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The Greek philosopher Plato once said, “Necessity is the mother of invention”. Well, he may have had critical limb ischemia (CLI) therapy in mind. Most cardiovascular specialists realize that the majority of patients presenting with ischemic rest pain and non-healing wounds have already progressed to a multilevel occlusive arterial disease by the time they seek help.
Evidently, the ability to revascularize these patients has become much more technically challenging with the high incidence of long and heavily calcified chronic total occlusions (CTO) in this CLI population. Unfortunately, the traditional approach of contralateral retrograde common femoral artery (CFA) access in these complex patients with multiple comorbidities is no longer sufficient for optimal success in providing in-line flow to the affected angiosome. Hence, necessity has naturally pushed for the invention of new alternative approaches to tackle arterial occlusive disease with new strategies. This has led to an explosion of techniques pioneered by master operators all over the world that have quickly spread throughout the endovascular specialty. We are fortunate to live in such a well-connected world and the exchange of bright ideas continues to fuel a rising wave of alternative access techniques. Fortunately, the industry is listening to the needs of the endovascular specialists and delivering dedicated equipment, which continues to raise the success rates of CTO interventions. We suggest approaching the important topic of alternative arterial access with the following questions:
1) WHAT is it?
2) WHY is it needed?
3) WHERE are the access sites?
4) HOW safe is it?
WHAT Is It?
It is reasonable to define alternative access as all other access sites besides retrograde common femoral artery (CFA) access, with the goal of endovascular revascularization of lower limb obstructive arterial disease.
WHY Do We Need It?
Hostile groins are becoming more frequent due to the obesity epidemic. Various other factors also contribute to hostile groins, creating a significant technical and procedural challenge, including previous cut down, fungal dermatitis, cellulitis, and recent groin complications (Figure 1). On the other end of the spectrum, extremely thin patients have their own share of vascular complications. Alternative access routes are often necessary to decrease peri-procedural morbidity.
Moreover, extreme iliac tortuosity and heavy iliac calcifications (Figure 2) predispose to life-threatening bleeding disasters if aggressive approaches are undertaken during the “up-and-over” delivery of equipment. Avoiding this technical challenge not only simplifies the procedure, but lowers the complication rate tremendously. It also improves torqueability and pushability, as well as crossing power. It would make much more sense to tackle an occlusion straight on, from an antegrade or retrograde approach, rather than significantly diminishing the vector of force through the friction encountered by the contralateral equipment.
Furthermore, in patients with ostial common iliac artery stents, previous endovascular aortic aneurysm repair, and aorto-femoral bypass, an “up-and-over” approach can not only cause iatrogenic stent graft deformations, but also renders equipment delivery very challenging (Figure 3).
Additionally, the proportion of cases with challenging anatomy such as long multi-segmental occlusions, heavy calcification, and occluded stents (Figure 4), is steadily rising in the CLI population, with patients who often suffer from severe comorbidities that significantly raise the perioperative surgical risk. One of the essential factors required for the success of an endovascular approach in these patients is the ability to push, torque, and cross very hard lesions. An antegrade femoral approach and/or retrograde tibiopedal access sites provide a big advantage from this standpoint. The success of these minimally invasive revascularization procedures ultimately helps wound healing and prolongs life.
Other advantages offered by retrograde tibiopedal access, especially in CTOP (CTO crossing approach based on plaque cap morphology) type 2 and 4 cap morphologies (Figure 5), are not only the ease of crossing of a concave distal cap from below, but also lower procedure time, contrast volume, patient/operator radiation exposure, and cost.
With the epidemic of type 2 diabetes, we are often faced with isolated distal tibiopedal disease in CLI patients. Even if these lesions are crossed from a contralateral retrograde common femoral access, it presents another technical challenge, especially in tall patients: distance. If dedicated long shaft balloons, which are not available in every lab, can reach, atherectomy devices and stents often don’t (with some exceptions). This is not a problem when the lesions are addressed from an ipsilateral femoral or retrograde tibiopedal approaches.
On the other hand, in the absence of dedicated .014-inch wire-compatible peripheral re-entry devices and with the additional cost of off-label coronary CTO re-entry devices, the re-entry challenge in tibiopedal interventions often requires dual access, including a retrograde tibiopedal access, and the application of coronary CTO techniques such as the controlled antegrade retrograde tracking (CART) and reverse CART techniques (Figure 7).
Alternative access from a radial approach also offers the advantage of coaxial alignment with an arterial segment (common iliac, external iliac, profunda, superficial femoral), which simplifies precise ostial treatment.
Finally, a significantly lower rate of vascular complications, bleeding, contrast volume, back pain and patient/operator radiation exposure in addition to the early ambulation/discharge all add to the list of benefits of radial and tibiopedal approaches, in addition to improved outcomes, simplifying outpatient throughput, and boosting patient satisfaction (Figures 8-9).
WHERE Are the Access Sites?
Figure 10 outlines the anatomical and extra- anatomical access sites, along with their directions.
Antegrade CFA is the dominant approach for CLI therapy (Figure 11). It offers adequate size sheath access (4-7 French[Fr]) to femoropopliteal and infrapopliteal obstructive disease with manageable distance, as well as superior torqueability, pushability, crossing ability, and support. However, in the presence of a large pannus, the technical challenge of puncturing the CFA target zone at an optimal angle through a very thick layer of adipose tissue may require a longer needle (spinal), and predisposes for bleeding and vascular complications (Figure 12). In addition, under ultrasound or fluoroscopy, it is sometimes difficult to get the wire in the superficial femoral artery (SFA) rather than the profunda, which adds procedural time, radiation exposure, and may require placing the sheath in the profunda first, then redirecting the wire into the SFA while pulling the sheath over another wire.
For these reasons, antegrade SFA access has been gaining more popularity (Figure 13). It is usually accessible without traversing a large layer of pelvic adipose tissue and there is no time wasted on redirecting the wire. However, the occasionally non-compressible location of the proximal segment predisposes for bleeding and vascular complications. The sweet spot that offers direct access to the SFA and is often compressible in most patients is the SFA ostium, as identified by ultrasound (US). It is recommended to evaluate the compressibility of this site by US and the presence of underlying femoral bone by US and fluoroscopy before puncturing. One must also use the smallest size sheath possible to do the job and consider the off-label use of braided, thin-walled radial sheaths (Merit Medical) to minimize arteriotomy size while avoiding kinking. Off-label closure of the SFA, preferably with extravascular devices under fluoroscopic and/or US guidance, is usually safe and feasible.1-3
The distal SFA, at the medial distal thigh (Figures 14-15) could rarely be the site of sheathless retrograde access with the introduction of an .018- or .014-inch microcatheter and wire to cross the occlusion, followed by hemostasis of the access site through antegrade balloon angioplasty. This is usually performed under fluoroscopic guidance when a stent (Figure 15) or heavily calcified distal SFA are targeted, but a native, non-calcified SFA can be accessed with US guidance in relatively thin patients (Figure 14).
Of note, antegrade (Figure 16) or retrograde popliteal and retrograde brachial access sites are losing their rankings against tibiopedal and radial access, with the advent of braided, thin-walled hydrophilic sheaths and dedicated radial-to-peripheral equipment (Terumo). In the rare circumstances where popliteal or brachial approaches are needed, there are multiple common factors to be taken into consideration for these two often-problematic access sites: (1) Ultrasound guidance is key, requiring special care to avoid the satellite veins and nerves (Figure 17); (2) Use of the lowest sheath size possible; (3) Manual patent hemostasis with longer hold times by the operator or experienced technologist; (4) Despite all precautions, these sites carry the highest risks of bleeding and vascular complications (Table 1, tables on page 20).
The radial-to-peripheral movement (R2P) is expanding throughout the United States and the rest of the world, especially with advent of dedicated sheaths, balloons, and stents meeting needs for the required length and deliverability of the equipment. Table 2 shows the improvements made by Terumo to their dedicated R2P equipment in order to make these procedures possible. Table 3 outlines the pros and cons of this approach, and Table 4 lists a few tips and tricks required for this strategy. Relatively proximal left-sided access is favored, as long as it is compressible by US. The right radial is convenient and still feasible in the right anatomy, as long as the aortic arch status is known and the culprit lesion can be reached. Personally, I keep a tape measure in my lab coat pocket for planning these procedures while in the clinic or hospital.
Even though this single-access approach is feasible for iliac and proximal femoral stenosis (with a 6 Fr-compatible covered stent for bailout options), it is not optimal for long, calcified occlusions, due to lower support and pushability. Lower procedural morbidity, early ambulation/discharge, and better patient satisfaction are all positive, but case selection is key.
The combination of radial and pedal (Figure 18) accesses maintains all these benefits; however, it is not a reasonable solution for interventions on iliac arteries larger than 7 mm, since larger covered stents are not 6 Fr sheath compatible and advancing a covered stent through a retrograde sheathless approach is not optimal.
Axillary access, which is gaining momentum in the structural heart interventional world, as well as with mechanical circulatory support, seems to be preferred over brachial access for large-bore sheath interventions from above (Table 1), due to its compressibility and better control of bleeding with certain backup endovascular strategies.5 A dry closure technique with balloon tamponade from ipsilateral radial access has been very rewarding.5
In general, retrograde tibiopedal access (Figure 19) is often thought to be synonymous to alternative arterial access; however, as noted in this section, it is not the only alternative route to treat CLI patients. It is encouraging to see that industry has engaged in manufacturing dedicated 2.9 Fr sheaths and a line of compatible balloons (Cook Medical) to tackle lesions primarily or secondarily from a retrograde approach. The interventional community culture has also embraced the off-label use of thin-walled radial sheaths to aid in crossing occlusive disease and delivering therapy. Given the significant advantages offered by a retrograde approach, including faster recovery times and early discharge, experienced operators have even proven the safety and efficacy of using it as the sole access site, according to the Tibiopedal Arterial access for Minimally Invasive retrograde revascularization (TAMI) technique.4 Less contrast is needed for selective retrograde injections. In CTOP class 2 or 4, retrograde crossing is often faster. There are also advantages regarding potential treatment of the entire lower extremity arterial system, with the possibility of treating both legs in one setting, if contrast volume allows and longer sedation is not an issue. There are also operators who believe in the benefits of a sheathless .018- or .014-inch retrograde approach, with the purpose of crossing lesions, then removing the retrograde equipment as soon as possible and working from above.
On the other hand, tibiopedal access can also be undertaken in an antegrade fashion (Figure 20), with or without sheath placement, to tackle mostly distal pedal disease in a small, selected proportion of patients. When used, tibiopedal access is often a secondary access with or without sheath placement (preferably a micropuncture sheath or only a micropuncture dilator). It is also used in certain complex trans-collateral retrograde tibial revascularization procedures (through the plantar loop) when there are hurdles regarding wire torqueability, equipment pushability, or pedal CTO crossability from a femoral approach.
However, absolute caution is needed regarding hemostasis. Compartment syndrome related to non-compressible access bleeding, in the setting of CLI, is a very significant risk factor for limb loss. If this is a secondary access (large majority of the time), internal balloon tamponade at the access site with post deflation angiogram is mandatory. If this is a single-access approach, the puncture should be as distal as possible, overlying bone and confirmed to be compressible by US.
With the epidemic of obesity and type 2 diabetes, the interventional community is seeing more and more isolated distal occlusive disease below the ankle. These patients often do not have acceptable outflow. Sheathless digital access at the dorsal forefoot can also save the day in below-the-ankle interventions when re-entry from the dissection plane into the true lumen is not successful (Figure 21).
Accessing occluded digital arteries under US or fluoroscopy (if heavily calcified) is occurring more frequently in amputation prevention centers. It can also be performed from the plantar surface, which requires very supportive .014- or .018-inch wires due to the very thick skin in this area. Figure 22 shows the anatomy of neurovascular structures as seen from the plantar surface of the foot.
Access of extra-anatomical arterial bypass grafts with the smallest size sheath possible is feasible and safe in certain compressible segments (Figures 23-25). Detailed review of operative reports including the specific type of bypass graft is mandatory. Micropuncture technique is recommended, as well as very supportive .018-inch wires, such as the V18 (Boston Scientific), Glidewire Advantage (Terumo), and Steelcore (Abbott Vascular), and sequential .021-inch dilator upsizing to target sheath size. Manual hemostasis is preferred, even though a few operators elect the off-label use of suture-based closure devices (Perclose, Abbott Vascular) under US guidance.
HOW Safe Is It?
In the midst of all the excitement regarding minimally invasive endovascular procedures with lower bleeding potential, faster ambulation, and better convenience for patients, operators should adopt a very cautious approach to alternative arterial access, as it can also lead to disastrous complications including limb loss (careful — there is no free lunch!).
The incidence of pseudoaneurysm at the tibiopedal access site (Figure 26) is rare (0.2-1.3%)6,7, but likely rising with the recent increased adoption of this technique. The use of hemostatic devices like the TR Band (Terumo) or VasoStat (Forge Medical) with a Doppler-based patent hemostasis protocol minimizes this complication.7 Prolonged compression or thrombin injection are most often effective, but surgical repair is recommended when the neck is relatively large.
Bleeding from non-compressible sites is problematic in the CLI population and should be detected very early. Manual blood pressure cuffs are helpful, but should be used for a short time to avoid the other extreme: thrombosis and worsening limb ischemia. Balloon-assisted focal compression with a safeguard device (Merit Medical) potentiated by manual hold of the device itself could be helpful. The worst-case scenario is the development of compartment syndrome, which often leads to amputation in this CLI population (Figure 27).
Other very rare complications include arteriovenous fistula, dissection, thrombosis, infection, distal embolization, and nerve injury. Some of these complications can be mitigated by very careful use of US, not only for access but also for wire advancement. This is one of the aspects of peripheral vascular interventions that requires a lot of finesse, subtle tactile “feel”, and considerable attention to detail of multiple technical factors.
For that reason, one must be very careful in treating the claudicant population with alternative arterial access. The very small likelihood of complications may lead a claudicant to amputation, which is hardly defensible. In the rare situation where tibiopedal access is the only reasonable option available to the patient, then a thorough discussion of the risk/benefit ratio is necessary.
For the non-surgical endovascular operators, before committing to a certain strategy and before burning any bridges for surgical bypass, a pre-procedural discussion with vascular surgery is always a good idea. It helps to outline the “anatomical and individual red lines” of endovascular therapy.
We conclude by returning to Plato: “The beginning is the most important part of the work”. The key to success in complex CLI therapy rests at its beginning: access, access, access.
Disclosure: Dr. Lichaa reports he is a consultant for BD and Cook Medical.
Dr. Hady Lichaa can be contacted at firstname.lastname@example.org or on Twitter @HadyLichaaMD
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- Spiliopoulos S, Kitrou P, Chisteas N, Karnabatidis D. Starclose SE hemostasis after 6F direct antegrade superficial femoral artery access distal to the femoral head for peripheral endovascular procedures in obese patients. Diagn Interv Radiol. 2016 Nov; 22(6): 542-547.
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- Mustapha J, Saab F, McGoff TN, et al. Tibiopedal arterial minimally invasive retrograde revascularization (TAMI) in patients with peripheral arterial disease and critical limb ischemia. On behalf of the Peripheral Registry of Endovascular Clinical Outcomes (PRIME). Catheter Cardiovasc Interv. 2020 Feb; 95(3): 447-454. doi: 10.1002/ccd.28639
- Thawabi M, Tayal R, Hawatmeh A, et al. Percutaneous transaxillary approach for peripheral endovascular interventions. Catheter Cardiovasc Interv. 2019 Aug 1; 94(2): 243-248. doi: 10.1002/ccd.28333
- Mustapha J, Diaz-Sandoval LJ, Jaff MR, et al. Ultrasound-guided arterial access: outcomes among patients with peripheral artery disease and critical limb ischemia undergoing peripheral interventions. J Invasive Cardiol. 2016 Jun; 28(6): 259-264.
- Patel A, Parikh R, Bertrand OF, Kwan TW. A novel patent hemostasis protocol—prevention of pseudoaneurysm after tibiopedal arterial access for evaluation and treatment of peripheral arterial disease. Cardiovasc Revasc Med. 2019 Jul; 20(7): 598-602. doi: 10.1016/j.carrev.2018.08.023