The aim of the study is to demonstrate that conduction system pacing (CSP) can preserve a normal ventricular function compared to right ventricular apical pacing (RVAP) in patients with pre-implant preserved left ventricular ejection fraction (LVEF) and a high burden of expected ventricular pacing due to atrioventricular conduction block (AV block).

After informed consent signature, patients with high degree AV block and normal LVEF will be randomized to permanent pacemaker stimulation with CSP vs RVAP.

All the patients have a complete evaluation before the procedure and at 3 and 6 months follow-up.

The STAY trial (Conduction System sTimulation to Avoid left ventricle dYsfunction) is a single-center, prospective, randomized, parallel, controlled study, comparing mid-term outcomes in a population undergoing pacemaker implantation due to a high degree atrio-ventricular block (AVB). The study was approved by the Hospital Ethics Committee, in accordance with the Declaration of Helsinki. All patients signed informed consent and were implanted between September 2019 until December 2022 in a 1:1 randomized fashion to conventional RVAP vs CSP (HBS or LBBS). Randomization was performed during the pre-procedural antibiotic infusion.

All the patients have a complete evaluation before the procedure and at 3 and 6 months follow-up, including demographic and clinical characteristics, physical examination, twelve-lead ECG, Minnesota score (MLWHFQ), and blood test with NT-ProBNP determination. Patients also have a transthoracic echography before the procedure and at 6 months follow-up.

At 6 months echocardiographic and clinical data will be compared.

Inclusion criteria:

1. Age of 18 years or more
2. Preserved or mild deteriorated LVEF (Simpson >40%) assessed by a recent (<1 month before implantation) transthoracic echocardiography.
3. Indication for pacing based on the presence of a high degree AVB, and consequently with an anticipated high burden of ventricular pacing (>50%).
4. Live expectancy of more than 6 months and capability to understand the protocol, signing the informed consent form and accomplish the follow-up.

Exclusion criteria:

1. Indication for implantable cardioverter defibrillator device.
2. Patients with previous LVD and a recovered LVEF
3. History of myocardial infarction/revascularization or cardiac surgery within 6 months before randomization
4. Pregnancy, active cancer treatment, or participation in another clinical trial with active treatment.

Data will only be available upon reasonable request.

The study is blinded for the patient and for the echocardiographers.