Feasibility and Safety of Using Carbon Dioxide Exclusively in Regular Endovascular Aortic Aneurysm Repair: Results of a Multicentre, Prospective, Zero Iodine Contrast Endovascular Aneurysm Repair Study.

Objective: Carbon dioxide (CO₂) angiography has emerged as a viable alternative to regular iodinated contrast medium (ICM) for guiding endovascular aneurysm repair (EVAR) procedures. This study aimed to evaluate the feasibility and safety of a standardised EVAR procedure using only CO₂ angiography.

Methods: A prospective, multicentre, national study enrolled consecutive patients between January 2023 and January 2024 with asymptomatic abdominal aortic aneurysms measuring ≥ 55 mm and for whom a standard endovascular graft (instructions for use) was anatomically feasible. The study involved the use of an automatic CO₂ injector to standardise intra-operative imaging. A strategy comprising five standardised steps was devised to visualise a target vessel (TV) that could not be seen during the first CO₂ angiogram. The five steps were: (A) place the introducer closer to the TV; (B) tilt the table by 5 - 10° in the direction opposite to the TV; (C) selectively cannulate the TV; (D) cannulate the contralateral gate (only for repositionable devices); CO₂ angiography was repeated in steps 1 - 2; and (E) use ICM.

Results: Two hundred and ninety-three patients were enrolled (10 centres), with a median age of 78 (interquartile range [IQR] 72, 83) years; 256 (87.4%) were male. The overall procedure time, fluoroscopy time, and injected CO₂ volume were 90 (IQR 65, 125) minutes, 15 (IQR 10, 22) minutes, and 600 (IQR 400, 800) mL, respectively. The 30 day mortality, complication, and re-intervention rates were 0.3% (n = 1), 6.8% (n = 20), and 2.4% (n = 7), respectively. CO₂ related adverse events were rare (1%; n = 3) and minor. A zero iodine contrast EVAR procedure was feasible in 240 (patients 81.9%). The five standardised steps were used extensively: step A, 170 procedures (58.0%); step B, 109 procedures (37.2%); step C, 21 procedures (7.2%); step D, 14 procedures (4.8%); and step E, 53 procedures (18.1%), with a median volume of 20 (IQR 10, 35) mL. Significant predictors for ICM use were aneurysm diameter > 70 mm and a lowermost renal artery positioned between 3 and 9 o'clock.

Conclusion: This study demonstrated that the standardised zero iodine contrast EVAR protocol reported here is both safe and feasible and is applicable in 82% of consecutive non-selected patients. Limitations primarily arose from anatomical factors, and adjunctive standardised manoeuvres can effectively address these challenges in most cases.