CRT improves outcomes in heart failure patients, but class II candidates (i.e. patients presenting non-LBBB or narrow LBBB patterns) benefit less from this treatment. The RESYNC-PETCT study explores advanced imaging guidance using 82Rubidium PET-CT and cardiac CTV to target coronary sinus lead placement with the aim to improve CRT response in this specific patient population. All genders will be included in this study. However, gender is not considered a variable in this clinical trial.

Patients participating in this study will benefit from an individualized approach to CRT implantation. The nuclear and radiological tests proposed in this research project will imply an additional radiation exposure compared to the standard care. However, the total additional radiation dose will remain below the recommended threshold for clinical trials so that the radiological risks associated to these investigations appear negligible and are counterbalanced by the improvement in LVEF and NYHA expected from a targeted coronary sinus lead positioning.

The objective of the RESYNC-PETCT study is to demonstrate that optimising the coronary sinus lead implantation by using combined data from 82Rubidium PET-CT scan and cardiac CTV reconstruction is a feasible approach to improve the LV electrical and mechanical synchronicity and therefore the clinical response in patients presenting non-LBBB patterns or LBBB patterns with QRS duration < 150ms.

Inclusion Criteria:

• Symptomatic heart failure (NYHA class II, III and IV) despite optimal medical treatment
• LVEF ≤ 35%
• Sinus rhythm
• Non LBBB pattern on 12-lead ECG with QRS > 130 ms
• LBBB pattern on 12-lead ECG with QRS > 130 ms and < 150 ms
• Patient is able to understand the nature of the research project and to provide written informed consent.
• Patient accepts to be informed about incidental findings discovered by 82Rubidium PET-CT scan and cardiac CTV that imply clinical management

Exclusion Criteria:

• Pregnancy (as per standard procedure)
• Age less than 18 years
• Severe chronic kidney disease (Glomerular filtration rate < 30mL/min) contraindicating a cardiac CTV
• Life expectancy of less than 12 months.