Abstract 2820: Distribution Of Latest Activation Site In Patients With Different QRS Configurations Undergoing Cardiac Resynchronization Therapy
Background Maximum effect of cardiac resynchronization therapy (CRT) may be achieved when the left ventricular lead is placed at the site with greatest activation delay. Speckle-tracking radial strain analysis has been opposed as a new echocardiographic technique to asses LV dyssynchrony. This study aimed to identify the site of latest activation with speckle-tracking in a large group of patients and to investigate the distribution of these segments in different QRS configurations.
Methods Two hundred and forty-eight consecutive heart failure patients (191 male, 55% ischemic cardiomyopathy, ejection fraction 23 ± 7%) undergoing CRT were included. Before device-implantation, a 12 lead ECG and 2D echocardiogram was obtained in all patients. Patients were divided into five different QRS configuration subgroups: narrow QRS, left bundle branch block (LBBB), right bundle branch block (RBBB), intraventricular conduction delay (IVCD) and right ventricular (RV)-pacing. LV dyssynchrony was assessed using speckle-tracking radial strain analysis on the LV short-axis view at the level of the papillary muscle. Time of segment activation was defined as the time between QRS onset to peak radial strain, LV dyssynchrony as time between peak radial strain of the earliest and the latest segment.
Results In all patients, site of latest activation was predominantly located in the lateral (27%), posterior (26%) and inferior (20%) segments. Mean time to peak radial strain was different between segments (posterior 432ms, lateral 426ms, inferior 400ms, anterior 394ms, septal 353ms, anteroseptal 343ms, p<0.001). Distribution of latest activation site was not unequal in the narrow, RBBB and IVCD subgroups, whereas segments of latest activation were unequally distributed in the LBBB en RV-pacing subgroups, p=0.001 and p<0.001 respectively. No difference in extent of LV dyssynchrony between different QRS subgroups was observed.
Conclusion Site of latest activation is unequally distributed in heart failure patients undergoing CRT, with the lateral, posterior and inferior segments taking up 73% of total latest segments. Distribution is also unequal in patients with LBBB or with RV-pacing. There is no difference in extent of dyssynchrony between QRS configurations.