Cardiac resynchronization therapy has been shown to be effective in reducing symptoms and mortality in heart failure patients. However, very few is known about the importance of the left ventricular pacing site. We study in a random order 11 different left ventricular pacing sites and compare their hemodynamics using pressure-volume catheters. The consequences on the surface ECG are also assessed.

Background. Cardiac resynchronization therapy has been shown to be effective in reducing symptoms and mortality in heart failure patients. However, very few is known about the importance of the left ventricular pacing site.

Design. Single-blind, monocentric, randomized cross-over study comparing 11 left ventricular pacing sites in a random order.

Intervention. Left ventricular DDD pacing on 11 ventricular sites, prior to the implantation. At each pacing site, a control hemodynamics will be obtained in AAI pacing at the same pacing rate. At each pacing site, 2 AV delays, a short and a long one, will be assessed.

Eligibility criteria. Patients referred for cardiac resynchronization therapy for heart failure

Outcomes. Hemodynamic measures using pressure-volume catheters.

Inclusion Criteria:

• Heart failure referred for cardiac resynchronization therapy
• NYHA Class III or IV
• Informed consent form signed

Exclusion Criteria:

• Hypertension not controlled by treatment
• Coronary ischemia not controlled by treatment