The optimal operative protocol to accomplish CO2-EVAR resulting from a prospective interventional multicenter study

Objectives: Carbon dioxide (CO2) angiography for endovascular aortic repair (CO2-EVAR) is used to treat abdominal aortic aneurysms (AAAs), especially in patients with chronic kidney disease or allergy to iodinated contrast medium (ICM). However, some technical issues regarding the visualization of the lowest renal artery (LoRA) and the best quality image through angiographies performed from pigtail or introducer sheath are still unsolved. The aim of this study was to analyze different steps of CO2-EVAR to create an operative standardized protocol. Methods: Patients undergoing CO2-EVAR were prospectively enrolled in five European centers from 2019 to 2021. CO2-EVAR was performed using an automated injector (pressure, 600 mmHg; volume, 100 cc); a small amount of ICM was injected in case of difficulty in LoRA visualization. LoRA visualization and image quality (1 = low, 2 = sufficient, 3 = good, 4 = excellent) were analyzed at different procedure steps: preoperative CO2 angiography from pigtail and femoral introducer sheath (first step), angiographies from pigtail at 0%, 50%, and 100% of proximal main body deployment (second step), contralateral hypogastric artery (CHA) visualization with CO2 injection from femoral introducer sheath (third step), and completion angiogram from pigtail and femoral introducer sheath (fourth step). Intraoperative and postoperative CO2-related adverse events were also evaluated. χ2 and Wilcoxon tests were used for statistical analysis. Results: In the considered period, 65 patients undergoing CO2-EVAR were enrolled (55/65 [84.5%] male; median age, 75 years [interquartile range (IQR), 11.5 years]). The median ICM injected was 17 cc (IQR, 51 cc); 19 (29.2%) of 65 procedures were performed with 0 cc ICM. Fifty-five (84.2%) of 65 patients underwent general anesthesia. In the first step, median image quality was significantly higher with CO2 injected from femoral introducer (pigtail, 2 [IQR, 3] vs introducer, 3 [IQR, 3]; P = .008). In the second step, LoRA was more frequently detected at 50% (93% vs 73.2%; P = .002) and 100% (94.1% vs 78.4%; P = .01) of proximal main body deployment compared with first angiography from pigtail; similarly, image quality was significantly higher at 50% (3 [IQR, 3] vs 2 [IQR, 3]; P ≤ .001) and 100% (4 [IQR, 3] vs 2 [IQR, 3]; P = .001) of proximal main body deployment. CHA was detected in 93% cases (third step). The mean image quality was significantly higher when final angiogram (fourth step) was performed from introducer (pigtail, 2.6 ± 1.1 vs introducer, 3.1 ± 0.9; P ≤ .001). The intraoperative (7.7%) and postoperative (12.5%) adverse events (pain, vomiting, diarrhea) were all transient and clinically mild. Conclusions: Preimplant CO2 angiography should be performed from femoral introducer sheath. Gas flow impediment created by proximal main body deployment can improve image quality and LoRA visualization with CO2. CHA can be satisfactorily visualized with CO2 alone. Completion CO2 angiogram should be performed from femoral introducer sheath. This operative protocol allows performance of CO2-EVAR with 0 cc or minimal ICM, with a low rate of mild temporary complications.