Eligible subjects shall meet all following criteria:
Appropriately signed and dated informed consent.
Age ≥18 years at time of consent.
CRT indication according to the 2021 ESC guidelines on cardiac pacing and CRT (class I and IIA indication in patients with LBBB QRS morphology) or to 2017 AHA/ACC/HFSA guidelines (COR I).
Sinus rhythm
QRS duration ≥130 ms
Left bundle branch block
Left ventricular ejection fraction ≤35%
Symptomatic heart failure NYHA class ≥ II
Documented stable medical treatment for at least 6 months
No cardiovascular intervention during the last 6 month
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History of persistent or permanent atrial fibrillation
Previous pacemaker or ICD implantation
Indication to pacing due to bradycardia
Patients considered for His bundle pacing or cardiac conduction pacing
Patients with unstable angina
Subject experienced a recent myocardial infarction, within 40 days prior to enrollment
Subject underwent coronary artery bypass graft or valve surgery, within 90 days prior to enrollment
Subject is post heart transplantation, or is actively listed on the transplantation list, or has reasonable probability (per investigator's discretion) of undergoing transplantation in the next year
Subject is implanted with a left ventricular assist device
Subject is on continuous or uninterrupted infusion (inotropic) therapy for heart failure
Subject has severe aortic stenosis (with a valve area of \<1.0 cm2 or significant valve disease expected to be operated within study period)
Subject has congenital heart disease
Subject has a mechanical right-sided heart valve
Subject has a life expectancy of less than one year in the opinion of the investigator
Pregnant or breastfeeding women, or women of child bearing potential and who are not on a reliable form of birth control
Subject is enrolled in one or more concurrent studies that would confound the results of this study
Patients who have contraindications to CT scanning.
Patients with chronic kidney diseases and estimated glomerular filtration rate (eGMR) calculated based on CKD-EPI 2009 \< 40 ml/min/1.73m2
