The Association of Left Ventricular Lead Position Related to Regional Scar by Speckle-Tracking Echocardiography with Clinical Outcomes in Patients Receiving Cardiac Resynchronization Therapy

Abstract

Response to cardiac resynchronization therapy is variable. The aim of this study was to test the hypothesis that left ventricular (LV) lead position in proximity to myocardial scar is associated with less favorable outcomes. A total of 149 patients were included in this substudy of the Speckle Tracking Assisted Resynchronization Therapy for Electrode Region trial using echocardiographic radial strain for basal and middle LV segments and transverse strain for apical segments to estimate scar. Sixty-four patients with high-dose rest (99m)Tc sestamibi single-photon emission computed tomographic imaging were used for validation in 508 LV free-wall segments. The relationship of LV lead position to segments estimated as scar was defined as concordant, adjacent, or remote. The prespecified primary end point was heart failure hospitalization or death over 2 years. Wall thickening < 10% by radial strain in LV free wall segments was associated with absent (99m)Tc sestamibi uptake indicative of scar with 77% sensitivity and 89% specificity and strain < 10% was accordingly used as the surrogate for scar. Event-free survival was most favorable in patients with nonischemic disease (79%), similarly favorable in patients with ischemic disease and LV leads remote from scar (74%), but significantly worse in patients with ischemic disease and LV leads adjacent to (61%) or within scar (41%) (P= .004). Preserved wall thickening at the LV lead site was independently associated with favorable outcome and additive to pacing at the site of latest mechanical activation (P= .001) and remained significant after adjusting for scar burden. Echocardiographic speckle-tracking strain has the potential to estimate free wall scar in patients with ischemic cardiomyopathy and influence LV lead positioning away from scar to improve clinical outcomes after cardiac resynchronization therapy.