Abstract 825: Effect of Cardiac Resynchronization Therapy on the Timing of Regional Myocardial Deformation
Background: Effect of CRT on the timing of regional myocardial strain is not fully described. We aimed to explore the effect of CRT on the timing of regional myocardial strain using speckle tracking echocardiography (STE).
Methods: STE and tissue Doppler imaging were performed in 91 patients before and 6 month after CRT. Time to peak longitudinal strain (Tϵ) from the onset of QRS was measured in 16 segments from three apical views. Time to peak systolic tissue velocity (Tv) was also measured in 12 basal and mid segments. Reverse remodeling was defined as 10% reduction in end-systolic volume.
Results: At baseline, Tϵ and Tv demonstrated specific pattern with earlier septal and delayed lateral contraction (Figure⇓). Tϵ in responders showed significantly earlier timing in mid inferoseptal (p=0.003) and anteroseptal segments (base, P=0.005, mid P=0.007) than in nonresponders, whereas the timing of free wall did not differ between responders and non-responders. After CRT, Tϵ in earlier segments (inferoseptal, anteroseptal and inferior wall) prolonged significantly (p<0.001), whereas other segments did not change timing. Accordingly, SD of Tϵ in 12 segments reduced after CRT (110±46 ms vs. 81±36 ms, p<0.001). Tv did not change in all segments and SD of Tv did not improve after CRT (43±16 vs. 46±16 ms, p=0.20).
Conclusions: Simultaneous electrical activation of LV free wall and septum with CRT achieves mechanical synchronization by delaying the timing of earlier contracting segment rather than directly shortening the timing in lateral wall. This could be explained by the increased wall stress on the septum as it contracts simultaneously with the opposing LV free wall.