Abstract Background Implanting leads for cardiac implantable electronic devices (CIED) requires venous access. Venous access is commonly established through the cephalic and subclavian vein. For CIED upgrades or revisions, the preferred cephalic vein access is often not viable. Several reports suggest that fluoroscopy-guided axillary vein puncture may reduce thoracic complications. Purpose This study reports on procedural outcomes of ultrasound-guided axillary vein access for CIED implantation, revision, or upgrade in a large tertiary care centre. Outcomes were compared to the traditional subclavian vein approach. Methods This retrospective, single-center non-randomized study, conducted from January 2021 to August 2023, analyzed patients undergoing CIED implantation, revision, or upgrade. Axillary access, initially introduced by one operator, was increasingly adapted by additional operators. The axillary access was obtained by ultrasound-guided visualization of the axillary vein at the deltopectoral groove (Figure 1A and B). Subsequently, the wire(s) were transcutaneously inserted. An adjacent skin incision allowed for threading the wire(s) followed by standard lead implantation (Figure 1C). The study evaluated the acute success of each venous access method and the incidence of adverse events. Those were defined as pneumothorax, hemothorax, and pocket hematoma. An intention-to-treat analysis was performed. A p-value assessed the comparative outcomes between the axillary and subclavian access methods. Results In this study, 986 patients (mean age 74, IQR 64-82 years, 35% women) underwent CIED implantation, revision, or upgrade with 1636 lead implants. Axillary access was used in 578 patients with 532 (92%) successful implantations. Subclavian access yielded a higher success rate with 394/408 patients (97%) (p=0.003). For device upgrades or revisions specifically, axillary access was successful in 68/79 patients (86%), versus 44/47 patients (94%) with subclavian access (p=0.193). Acute complications were less frequent with axillary access (0.3%, 2/578 patients) and consisting of two cases of pneumothorax requiring intervention. In CIED implantations via subclavian access, complications occurred in 17/408 patients (4.2%) (p<0.001) including pneumothorax in 12 patients (2.9%, with 2% requiring intervention), hemothorax in three patients (0.7%), and pocket hematoma in two patients (0.5%). No additional complications were observed in the axillary group. Conclusion The implementation of transcutaneous, ultrasound-guided axillary access for CIED implantations, revisions and upgrades in a major CIED training centre is feasible. Complication rates were low compared to subclavian venous access.Figure 1