Initial experience with color-flow duplex scanning of infrainguinal bypass grafts

Outcome of Surgical and Endoluminal Intervention for Infrainguinal Bypass Anastomotic Strictures

The objective of this study was to compare the outcomes of percutaneous transluminal angioplasty (PTA) versus open surgical repair of anastomotic strictures affecting infrainguinal bypasses. Anastomotic strictures affecting 39 bypasses in 36 patients were identified among 593 consecutive infrainguinal arterial reconstructions performed between 1994 and 2004. The mean age of affected patients was 65 ±2 years (range: 61 to 101 years). The original bypasses, with vein grafts outnumbering prosthetic grafts 2 to 1, were performed for acute (5%) and chronic (54%) limb-threatening ischemia, disabling claudication (28%), or popliteal aneurysms (13%). Anastomotic strictures were first recognized an average of 16 ±3 months (range 2 to 92 months) postoperatively. Strictures affected the distal anastomosis in 62% of cases and the proximal anastomosis in 38%. Primary patency, assisted primary patency, secondary patency, and limb salvage were assessed following PTA or open surgical repair of the strictures. Anastomotic strictures were detected following acute (41%) and chronic (18%) limbthreatening ischemia, claudication (13%), or during routine graft surveillance (28%) in asymptomatic patients. Graft thrombosis, occurring in 51% of patients at the time of presentation, was not affected by the site of anastomotic stricture, although prosthetic grafts were affected more than vein grafts (92% vs 31%). Interventions included PTA (67%) and conventional open procedures (33%). The latter included vein patch angioplasty, short interposition grafts, and redo bypasses. The stricture site and bypass material used in the original revascularization did not affect reintervention patency rates. Sixteen (62%) of the endovascular procedures were performed on a graft presenting with thrombosis, while only 4 (31%) were initially treated with operative therapy. Treatment of thrombosed grafts resulted in an 18-month patency of 32% compared to an 80% patency in treating grafts that were not occluded at the time of presentation (p <0.05). No anastomotic stricture repaired operatively required reintervention, whereas 42% of those treated by PTA required a mean of 1.3 additional reinterventions (p <0.03). Anastomotic strictures affecting infrainguinal bypass grafts contribute to low patency rates. Outcomes can be significantly improved if these strictures are identified before graft thrombosis. Open surgical repair, compared to PTA, provides improved graft function as evident by fewer subsequent interventions required to maintain graft patency.

Current approach to peripheral arterial sonography

Color and pulsed Doppler imaging have assumed a prominent role for evaluating noninvasively lower-extremity arterial occlusive disease. In conjunction with indirect arterial tests, ultrasound imaging is recommended to screen for lower-extremity disease. It provides not only specific information regarding location, severity, and frequency of disease, but it can also determine the optimal therapeutic approach before more invasive procedures. Using ultrasound for graft surveillance is mandatory for identifying flow-reducing lesions that may lead to subsequent bypass failure. As new developments become perfected and clinically available, ultrasound contrast agents, three-dimensional imaging, and B-flow imaging each seem to have great potential for assessing peripheral arterial disease. In all likelihood, these additions will further improve the diagnostic capability of ultrasound and may also lead to the development of new vascular applications for this modality.

The natural history of intermediate and critical vein graft stenosis: recommendations for continued surveillance or repair

OBJECTIVE

Duplex ultrasound surveillance (DUS) after autogenous lower extremity bypass grafting is controversial. Specific criteria mandating graft revision are not uniform. It has been suggested that grafts harboring critical stenoses undergo revision, whereas those with intermediate stenoses undergo arteriography with selective repair. We sought to define the natural history and determine the risk of graft occlusion associated with unrepaired vein graft stenoses.

METHODS

We analyzed serial vascular laboratory and clinical data of 156 autogenous infrainguinal vein grafts in 142 patients. Grafts were categorized into three groups according to the first DUS-detected (index) lesion: (1) normal (peak systolic velocity [PSV] < 200 cm/s, velocity ratio [V(r)] < 2); (2) intermediate stenosis (200 cm/s < PSV < 300 cm/s, 2 < V(r) < 4); and (3) critical (PSV > 300 cm/s, V(r) > 4). Our policy was to repair grafts with critical lesions and monitor all others. The risks of stenosis progression, graft revision, and graft thrombosis for each group were compared.

RESULTS

Serial DUS was normal in 100 (64%) grafts. The incidence of graft thrombosis in the normal group was 3% per year (mean follow-up, 27.5 months). Intermediate lesions developed in 32 grafts (20%) and were followed. Among these 32 grafts with intermediate stenoses, 63% progressed to critical and were revised, and 32% resolved or stabilized (mean follow-up, 26 months). Only one graft occlusion occurred in grafts with intermediate lesions subjected to serial DUS monitoring (incidence 1.5% per year, P = not significant). In the third group, 16 of 25 grafts with critical lesions were successfully revised and remain patent. In nine cases, critical lesions were not repaired, resulting in seven (78%) occlusions, all within 4 months of DUS detection.

CONCLUSIONS

Serial surveillance is safe and effective for grafts with intermediate stenoses. The graft occlusion rate for such grafts with careful monitoring is no different from grafts without stenosis, and therefore, arteriography is not indicated in the absence of progression to critical stenosis. The short-term risk of graft occlusion in the presence of an unrevised critical stenosis is nearly 80%. These data have important clinical implications concerning the natural history of vein graft lesions.

Patency and characteristics of lower extremity vein grafts requiring multiple revisions

OBJECTIVES

Multiple (> 1) revisions of lower extremity vein grafts may be required to maintain patency. Characteristics of recurrent lower extremity vein graft lesions and the patency achieved after multiple revisions have not been emphasized in reports on infrainguinal vein graft stenosis. This study was performed to determine (1) the patency of multiply revised lower extremity vein grafts and (2) the timing, location, and angiographic and duplex features of the recurrent lesions.

METHODS

Lower extremity vein grafts that were followed in a duplex surveillance protocol and required revisions from January 1990 through December 1998 were identified. All revisions were preceded by angiography. In multiply revised lower extremity vein grafts, the immediate preoperative angiogram and duplex examination findings, as well as the angiogram made before the previous revision and the duplex study done after the previous revision, were reviewed to characterize recurrent lesions at the time of previous and current graft revision. The patencies of grafts undergoing single and multiple revisions were compared.

RESULTS

A total of 233 lower extremity vein graft revisions were performed; of these, 50 (21%) were repeat revisions. Of grafts requiring more than one revision, 98% were normal on duplex examination after the initial revision. Five-year assisted primary patency of multiply revised grafts (91%) was not different from that of grafts with a single revision (89%; P not significant). Of 60 lesions repaired in the 50 repeat revisions, 29 (48%) were at the previously revised site, and 31 (52%) were at new sites. The time between revisions was less if the same site was revised (11 +/- 2 months) than if a different site required revision (20 +/- 4 months; P <.05). Arteriographic evidence of a minor (< 50% diameter) lesion was present at the time of the initial revision in 23% of cases in which revision of a second site was subsequently required.

CONCLUSION

In our experience, 21% of lower extremity vein grafts requiring initial revision ultimately require additional revisions. Multiply revised lower extremity vein grafts have excellent long-term patency. Lesions occur with equal frequency at the site of prior revision and new sites. Lesions prompting revision at new sites occur significantly later and are infrequently detected on prior imaging studies.

Duplex scanning alone is not sufficient imaging before secondary procedures after lower extremity reversed vein bypass graft

PURPOSE

Duplex surveillance of lower extremity reversed vein bypass grafts (LERVG) is a means of identifying patients at risk for occlusion. The perceived accuracy of duplex scan as a means of identifying stenoses has led many surgeons to perform graft revision on the basis of duplex scan alone. This may result in missing additional lesions that are threatening patency. To assess the role of duplex scan as the sole imaging method before revision of LERVGs, we reviewed consecutive patients undergoing revisions who underwent preoperative arteriography after identification of duplex scan abnormalities.

METHODS

Duplex scan results, operative reports, and preoperative arteriograms for patients undergoing LERVG revision from January 1990 to December 1997 were reviewed. A standard duplex scan surveillance protocol was followed, and attempts were made to survey the entire graft, including inflow and outflow. Duplex scan results were compared with the results of preoperative arteriograms and the operation performed to determine if all significant lesions were identified by means of duplex scan alone.

RESULTS

Two hundred five LERVG revisions were performed. The 5-year assisted primary patency rate was 91%. In 119 cases (58%), arteriography did not contribute significantly to duplex scan findings. Arteriography significantly contributed to operative planning in 86 cases (42%). In 38 cases (19%), only a low-flow state was identified by means of duplex scan, and a correctable stenosis was identified by means of arteriography. In 48 cases (23%), additional significant lesions corrected at operation were identified by means of arteriography. These included 26 inflow, 16 graft, and 8 outflow lesions. Arteriography was most useful as a means of determining the revision procedure performed when there were inflow lesions (P <.05) or when the proximal anastomosis was to the profunda or superficial femoral arteries (P <.05). All frequently performed bypass graft configurations had some discrepancy between arteriographic and duplex scan findings.

CONCLUSION

Available data do not permit prediction of which LERVG are immune from missed lesions in a duplex scan surveillance protocol. This suggests to us that arteriography is mandatory before LERVG revisions.

The utility of duplex scanning in infrainguinal vein graft surveillance: results from a randomised controlled study

OBJECTIVES

To evaluate the utility and efficacy of colour-coded duplex scanning as an adjunct to clinical surveillance of infrainguinal vein bypass surgery.

DESIGN

Prospective controlled randomised trial.

METHODS

The trial included 179 consecutive patients undergoing 185 primary infrainguinal vein graft reconstructions during a 3-year period. Patients alive without amputation and with open graft at 1 month were randomised to a surveillance program based on clinical examination and ankle-brachial pressure index measurement (ABI group) or additional duplex scanning (DD group). All patients were scheduled for surveillance at 1, 3, 6, 9 and 12 months after operation.

RESULTS

Surveillance identified four failing grafts in the ABI group and 11 in the DD group which were revised. The number of occluded grafts was seven in ABI group and 12 in DD group. At 1-year overall cumulative assisted primary patency rates in the ABI group and in the DD group were 74% and 65% respectively (p = 0.21), corresponding secondary patency rates were 84% and 71% (p = 0.04) and limb salvage rates 88% versus 81% (p = 0.23) respectively.

CONCLUSIONS

This study failed to show any beneficial effect of duplex scanning in a surveillance program, which was difficult to accomplish as a part of routine clinical work. However, the main difference in outcome appeared during the first postoperative month before the commencement of the surveillance program.

One-point measurement of the peak-to-peak pulsatility index as an indicator for evaluation of infrainguinal bypass procedures

While duplex scanning has been advocated as the most accurate modality for postoperative graft surveillance, it is time-consuming for evaluating the entire graft. The aim of the present study was to determine which parameter predicts graft failure most simply and precisely, by examining 62 men and 1 woman who collectively underwent 71 infrainguinal arterial bypasses. A total of 212 scannings were obtained using a duplex scanner, and the peak systolic velocity (PSV), PSV ratio, and peak-to-peak pulsatility index (PPI) were analyzed. This analysis revealed 7 occlusions, 9 stenoses, and 1 arteriovenous fistula. When a PSV < 45 cm/s and/or a PSV ratio > 2.0 was defined as graft failure the sensitivity was 84.0% and the specificity was 81.8%: however, a PPI < 7.0 at the midgraft, indicating graft failure, showed a sensitivity of 100% and a specificity of 83.3%. The PPI exhibited better sensitivity and specificity than the PSV, even though the PPI needs only to be measured at the midgraft whereas the PSV should be measured at at least two points. Thus, we believe that the PPI could be the most useful and simple parameter to assess infrainguinal bypass grafts.

Ongoing vascular laboratory surveillance is essential to maximize long-term in situ saphenous vein bypass patency

PURPOSE

The purpose of this study was to assess the contribution of ongoing graft surveillance to maximize long-term patency of lower limb in situ saphenous vein bypasses.

METHODS

From January 1981 to October 1994, 556 autogenous grafts were constructed in 499 patients. The distal anastomosis was at the popliteal level in 207 (37%) and the tibial level in 349 (63%). All patients were enrolled in a prospective surveillance protocol to identify lesions that compromise graft patency and were evaluated at 1 day, 1 week, 6 weeks, and 3 months. Surveillance studies were then obtained every 3 months for the first 2 postoperative years and every 6 months thereafter.

RESULTS

Four-hundred-fifty abnormalities were detected in 236 grafts. The median interval from the initial procedure to detection of an abnormality was 12 months (range 0 to 113 months) and varied with the location of the defect. Later in the life of the graft, progression of atherosclerotic disease manifested as inflow obstruction at a median of 15 months, and outflow disease threatened the graft at a median of 29 months (r = 0.0003). Of the 450 surveillance abnormalities, 294 (65%) occurred within the first 2 years after operation, and 156 (35%) developed more than 2 years after operation. Of the 236 grafts that developed surveillance abnormalities, 50 (21%) developed the initial defect more than 2 years after the initial bypass procedure. Eleven percent of grafts remaining free of abnormality after 2 years went on to fail. Sixty-seven interventions were performed on 62 extremities after 24 months, with 30 involving previously unrevised grafts.

CONCLUSIONS

Because lesions amenable to revision continue to develop years after vein bypass construction, perpetual surveillance is required to ensure optimal rates of graft patency.

Do normal early color-flow duplex surveillance examination results of infrainguinal vein grafts preclude the need for late graft revision?

PURPOSE

Optimal duration of postoperative duplex surveillance of infrainguinal vein grafts is not known. Previous reports have suggested nearly all vein graft stenoses are present within the first postoperative year, and normal duplex examination results during this time eliminate the need for ongoing graft surveillance. To determine whether surveillance may be safely discontinued in patients with normal early postoperative surveillance studies, we reviewed the color-flow surveillance examinations in our patients who underwent infrainguinal reverse vein graft revisions during a 4 1/2 year period.

METHODS

Clinical and vascular laboratory records were reviewed of all patients who underwent infrainguinal reverse vein bypass grafting followed by subsequent graft revision for a duplex scanning-detected abnormality at our institution between January 1990 and July 1994.

RESULTS

Of 447 infrainguinal reverse vein bypasses performed, 36 (8.1%) underwent surgical revision as a result of an abnormal finding during routine duplex surveillance. The initial postoperative duplex examination was obtained within 2 weeks of graft implantation in 23 (64%) patients, between 2 weeks and 3 months in 10 (28%) patients, and between 3 and 6 months in three (8%) patients. Duplex abnormalities prompting revision included 11 (31%) grafts with a mid-graft peak systolic velocity (PSV) < or = 45 cm/sec, 23 (64%) grafts with a focal PSV > or = 200 cm/sec, one graft with a PSV > or = 150 cm/sec but < 200 cm/sec, and one thought to be occluded by duplex but found to be patent by angiography. Abnormal duplex findings were initially detected within 2 weeks of graft implantation in five (14%) patients, between 2 weeks and 3 months in eight (22%) patients, from 3 to 6 months in 12 (33%) patients, from 6 to 12 months in six (17%) patients, and > 1 year in five (14%) patients. In only 25% of cases were mid-graft PSVs < or = 45 cm/sec or focal velocities > or = 200 cm/sec identified on the initial examination; 75% were found during subsequent surveillance.

CONCLUSIONS

Although most reverse vein graft abnormalities detected by duplex surveillance and prompting graft revision appear within the first postoperative year, many are not detected on the initial examination. In our recent experience 31% of duplex abnormalities leading to vein graft revision were first detected more than 6 months after operation. Discontinuation of graft surveillance based on normal early findings will result in thrombosis of some vein grafts that may otherwise be salvaged.

Postoperative lower extremity bypass surveillance: beyond ankle arm blood pressures

Surveillance is essential to the postoperative follow-up of lower extremity bypass grafts. Early, intermediate, and late thrombosis place the patient's limb at risk, so detection of problems before the graft fails is critical. Because contrast angiography is not routinely performed for surveillance, most vascular surgeons rely on history, physical examination, and noninvasive vascular studies (NVS) to assess perfusion to the lower extremity after bypass grafting. These NVS include ankle/brachial waveforms, blood pressures, and indexes before and after exercise. The purpose of this study is to report our findings with duplex color-flow ultrasonography (DCU) to examine lower extremity bypass grafts. According to our protocol, we monitor lower extremity grafts with ankle/brachial Doppler pressures, analogue waveforms, and lower extremity exercise when possible. These NVS are performed by nurses in the vascular laboratory before the patient is discharged from the hospital, at least twice during the first year, and then annually. DCU is also performed at least two times during the first year and then annually. If the study results are abnormal or if the patient has symptoms, testing is usually repeated. When abnormalities persist contrast angiography may be warranted. We have detected anatomic and hemodynamic changes in lower extremity bypasses by use of our protocol. By adding DCU to ankle/brachial blood pressures, we have identified aneurysmal dilation, diffuse atherosclerosis, focal narrowing, arteriovenous fistulas caused by unligated venous branches, retained venous valves, and disease progression proximal or distal to the graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of anastomotic bypass graft stenosis with directional atherectomy: short-term and intermediate-term results

PURPOSE

Areas of anastomotic stenosis in lower-extremity bypass grafts (BPGs) were treated by means of directional atherectomy (DA) in hopes of achieving better patency rates than have been reported with percutaneous transluminal angioplasty (PTA).

MATERIALS AND METHODS

During a 4-year period, 17 patients (11 men and six women) with 23 areas of anastomotic stenosis in 18 lower-extremity BPGs were selected for treatment with DA. Urokinase thrombolysis was initially performed in eight BPGs that were thrombosed at the time of presentation. Adjunctive preatherectomy PTA was performed in six lesions, and postatherectomy PTA was performed in three lesions.

RESULTS

The technical success rate for DA was 92% (23 of 25 sites). There was less than 50% restenosis at 74% of the areas of stenosis (14 of 19 sites), with a mean follow-up time for the sites of 13 months. The graft patency rate was 88% (14 of 16 grafts), with a mean follow-up time for the grafts of 14 months. Areas of stenosis treated with DA alone had the same patency rates as those treated with DA and PTA.

CONCLUSIONS

DA is an effective treatment method for anastomotic peripheral arterial BPG stenosis. The intermediate-term patency rates following DA are superior to those reported for PTA and similar to those reported for surgical revision.

Surgical treatment of threatened reversed infrainguinal vein grafts

PURPOSE

Current information concerning the results of surgical revision of threatened infrainguinal vein grafts is largely limited to in situ conduits. Infrainguinal grafts may be threatened by intrinsic graft lesions or significant stenosis in the adjacent inflow or outflow arteries. To assess the results of operative revision of infrainguinal reversed vein grafts, we reviewed our experience with surgical revision of threatened infrainguinal reversed vein grafts identified through a program of postoperative clinical and vascular laboratory graft surveillance.

METHODS

All patients who underwent surgical revision of a threatened but patent infrainguinal reversed vein graft from January 1987 through April 1993 were identified through review of our vascular registry. Data were analyzed for type of vein used, date of original reversed vein graft, clinical and vascular laboratory findings leading to reversed vein graft revision, results of preoperative angiography, patient risk factors, operative techniques and complications, and long-term assisted primary graft patency and limb salvage.

RESULTS

Ninety-six patients with 100 infrainguinal reversed vein grafts (69) femoral-popliteal, 31 femoral-tibial) underwent 117 surgical vein graft revisions or inflow procedures during the study period. Eighty-one percent of the original reversed vein grafts consisted of a single segment of greater saphenous vein. All revised grafts had at least a 50% stenosis in the graft itself or the proximal or distal artery. A single revision was performed in 85 grafts, two revisions in 13 grafts, and three revisions in two grafts. There were nine (8%) isolated inflow procedures, eight (7%) vein patch angioplasties, 62 (53%) interposition vein grafts, and 29 (25%) vein graft extensions to a new distal anastomotic site. The remaining nine (8%) procedures consisted of combinations of the above. Median time to primary graft revision after initial graft implantation was 15 months (range 2 days to 316 months). Mean time to secondary revision after primary revision was 21 months. Operative mortality was 0.9%. Cumulative assisted primary patency of the original grafts revised for stenotic lesions was 99%, 96%, and 92% at 1, 3, and 5 years, respectively. Limb salvage was 99%, 97%, and 97% at 1, 3, and 5 years, respectively.

CONCLUSIONS

Although surgical revision of reversed vein graft requires much use of alternative vein sources, these procedures can be performed with minimum mortality and provide excellent assisted primary graft patency and limb salvage.

Surveillance of lower extremity vein grafts

Development of stenosis in lower extremity vein grafts or its anastomotic segments is responsible for most graft failures. While these lesions can be treated by minor procedures, timely identification may improve long-term graft patency. In this review, diagnostic methods that are currently applied for vein graft surveillance, criteria for stenosis and recommendations for intervention are discussed.

The role of colour flow duplex screening in infra-inguinal vein grafts

To assess the indications for routine colour flow duplex surveillance, 43 infra-inguinal autogenous vein grafts were prospectively entered into a surveillance protocol. Screening consisted of measurements of ankle brachial indices (ABIs) and colour flow duplex imaging of the entire graft length. Twelve significant stenoses have been detected in 10 grafts (23%) using duplex, all within 6 months of surgery. All grafts at risk had arteriography confirming the duplex findings, but detecting one additional stenosis. Two grafts at risk were not detected by duplex scanning (sensitivity 83%). All grafts at risk (12) had a serial fall in resting ABI of more than 0.1. Most of the detected graft stenoses could be corrected surgically, improving the 1 year primary cumulative patency rate of 54% to a secondary patency rate of 88%. This study suggests that resting ABI measurements are a very sensitive (sensitivity: 100%) and simple primary screening procedure, provided that all grafts with ABI changes of more than 0.1 are further evaluated. The interval specificities of ABI measurements were 77% at 3, 71% at 6, 67% at 12 and 78% at 18 months (mean 73%). About 60% of ABI-screened grafts needed further evaluation because of ABI changes of greater than 0.1, incompressibility of arteries (ABI greater than 1.3) or extension of the graft to the ankle or pedal arteries. Colour flow duplex scanning was very useful in excluding or identifying and localising graft problems and deciding on further invasive diagnostic and therapeutic procedures. Ankle brachial index measurements as the primary examination for selecting patients for colour flow duplex scanning seems to be a safe screening procedure.

Color-flow duplex criteria for grading stenosis in infrainguinal vein grafts

Color-flow duplex scanning of infrainguinal vein bypasses was used to identify failing grafts. Several duplex parameters were compared to determine their value in identifying and quantifying the degree of stenosis. Intraarterial digital subtraction angiography was used as the "gold standard" to determine the severity of the stenosis. The goal of this study was to identify specific color-flow duplex criteria for grading stenotic lesions. After a retrospective analysis some of these parameters were prospectively validated. The surveillance protocol required a color-flow duplex scan every 3 months for the first year and every 6 months during the second year. One hundred sixteen vein grafts in 112 patients were studied. Forty-three stenoses were identified and classified into categories from 30% to 49%, 50% to 69%, and 70% to 99% diameter reduction. These stenoses were identified in either the bypass graft or adjacent inflow or outflow arteries. Failing grafts were evaluated further by intraarterial digital subtraction angiography. Patients with normal appearing bypasses (without suspected stenotic lesions) had intravenous digital subtraction angiography. The five duplex parameters that were studied included the following: (1) graft peak systolic velocity (PSV-graft), (2) the maximum peak systolic velocity (at the site of a stenosis or in normal grafts at the narrowest segment of the bypass) (PSV-max), (3) the ratio between PSV-graft and PSV-max, (PSV-index), (4) end-diastolic velocity (EDV) at a stenosis or from narrowest graft segment, (5) color-flow image diameter measurements. For discrimination of different degrees of stenosis, threshold values of these parameters were calculated by receiver operating characteristic analysis. Diameter reduction measured by color-flow imaging was best to identify all stenotic lesions greater than 29% (sensitivity 88%, specificity 99%). Peak systolic velocity-index proved optimal identification of stenoses greater than 49% (sensitivity 89%, specificity 92%), and 70% to 99% stenoses were associated with increased EDV (sensitivity 91%, specificity 100%). The PSV-index criteria were then validated prospectively in a separate group of vein grafts. The data support the value of surveillance of femorodistal vein grafts and demonstrate that calculation of the degree of graft stenosis is feasible.