Reversed and Nonreversed Transposed Autogenous Vein Grafting for Atherosclerotic Lower Extremity Occlusive Disease

Shant M. Vartanian and Michael S. Conte

Vein bypass grafting for lower extremity occlusive disease remains the gold standard against which new reconstructive techniques are compared. The greater saphenous vein (GSV) is the optimal conduit for the vein bypass and may be employed in either a reversed or nonreversed orientation.

Patient Selection and Preoperative Evaluation

The quality of the conduit used is the single greatest factor in determining the outcome of lower extremity bypass grafts. Optimal planning requires knowledge of the location and quality of available vein. Infrainguinal bypass conduit is used preferentially in the following order: ipsilateral GSV, contralateral GSV, lesser saphenous or arm veins, composite (spliced) grafts, and nonautogenous grafts (biologic or synthetic). Up to 40% of patients do not have adequate ipsilateral GSV. Contralateral GSV should be considered next unless the donor limb also has evidence of advanced peripheral artery disease (PAD) by either clinical or hemodynamic assessment (e.g., ankle-to-brachial index [ABI] <0.5). Vein mapping with ultrasonography avoids unnecessary exploration of inadequate conduits, resulting in a more efficient operation and less wound morbidity. Adequate vein has a caliber of at least 3 mm and does not harbor noncompressible or thrombosed segments. However, marginal segments are not reliably identified on preprocedure imaging, and the best tool to assess vein quality is intraoperative inspection. If sclerotic or nondistensible segments are encountered, it is far better to excise the segment and splice two healthy ends of vein rather than retain a marginal segment that could increase the likelihood of graft failure.

In cases where sufficient vein of adequate quality is in short supply, a variety of techniques can help minimize the length of vein needed. A patch angioplasty can move the proximal or distal anastomosis by several centimeters. Tunneling anatomically minimizes the length of vein needed. Excellent outcomes can also be achieved with grafts originating beyond the common femoral artery. Hybrid endovascular and open surgical techniques can be employed in carefully selected cases to move the site of inflow distally. For example, endovascular treatment of mild to moderate superficial femoral artery (SFA) disease followed by a distal-origin graft from the popliteal artery can reduce the length of vein needed by half. However, endovascular treatment of more severe femoropopliteal disease (e.g., Trans-Atlantic Inter-Society Consensus [TASC] C or D lesions) upstream of a bypass is to be discouraged as a strategy, because a good-quality venous conduit generally outlasts such extensive endoluminal SFA interventions.

Operative Technique

The anesthetic technique largely depends upon the patient’s underlying comorbid conditions and the operator’s preference. In patients with significant pulmonary disease, epidural anesthesia can help attenuate postoperative pulmonary complications. Regional anesthesia has the additional benefit of facilitating postoperative pain control, particularly in patients with chronic pain from critical limb ischemia (CLI), who might have a high tolerance to narcotic analgesia. For patients in whom there are questions regarding the quality of lower extremity veins, general anesthesia is preferred should there be need for harvesting arm vein. The addition of an epidural to a general anesthetic provides excellent perioperative analgesia for lower extremity surgery.

Because the quality of the conduit is the most important, and yet the most variable, determinant of a successful operation, our preference is to expose the vein first. Ultrasound mapping, repeated by the surgeon in the operating room just before draping, facilitates planning of incisions. The skin is opened directly over the course of the saphenous vein with a scalpel, with care not to create long subcutaneous flaps. Flaps can undermine skin perfusion, and subcutaneous ischemia can lead to wound necrosis. Large flaps, and therefore larger potential spaces, are also more likely to develop hematomas or seromas. We often leave one or more bridges of intact skin (approximately 3 cm) along the course of the exposure to facilitate closure. A minimal-touch technique of handling saphenous vein is used, because even minor manipulation of the vein has been shown to traumatize the underlying endothelium, possibly setting the stage for subsequent vein graft stenosis. Gentle traction is generated by placing a silicone–elastic (Silastic) sling behind the vein, which facilitates identification of tributary branches. Electrocautery is avoided in direct proximity to the vein, because uncontrolled discharge of current can result in injury to the vein wall.

The saphenofemoral junction is exposed and fully mobilized by ligating its multiple branches. This enables the vein to be later transected with a small anterior cuff of femoral vein that creates a generous anastomotic patch. Branches are ligated with fine silk ligatures 2 mm from the saphenous vein itself, so that upon distention the ligature does not narrow the vein. We leave the vein in situ until the inflow and outflow sites, as well as the graft tunnel, have been fully prepared and the required length has been carefully measured. This minimizes warm ischemia to the vein and also ensures that an adequate length of vein is exposed. We always take an additional 2 to 3 cm of vein beyond what is measured to accommodate unexpected findings at the anastomotic sites. Once the length required has been confirmed, the vein is transected distally and then gently flushed with a neutral-buffered crystalloid solution (Plasmalyte) containing heparin sodium (2 units/mL) and papaverine hydrochloride (0.12 mg/mL). Controlled, gentle distention facilitates identification of remaining tributaries and leaks as the vein is mobilized up to the groin. A small Satinsky-style vascular clamp is applied to the saphenofemoral junction, the vein is sharply transected, and the stump is controlled with a back-and-forth running mattress polypropylene suture.

The anatomic location of graft inflow and outflow is typically known preoperatively, based upon angiographic findings. Nevertheless, confirmation is needed at the time of surgery, and modifications to the surgical plan are sometimes required. For example, the common femoral artery is a common site of inflow. During exposure, it may become evident that heavy calcification precludes clamp placement in traditional sites for proximal and distal control. It may be necessary to expose and control the external iliac artery proximally or secondary branches of the profunda distally. If there is severe common femoral disease, endarterectomy with patch angioplasty is preferred because it creates durable inflow and simplifies the graft anastomosis.

If a large size discrepancy is present between the proximal and distal ends of the conduit, using the vein in a nonreversed fashion avoids technical challenges of having to sew a large patulous vein segment into a small-caliber tibial vessel. When using the vein in the nonreversed orientation, a valvulotome is used to lyse the venous valves. The first valve just beyond the saphenofemoral junction is often easily excised under direct vision with a Potts scissors. Prograde flow is needed to coapt the bivalve leaflets, allowing capture with a valvulotome. Lysis can be done either while flushing the vein by hand or after creating the proximal anastomosis, but the vein must be kept distended whenever the valvulotome is used. Valve lysis is a simple but critical skill that requires training and experience. Careful positioning of the valvulotome is essential, in particular with the Mills valvulotome (our preference). Branch points can be inadvertently torn, resulting in venotomies that are difficult to fix without narrowing the vein. The valvulotome may be inserted into the vein through one or two side branches or from the distal end of the vein. Successful lysis is demonstrated by vigorous pulsatile flow through the end of the graft. If there is no pulsatile flow, then a retained valve is likely and the entire graft should be reinterrogated.

The vein graft can be tunneled either anatomically or subcutaneously, and each method has its own advantages. The benefit of a subcutaneous tunnel is that the superficial location facilitates postoperative monitoring and surgical correction of midgraft stenosis that can develop over time. The saphenous vein graft can be left in its own wound bed, or a new subcutaneous tunnel can be created laterally should the anterior tibial artery serve as the outflow site. A potential drawback of leaving the graft in the wound bed is that wound breakdown can expose the graft, and its superficial location can make subsequent coverage somewhat challenging. In contrast, tunneling anatomically, below the sartorius muscle and through the popliteal space—or through the interosseus membrane into the anterior compartment of the leg, should the anterior tibial artery be the target—avoids this potential complication. Also, as the anatomic tunnel is more direct than the circuitous subcutaneous tunnel, so the length of vein needed is less. However, subsequent surgical revisions are more difficult.

Prior to arterial occlusion, heparin is given (100 U/kg) and allowed to circulate for 3 minutes. When clamping, apply only the minimal occlusive force needed. The graft is anastomosed to the inflow vessel in an end-to-side fashion. We always perform the proximal anastomosis first so that the graft can be tunneled under arterial pressure. This minimizes the risk of flow-limiting kinks or twists during tunneling and maintains excess length at this stage. The graft should never be trimmed until the distal arteriotomy has been finalized.

Care should be taken in determining the location of the distal arteriotomy because excessive calcification can complicate the distal anastomosis and should be avoided if possible. For infrageniculate exposures, a thigh tourniquet has many advantages. Exposure is simplified because circumferential control is unnecessary. Multiple collateral vessels at the outflow site can be left unexposed and unharmed. A thigh tourniquet leaves the operative field unobstructed, and clamp injury to heavily calcified vessels is avoided. The distal anastomosis is then created in standard end-to-side fashion. Rarely, a patch is required on the distal end if a longer arteriotomy is made as a result of unforeseen intimal disease (e.g., dissection or thrombus).

Assessing the function of the bypass begins with simple observation. A pulse should be palpable in the operative field distal to the anastomosis. However, in a cold, vasoconstricted leg, it may be difficult to obtain palpable pedal pulses immediately after completion. Capillary refill, though, should be noticeably improved. A Doppler probe can provide additional qualitative assessment. Up to 10% of lower extremity bypasses can have technical defects, such as retained valves or an imperfect anastomosis, which can lead to early graft failure. Routine completion assessment should therefore include contrast angiography and/or an intraoperative ultrasound. Direct injection of papaverine (60–90 mg) into the graft relieves spasm and facilitates the examination. These studies are complementary, with ultrasound providing physiologic information that can uncover subtle lesions not visible by arteriography. Velocity measurements in questionable areas can help determine the need for intraoperative revision. In operating rooms without portable C-arm fluoroscopy, a sufficient angiographic examination can be performed with flat plate radiographs.

Only gold members can continue reading. Log In or Register to continue

Share this:

• X
• Facebook

Related

Related posts:

1. Technical Aspects of Percutaneous Carotid Angioplasty and Stenting for Arteriosclerotic Disease
2. In-Situ Treatment of Aortic Graft Infection with Prosthetic Grafts and Allografts
3. Treatment of Acute Upper Extremity Venous Occlusion
4. Intraoperative Assessment of the Technical Adequacy of Carotid Endarterectomy

Stay updated, free articles. Join our Telegram channel

Join

Full access? Get Clinical Tree