Abstract
The aim of this study was to use 3-dimensional (3D) speckle-tracking echocardiography to test the hypothesis that left ventricular (LV) dyssynchrony may negatively affect LV torsional mechanics in patients with idiopathic dilated cardiomyopathy (IDC) and that LV torsion may improve after cardiac resynchronization therapy. This study included 65 subjects; 20 with IDC with ejection fractions ≤35% and wide QRS complexes (≥120 ms), 20 with IDC with ejection fractions ≤35% and narrow QRS complexes (<120 ms), and 25 controls. LV dyssynchrony index was determined as the SD of time to peak 3D speckle-tracking radial strain and regional heterogeneity of LV rotation (rotational dispersion index) as the SD of 3D speckle-tracking time to peak rotation. All rotational indexes were significantly impaired in patients with IDC, while LV torsion in patients with IDC with wide QRS complexes was significantly smaller than that in patients with IDC with narrow QRS complexes and controls. Conversely, LV dyssynchrony index (127.3 ± 24.0 ms [p <0.01 vs controls and vs patients with narrow QRS complexes] vs 88.8 ± 22.5 ms [p <0.01 versus controls] vs 30.9 ± 10.0 ms) and rotational dispersion index (115.1 ± 27.5 ms [p <0.01 vs controls and vs patients with narrow QRS complexes] vs 96.0 ± 23.4 ms [p <0.01 versus controls] vs 45.0 ± 13.7 ms) were significantly higher in patients with IDC with wide QRS complexes. Multivariate analysis showed that the LV ejection fraction (β = 0.688, p <0.001) and rotational dispersion index (β = -0.249, p <0.01) were independent determinants of LV torsion. Moreover, LV torsion in patients with IDC with wide QRS complexes improved after cardiac resynchronization therapy (p <0.05), along with reductions in LV dyssynchrony and rotational dispersion indexes. In conclusion, these findings obtained with a novel 3D speckle-tracking system feature a novel aspect of LV torsional mechanics and demonstrate its association with LV dyssynchrony.
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