When deriving the spatial QRS-T angle from the 12-lead electrocardiogram, which transform is more Frank: regression or inverse Dower?

INTRODUCTION: Our primary objective was to ascertain which commonly used 12-to-Frank-lead transformation yields spatial QRS-T angle values closest to those obtained from simultaneously collected true Frank-lead recordings.
MATERIALS AND METHODS: Simultaneous 12-lead and Frank XYZ-lead recordings were analyzed for 100 postmyocardial infarction patients and 50 controls. Relative agreement, with true Frank-lead results, of 12-to-Frank-lead-transformed results for the spatial QRS-T angle using Kors' regression versus inverse Dower was assessed via analysis of variance, Lin's concordance, and Bland-Altman plots.
RESULTS: Spatial QRS-T angles from the true Frank leads were not significantly different than those derived from the Kors' regression-related transformation but were significantly smaller than those derived from the inverse Dower-related transformation (P < .001). Independent of method, spatial mean QRS-T angles were also always significantly larger than spatial "maximum" ("peaks") QRS-T angles. DISCUSSION: Spatial QRS-T angles are best approximated by regression-related transforms. Spatial mean and spatial "peaks" QRS-T angles should not be used interchangeably. Published by Elsevier Inc.