To investigate the hemodynamic, inter and intraventricular desynchrony effects of anodal stimulation and triple site pacing compared with the usual dual site pacing by echocardiography and Tissue Doppler Imaging.

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.

Inclusion Criteria:

• Patients with biventricular pacemakers who met currently accepted indications for CRT, including dilated cardiomyopathy with LV ejection fraction < 35% (ischemic and nonischemic etiologies) with New York Heart Association class III to IV congestive heart failure and QRS duration > 120 ms.

Exclusion Criteria:

• Patients with first generation CRT device
• Integrated bipolar defibrillator device
• Atrial fibrillation during the screening phase
• Patients who cannot tolerate triple site pacing for several minutes (i.e diaphragmatic pacing)
• Patients with epicardial LV leads
• Patients with LV leads located out of the lateral or posterolateral areas