Intraventricular conduction delay alone or in combination with AV conduction delay is associated with a dyssynchronous activation of the ventricles and may result in LV function impairment.

Conduction system pacing can restore physiologic ventricular activation in the presence of intraventricular and atrioventricular conduction delays.

Patients with intraventricular conduction delay alone or in combination with AV conduction delay who have a permanent pacemaker indication due to intermittent bradycardia and have predominantly intact AV conduction may benefit from continuous CSP.

Study design: Multicenter, prospective, randomized, cross-over, patient-blinded study

Study Objectives:

• Primary objective: The primary objective of the study is to demonstrate that CSP is associated with better LVEF and GLS preservation at 12-month follow-up in comparison to native conduction with wide QRS. The percentages of patients with a ≥10% decline in LVEF and or ≥ 15% decline in GLS between groups will be considered for the primary outcome.
• Principal secondary objectives: NYHA class at 12 months, Walking distance in 6 minutes walking test, Quality of life (EQ EQ 5D), To evaluate reverse ventricular remodeling response and dyssynchrony parameters based on echocardiographic data at 12 months follow-up, To evaluate device battery longevity estimation at 12-month follow-up, To evaluate HF related hospitalizations/ER visits at 12 months follow-up, To evaluate mortality (global and cardiovascular) at 12-month follow-up, To evaluate incidence of ventricular arrhythmias at 12-month follow-up, To evaluate differences in LVEF and remodeling parameters depending on the final CSP modality (LBBP vs LVSP), To evaluate device related complications at 12-month follow-up, To evaluate differences between pacing indication groups (acute LBBB vs unknown/chronic wide QRS)and To evaluate percentage of patients randomized to continuous pacing who loose AV conduction after 12 months of continuous pacing Primary Endpoint: LVEF decrease ≥ 10% and/or GLS decrease ≥ 15% at 12-month follow-up with respect to baseline value

Study population criteria

• Inclusion criteria: age > 18 years, Any indication for cardiac pacing with an expected VP burden ≤ 10% after 1-month run-in period, Baseline wide QRS (≥150 ms) with normal PR or QRS ≥ 130 ms + PR≥230 ms, Confirmed CSP criteria (LBBAP including LBBP and LVSP), LVEF≥50% and Signed and dated informed consent.
• Exclusion criteria: Pregnant woman, Age < 18 years, Permanent or long-lasting atrial fibrillation, Previous PM/ICD, Unstable angina, acute Myocardial Infarction (MI), Coronary Artery Bypass Graft (CABG), Percutaneous Coronary Angioplasty (PCI), valve repair or replacement within 90 days prior enrollment, Moderate-severe valvular heart disease (not repaired), Already included in another clinical study that could confound the results of the present study, Infiltrative disease or any other genetically or acquired primary myocardial disease, Life expectancy < 2 years and LVEF <50%

Sample size: 120 patients will be enrolled in the study.

Devices: Only CE-marked pacemaker devices locally approved and commercially available shall be used in this protocol.

Statistical considerations: Once patients have signed the informed consent at baseline visit, patients will be considered as "Enrolled population" in the statistical analysis.

The sample size is based on the primary endpoint: LVEF decrease ≥ 10% and/or ≥ 15% decrease in GLS at 12-month follow- up with respect to baseline value.

Accounting for an attrition rate of 15% due to lost to follow-up or cross-over and considering the block size for randomization, 120 patients shall be enrolled

Inclusion Criteria:

• age > 18 years
• Any indication for cardiac pacing with an expected VP burden ≤ 10% after 1- month run-in period
• Baseline wide QRS (≥150 ms) with normal PR or QRS ≥ 130 ms + PR≥230 ms
• LVEF≥50%
• Confirmed CSP criteria
• Signed and dated informed consent

Exclusion Criteria:

• Pregnant woman
• Permanent or long-lasting atrial fibrillation
• Previous PM/ICD
• Unstable angina, acute Myocardial Infarction (MI), Coronary Artery Bypass Graft (CABG), Percutaneous Coronary Angioplasty (PCI), surgical valve repair or replacement within 90 days prior enrollment
• Moderate-severe valvular heart disease (unrepaired)
• Already included in another clinical study that could confound the results of the present study
• Infiltrative disease or any other genetically or acquired primary myocardial disease
• Life expectancy < 2 years
• LVEF <50%