle (from 0 to 40 ms) and simultaneous measurement of the stimulated QRS width on ECG. The final VVD result was assumed to the narrowest QRS. Echocardiography was performed in all patients before CRT implantation and then every 6 months. Observation period was 2 years. Results: For 24 month follow-up there was significant reducion in the QRSst 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 in 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.