Abstract 9315: Regional Heterogeneity of Systolic Dysfunction Leads to Ventricular Dyssynchrony in Patients with Idiopathic Dilated Cardiomyopathy and Narrow QRS Complex; 3-Dimensional Speckle-Tracking Strain Analysis

Abstract

Background: Although left ventricular (LV) mechanical dyssynchrony is commonly observed in patients with wide QRS complex, some patients with a relatively narrow QRS complex also present with significant mechanical dyssynchrony. Moreover, regional heterogeneity of 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 nor is its association with LV dyssynchrony fully understood. The objective was to test, by means of novel 3-dimensional (3-D) speckle-tracking strain, the hypothesis that regional heterogeneity of myocardial systolic dysfunction is associated with LV dyssynchrony. Methods: We studied 54 consecutive IDC patients with ejection fraction (EF) of 34±12% and QRS duration of 102±13ms (all<120ms), and 30 age-matched normal controls. The 3-D speckle-tracking LV dyssynchrony (LV dyssynchrony index) was quantified from all 16 LV sites to determine the standard deviation 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 standard deviation of peak 3-D speckle-tracking strain. Results: The LV dyssynergy and dyssynchrony indices of IDC patients were significantly larger than those of normal controls (10.8±2.2 vs. 8.3±1.5%, and 81±39 vs. 24±8 ms, respectively, p<0.001). 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=0.70, p<0.001) and LVEF (β=-0.34, p=0.001) were independent determinants of the LV dyssynchrony index. Conclusions: 3-D speckle-tracking strain revealed that the myocardial systolic dysfunction of IDC patients with a narrow QRS complex has a consistent and marked heterogeneous regional distribution. This regional heterogeneity as well as systolic dysfunction is thought to lead to LV dyssynchrony. The study presented here offers new insights into LV dyssynergy and dyssynchrony.