Vectorcardiographic direction of ventricular activation as a predictor of long-term outcomes after cardiac resynchronisation therapy

Background: Predicting clinical outcomes after cardiac resynchronisation therapy (CRT) remains a challenge. Although QRS duration is crucial as an indication for CRT, it is a poor predictor of clinical outcomes. Objectives: To determine whether the direction of ventricular activation, measured using the ratio of the temporospatial isochrone to QRS duration (TSIQRSd) on vectorcardiography (VCG) predicts clinical outcomes after CRT. Methods: In this retrospective study, TSIQRSd, QRS area, QRS duration (QRSd) and QRS morphology (LBBB), derived from pre-implantation ECGs, were assessed in relation to the primary endpoint of cardiac mortality after CRT. Results: In patients (n=720, age 72.8 ± 11.8 years, 71.3% male) undergoing CRT over 7.7 years (median follow-up period of 3.7 [interquartile range 2.3–5.1] years), TSIQRSd