Peak QRS/T ratio and the spatial ventricular gradient differentiate acute vs chronic left bundle branch block after transcatheter aortic valve replacement

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Background: Differentiating chronic from acute left bundle branch block (LBBB) is useful in various cardiac disorders. Peak QRS/T ratio, a measure of cardiac memory, can differentiate chronic from acute LBBB with high sensitivity and specificity, but its utility in post-transcatheter aortic valve replacement (TAVR) patients with LBBB is unclear. Objective: This study aimed to validate the QRS/T ratio for differentiating chronic/acute LBBB in post-TAVR patients and assess whether the spatial ventricular gradient (SVG), which integrates 3-dimensional depolarization/repolarization throughout the cardiac cycle, could also distinguish chronic from acute LBBB. Methods: This was a post hoc analysis of a prospective, observational, single-center TAVR study. After TAVR, patients were classified as acute (new <24 hours) or chronic/preexisting LBBB. Electrocardiograms were transformed into vectorcardiograms, and peak QRS/T ratio and SVG were calculated. Sensitivity, specificity, and area under the receiver-operating curve (AUROC) assessed how QRS/T ratio and SVG differentiated chronic from acute LBBB. Results: < .0001, for chronic vs acute LBBB, respectively. A peak QRS/T ratio of ≥2.7 and an SVGz of ≥15 mV·ms had 100% sensitivity, 98.1% specificity, and an AUROC of 0.991 for chronic LBBB. Over long-term follow-up, patients transitioned from acute to chronic LBBB vectorcardiographic phenotype. Conclusion: Peak QRS/T ratio and SVG differentiate chronic from acute LBBB in post-TAVR patients with 100% sensitivity, 98% specificity, and an AUROC of 0.99.

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