Multicenter randomized controlled trial which will include patients with left ventricular ejection fraction >50% requiring a first implant of a cardiac pacemaker with expected high pacing percentages.

Patients will be randomized 1:1 to right ventricular apical pacing vs left septal or deep septal pacing. The primary endpoint will be pacing-induced cardiomyopathy during the first year of follow-up.

Inclusion Criteria:

• First implant of a single-chamber or dual chamber pacemaker due to persistent bradycardia associated with high degree atrio-ventricular (AV) block (complete AV block or second degree type II AV block), with second-degree type I AV block (symptomatic or associated with intra-hisian or infra-hisian block), or with atrial fibrillation with symptomatic slow ventricular rate (<45lpm).
• LVEF>50% at echocardiography performed maximum 7 days before pacemaker implant.
• Informed consent signature.

Exclusion Criteria:

• Life expectancy <12 months
• Severe cardiac valvular abnormality requiring intervention
• Unstable Angina, Acute myocardial infarction, coronary revascularization, valvular surgery or valvular percutaneous intervention in the 90 days prior to pacemaker implant.
• Inclusion in another trial which may influence the results of this study.

The study protocol and the informed consent form will be available upon request during the whole duration of the study.

During the whole duration of the study

Request to the principal investigator.