Abstract 2817: The Impact of Exercise-Induced Changes in Intraventricular Dyssynchrony on the Functional Improvement in Patients with Non-Ischemic Cardiomyopathy
Background: We studied whether dynamic changes in LV asynchrony may affect the functional improvement of LV in medically treated patients with non-ischemic cardiomyopathy (CMP).
Methods: Supine bicycle exercise was performed in 41 patients (age 51±12 years, EF 33±8%). Using tissue Doppler imaging, the average of peak systolic velocities of 6 basal LV segments were obtained at rest (Vb) and peak exercise (Vp). ΔV was calculated by [Vp-Vb], reflecting the contractile reserve. Dyssynchrony index (SD4) was defined as the standard deviation of the time to peak systolic velocities at 4 basal & mid segments of septum and lateral wall on apical 4 chamber view. ΔSD4 was calculated as [peak exercise SD4 - resting SD4]. Follow-up echocardiography was done in 35 patients after medication for 11.2±4.2 months. Functional changes of LV was assessed by ΔEFFU and %change of ESV (ΔESVFU).
Results: Baseline SD4 was 24±17 ms. During exercise, SD4 increased in 24 patients (ΔSD4=+14±12 ms), whereas decreased in 17 patients (ΔSD4=-17±14 ms). ΔSD4 correlated with ΔV (r=-0.36, p=0.021) and exercise-induced increase in MR (ΔJet/LA area (%); r=0.31, p=0.05 and ΔPISA radius at 40cm/s of aliasing v; r=0.46, p=0.003). ΔV and ΔPISA were related to the follow-up change of LV function. Especially, ΔSD4 independently correlated with ΔEFFU (β= -0.82, p<0.001) and also with ΔESVFU (β= 0.40, p=0.021)(Fig⇓). However, baseline SD4 didn’t affect ΔEFFU. On ROC curve analysis, sensitivity and specificity of ΔSD4 <4.0 ms were 82% and 78% for predicting ΔEFFU >+5% and 70% and 63% for predicting ΔESVFU <-15%.
Conclusion: Exercise-induced changes in dyssynchrony (ΔSD4) can predict the functional improvement in non-ischemic CMP.