Relationship between vectorcardiographic QRSarea, myocardial scar quantification, and response to cardiac resynchronization therapy

Abstract Purpose To investigate the relationship between vectorcardiography (VCG) and myocardial scar on cardiac magnetic resonance (CMR) imaging, and whether combining these metrics may improve cardiac resynchronization therapy (CRT) response prediction. Methods Thirty-three CRT patients were included. QRS area , T area and QRST area were derived from the ECG-synthesized VCG. CMR parameters reflecting focal scar core (Scar 2SD , Gray 2SD ) and diffuse fibrosis (pre-T1, extracellular volume [ECV]) were assessed. CRT response was defined as ≥15% reduction in left ventricular end-systolic volume after six months' follow-up. Results VCG QRS area , T area and QRST area inversely correlated with focal scar ( R  = −0.44–−0.58 for Scar 2SD , p  ≤ 0.010), but not with diffuse fibrosis. Scar 2SD , Gray 2SD and QRS area predicted CRT response with AUCs of 0.692 ( p  = 0.063), 0.759 ( p  = 0.012) and 0.737 ( p  = 0.022) respectively. A combined ROC-derived threshold for Scar 2SD and QRS area resulted in 92% CRT response rate for patients with large QRS area and small Scar 2SD or Gray 2SD . Conclusion QRS area is inversely associated with focal scar on CMR. Incremental predictive value for CRT response is achieved by a combined CMR-QRS area analysis.