Regional left ventricle mechanical asynchrony in patients with heart disease and normal QRS duration: Implication for biventricular pacing therapy

YU, C.-M., et al.: Regional Left Ventricle Mechanical Asynchrony in Patients with Heart Disease and Normal QRS Duration: Implications for Biventricular Pacing Therapy.LV electromechanical delay results in asynchronized contraction. However, it is not known if the presence of cardiac diseases without QRS prolongation may result in inter- or intraventricular asynchrony. This study investigated the occurrence of systolic mechanical delay in different regions of the LV in patients with underlying heart diseases and normal QRS duration. Tissue Doppler imaging (TDI) was performed in 141 patients(age 63.7 ± 11.5 years)with underlying heart diseases (82% had ischemic heart disease) and 92 normal healthy volunteers(age 63.9 ± 9.8 years)based on the four-basal and four-mid-segment model by apical views. Of these, 124 patients had normal QRS duration(≤120 ms)while 17 were prolonged due to LBBB or intraventricular conduction defect. Patients with normal QRS duration had significantly lower peak myocardial isovolumic contraction velocity(IVCM), sustained systolic velocity(SM), and prolonged time to peakIVCMandSMin almost all myocardial segments when compared to controls. The time to peakIVCM(basal lateral vs basal septal segment:61.0 ± 29.4 vs 53.3 ± 24.1 ms, P 50ms (47 vs 24%, chi-square = 4.6, P < 0.05). In conclusion, the presence of cardiac diseases was characterized by LV global mechanical delay; and, intraventricular asynchronized contraction characterized mostly by further mechanical delay in the free-wall region. These changes occur even in those with normal QRS duration. (PACE 2003; 26[Pt. I]:562–570)