Abstract
Background
Despite the impressive results of the large CRT trials, it has been observed that, on an individual basis, about 30% of patients fail to respond to cardiac resynchronization therapy (CRT). The evaluation of left ventricular (LV) dyssynchrony, myocardial scar, and coronary venous anatomy by image subtraction in Late Iodine Enhancement Computed Tomography (LIE-CT) has the potential to comprehensively characterize non-responders.
Purpose
To assess the feasibility and the utility of image subtraction in LIE-CT in CRT patients and compare findings between responders and non-responders.
Methods
Monocentric prospective study of CRT patients at least 6 months after implantation who underwent post-procedural CT between March and October 2018. CRT-responders were defined as patients with an absolute increase in LV ejection fraction >5%.
CT-derived residual global and segmental dyssynchrony metrics, extent and location of myocardial scar, coronary venous anatomy, and position of LV lead relative to scar and segment of latest mechanical contraction were analyzed.
Results
Among the 29 patients (mean age 71±12 years; 72% men), 18 were responders (62%). All CT metrics evaluating residual dyssynchrony such as wall motion indexand wall thickness indexwere worse in non-responders (p<0.0001 for both). In LIE-CT, predictive factors of CRT-non-response were an LV lead localized in an region of myocardial scar (p=0.0007), in a region with akinesia or dyskinesia (p=0.007), and with myocardial thickness <6mm (p=0.002). Percentage of fibrosis of the myocardial mass and the presence of fibrosis in postero-lateral region were not predictive of CRT-non-response (p=0.9 and p=0.3, respectively). Of the 11 non-responder patients, 8 (73%) had at least one other coronary venous branch visualized by CT; and among those, 3 (38%) were located in an non-akinetic area with late segmental contraction.
Wall Motion and LIE-CT
Conclusion
Image subtraction in LIE-CT in patients who had CRT is feasible and allows better characterization of CRT-non-responders, who have a greater amount of residual dyssynchrony than responders. Distribution of fibrosis in relation to the LV lead and presence of alternative venous branches may help patient management.
Basal septal perforator vein mimicking the “late iodine enhancement” in delayed phase cardiac CT for myocardial scar assessment
