Three-dimensional propagation imaging of left ventricular activation by speckle-tracking echocardiography to predict responses to cardiac resynchronization therapy

Background: On the basis of the electromechanical coupling theory, an activation imaging system has been developed with three-dimensional speckle-tracking echocardiography. The aim of this study was to determine the association between left ventricular (LV) propagation patterns by activation imaging and response to cardiac resynchronization therapy (CRT).

Methods: This was a retrospective, single-center study. Eighty-one patients undergoing CRT, of whom 50 (61.7%) had left bundle branch block (LBBB), were enrolled. Activation imaging studies were performed with a three-dimensional speckle-tracking echocardiographic system, which allowed visualization of LV activation propagation and measurement of the time from the QRS complex to activation onset. A CRT volume responder was defined as a patient with ≥15% reduction of LV end-systolic volume at 6 months after CRT. Clinical outcomes were assessed with the composite end point of death due to cardiac causes or unplanned hospitalization for cardiac diseases.

Results: In patients with LBBB, the main activation pattern (74%) was a U-shaped propagation pattern, which was characterized as propagation from the midseptum to the lateral or posterior wall through the apex. In patients without LBBB, various non-U-shaped propagation patterns were observed in the majority of patients (97%). Among the 41 CRT responders, almost all (87.8%) had the U-shaped propagation pattern. During follow-up (median, 20 months), 29 patients (35.8%) reached the clinical end points. In a multivariate Cox proportional hazards model, a U-shaped propagation pattern was associated with the end points independently of LBBB or LV end-diastolic volume.

Conclusions: The U-shaped propagation pattern on three-dimensional speckle-tracking echocardiography was significantly associated with a favorable CRT response. Activation pattern analysis may provide additional information to predict response to CRT.