Thirty patients who underwent CRT and had evidence of anodal stimulation will be included in the study. All patients undergo a conventional echocardiography after 10 minutes of continuous triple site pacing and after 10 minutes of continuous dual site pacing (Customary biventricular pacing).Echocardiography studies will be performed to measure dP/dT using continuous flow Doppler velocity profiles of mitral regurgitation, LV volumes and Left ventricular ejection fraction. Left intraventricular desynchrony is assessed by using TDI.