Abstract 17480: Strain-Time Curve Analysis by Speckle Tracking Echocardiography in Cardiac Resynchronization Therapy - Insight Into the Pathophysiology of Responders vs. Non-Responders

Abstract

Background: Patients who have non-ischemic heart failure etiology, wide QRS complex, and left bundle branch block (LBBB) on ECG show better response to cardiac resynchronization therapy (CRT). While it is widely accepted that these patients have the most pronounced left ventricular (LV) dyssynchrony, echocardiographic methods aimed at quantifying LV dyssynchrony failed to predict outcome. We hypothesized that patients with favorable outcome from CRT have a characteristic strain distribution pattern that singles them out of the others. Methods: From 313 CRT patients on our database with long-term echocardiographic follow up, we randomly selected 10 non-ischemic cardiomyopathy patients with LBBB who were CRT responders (LV end-systolic volume (LVESV) reduction at follow-up ≥15%) and 9 patients who were CRT non-responders. Longitudinal (ε long ) strain data were obtained by speckle tracking echocardiography before and after CRT implantation, 8±5months apart. Standardized segmental ε long -time curves obtained by averaging individual patient data were compared before and after CRT. Results: In responders, LVESV decreased from 184±74 to 111±63ml and LV ejection fraction increased from 25±9 to 40±11%, (p<0.05 for both). In non-responders, LVESV did not change significantly from 244±115 to 274±113ml and LV ejection fraction from 20±8 to 21±5% (p=ns). Pre CRT septal ε long -time curves in both groups showed early septal contraction with mid-systolic decrease, while lateral ε long showed early stretch followed by vigorous mid to late contraction (Figure). ε long amplitudes are significantly higher in the responder group (p<0.01). Post CRT improvement in ε long is significantly worse in the non-responder group. Conclusion: While CRT responders and non-responders with LBBB and non-ischemic etiology show a similar strain pattern prior to CRT, significantly lower strain amplitudes in the non-responders may account for their poor response to CRT.