The treatment for complex iliac occlusions has switched from open surgery to endovascular-first approaches (6). In addition, multivessel accesses are often required during the intraluminal procedure, but the superiority of the crossing direction (antegrade vs. retrograde) is still unknown. Considering the pushability of catheters and the working efficiency, the antegrade approach is empirically preferred for EIA lesions, while the retrograde approach is preferred for CIA CTOs. However, antegrade accesses from the contralateral femoral artery or left brachial artery are also available for CIA lesions. After failure of the initial retrograde crossing approach in 99 patients with aortoiliac CTOs, Miion et al. chose the antegrade approach from the brachial artery and maintained a high technical success rate of 93% (6).
Previous studies have shown no connection between the crossing strategy and lesion position. For example, Kokkinidis DG et al. retrospectively analyzed 188 lesions and failed to find any association except for the EIA with antegrade crossing (7). However, most of their patients underwent successful crossing with the initial attempt, so it is unknown whether the other crossing approach was available for those lesions. In our study, we focused on lesions with an unsuccessful initial crossing strategy and those that were managed by the final approach, which more clearly demonstrates the optimal crossing strategy. Finally, our study showed that the final crossing direction was not associated with EIA CTOs; in contrast, CIA CTOs were more likely to be crossed successfully with the retrograde approach. In addition, antegrade crossing was more efficient than retrograde crossing for CIA and EIA CTO lesions.
In this study, two or three accesses were used to cross the CTO lesions. The brachial approach had the advantages of allowing a direct line for recanalization and increasing the torque force that could be applied to guidewires. As a result, the transbrachial approach was considered when contralateral crossover failed or was not appropriate due to the anatomy of the lesions. For example, brachial access would increase the probability of crossing for a flush iliac artery occlusion, which is a CTO lesion without a stump in the origin of the CIA. The guidewire and catheter approaches from the contralateral femoral artery are prone to slipping in the aorta because of the lack of required support (4, 8). As shown in our study, the presence of a stump in the CTO lesions was associated with the use of contralateral access (72% vs. 27%). Retrograde crossing is the preferred strategy used by some operators, as it is straight, short, and easy to manipulate, yet it has the disadvantage that it usually involves advancing into the subintimal space, which is a difficult issue for perforating thickened aortic intima and causes serious complications owing to aortic dissection. Therefore, the subintimal approach is supposed to prevent dissection from extending to the level of the aortic bifurcation, and re-entry techniques are needed (9).
As noted in the literature, anatomic characteristics may be related to crossing approaches. Severe calcification, thrombosis, and rigid plaques are hindrances for the advancement of guidewires in the true lumen (10, 11). Statistically, we found that longer lesions with severe TASC categories were more likely to be crossed with the antegrade approach. Furthermore, the antegrade crossing approach was associated with fewer subintimal crossing and re-entry techniques. According to our data, multivariate logistic regression demonstrated that subintimal crossing was associated with severe calcifications, the retrograde approach, and long lesions.
Primary stents were deployed in all our patients. Primary stenting is preferred for preventing the arterial wall from retracting, and it can obtain an adequate patency rate, as nearly half of all CTO lesions cross through the subintimal space (12, 13). In recent years, the majority of our stents have been self-expandable because balloon-expandable stents are not always available in our center. Usually, self-expandable stents are more flexible and are preferred for tortuous iliac arteries and for kissing stenting of the aortic bifurcation (14). On the other hand, balloon-mounted stents are deployed for lesions that require a strong supporting force and a strictly precise placement. To prevent thromboembolism and artery rupture, covered stents may be suitable (15). However, there is no clinical evidence of a significant advantage of one type of stent over the other based on long-term outcomes. The choice of stent depends not only on the lesion to be treated but also on the size of the introducing sheath as well as the familiarity with and availability of specific devices.
According to the TASC II guidelines, open surgery remains the gold standard of treatment for complex aortoiliac disease because it has excellent short- and long-term patency rates, which are as high as 85%-92% (11, 16, 17). The primary 2-year patency rate for complex and extensive lesions treated with endovascular procedures was 94% in one multicenter study, which is comparable to the outcomes of TASC A and B lesions (18). Even the long-term outcomes of stent placement in complex aortoiliac CTOs are acceptable, such as the 5-year patency rate of 88% found in the study conducted by Ichihashi et al (19). In our retrospective study, the 1- and 5-year primary patency rates were 97.3% and 80.1%, respectively. Once crossed successfully, there were no significant differences in the long-term patency rates according to the crossing strategy.
Our retrospective study should be explicated within the context of some limitations. Based on the real-world setting, the current comparison of the antegrade crossing approach versus the retrograde crossing approach may result in differences in baseline data and outcomes, which is the same as that found in most observational research. The data, such as the technical success rate, patency rate, and complication rate, were not consistent with the general outcomes of other research because our study focused only on the surgical attempts of extreme complex iliac artery CTO lesions with two crossing directions. In some respects, the choice of vascular access depends not only on the anatomic characteristics but also on the experience of the operator. As a result, further prospective studies should be designed to explore the optimal crossing strategy for complex iliac artery CTOs.