The aim of this study was to define the prevalence of mechanical (atrio-ventricular, interventricular and intraventricular) dyssynchrony in heart failure patients with different QRS durations.

A total of 46 patients with heart failure (dilated cardiomyopathy with LVEF<40%, NYHA II-IV) were prospectively evaluated using 12-lead electrocardiogram and complete echocardiographic examination including tissue Doppler imaging. All the patients had sinus rhythm and the dilated cardiomyopathy was primitive in 37% of patients and ischemic in the others.

According to QRS duration, 16 patients had QRS ≥150ms (group 1), 15 patients had QRS duration between 120 and 149ms (group 2) and 15 patients had QRS duration<120ms (group 3). Interventricular dyssynchrony (IVD) was present in 62% of group 1, 13% of group 2 and was absent in group 3 (P<0,001). Intraventricular dyssynchrony (IntraVD) was present respectively in 94%, 40%, 20% of groups 1,2, and 3 (P<0,001). However, there was no significant difference in the prevalence of atrioventricular dyssynchrony (AVD) between the three groups. A multiparametric approach by focusing on criteria combination found that the association of IVD+IntraVD+AVD was present only in group 1 and the combination of two criteria was seen only in group 1 and 2 with a significantly higher prevalence in group 1 (P<0,01).

The prevalence of mechanical dyssynchrony increases with the increasing QRS duration and the combination of criteria is significantly more prevalent when the QRS width is ≥150ms. Intraventricular dyssynchrony can be observed in heart failure patients with a narrow QRS complex and may be useful in predicting left ventricular reverse remodelling after CRT. The lack of dyssynchrony in some patients with standard CRT indication by QRS duration may sometimes explain the non-responder's rates.