Abstract 9321: Left Ventricular Dyssynchrony as a Determinant of Torsional Mechanics in Patients with Dilated Cardiomyopathy

Background: Although left ventricular (LV) torsion is mainly determined by LV contraction, the impact of dyssynchrony on LV torsional behavior is not fully investigated. Since LV function in reality is a three-dimensional (3-D) phenomenon, 3-D echo methods appear to be advantageous to assess LV torsion. We therefore used 3-D speckle-tracking echocardiography to assess the impact of LV dyssynchrony on LV torsional mechanics in patients with dilated cardiomyopathy (DCM). Methods: This study included 65 subjects; 20 DCM with ejection fraction (EF) ≤35% and wide QRS (≥120ms), 20 DCM with EF≤35% and narrow QRS (<120ms), and 25 normal controls. LV torsion was quantified by means of 3-D speckle-tracking echocardiography. LV dyssynchrony was determined as the standard deviation of time-to-peak radial strain from 16 LV segments (dyssynchrony index). Similarly, regional heterogeneity of LV rotation was quantified as the standard deviation of time-to-peak rotation from 16 LV segments (rotational disparity index). Results: LV torsion in DCM with wide QRS was significantly smaller than that in DCM with narrow QRS and normals (0.41±0.25*† vs. 0.85±0.39* vs. 2.51±0.70 degrees/cm, *p<0.01 vs. normals, †p<0.01 vs. narrow QRS DCM). LV dyssynchrony and rotational disparity index in DCM with wide QRS were significantly larger than those in DCM with narrow QRS and normals (dyssynchrony index; 127.3±24.0*† vs. 88.8±22.5* vs. 30.9±10.0 ms, rotational disparity index; 115.1±27.5*† vs. 96.0±23.4* vs. 45.0±13.7 ms, *p<0.01 vs. normals, †p<0.01 vs. narrow QRS DCM). Furthermore, multivariable analysis revealed that the EF (β=-0.038, p<0.001) and rotational disparity index (β=-0.007, p<0.01) were independent determinants of LV torsion. Conclusions: LV dyssynchrony negatively affects the LV torsional mechanics in DCM patients. This approach may play a clinical role in management of such patients.