Several approaches are being utilized for the endovascular treatment of femoral-popliteal CTOs. An antegrade intraluminal approach had been the traditional method of revascularization, however, this technique may fail in up to 25% of cases, particularly with long, heavily calcified lesions (Jacobs et al. 2006; Conrad et al. 2006). Intentional subintimal dissection with true lumen re-entry, as first described by Bolia et al., is an appealing alternative strategy for treatment of CTOs, but it is not uncommon to fail true lumen access using a wire alone (Bolia et al. 1990). The Outback re-entry device is one of several support devices that has shown to be successful in transfemoral access, and more recently via transpedal access, when wire escalation techniques fail (Beschorner et al. 2009; Gandini et al. 2013; Patrone and Stehno 2019; Hayakawa et al. 2020). At our own practice, while the majority of femoral-popliteal CTOs can be crossed using standard techniques (mainly wire escalation therapies via transepdal or even dual access), < 5% of cases require the use of a support device. In this case series, we show that the Outback re-entry device can just as easily be utilized in high complexity lesion subsets such as femoral-popliteal CTOs, when wire escalation/dissection techniques fail. While the treatment of complex PAD via a transpedal approach is not new, the feasibility of using re-entry devices for femoral-popliteal CTOs through pedal access sites is not yet widely reported (Scott et al. 2007; Clark et al. 2016). The ability to treat complex PAD via the transpedal approach with the same armamentarium available with the femoral access site is important to realize because one of the concerns that many operators have in adopting the transpedal approach is the availability of support equipment for complex cases.
The endovascular treatment of PAD via the transpedal approach is also a possible way to follow the current trend in healthcare of providing patients with safe, effective care while decreasing costs and minimizing risks. The risks associated with femoral artery access have been well published which has led to the development of smaller, alternative access sites. In our coronary counterparts, radial access has been proven to be a safer alternative to femoral access (Kiemeneij et al. 1997; Jolly et al. 2009; Sajnani and Bogart 2013; Vora and Rao 2014). Other benefits to the transpedal approach may include less contrast utilization, less radiation exposure, and less post procedure monitoring (decreased time to ambulation). This is especially important as many of these procedures can be performed in the outpatient based lab setting – which may decrease health care costs by reducing inpatient hospital monitoring.
Ideally, transpedal retrograde revascularization using the Outback re-entry device is best suited if prior antegrade attempts are unsuccessful and in cases with at least 2 tibial vessels (should access vessel closure occur). Pedal vessel selection and determining the appropriateness of the access site should be guided by duplex ultrasound. In addition, it is important to be aware of potential procedure complications such as vessel perforation, and dissection of the treated or accessed vessel. For these reasons, the contralateral femoral site should be always prepared in case of bailout.
Limitations
This is a small, single center retrospective series of selected patients and larger studies are necessary to better evaluate safety and efficacy. For the purposes of this paper, follow-up was limited to 1 month and our results cannot be extrapolated to determine long-term vessel patency using this approach. Furthermore, the procedures were performed by operators familiar with transpedal access and the results may not be generalizable to those with less experience in the transpedal technique especially since ultrasound guided access may be difficult and time-consuming to operators unfamiliar with the approach.
While radial access was still necessary to visualize the proximal cap and length of the CTO, smaller 4-Fr sheaths are still utilized and the femoral artery is still avoided which will result in less complications. Furthermore, Clark et al. reported a case of transpedal only access for treatment of a superficial femoral artery CTO - which highlights the fact that in some cases the filling of the proximal cap through collaterals may be sufficient (therefore making radial access unnecessary) (Clark et al. 2016). Although more studies need to be performed to further evaluate the scope of PAD treatment via the transpedal access site, the ability to use re-entry devices via transpedal access is an important step towards increased utilization of alternative access sites.