Cardiac Resynchronization Therapy (CRT) is an established treatment for patients with advanced heart failure and left ventricular dyssynchrony (LVD). Too many patients do not clinically improve with CRT. New LVD markers other than QRS duration are needed.

Study objective : feasibility assessment of rest and real-time stress 3D Blood-Pool Gated SPECT (BPGS) with a new designed cardiac imaging camera (DSPECT, Spectrum Dynamics®, Ceasaria, Israel) to quantify LVD.

Sequential 5 min Gated blood pool D-SPECT acquisition at rest and during last stage of dobutamine and atropin infusion (>85% PHR).

Rest and stress left ventricular ejection fraction, phase standard deviation and entropy will be determined using a fully automatic commercial software (QBS, Cedars-Sinai, Los Angeles, CA).

Inclusion Criteria:

Chronic heart failure with LVEF < 35 %, QRS > 120 ms, NYHA III/IV, optimal medical therapy for more than one month.

• Patient with stable hemodynamic for more than one month,
• More than 18-year old man or woman,
• Patient having given his free, inform and signed consent,
• Patient place setting by the social security system,

Exclusion Criteria:

• Psychiatric disorder
• Any contra-indication to Technetium,
• Any contra-indication to dobutamin or atropin
• Personal or family history of sudden death
• Previous severe ventricular arrhythmia
• Obstructive cardiomyopathy, severe aortic stenosis,
• Pulmonary hypertension,
• History of renal, lung, hepatic, cardiac transplantation,
• Pregnant or breast-feeding Woman,
• Patient who can not conform to the requirements of the protocol,
• Patient included in another medical study,