Posted on October 4, 2017 by RADPAD
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This is an extremely interesting article on using the venous system to re-vascularize “cold feet” and the challenges that come with the process. Saving limbs has become the rally cry for vascular surgeons around the world. They know that the patient’s chances for any long term success are tied to keeping their limbs.
CLI Perspectives is headed by section editor J.A. Mustapha, MD, Metro Health Hospital, Wyoming, Michigan.
Dr. Mustapha interviews Steven Kum, MBBS, FRCS, Novena Vascular & Varicose Vein Centre, Mount Elizabeth Hospital; Director of Vascular Services, Department of Surgery, Changi General Hospital, Singapore.
J.A. Mustapha, MD
End-stage critical limb ischemia (CLI) is what we refer to as patients who have had revascularization attempts and are still facing major amputation. These patients are also referred to as Rutherford 6. During recent presentations at the 2016 Amputation Prevention Symposium (AMP) and 2016 Vascular InterVentional Advances (VIVA) conferences, Dr. George Adams and Dr. Jihad Mustapha presented data from the LIBERTY trial that showed 78% of Rutherford 6 patient were discharged home within 27 hours after endovascular revascularization, without limb loss. Their 30-day follow-up visit showed a similar high number of patients with their target limb still intact. Is it time to reconsider the fate of patients with Rutherford 6 and consider drastic forms of revascularizations prior to major amputations? Dr. Steven Kum of Singapore believes that patients with end-stage disease can still benefit from a unique procedure called arterial venous flow reversal. Dr. Kum, a vascular surgeon, developed an endovascular procedure to not only create the fistula, but also allow the venous conduit to arterialize over time.
J.A. Mustapha, MD: Can you explain the arterial venous flow reversal (AVR) concept?
Steven Kum, MBBS: Thanks, Jihad, for the invitation to contribute. Well, essentially, if we have an arterial system that cannot be opened, we preferentially pressurize the venous system and route oxygenated blood flow through this system. It’s a little analogous to traffic between two cities. Should a freeway be unserviceable in one direction, we hop over to the other side of the road to take advantage of the undiseased path (i.e., the veins) to reach where we want to go. This flow is reversed not only in the major veins, but also the smaller veins in the foot.
Dr. Mustapha: Can you explain the physiological changes that happen and the time frames for the changes?
Dr. Kum: Flow reversal is not a new concept. It is still occasionally done in the coronary system during a coronary bypass when the surgeon has to perform retrograde perfusion. There have been many reports in the past of surgical venous arterialization and contemporary surgical series are encouraging. We are still trying to understand the physiological changes. Immediately after flow reversal, arterialization of the veins and pressurization of the venous system occurs. We believe that this pressurization leads to oxygenation of the capillary bed.
Dr. Mustapha: To date, how many cases have been performed at your center and how many do you predict have been performed worldwide?
Dr. Kum: We have performed just under 15 cases in our center, but I have been closely involved in several European centers with a U.S. feasibility trial starting soon this year. I anticipate that as we push beyond the extreme interventions that we are already now doing, we are in a sense victims of our own success and will see more of these patients with end-stage disease. Preventing amputations saves legs and lives, but together with better medical therapy, our patients are surviving longer and have more severe disease every time we re-intervene. This may offer a solution for the global CLI pandemic.
Dr. Mustapha: Can you describe the technical procedure and give an understanding of the end results?
Dr. Kum: We have started using the LimFlow system (LimFlow SA) to do percutaneous deep venous arterialization (DVA) for several years now. The AV flow reversal leads to DVA.
Essentially, after antegrade 7 French (F) access and retrograde 5F venous access under ultrasound guidance, we do a double injection angiogram of both the artery and the veins at the intended area of crossing between the artery and the vein (the “crossover point”). After sufficient pre-dilatation, a 7F catheter (the “A” catheter), housing an ultrasound-emitting crystal is introduced into the artery in an antegrade fashion and positioned adjacent to the crossover point. Similarly, a 5F venous catheter (the “V” catheter), housing an ultrasound-receiving crystal, is introduced via the retrograde 5F sheath and positioned adjacent to the “A” catheter. With the help of a computer system, the 2 catheters are aligned. A needle system moves between the artery and vein followed by a wire, creating the arteriovenous fistula (AVF). The AVF is then ordinated and matured with a covered stent. Subsequent covered stents are used to serve as an endovenous conduit to drive a large volume of blood to the ankle. These covered stents serve to cover the numerous venous branches/collaterals that may “bleed off” the flow towards the heart rather than down to the foot. A key obstacle to the blood flowing to the foot is the valves in the foot. These impediments are, in my opinion, best addressed with a valve cutter. The team at LimFlow has designed a unique tool to address this issue percutaneously.
Dr. Mustapha: How do you determine if a patient is a good candidate for the procedure?
Dr. Kum: We must remember that the patients we have selected are end-stage CLI patients. This implies that they have no reasonable endovascular or open surgical bypass options for revascularization. As peripheral arterial disease is a systemic disease, we would expect the same disease process in the other vascular beds. Coupled with the advanced age of these patients, we could say these patients are fragile. Clinical selection of these patients relies heavily on good old clinical evaluation and some tests. In general, heart function should be more than 40%, and renal function reasonable. The extent of soft tissue loss and infection should not be too severe and we rely on the Society of Vascular Surgery Wound, Ischemia and foot Infection (WIfI) classification system to guide us on the suitability of these patients.
In addition, several other angiographic and sonographers criteria should be met. The target vein for retrograde access should be greater than 3 mm in size, and the inflow artery just proximal to the crossing point should be greater than 3.5 mm in diameter, especially in calcified vessels. This means that aggressive pre dilatation of the inflow vessels is essential.
Dr. Mustapha: Have you considered performing the AVR procedure on patients with Rutherford 5?
Dr. Kum: In our initial experience, we started treating end-stage patients as we deemed that these patients had no other alternative. As our technique and experience with the procedure has grown, we have started treating patients who are not end stage. A consideration would be to offer the procedure to someone who required a specific angiosome to be revascularized. Percutaneous DVA would be able to reperfuse the specific angiosome, sparing a non-contributory angiosome from potential restenosis. In my opinion, this holds promise, as we leave existing collateral circulation alone.
Dr. Mustapha: Do you follow a specific post-operative follow-up algorithm?
Dr. Kum: Post procedure, we encourage the continuation of therapeutic anticoagulation for 48 hours. Closure devices are regularly employed post procedure to allow this. Intravenous antibiotics are continued as per institution protocol. In general, we err on the side of caution and prefer a longer course of intravenous antibiotics due to the large amount of covered stent implanted, especially if the foot wound is infected. In anticipation of foot swelling, which is a sign of successful venous perfusion, we elevate the foot for 48 hours and ambulate the patient thereafter.
Dr. Mustapha: What is your advice to operators who are considering doing arterial venous flow reversal in their institutions?
Dr. Kum: There is a learning curve and the LimFlow device makes it much simpler to perform. It is absolutely crucial that these centers have good wound care programs. Venous arteriolization, in my opinion, is able to perfuse the foot. Wound care is somewhat different from a standard arterial revascularization (the details which cannot be covered here). As with all programs, a dedicated team will ensure that a good angiographic result translates to a good clinical result. This is especially true in percutaneous DVA.
Read the original interview:
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Posted on January 20, 2017 by RADPAD
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Posted on September 12, 2016 by RADPAD
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Last year, Cath Lab Digest published an interview covering alternative access for chronic total occlusions in critical limb ischemia. J.A. Mustapha, MD, interviewed Andrej Schmidt, MD, Department of Angiology, Leipzig Heart Center, Leipzig, Germany.
Read the full article below or click the link for the original publicaiton:
CLI Perspectives is headed by section editor J.A. Mustapha, MD,
Metro Health Hospital, Wyoming, Michigan.
Critical limb ischemia
Chronic total occlusions (CTO)
Volume 23 – Issue 2 – February, 2015
J. Mustapha: What is your preferred access method for crossing complex superficial femoral artery (SFA) CTOs, with the exception of ostial SFA disease?
A. Schmidt: Most SFA CTO crossing is performed via ipsilateral antegrade approach.
J. Mustapha: Why do you prefer an ipsilateral antegrade approach?
A. Schmidt: For multiple beneficial reasons, including shortening the distance from the access site to the CTO, enhancement of pushability, and much better wire and catheter torque.
J. Mustapha: Do you ever perform a contralateral access approach for SFA CTOs?
A. Schmidt: Yes, mostly in patients who are not good candidates for antegrade access such as obese patients, those with proximal disease, ostial SFA disease, or CTOs. Mostly, I prefer antegrade access for SFA CTOs.
J. Mustapha: Many of us have seen you perform live cases and have witnessed your excellent techniques in retrograde popliteal and SFA access in complex CTO crossing. Why do you access these segments?
A. Schmidt: We access distal to the CTO cap of the SFA or popliteal CTO only when we fail to cross from antegrade approach first. The reason we access close to the CTO is similar to the reasoning of the antegrade access, close to the CTO cap, which in turns helps with retrograde pushability and torqueability.
J. Mustapha: What advice would you give practitioners who would like to perform similar retrograde access in the SFA/popliteal?
A. Schmidt: Proceed with caution, as this should only be attempted after an antegrade approach fails. Be sure to have a balloon across the occluded target lesion and the guidewire across the distal access before taking the access catheter out, so that in case a problem (dissection, occlusion) occurs at the distal entrance, balloon angioplasty can be done to fix it. Hemostasis is principally done by external compression.
J. Mustapha: What is the average time of your balloon inflation?
A. Schmidt: The time depends on the size of the access catheter or the sheath used. Most of the time, we use the smallest catheter possible, .018-inch to .035-inch. Therefore, we perform a three-minute balloon inflation followed by an angiogram.
J. Mustapha: Is this the same for a stick in a stent vs no stent?
A. Schmidt: Yes.
J. Mustapha: Do you worry about harming the stent after getting access in it?
A. Schmidt: No. So far, in our experience, we have not had any issues with stents in these situations. Keep in mind, we only get an access in the stent in extreme cases and place the smallest catheter possible.
J. Mustapha: Moving to retrograde tibial access, which access method do you use to enter the artery, angiogram-guided or ultrasound-guided?
A. Schmidt: We use angiogram-guided access.
J. Mustapha: Which is your preferred tibial artery for retrograde access and which part of the artery do you like to enter?
A. Schmidt: My preferred artery is the anterior tibial artery and I prefer to enter it proximally.
J. Mustapha: Why proximal versus distal?
A. Schmidt: Proximally, because the vessel diameter is larger and accommodates a 4 French sheath if needed.
J. Mustapha: How do you get the access?
A. Schmidt: First we position the foot supine and support it with a rolled-up towel, then perform an angiogram in left oblique 30° view, and enter the needle thru the skin into the artery. If no blood returns, we perform an oblique view with repeat angiogram which helps show the tip of the needle and artery.
J. Mustapha: How do you obtain hemostasis after the proximal tibial access?
A. Schmidt: Most of the time, we use an external blood pressure cuff. Occasionally, we use an intra-arterial balloon.
J. Mustapha: If needed, what are your tips and tricks for getting distal tibial access?
A. Schmidt: Starting with the dorsalis pedis access, foot positioning is important. First we position the foot supine and support it with a rolled-up towel, then the C-arm is positioned at about 15° ipsilateral and 10° cranial. We then use the quick access needle holder, followed with an angiogram. Also, we can puncture and perform contrast injection simultaneously, as needed.
J. Mustapha: Do you recommend road mapping for tibial access?
A. Schmidt: No, side movements of the artery due to puncture needles are not noticed, which may lead to accidental venous access and failed attempts. Also, I don’t recommend coming in from a lateral approach.
J. Mustapha: How do you know your needle is in line with the artery?
A. Schmidt: After angiogram is done, make the needle form one line with the artery (Figure 1A-B).
J. Mustapha: What do you do in the setting of no blood return?
A. Schmidt: Obtain oblique orthogonal views at 55-65°, load the guidewire into the needle, and perform contrast injection via the proximal sheath and pull back very slowly. Keep testing if the guidewire makes it through. Another method is to pull back slowly and inject contrast from the needle holder until you see contrast in the artery, then advance the guidewire (Figure 2A-G).
J. Mustapha: Any tips on how to get peroneal access?
A. Schmidt: Start with an anterior approach. Place the C-arm at ipsilateral LAO 30° (Figure 3A), perform antegrade angiogram, and position the needle in line with the artery. If no success, then move the C-arm to right anterior oblique (RAO) 70° (Figure 3B) and repeat angiogram. Redirect the needle toward the artery, puncturing the peroneal artery through the membrana interossea.
J. Mustapha: Which puncture site is safer?
A. Schmidt: The distal tibial access approach is safer, as it is not associated with compartment syndrome.
J. Mustapha: What needles to you use for proximal and distal tibial access?
A. Schmidt: For proximal anterior tibial, posterior tibial, and peroneal access, we use a 7cm, 21g needle. For distal tibials, we use a 4cm, 21g needle.
J. Mustapha: Please advise what NOT to do in infrapopliteal retrograde access.
A. Schmidt: One should not access communication arteries, especially those off of the peroneal artery, as shown in Figure 4.
J. Mustapha: How do you minimize radiation exposure?
A. Schmidt: My angiographical approach to retrograde pedal and tibial puncture is quick and precise, minimizing radiation exposure. I attribute this to experience and the right equipment (Figure 5A). I wear a ring dosimeter (Figure 5B) to measure my exposure.
Disclosure: Dr. Mustapha reports he is a consultant to Bard Peripheral Vascular, Covidien, Cordis, CSI, Spectranetics, and Boston Scientific. Dr. Schmidt reports occasional consulting for Bard and Medtronic.
Dr. Andrej Schmidt and Dr. J.A. Mustapha can be contacted at firstname.lastname@example.org
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