Introduction: Ablation Index guided ablation according to the CLOSE protocol is very effective in terms of chronic pulmonary vein isolation (PVI). However, the optimal RF power remains controversial. Here, we thought to investigate the efficiency and safety of an AI guided fixed circumferential 50W high power short duration (HPSD) PVI using the CLOSE protocol Methods and results: In a single-centre prospective “proof of concept” trial 40 patients underwent randomized PVI using AI guided RF ablation without oesophageal temperature monitoring. In 20 patient fixed 50W HPSD was used irrespective to the anatomical localization. 20 subjects were ablated with standard power settings (20W posterior and 40W roof and anterior wall). Additionally, 80 consecutive patients were treated according to the HPSD protocol to gather additional safety data. All patients underwent post-procedural oesophago-gastro-duodenoscopy to reveal oesophageal lesions (EDEL). The mean total procedural time was 80.3±22.5 minutes in HPSD compared to control 109.1±27.4 (p<0.001). The total RF-time was significantly lower in HPSD 1379±505 sec vs. control 2374±619 sec (p<0.001).There were no differences in periprocedural complications. EDEL occurred in 13% in the HPSD and 10% in control group. EDEL occurring in the 50W HSDP patients were smaller, more superficial and had a faster healing tendency. Conclusions: A fixed 50W HPSD circumferential PVI relying to the ablation index and CLOSE protocol reduces the total procedure time and the total RF time compared to standard CLOSE protocol, without increasing the complication rates. The incidence of oesophageal lesions was similar using 50W at the posterior atrial wall.