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

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, T and QRST were derived from the ECG-synthesized VCG. CMR parameters reflecting focal scar core (Scar, Gray) 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, T and QRST inversely correlated with focal scar (R = -0.44--0.58 for Scar, p ≤ 0.010), but not with diffuse fibrosis. Scar, Gray and QRS 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 and QRS resulted in 92% CRT response rate for patients with large QRS and small Scar or Gray.

CONCLUSION

QRS is inversely associated with focal scar on CMR. Incremental predictive value for CRT response is achieved by a combined CMR-QRS analysis.