Influence of Pacing Site Characteristics on Response to Cardiac Resynchronization Therapy

Abstract

screened for study eligibility. Inclusion criteria were the following:Background-Transmural scar occupying left ventricular (LV) pacing regions has been associated with reduced response to cardiac resynchronization therapy (CRT). However, spatial influences of lead tip delivery relative to scar at both pacing sites remain poorly explored. This study evaluated scar distribution relative to LV and right ventricular (RV) lead tip placement through coregistration of late gadolinium enhancement MRI and cardiac computed tomographic (CT) findings. Influences on CRT response were assessed by serial echocardiography. Methods and Results-Sixty patients receiving CRT underwent preimplant late gadolinium enhancement MRI, postimplant cardiac CT, and serial echocardiography. Blinded segmental evaluations of mechanical delay, percentage scar burden, and lead tip location were performed. Response to CRT was defined as a reduction in LV end-systolic volume ≥15% at 6 months. The mean age and LV ejection fraction were 64±9 years and 25±7%, respectively. Mean scar volume was higher among CRT nonresponders for both the LV (23±23% versus 8±14% [P=0.01]) and RV pacing regions (40±32% versus 24±30% [P=0.04]). Significant pacing region scar was identified in 13% of LV pacing regions and 37% of RV pacing regions. Absence of scar in both regions was associated with an 81% response rate compared with 55%, 25%, and 0%, respectively, when the RV, LV, or both pacing regions contained scar. LV pacing region dyssynchrony was not predictive of response. Conclusions-Myocardial scar occupying the LV pacing region is associated with nonresponse to CRT. Scar occupying the RV pacing region is encountered at higher frequency and seems to provide a more intermediate influence on CRT response. (Circ Cardiovasc Imaging. 2013;6:542-550.)

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

“…Electrical stimulation in regions of scar can also be pro-arrhythmic [53,54] and is associated with increased morbidity and mortality [8,55]. Unsurprisingly, the presence of myocardial scar at the site of LV stimulation during CRT is associated with non-response [8,56]. …”

Model-Based Navigation of Left and Right Ventricular Leads to Optimal Targets for Cardiac Resynchronization Therapy

“…20,21 The latter is of potential importance as its prevalence is significantly higher for RV lead targets than for LV targets. 22 In recognition of these findings, a new paradigm of imageguided CRT has recently been proposed, whereby imaging markers of myocardial health are used to recommend lead placement to preferred targets. To date, this concept has been evaluated for the delivery of LV leads to dyssynchronous but viable (nonscarred) segments using the echocardiographic surrogate marker of radial strain.…”

“…Predefined ranking was established based on prior published data. 22 This algorithm ensured that; (1) The LV lead was directed to the segment with (i) lowest scar burden, (ii) greatest mechanical delay, and (iii) greatest geographic distance from the prescribed RV lead tip location; and (2) the RV lead tip was directed to the segment with lowest scar burden. The algorithm used an iterative mathematical formula starting with the RV lead assignment, and then sequentially removing the LV lead targets with lowest rank.…”

“…22 To minimize artifact related to the CRT lead system, we reconstructed images using a 2.5-mm slice thickness and displayed this data set using 3D multiplanar reconstruction, averaging signal of 4 consecutive slices (MIP thickness 10 mm). The tips of the LV and RV lead were separately localized on axial images and orthogonal short-and long-axis projections generated.…”

“…The former response criterion was defined as a reduction in the LVESV≥15% at 6 months after implantation, as previously described. 22,32 Super responders were defined by a reduction in the LVESV ≥30% at 6 months after implantation. Predefined thresholds for the following clinical variables were used to define secondary clinical end points: NYHA functional class improvement by ≥1 class, 6-minute walk test increase by ≥30 m or 10%, and QOL score improvement (reduction) by ≥10 points.…”