Claudication

Patients who are significantly disabled by claudication, such that they are unable to perform their primary occupations or comfortably carry out the activities of daily living, and those whose lifestyles are significantly limited are potential candidates for infrainguinal bypass. A trial of smoking cessation, lifestyle modification, and exercise, with or without medical therapy, is usually indicated before operative intervention (see Chapter 109). There is consensus that bypass is preferable to angioplasty in patients with TransAtlantic Inter-Society Consensus (TASC) type D lesions, that is, complete common femoral artery (CFA) or superficial femoral artery (SFA) occlusions or complete popliteal and proximal trifurcation occlusions; however, it may also be applied to patients with types B and C lesions (see Chapter 109).¹ Operation should be offered only if the benefit-to-risk ratio is high and if anatomic characteristics suggest a favorable and durable result. The primary reason for intervention in claudicants is to improve lifestyle, given that the risk of severe clinical deterioration (20%) or major limb amputation (5%) during a 3- to 5-year period is low.^1,2 In most centers with extensive infrainguinal bypass experience, claudicants constitute only 15% to 30% of patients, with the majority of the remaining patients undergoing bypass for CLI. Although these data reflect practice patterns in tertiary referral centers, they may not reflect the realities of community-based practices.³

Critical Limb Ischemia

Patients with CLI generally require intervention. Such patients fall into Fontaine III and IV⁴ and Rutherford 4 to 6 categories (see Chapter 108).^5–7 The most recent European consensus document defines CLI as follows: persistent, recurring ischemic rest pain requiring opiate analgesia for at least 2 weeks and ankle systolic pressure lower than 50 mm Hg or toe systolic pressure lower than 30 mm Hg; or ulceration or gangrene of the foot or toes and ankle systolic pressure lower than 50 mm Hg; or toe systolic pressure lower than 30 mm Hg (or absent pedal pulses in diabetics).⁸ Wolfe and Wyatt⁹ further subdivided patients meeting the standard definition of CLI into those with critical or subcritical ischemia on the basis of subsequent amputation risk. Subcritical ischemia is present in patients with rest pain and ankle pressure higher than 40 mm Hg. Critical ischemia is defined as rest pain and tissue loss or ankle pressure lower than 40 mm Hg. This distinction is based on a retrospective analysis of 20 publications analyzing 6118 patients. At 1 year, 27% of patients with subcritical ischemia achieved limb survival without revascularization, in contrast to only 5% in the group of patients with critical ischemia. In practice, these data indicate that certain extremely high risk patients with subcritical ischemia might be managed medically (nonoperatively) but that virtually all patients with true CLI require either bypass or major limb amputation.

In nearly all patients in whom infrainguinal bypass is indicated, suitable target arteries can be identified (Fig. 113-1) if diagnostic angiography is properly performed.^32,33 Only a tiny fraction of individuals, usually those with multiple failed reconstructions, have no identifiable target artery.³⁴ Detailed runoff views are necessary, including magnification and lateral views of the foot. Such films can be obtained in nearly all patients with adjunctive techniques such as foot warming, local administration of intra-arterial vasodilators, and proper positioning of the diagnostic catheter. It is frequently helpful to advance the catheter selectively into the SFA or popliteal artery to obtain adequate views of the infrapopliteal and pedal circulations, especially in patients with diabetes mellitus. Intra-arterial runoff films with bolus injections performed while the diagnostic catheter is positioned in the aorta may fail to adequately define the runoff. If percutaneous access has been achieved from a contralateral, retrograde femoral approach, selective films can be obtained by advancing a wire and then an appropriate diagnostic catheter over the aortic bifurcation and selectively down the affected extremity. In selected patients with normal inflow based on physical examination and noninvasive studies, an ipsilateral antegrade approach may be more expeditious to identify suitable runoff vessels, with the additional advantage of requiring a reduced contrast load (Fig. 113-2). Such an approach is especially useful in diabetic patients with renal insufficiency and noninvasive studies that suggest isolated infrapopliteal disease.

Despite optimal angiographic techniques, there may be a small number of patients in whom no suitable target can be identified. Selective exploration of dorsal pedal or distal posterior tibial arteries with flow detectable by Doppler or duplex imaging may identify a graftable recipient artery. Pomposelli et al³⁴ reported a surprisingly high success rate under these circumstances, although I believe that this situation is relatively uncommon if diagnostic angiography has been pursued to its fullest advantage. In short, there are few patients who are truly unreconstructable from an anatomic standpoint owing to the lack of a suitable outflow target vessel.

Autogenous Vein Assessment

Since Kunlin’s first description of the successful use of autogenous vein to bypass femoropopliteal arteriosclerosis obliterans,^35,36 there is nearly universal agreement that autogenous vein is the best conduit for infrainguinal bypass at all levels.^37,38 The great saphenous vein (GSV) is the most readily available and durable conduit. Assessment of vein availability and quality is critical and should be carried out before embarking on the operation.^39–41 I routinely perform duplex mapping of the GSV in all patients before surgery; if the ipsilateral GSV is absent, unsuitable, or of insufficient length for the anticipated bypass, I also scan the ipsilateral small saphenous vein, the contralateral great and small saphenous veins, and the upper extremity veins, if necessary, to locate a suitable vein and to identify any extenuating circumstances that might arise during the conduct of the operation. Patients are scanned with a light tourniquet in place with the limb dependent, as described by Blebea et al.⁴² I prefer to use veins that are soft, compressible, and at least 3 mm in diameter. Calcified or sclerotic veins are rejected. Soft, compressible veins between 2 and 3 mm in diameter are worthy of exploration, but if they do not distend appropriately, the operation should be modified either by harvesting a better-quality vein (based on preoperative duplex studies) or by shortening the length of the proposed bypass, if possible, by selecting alternative inflow or outflow sites. The type and quality of the bypass conduit are the most important determinants of infrainguinal bypass success; efforts to maximize conduit quality will be rewarded.

Vein harvesting can be performed through long continuous incisions, through skip incisions, or endoscopically. Endoscopic vein harvest has become common in cardiac surgery. Although there are a few enthusiasts, it has not been widely adopted by vascular surgeons for leg bypass, likely owing to equipment costs, learning curve issues, and concerns about damaging vein segments when a long conduit is needed. There are no convincing data to support any specific harvesting technique.^43–47 Regardless of the harvesting technique, poor-quality or marginal vein should be rejected. The search for high-quality vein is worth the time and effort, even if vein splicing or bypass shortening is required. Every effort should be made to perform all infrainguinal bypasses with vein conduit (an all-autogenous policy). Long-term results should not be sacrificed for the sake of expediency at the initial operation. Saphenous vein performs well in the reversed,^48–52 nonreversed,⁵³ and in situ^54–62 configurations; the technique chosen is dictated primarily by conduit availability, anatomic considerations, and surgeon preference and experience.

Concomitant Inflow Disease

Adequate inflow should be ensured before commencing with infrainguinal bypass. Selected inflow lesions can be treated either percutaneously in advance, at the time of preoperative diagnostic arteriography, or at the same operative sitting if need be. Iliac artery lesions of hemodynamic significance should be addressed in nearly all claudicants before proceeding with infrainguinal bypass. For patients with CLI, an iliac lesion with a resting gradient of less than 5 to 10 mm Hg may be acceptable if the pulse and Doppler waveform at the selected inflow site (e.g., femoral artery) are normal. In patients with claudication or CLI presenting with rest pain alone in the absence of tissue loss, an isolated iliac angioplasty without concomitant infrainguinal bypass may suffice if the iliac lesion is of sufficient hemodynamic importance. In such patients with tandem lesions, the profunda-popliteal collateral index may be helpful in predicting whether an inflow procedure alone will be sufficient to alleviate the patient’s symptoms.⁶³ An index greater than 0.25 indicates a large pressure gradient across the knee joint and suggests that inflow disease correction and profundaplasty alone are unlikely to be adequate.^66–68

Proximal Anastomotic Site

Before operation, the surgeon must define the inflow source, which need not be the CFA. There is abundant evidence that originating shorter bypasses from the deep femoral, superficial femoral, popliteal, or, in rare cases, one of the tibial arteries results in patency rates equivalent to those achieved when the CFA serves as the bypass origin. Short bypasses are frequently useful in patients with diabetes mellitus and primary infrapopliteal arterial occlusive disease as well as in individuals with limited available vein conduit who present with failure of a previous reconstruction. On the basis of hemodynamic data and anatomic imaging, the surgeon should commence the operation with the optimal inflow site in mind. However, if unanticipated arterial disease is identified or vein quality and length are worse than anticipated once the operation is under way, the surgeon should already have alternative bypass origins in mind that can be used to shorten the length of the bypass without compromising hemodynamics. If there is uncertainty about the appropriateness of the inflow site at exploration, its hemodynamic suitability should be assessed by direct intra-arterial pressure measurements that can be compared with the transduced radial artery pressure. A resting gradient exceeding 10 mm Hg is significant, as is a drop in pressure exceeding 15% after the administration of intra-arterial papaverine.^64,65,69 If a significant gradient is identified at the selected inflow site, a more proximal inflow site above the culprit lesion should be selected, or the responsible lesion should be addressed by local endarterectomy or angioplasty. This problem occasionally arises with iliac or common femoral lesions whose hemodynamic significance was not appreciated at the time of preoperative arteriography, particularly lesions consisting primarily of posterior plaque that may have been masked if appropriate oblique projections were not obtained.

Whenever the CFA is used as the site of origin for bypass, significant occlusive disease involving the origin and proximal deep femoral artery should usually be addressed at the time of the infrainguinal bypass. The endarterectomy often begins in the CFA. After the division of veins that cross the anterior surface of the deep femoral artery, the femoral arteriotomy is carried out beyond the posterior tongue of disease that extends a variable distance down the deep femoral artery, usually at least to its first or second portion. Tacking sutures may or may not be needed at the distal endpoint. The arteriotomy can be closed with a vein patch or a segment of endarterectomized SFA. This patch can then be opened longitudinally to serve as the origin for the infrainguinal bypass (modified Linton’s patch technique; Fig. 113-3). Alternatively, if the vein caliber is good (>4 mm), a longer venotomy can be made in the vein conduit, which then serves simultaneously as a profundaplasty patch and the bypass origin; this technique should not be used if the arterial wall is markedly thickened or if the caliber of either the native donor artery or the vein graft artery is small to avoid compromising the origin of the vein graft at the heel of the anastomosis. Incorporation of a venous side branch as part of the anastomotic heel is another useful technique when the donor arterial wall is thick or there is a caliber mismatch between the donor artery and the vein bypass conduit (Fig. 113-4). Correction of significant deep femoral disease at the time of infrainguinal bypass is clinically important; should the bypass ever fail, adequate deep femoral artery perfusion may prevent the development of severe, recurrent limb ischemia.

Distal Anastomotic Site

Although inflow artery selection is generally straightforward, outflow site selection frequently requires greater judgment. The general principle of infrainguinal reconstruction is to bypass all hemodynamically significant disease and to insert the bypass into the most proximal limb artery that has at least one continuous runoff artery to the foot. Thus, if the popliteal artery reconstitutes distal to an SFA occlusion and at least one tibial or peroneal artery is continuous to the foot, the popliteal artery would be selected as the outflow site. It is possible, however, and sometimes desirable to bypass to an isolated or so-called blind popliteal segment.

Standard Anterior Approach to the Common Femoral and Profunda Femoris Arteries

A thorough knowledge of anatomy and facility with multiple surgical exposures are critical to the success of infrainguinal bypass.⁸² The standard approach to the CFA and the profunda femoris artery (PFA) is provided by a vertical incision overlying the CFA. This anterior approach allows complete exposure and mobilization of the CFA and its bifurcation; more proximal exposure can be obtained by division of the recurrent portion of the inguinal ligament or the entire ligament (Peter Martin incision). Distal extension allows exposure of the PFA. Division of the lateral femoral circumflex vein offers access to the proximal PFA; careful progressive division of numerous crossing veins allows extensive exposure of the PFA. In selected patients, alternative exposures have been described.

Alternative Approaches to the Profunda Femoris Artery

If previous infection or scarring from multiple previous reconstructions makes standard exposure difficult and if there are no significant occlusive lesions in the CFA or proximal PFA, the mid or distal PFA can be approached laterally, anteromedially, or posteromedially (Fig. 113-5).^71,83–86 The lateral approach is the most useful for infrainguinal bypass; the incision is placed in the upper thigh lateral to the sartorius muscle. The sartorius and SFA are retracted medially. The raphe between the adductor longus and vastus medialis is incised to expose the PFA. This approach is useful when vein conduit length is limited or femoral triangle scarring is prohibitive. The surgeon must be certain that there are no hemodynamically significant lesions proximal to the PFA if this approach is used. With these caveats in mind, use of the PFA as an origin for distal bypass does not compromise long-term patency^85,86; similarly, the SFA⁸⁷ and popliteal artery^85–88 can be used as an inflow source in carefully selected patients without compromising graft patency.

Exposures of the Popliteal and Tibioperoneal Arteries

The standard exposures of the above-popliteal and below-knee arteries are through medial leg incisions, usually made by deepening the saphenectomy incision. Lateral approaches to these vessels are occasionally useful and are well described elsewhere.⁸⁸ The posterior tibial and proximal to mid peroneal arteries are usually approached medially. The distal third of the peroneal artery is most expeditiously exposed by means of a lateral leg incision directly over the distal fibula. A short segment of fibula is carefully removed to expose the distal peroneal artery immediately beneath it.

Posterior exposures of the popliteal, posterior tibial, and peroneal arteries are sometimes useful (Fig. 113-6).^89,90 Diabetic patients frequently have relatively normal inflow to the popliteal trifurcation. If the inflow site is the below-knee popliteal artery and the most appropriate target artery is the distal posterior tibial or distal peroneal artery, and if the lesser saphenous vein is of good quality on duplex imaging, the entire operation can be conducted with the patient in a prone position through a posterior approach. These approaches have been well described by Ouriel⁹⁰ and should be considered not only in selected reoperative situations (e.g., failed bypass through a medial approach) but also if conduit length is limited and ipsilateral GSV is unavailable. Commitment to an all-autogenous bypass approach requires ingenuity and familiarity with numerous anatomic exposures and techniques to allow shortening of the bypass or to permit operation in a virgin field that is unscarred by previous operations. When such distal origin bypass grafts are used, a pneumatic tourniquet instead of vascular Silastic loops or clamps is occasionally useful in the presence of severe distal arterial calcification.⁹¹ A thorough working knowledge of alternative exposures and the occasional use of the pneumatic tourniquet are of great benefit in performing reoperative bypass.

Autogenous Grafts

The preferred conduit is the GSV as it outperforms all other conduit choices. If the ipsilateral GSV is absent, I do not hesitate to harvest the contralateral GSV and see no merit in saving this vein for possible use later.⁹² Numerous reports suggest that the contralateral GSV is subsequently needed in no more than 20% to 25% of patients. I therefore advocate using it when necessary and performing a more difficult alternative vein reconstruction at a later time in those relatively few patients who require it. Exceptions occur whenever the contralateral limb is already ischemic, as manifested by severe claudication, rest pain, or ischemic ulceration. If the contralateral limb is asymptomatic and the ankle-brachial index exceeds 0.6, I have experienced no significant wound healing complications from harvesting the GSV from the groin to the midcalf level. This approach usually allows the bypass to be performed with one segment of GSV and obviates the harvesting of arm vein and vein splicing. Other groups prefer to harvest arm vein if the ipsilateral GSV is unavailable and to save the contralateral GSV for later use.^96,109

Alternative veins are used when the GSV is unavailable or of insufficient length.¹¹⁰ Duplex mapping is useful in identifying suitable vein sources. The small saphenous vein is suitable if the proposed bypass is relatively short. It is possible to perform a common femoral–to–above-knee popliteal bypass or a PFA–to–below-knee popliteal bypass with one complete segment of lower saphenous vein harvested from the ankle to the knee. If a longer bypass with spliced vein is necessary, I prefer to use arm vein because it is less awkward to harvest. LoGerfo et al¹¹¹ and Holzenbein et al¹⁰⁰ described novel techniques of harvesting the upper arm basilic, median cubital, and cephalic veins in continuity with valve lysis of the basilic segment and use of the cephalic segment in a reversed configuration to provide a relatively long, unspliced autogenous conduit. The femoropopliteal deep vein is occasionally useful for shorter bypasses but is difficult to harvest; arm vein is therefore generally preferred. Treiman et al¹⁰⁷ reported the use of the radial artery as a bypass conduit in selected patients requiring short infrageniculate bypasses, with good early results. Cryopreserved vein grafts are expensive and have not performed well in clinical practice^103,104; they may serve a niche role when revascularization is required after the removal of an infected bypass graft and autogenous vein is unavailable to create a new bypass through clean tissue planes.¹⁰⁴

Prosthetic Grafts

PTFE is the most commonly used prosthetic conduit for infrainguinal bypass, although reports suggest that in the above-knee position, it is not superior to Dacron.^112–114 A prospective randomized trial from the United Kingdom reported by Devine et al¹¹⁵ suggested that heparin-bonded Dacron was superior to PTFE for above-knee popliteal bypasses. The 3-year primary patency for heparin-bonded Dacron was 55% compared with 42% for PTFE (P < .044). Both of these patency rates are inferior to those of GSV, however, and the early apparent advantage of heparin-bonded Dacron over PTFE disappeared with longer follow-up.¹¹⁶

Graft Comparison

Table 113-1 summarizes the available level I data comparing conduit types with outcome.^{114–120,127,136–140} Vein is superior to all prosthetic materials, even in the above-knee position.^140–142 The randomized clinical trials comparing human umbilical vein with PTFE have been inconclusive.^138,139,143 The addition of rings to PTFE conferred no benefit in the single prospective randomized clinical trial conducted.¹⁴⁴ Thus, the most prudent recommendation is that autogenous vein be used whenever possible for infrainguinal bypass. This dictum holds true not only for primary infrainguinal bypasses but also for reoperations, in which vein conduits outperform all other options.^145,146 For long bypasses, ipsilateral GSV, contralateral GSV, and spliced vein are employed in decreasing order of preference. If only 5 to 15 cm of extra length is required and a more distal origin site is not feasible, eversion endarterectomy of a proximal segment of the SFA with anastomosis to the available vein conduit is a useful technique that avoids the harvesting and splicing of additional vein (Fig. 113-10).¹⁰² For shorter bypasses, arm vein or small saphenous vein is effective, with the latter being especially useful when a posterior approach is applicable.

If vein is truly unavailable, PTFE, human umbilical vein, or Dacron is a reasonable option for above-knee bypass. The initially favorable results with heparin-bonded Dacron were not confirmed during subsequent follow-up,^115,116 so there appears to be no advantage to heparin-bonded Dacron conduit for above-knee bypass. A prospective randomized trial of human umbilical vein versus heparin-bonded Dacron showed no difference in patency in the above-knee popliteal position,¹⁴⁷ and published trials of PTFE versus Dacron have shown no clear difference.^{112–114,116} For infrageniculate insertion sites, PTFE with distal anastomotic modification (cuff, boot, or patch) is recommended if vein is unavailable. There is inadequate evidence to state a preference in terms of standard ePTFE versus heparin-bonded or carbon-coated PTFE. The single prospective randomized trial of standard PTFE versus carbon-impregnated PTFE for infrageniculate bypass showed approximately 30% primary patency, with no difference between groups at 3 years.¹⁴⁸

Reversed Vein Bypass

Harvest of the GSV begins with a groin incision two fingerbreadths lateral to the pubic tubercle. Preoperative duplex vein mapping and drawing of a line with indelible ink directly over the vein conduit are helpful in following the course of the vein and avoiding the creation of skin flaps. The saphenofemoral junction at the fossa ovalis should be identified to ensure that the GSV and not an anterior or large posteromedial branch is being exposed. Once the main trunk is identified, the incision is extended distally, directly over the vein, with a No. 10 blade or Cooley scissors. I frequently leave short skin bridges, especially in the thigh and about the knee level, to avoid the creation of long flaps. If exposure or branch ligation is difficult or if the course of the main vein is unclear, the skin directly over the vein is divided. The periadventitial tissue, not the vein wall itself, is grasped gently to avoid damage to the conduit. Side branches are meticulously ligated and divided with 3-0 or 4-0 silk; leaving a short stump is preferable to placing a ligature too close to the main trunk and compromising the lumen. When it is first exposed, the vein should be soft and blue. Sclerotic segments are whitish and rubbery. Vein spasm can turn a blue vein white and should be treated with local papaverine irrigation.

Sufficient length of vein should be harvested for the proposed bypass to be performed. If adequate vein of good quality is not available, alternative inflow or outflow arteries should be considered to shorten the bypass; otherwise, alternative vein must be harvested from another site and spliced on a back table. Vein quality is extremely important, and segments less than 3 mm should not be used. Once an adequate length of vein is identified, it is ligated proximally and distally and prepared on the back table by a senior surgeon while the rest of the team exposes the inflow and outflow arteries.

The vein is cannulated with a 3-mm olive tip or Marx tip needle and gently distended with cooled autologous blood (50 to 60 mL) to which 1000 units of heparin and 60 mg of papaverine have been added. The vein should flow readily, should distend smoothly, and should be free of fibrotic, nondistensible segments, strictures at branch ligature sites, and bleeding from missed branches. Missed or small avulsed branches are repaired with longitudinally oriented 6-0 or 7-0 Prolene sutures on a BV-1 or BV-175 needle. Overly forceful distention of the conduit should be avoided because it damages the endothelium. The entire length of the conduit is inspected to ensure that there are no sclerotic areas, no areas of persistent spasm, and no bleeding branches. Once preparation is complete, the distal end of the vein is ligated with 3-0 silk, leaving the suture ends long; the prepared conduit is stored in chilled blood until the graft is ready to be tunneled. Proper intraoperative planning should result in minimal vein storage time. Many believe that autologous blood, rather than saline, better preserves graft endothelium.¹⁴⁹

Proper graft tunneling of reversed grafts is important. For primary leg bypasses with GSV, I prefer to tunnel the graft in a deep anatomic plane to avoid kinking and graft exposure should wound complications ensue. For above-knee popliteal bypasses, a subsartorial plane is frequently easier than a true anatomic tunnel. A large-caliber hollow-bore metal tunneler with a removable obturator is used. For below-knee popliteal and proximal to mid posterior tibial or peroneal bypasses, I generally prefer an anatomic tunnel between the two heads of the gastrocnemius for initial bypasses. It is often wise to tunnel reoperative bypasses subcutaneously; this approach avoids scarring and makes graft surveillance and revision easier, which is advantageous because the alternative vein conduits often used in these circumstances are at higher risk for the development of graft stenosis. Bypasses to the anterior tibial artery can be tunneled through the interosseous membrane (anatomic) or a lateral subcutaneous plane.

Arm Vein Harvest and Vein Splicing

If leg vein length is inadequate or unavailable or if additional conduit is required, arm vein should be used. Arm veins, especially the basilic vein, are more fragile and demanding to harvest. Branches should be carefully identified and ligated a short distance away from their junctions with the main trunk to avoid troublesome bleeding from an injury at the crotch between the branch and the parent vein. Large branches are double-ligated. The initial irrigation and distention of the vein are performed with heparinized saline and papaverine because defects in thinner walled arm veins are more difficult to visualize and to repair if blood is used as the initial irrigant. Once major leaks have been controlled, the vein graft is prepared and stored in chilled blood as mentioned earlier. It is worth considering that arm veins frequently harbor abnormal segments containing intrinsic lesions such as webs, synechiae, and sclerotic valves. Angioscopy of such high-risk conduits may be a useful adjunct (see later under Angioscopy).

In Situ Vein Bypass

In situ bypass can be used successfully in many patients with intact ipsilateral GSVs. Proponents suggest that the vein-artery size match is frequently optimized by this technique.¹⁵⁰ This technique requires the use of a radial cutting blade (Mills valvulotome)⁵⁶ or fixed-diameter circumferential blades such as the Hall⁵⁷ and LeMaitre valvulotomes to accomplish valve lysis.^60,151 The proximal segment of GSV is initially mobilized in the groin as it would be for reversed vein bypass, described earlier. The distal GSV is then mobilized in the region of the projected distal arterial anastomosis. The vein may be exposed by an open technique along its entire length, through skip incisions, or endoscopically. After systemic heparinization, the vein is transected below a Satinsky clamp placed at the saphenofemoral junction, and the stump is closed with running 5-0 Prolene suture. The most proximal valve is excised under direct vision with Potts scissors, and the vein is spatulated and sewn end to side to the selected arterial anastomotic site, usually the CFA. Arterial flow is allowed into the vein conduit; if the conduit is of large caliber, a circumferential valvulotome can be inserted from distal to proximal to lyse the valves. Many surgeons prefer to more carefully control valve lysis by progressive serial valvulotomy through large side branches, progressing from proximal to distal. The Mills valvulotome is introduced through side branches; the leaflets are usually just distal to branches and are oriented parallel to the skin. Under arterial pressure, the valve sinuses distend, and the valve leaflets are displaced toward the center of the lumen, where they can be safely engaged by the valvulotome and cut by sharp retraction on the valvulotome under direct visualization. The final valves are lysed from the distal end of the vein. The quality of the vein and the success of lysis are then assessed; flow should be highly pulsatile from the end of the conduit before the distal anastomosis is performed.

After completion of the anastomoses, the quality of pulsation and flow is assessed by palpation and handheld Doppler interrogation. The entire graft should be evaluated from proximal to distal; it can be manually compressed or occluded distal to the Doppler probe. The presence of continuous outflow despite distal graft compression indicates an arteriovenous fistula; these branches should be ligated. With either the reversed or the in situ technique, careful handling of the vein is important. The assurance of adequate valve lysis and the detection of major arteriovenous fistulae can be challenging; the type of completion study used depends on the type, source, and quality of the conduit and surgeon preference.