Dr. J.A. Mustapha: Dr. Fisher, please discuss the value of connections between the anterior and the posterior circulation and pedal loops.
Dr. Bryan T. Fisher, Sr.: The pedal loop is the third and arguably most vital part of lower extremity perfusion and wound healing. It is known that outflow is correlated with patency, yet some would argue that we don’t pay enough attention to the distal foot circulation. To entertain treatment of the pedal arch and vessels distal to the tibiotalar joint, it is vital to understand the arterial anatomy of the foot (Figure 1). To do so affords the opportunity to reliably and effectively increase flow to the forefoot, setting the stage for relieving the disabling symptoms of critical limb ischemia.
Dr. Mustapha: What are reasons why you might attempt pedal loop reconstruction?
- Conduit for retrograde crossing of a chronic total occlusion (CTO) from another tibial vessel (i.e., antegrade posterior tibial [PT] to retrograde dorsalis pedis artery [DP] and PT via the pedal arch to cross a lesion that is unable to be traversed in an antegrade fashion).
- Planned open bypass, especially with single-vessel runoff.
- Presence of “small vessel” stenotic/occlusive disease (a loosely applied term to describe diseased vasculature distal to the DP and PT).
- Presence of digital ulcer and the presence of abnormal waveforms in the toes.
Dr. Mustapha: What are the wires, catheters, and balloons you use in pedal loop intervention?
Dr. Fisher, Sr.: The case is broken down into access, treatment setup, lesion crossing, treatment, and reassessment.
- Access is unremarkable, other than the advantage of obtaining antegrade access throughout the lower extremity to increase pushability and torqueability while conserving wire/catheter length.
- Treatment setup is achieved by command wire placement and introduction of a longer sheaths from the common femoral, and lower profile 10 cm sheaths below the calf. At this point, the patient is heparinized. Next, a triaxial system is introduced (Corsair catheter [Asahi Intecc], Navicross [Terumo], Command wire [Abbott Vascular]).
- Lesion crossing is achieved with a combination of microchannel navigation, leading loop, and progression to slightly heavier tipped wires. A double-angle technique is used with the Regalia wire (Asahi Intecc) or the Fielder XT (Asahi Intecc) to facilitate crossing of the often tortuous distal foot vessels. My catheter support of choice is the Corsair telescoped within a Navicross, as the former provides very good pushability, and crosses most very tight lesions to facilitate wire exchange and vessel modification, and the latter provides additional support for wire/catheter manipulation in the foot. Subintimal angioplasty affords a realistic opportunity for wound healing, though true lumen treatment, when possible, is considered ideal.
- Treatment is achieved through a combination of vessel preparation (atherectomy) and balloon angioplasty. If the vessel is larger than 1.5-2 mm, I typically attempt to interrogate the loop with intravascular ultrasound (IVUS) both before and after treatment. Doing so gives me a precise ability to size a balloon without guessing, based on angiographic visualization. If IVUS is not possible due to tortuosity or small size, I will typically start with a 2 mm balloon that traverses the entire pedal arch and extends into the lateral plantar (posterior) and DP (anterior). Slow, deliberate insufflation is performed, with careful attention paid to tactile feedback and fluoroscopic visualization. Long inflation times are used, especially if the vessel can accommodate a 2.5 mm balloon. In the case of this minimum vessel diameter, I have had success with Chocolate balloon (Medtronic) angioplasty and have noted a smaller, less lumen-intrusive intimal flap with longer insufflations (~4 minutes at nominal pressure). It is imperative to have a minimal vessel size of 2.5 mm, as the nitinol cage can catch on small arterial wall defects and result in difficult balloon retrieval, even after insufflation.
Dr. Mustapha: Do you currently use atherectomy in the pedal loop?
Dr. Fisher, Sr.: Atherectomy is often a viable and successful option in the treatment of pedal loop disease. In fact, I have found that the inability to perform atherectomy sometimes limits my ability to cross the lesion with a balloon catheter for angioplasty. With regard to the type of atherectomy, the orbital modality has been used with the most frequency and success. When used, the Diamondback orbital atherectomy system (Cardiovascular Systems, Inc. [CSI]) is used at the lowest rotational speed for limited areas of heavily calcified, stenotic disease. It cannot be emphasized that atherectomy distal to the tibiotalar joint should only be attempted by advanced operators. In the pedal arch, inexperience can lead to severe vessel injury and major limb loss.
Dr. Mustapha: How do you size pedal angioplasty balloons and do you use specialty balloons?
Dr. Fisher, Sr.: Sizing, for me, is very simple. I use IVUS and/or transcutaneous ultrasound for every case. Intravascular ultrasound use becomes challenging in the pedal arch, because the vasculature can decrease to sizes that are sub-1.5 mm and tortuous. In the event that IVUS is not possible, I start small with a 1.5-2 mm balloon and subsequently escalate therapy when appropriate. I tend to only use plain old balloon angioplasty (POBA) in this area when the vessel is less than 2 mm in maximal diameter. Anything larger than 2.5 mm permits the use of a Chocolate balloon. Long insufflation times (3-4 minutes) are standard.
Dr. Mustapha: Can you describe the need for digital balloon angioplasty?
Dr. Fisher, Sr.: Digital angioplasty is a part of the final frontier in the treatment of distal vessel CLI. Digital vessels can also exhibit segmental occlusion with the challenge being their small size (<1.5 mm) and possibility of spasm-induced re-occlusion after treatment. Small diameter vessels require slow, deliberate insufflation and the judicious use of vasodilators (we prefer 200-400 mcg nitroglycerine, as tolerated, every 30-40 minutes).
Disclosure: Dr. Fisher, Sr., reports the following – Medical Advisory Board: Philips
Abbott Vascular, Bard PV. Physician Advisor/Research: CSI, Bard PV, Abbott Vascular, Philips, Medtronic, Terumo.
Dr. Bryan T. Fisher, Sr., can be contacted at email@example.com.
Dr. J.A. Mustapha can be contacted at firstname.lastname@example.org.
A Pedal Loop Case
Bryan T. Fisher, Sr., MD
A 58-year-old gentleman with a history of smoking and type II diabetes mellitus presented with persistent great toe pain while recumbent and with walking. He had been seen by another interventionalist who obtained non-invasive studies (Figures 1-2), and told the patient that he suffered from small-vessel disease and would either have to “deal with it” or have a below-the-knee amputation.
After obtaining antegrade access, we first treated the common plantar lesion with orbital atherectomy and balloon angioplasty. Multiple attempts were made at crossing the medial plantar artery, but were unsuccessful. An .014-inch Command wire (Abbott Vascular) was used to navigate into the dorsalis pedis artery. A distal anterior tibial (AT) lesion was treated, followed by preparation for crossing the medial plantar lesion in a retrograde fashion from the antegrade AT approach. A Corsair catheter (Asahi Intecc) and Regalia wire (Asahi Intecc) were used to traverse the lesion after forming a loop in the wire (Figure 3). After crossing the lesion, we exchanged for a Viper wire (CSI) and modified the lesion with the 1.25 mm micro-crown on low speed with 2 passes. Intravascular ultrasound was performed, followed by balloon angioplasty with a 2.5 x 100 mm balloon (Figure 4), with a good final result (Figures 5-6).