Regional Heterogeneity of Systolic Dysfunction Is Associated with Ventricular Dyssynchrony in Patients with Idiopathic Dilated Cardiomyopathy and Narrow QRS Complex

Background: Regional heterogeneity of left ventricular (LV) contraction, known as dyssynergy, in idiopathic dilated cardiomyopathy (IDC) patients has been previously reported, but no comprehensive analysis of this abnormality has been made. The purpose of this study was to test the hypothesis that regional heterogeneity of systolic dysfunction is associated with LV dyssynchrony in IDC patients with a narrow QRS complex using novel three‐dimensional (3D) speckle‐tracking strain. Methods: We studied 54 consecutive IDC patients with ejection fraction (EF) of 34 ± 12% and QRS duration of 102 ± 13 msec (all <120 msec), and 30 age‐matched normal controls. The 3D speckle‐tracking LV dyssynchrony (LV dyssynchrony index) was quantified from all 16 LV sites to determine the standard deviation (SD) of time‐to‐peak strain. Similarly, regional heterogeneity of LV systolic function (LV dyssynergy index) was quantified from all 16 LV sites to establish the SD of peak 3D speckle‐tracking strain. Results: The LV dyssynergy and dyssynchrony indices of IDC patients were significantly larger than those of normal controls. Furthermore, IDC patients showed significantly higher Z‐scores for septum and inferior regions than for the free wall (3.34 ± 1.21 vs. 1.69 ± 1.06 and 2.79 ± 1.30 vs. 1.69 ± 1.06, respectively, P < 0.001). An important findings of multivariable analysis was that the LV dyssynergy index (β = 0.69, P < 0.001) and LVEF (β = ?0.34, P = 0.001) were independent determinants of the LV dyssynchrony index. Conclusion: 3D speckle‐tracking strain revealed that the myocardial systolic dysfunction of IDC patients with a narrow QRS complex has a marked heterogeneous regional distribution. This regional heterogeneity as well as systolic dysfunction is thought to lead to LV dyssynchrony.