Abstract 6122: Impact of Temporal Heterogeneity in Regional Cardiac Mechanics on Dyssynchrony Assessment by Tissue Velocity Versus Strain Echocardiography: Lessons from an Experimental Model of Heart Failure
Background: We evaluated the relative usefulness of tissue Doppler (TDE) and strain (SE) echocardiography in depicting mechanical synchrony in a well-validated dog model of tachypacing induced heart failure with left bundle branch ablation.
Methods: Twelve dogs underwent sequential left bundle branch ablation, 3-week atrial and 3-week biventricular pacing at 200 bpm inducing dyssynchronous heart failure (DHF) and resynchronization (CRT) respectively. Conventional, TDE and SE was performed at DHF, immediately after (acute CRT) and at 3 weeks of biventricular pacing (chronic CRT). Mechanical dyssynchrony (MD, longitudinal) was determined by 4 indices: time delay between basal segments of 2 opposing walls (septal-lateral and anteroseptal-posterior) by peak systolic velocity during ejection phase (TDSV-Ejection), peak positive systolic velocity (TDSV), peak strain (TDSTRAIN) and 12-segment standard deviation of time to peak strain (Dyssynchrony index or DI).
Results: All indices of dyssynchrony except TDSV-Ejection improved substantially with acute CRT (Figure A⇓) compared to DHF and all remained significantly better at 3 weeks CRT. TDSV-Ejection underestimated MD at DHF stage consequent to misidentification of septal systolic peaks in DHF that tended to generally precede aortic valve opening (Figure B⇓).
Conclusion: Acute improvements in dyssynchrony with CRT are sustained with chronic CRT. Regional temporal heterogeneity of septal and lateral wall mechanics in DHF results in misidentification of systolic tissue velocity peaks during the ejection phase. Strain derived indices are less susceptible to these changes and may more accurately reflect dyssynchrony.