Background Cardiac Resynchronization Therapy (CRT) is proven to improve survival and heart function of patient with certain electrical conduction abnormality and heart failure. However, in patient with certain electrical conduction abnormality, being nonresponder is observed in up to 40% in patient receiving CRT. Conventionally the surgical approach of CRT is to implant one pacing lead in the right heart and one in the left heart to resynchronize the contraction and the pacing lead in the left heart is usually placed in the posterior or lateral portion of the left heart. However, this single approach may not be optimal, especially for those patients with conduction abnormality known to have no response to CRT. Purpose of the clinical investigation The purpose of the Activation Pattern and Acute Hemodynamics of His and Left Bundle Pacing is to study the acute effect on the heart function and conduction abnormality of His and left bundle pacing in conventional CRT candidate. During CRT implantation, Hisbundle lead and Left bundle pacing lead will be placed and the acute effect on heart function will be studied by a wire placed in the left ventricle of the heart and the activation pattern will be studied by a noninvasive global mapping system. The pacing approach that optimally corrects conduction abnormality and improvement on the heart function acutely will be determined

Inclusion Criteria:

• Adult (aged 18 or above) of both sexes
• Candidate for CRT therapy according to international guidelines.7
• Informed consent by the patient
• Already received stable dose of guideline directed medical therapy for at least 3 months

Exclusion Criteria:

• Pregnant
• Participating in another study