Mechanical dyssynchrony in patients with chronic heart failure and left bundle branch block

Background. The main problem in patient selection for cardiac resynchronization therapy (CRT) is the lack of unified approaches to the definition of mechanical dyssynchrony (MD) and selection criteria, particularly, in patients with left bundle branch block (LBBB). Aim: To study mechanical dyssynchrony indices and three-dimensional Echo (3DE) criteria of global and local contractility function in patients with chronic heart failure (CHF) and LBBB during different types of isolated left ventricle (LV) pacing. Methodology and Research Methods . The experimental intraoperative study involved 88 points obtained from 12 patients with CRT class IA indications and LBBB. During isolated LV pacing as part of CRT implantation procedure endocardial and epicardial pacing were obtained. Transesophageal Echo (TEE) cineloops recording and paced QRS complex morphology registrations by means of LabSystem Pro Electrophysiological Recording System (Bard Electrophysiology, USA) were performed during each stimulation episode. Philips Qlab 10 software was used for TEE data analysis. Results. The global (3D EF, 23.8 [22; 28.4], GLS, –5.33% [10.90%; –15.4%]) and local contractility (ExсAvg 3.5 [2.1; 5.6]) criteria and dyssyncrony indices (SDI-16, 14.9 [8.9; 23.1]) showed severe systolic dysfunction and intraventricular dyssynchrony – typical signs in this patient group, and differed significantly (3D EF, p = 0.003; GLS, p = 0.004; ExcAvg, p < 0.001; Tmsv-6 SD, р = 0.03) depending on the stimulation method and site. A moderate direct correlation between SDI-16 and the QRS duration (common electical dyssynchrony criterium) and inverse correlation with ExcAvg and 3D LVEF also describes LV response.