Regional Left Ventricular Electrical Activation and Peak Contraction Are Closely Related in Candidates for Cardiac Resynchronization Therapy

Objectives: This study determined the relationship between the timing of left ventricular (LV) electrical activation and peak contraction at potential LV pacing locations in candidates for cardiac resynchronization therapy (CRT). Background: Targeting the LV lead to the region of latest electrical activation or the segment of latest peak contraction has both been shown to improve CRT response. Whether these regions correspond within CRT patients is uncertain. Methods: Twenty-eight consecutive CRT candidates underwent intraprocedural coronary venous electroanatomic mapping using EnSite NavX. Peak contraction time of the mapped LV regions was determined using longitudinal strain derived from speckle tracking echocardiography. Electrical activation and peak contraction times were correlated on a per patient basis, and the regions of latest electrical activation and latest peak contraction were compared. Results: Successful measurements by both techniques allowed analysis in 23 of 28 patients. There was a strong positive correlation between electrical activation and peak contraction times within each patient (R2 = 0.85 ± 0.09). However, the magnitude of the electrical activation-peak contraction relationship varied greatly among patients (slope of regression line: 4.05 ± 3.23). The regions of latest electrical activation and latest peak contraction corresponded in 19 of 23 (83%) patients and were adjacent in 4 patients. Conclusions: There is a close relationship between the timing of LV electrical activation and peak contraction in CRT candidates. This finding suggests that a strategy of determining the latest activated LV region based on speckle tracking echocardiography corresponds to that based on intracardiac measurements of electrical activation