Surveillance of lower extremity vein grafts

Chapter VI: Follow-up after revascularisation

Structured follow-up after revascularisation for chronic critical limb ischaemia (CLI) aims at sustained treatment success and continued best patient care. Thereby, efforts need to address three fundamental domains: (A) best medical therapy, both to protect the arterial reconstruction locally and to reduce atherosclerotic burden systemically; (B) surveillance of the arterial reconstruction; and (C) timely initiation of repeat interventions. As most CLI patients are elderly and frail, sustained resolution of CLI and preserved ambulatory capacity may decide over independent living and overall prognosis. Despite this importance, previous guidelines have largely ignored follow-up after CLI; arguably because of a striking lack of evidence and because of a widespread assumption that, in the context of CLI, efficacy of initial revascularisation will determine prognosis during the short remaining life expectancy. This chapter of the current CLI guidelines aims to challenge this disposition and to recommend evidentially best clinical practice by critically appraising available evidence in all of the above domains, including antiplatelet and antithrombotic therapy, clinical surveillance, use of duplex ultrasound, and indications for and preferred type of repeat interventions for failing and failed reconstructions. However, as corresponding studies are rarely performed among CLI patients specifically, evidence has to be consulted that derives from expanded patient populations. Therefore, most recommendations are based on extrapolations or subgroup analyses, which leads to an almost systematic degradation of their strength. Endovascular reconstruction and surgical bypass are considered separately, as are specific contexts such as diabetes or renal failure; and critical issues are highlighted throughout to inform future studies.

Timing of Doppler ankle brachial pressure index

Are there any guidelines or research evidence to support when it is appropriate to perform a Doppler ankle brachial pressure index (ABPI) after a client has had arterial bypass surgery on their leg? Some vascular surgeons say never, some say six months. As these clients often have reperfusion oedema, it is useful to know ABPI to assist the choice of compression.

A Comparison of Distal End-to-side and End-to-end Anastomoses in Femoropopliteal Bypasses

OBJECTIVES

to compare end-to-side (ETS) and end-to-end (ETE) distal anastomoses. Design retrospective cohort study.

METHODS

retrospective cohort study. Between 1988 and 1992, 204 femoropopliteal bypasses (188 patients) were performed for claudication (55%), rest pain (22%) and tissue loss (23%). One hundred and eighteen ETS were compared with 86 ETE in terms of patency or a mean (range) follow-up of 68 (0.5-120) months.

RESULTS

overall patency was 86%, 66% and 57% at 1, 5 and 8 years, respectively. Multivariate analysis showed ETE anastomoses (p =0.04), and also knee bypass ( p =0.05) and venous conduit ( p =0.004) to be significantly associated with impaired patency.

CONCLUSIONS

ETE may improve femoropopliteal bypass patency.

Factors influencing the development of vein-graft stenosis and their significance for clinical management

OBJECTIVES

To assess the influence of clinical and graft factors on the development of stenotic lesions. In addition the implications of any significant correlation for duplex surveillance schedules or surgical bypass techniques was examined.

PATIENTS AND METHODS

In a prospective three centre study, preoperative and peroperative data on 300 infrainguinal autologous vein grafts was analysed. All grafts were monitored by a strict duplex surveillance program and all received an angiogram in the first postoperative year. A revision was only performed if there was evidence of a stenosis of 70% diameter reduction or greater on the angiogram.

RESULTS

The minimum graft diameter was the only factor correlated significantly with the development of a significant graft stenosis (PSV-ratio > or = 2.5) during follow-up (p = 0.002). Factors that correlated with the development of event-causing graft stenosis, associated with revision or occlusion, were minimal graft diameter (p = 0.001), the use of a venovenous anastomosis (p = 0.005) and length of the graft (p = 0.025). Multivariate regression analysis revealed that the minimal graft diameter was the only independent factor that significantly correlated with an event-causing graft stenosis (p = 0.009). The stenosis-free rates for grafts with a minimal diameter < 3.5 mm, between 3.5-4.5 and > or = 4.5 mm were 40%, 58% and 75%, respectively (p = < 0.05). Composite vein and arm-vein grafts with minimal diameters > or = 3.5 mm were compared with grafts which consisted of a single uninterrupted greater saphenous vein with a minimal diameter of < 3.5 mm. One-year secondary patency rates in these categories were of 94% and 76%, respectively (p = 0.03).

CONCLUSIONS

A minimal graft diameter < 3.5 mm was the only factor that significantly correlated with the development of a graft-stenosis. However, veins with larger diameters may still develop stenotic lesions. Composite vein and arm-vein grafts should be used rather than uninterrupted small caliber saphenous veins.

Percutaneous angioplasty for infrainguinal graft-related stenoses

OBJECTIVE

To assess the success of percutaneous transluminal angioplasty (PTA) in treating infrainguinal graft-related stenoses.

DESIGN

Retrospective analysis of stenoses undergoing PTA over 6 years.

MATERIALS

Fifty-seven stenoses in 42 grafts.

METHODS

Site, length and type of stenoses recorded. Follow-up till discharge, graft occlusion or death.

RESULTS

PTA was successful in 48/57 stenoses in 36 grafts (G), with a poor result in seven. Further PTA was required in seven stenoses (7 G). One graft occluded at PTA and one stenosis was inaccessible. Overall graft (G) patency (median 13 months) was 82% (1 year patency 84%). Of 48 successful PTAs (37 G), 36 remained patent (28 G), eight (4 G) occluded and four were lost to follow-up (4 G). Fourteen of thirty-six stenoses which remained patent required further intervention (seven PTA, six jump grafts, one vein patch). The four occlusions were associated with small veins (two), multiple stenoses (one) and a PTFE graft which occluded 10 days following PTA. Of the seven PTAs with a poor angiographic result, five remained patent, three after further intervention.

CONCLUSION

PTA is the best treatment for localised stenoses. Stenoses > 2 cm or multiple (three or more) stenoses are best treated surgically. Follow-up is essential, as 20% require further intervention.

Comparison of clinical follow-up and duplex surveillance of infrainguinal vein bypasses

The evidence in support of surveillance has been principally based on the favourable primary-assisted patency of stenosed grafts following revision (60-80% at 5 years) compared with the poor secondary patency of revised occluded grafts (20-40% at 5 years). Both the capital cost and workload generated by surveillance are considerable. More information is needed on the benefits of surveillance compared with clinical follow-up. A retrospective comparison of 50 vein grafts (44 reversed, six in situ) undergoing colour-coded duplex surveillance and 50 vein grafts (46 reversed, four in situ) under clinical follow-up, with duplex scans obtained only when clinically indicated, has been performed. Four (8%) stenoses of > or = 50% were identified in the surveillance group. One 50% proximal anastomotic stenosis failed to progress on sequential scans. Three stenoses were treated (one mid graft, two popliteal) by vein patch angioplasty (two cases) and transluminal angioplasty (one case). Both groups were followed-up for 12 months. Secondary patency at 12 months (88% surveillance; 80% clinical follow-up) was not significantly different (P = 0.3). Similarly, limb salvage at 12 months (94% surveillance; 88% controls) was not significantly different (P = 0.4). A large randomized prospective study comparing duplex surveillance and clinical follow-up is warranted.

Natural history of infrainguinal vein bypass stenoses: early lesions increase the risk of thrombosis

OBJECTIVES

To describe the natural history of stenoses in infrainguinal vein bypasses and to identify factors predicting outcome.

METHODS

Forty-two patients with non-revised vein bypass stenoses were followed prospectively by ultrasound Duplex scanning and ankle blood pressure measurements.

RESULTS

During a median follow-up of 8 (range 0-22) months 18 (43%) (95% confidence limits 28-59%) bypasses thrombosed and 6 (14%) (95% confidence limits 5-29%) patients were amputated. Bypass patency was lower in 12 patients with stenoses associated with reduction in ankle brachial index (ABI) exceeding 0.15 than in 30 patients with no or only marginal reduction in ABI (12 month patency 33% vs. 68%, p = 0.005). Among the 30 patients without distal pressure reduction, stenoses identified within 3 months from surgery were associated with an increased risk of thrombosis as compared to stenoses identified at a later stage (12 month patency 51% vs. 92%, p = 0.03).

CONCLUSION

Time interval from surgery to stenosis detection seems to be an independent parameter influencing outcome in patients with vein bypass stenoses.

The effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts

OBJECTIVES

Vein graft surveillance is widely acknowledged to be of benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to examine the effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts.

DESIGN

A prospective study of 69 consecutive prosthetic bypass grafts was undertaken over a 3 year period.

METHODS

Patients were seen at 3 monthly intervals after surgery and underwent measurement of ankle brachial pressure indices and a colour Duplex scan of the graft.

RESULTS

The surveillance programme was able to detect treatable lesions in five grafts and in the run-off vessels of two other grafts prior to occlusion. However 14 grafts failed after the first 30 days, 12 of which were not predicted by the surveillance programme.

CONCLUSIONS

Surveillance appears to be of limited benefit in the maintenance of patency of synthetic infrainguinal bypass grafts.

The influence of gender on the outcome of arterial procedures in the lower extremity

OBJECTIVES

To determine the outcome of arterial reconstructive procedures, we audited retrospectively peripheral bypass grafts and endarterectomies performed between 1982 and 1990.

MATERIALS AND METHODS

1005 peripheral arterial procedures were performed in 862 lower limbs in 782 patients. 62% of the limbs were critically ischaemic. The procedures include 565 bypasses, 346 endarterectomies and 94 combinations of both. 30% of the patients were women. Follow-up information was obtained from practitioners in charge of post-hospital care by questionnaires. Factors potentially affecting patency were investigated by multivariate analysis and patency rates were calculated by life-tables.

MAIN RESULTS

Overall secondary patency was 61% at one year and 35% at 5 years. Bypasses and endarterectomies in women yielded lower patency rates than in men (49% vs. 67% at 1 year, p < 0.001). The relative risk of failure in women as compared to men was 1.30. The risk of failure was further increased by "redo" surgery (relative risk 1.51), diabetes (1.40), critical ischaemia (1.34) and crural procedures (1.34).

CONCLUSIONS

Secondary patency rates were significantly lower in women than in men. This is in agreement with some other studies, although gender has gained little attention as a risk factor in vascular surgery.

Seeding with omental cells prevents late neointimal hyperplasia in small-diameter Dacron grafts

BACKGROUND

The influence of complete endothelialization of a prosthetic graft on development of late neointimal hyperplasia is unknown. This study was designed to investigate the effect of complete coverage with endothelial-like cells on late neointimal hyperplasia in small-diameter Dacron grafts seeded with omental cells in a canine model.

METHODS AND RESULTS

Four-mm-ID Dacron grafts were seeded with cells from omentum and implanted in the carotid arteries in 24 mongrel dogs. Each dog received one seeded and one nonseeded graft. The graft patencies were assessed by angiography at 1, 5, 12, 26, and 52 weeks after surgery. The prostheses were explanted at 5, 12, 26, and 52 weeks after surgery and underwent microscopic studies. The actuarial patency rates at 1, 5, 12, 26, and 52 weeks were 100%, 95%, 95%, 95% and 95% for seeded grafts and 100%, 86%, 49%, 40%, and 13% for nonseeded grafts, respectively. The seeded grafts exhibited a uniform endothelial-like luminal monolayer without the development of late neointimal proliferation or anastomotic neointimal hyperplasia. Neointimal tissue thickness increased up to 6 months; no additional progression of the subendothelial tissue thickness was observed, in fact there was an insignificant decrease.

CONCLUSIONS

Seeding with omental cells prevents development of late neointimal hyperplasia of small diameter prosthetic vascular grafts in a canine model.

The long-term outcome of infrainguinal vein graft surveillance

OBJECTIVES

Vein graft surveillance is of proven benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to look at the longer term outcome of a vein graft surveillance programme on graft patency.

METHODS

One hundred and twelve consecutive vein grafts in 106 patients were prospectively entered into a vein graft surveillance programme. The median (range) follow up was 34 (1-76) months.

RESULTS

There were 23 (21%) early (less than 1 month) failures and a further 15 grafts occluded during follow up. The primary, primary assisted and secondary patencies at 4 years were 27%, 59% and 67% respectively. Thirty-eight grafts (34%) developed at least one stenosis at a median interval of 5 months after the operation. Eight (21%) of these stenoses occurred more than 12 months after surgery and would have been missed had surveillance been curtailed after 1 year.

CONCLUSIONS

The benefits of graft surveillance extend beyond one year and surveillance should therefore continue indefinitely.

Simple hyperaemia test as a screening method in the postoperative surveillance of infrainguinal in situ vein bypasses

OBJECTIVES

To develop a simple protocol for ultrasound Duplex surveillance of infrainguinal vein bypasses.

DESIGN

The value of three Doppler waveform parameters, obtained from a single point of the bypass, for identification of stenoses was studied in 91 in situ vein bypasses. Midgraft peak systolic velocity (PSV), pulsatility index (PI) and ratio of hyperaemic and resting time-average mean velocities (TAMV), (TAMV ratio = TAMVhyperaemia/TAMVrest) were correlated with the presence and severity of stenoses as assessed by conventional Duplex scanning and ankle-brachial index (ABI) measurements. The optimal value of the waveform parameters for discrimination between bypasses with and without evidence of stenoses was determined by receiver operating characteristics (ROC) analysis.

MAIN RESULTS

Complete Duplex scanning of the entire graft revealed an increase in the peak systolic velocity by a factor 2.5 indicative of significant stenoses in 24 (26%) patients. A PSV below 55 cm/s was a poor indicator of stenoses (sensitivity 46%, specificity 76%) and PI < or = 3.8 only allowed suboptimal discrimination between normal and stenotic bypasses (sensitivity 63%, specificity 75%). The hyperaemic response assessed by TAMV ratio proved the best parameter for identification of graft stenoses. A TAMV ratio of 2.0 or less correctly identified 21 of the 24 lesions (sensitivity 88%, specificity 75%) and none of the three bypasses with evidence of stenoses and TAMV ratios exceeding 2.0 failed during follow-up.

CONCLUSIONS

Single point waveform analysis of vein bypass velocity profile at rest and during reactive hyperaemia is a simple screening method providing diagnostic and prognostic information which may be of value in the postoperative surveillance of infrainguinal vein bypasses.

Insonation and impedance analysis in graft surveillance

Seventy consecutive patients with infrainguinal bypass grafts entered a 1-year graft surveillance programme involving colour duplex scanning, direct graft insonation and computer-assisted impedance analysis. Graft patients with a positive duplex scan, high frequencies on graft insonation or an impedance value above 0.50 subsequently underwent arteriography. Sixteen patients were excluded before the initial surveillance visit. The 54 remaining patients with grafts (30 vein, 24 synthetic) underwent a total of 137 surveillance visits, with 21 grafts confirmed to be 'at risk'. The sensitivity of an impedance value above 0.55 in identifying these grafts was 86 per cent, rising to 95 per cent when combined with graft insonation. Duplex scanning did not identify any abnormalities in 11 grafts that were either shown by arteriography to be 'at risk' or occluded before arteriography. Impedance measurement and graft insonation are simple screening techniques with a high sensitivity (when combined), which identify 'at risk' infrainguinal grafts. Positive graft insonation or an impedance value over 0.55 will identify all 'at risk' vein grafts while minimizing the number of unnecessary arteriograms.

Percutaneous transluminal angioplasty of infrainguinal vein graft stenosis: long-term outcome

The aim of this prospective study was to examine the long-term outcome of infrainguinal vein graft stenosis managed by percutaneous transluminal angioplasty (PTA) as first-line treatment. Thirty-three infrainguinal vein graft stenoses detected by graft surveillance during a 44-month period were treated initially by PTA. The median (range) follow-up after angioplasty was 39 (18-56) months. Although 19 stenoses were successfully treated by a single PTA, 14 stenoses recurred at a median (range) interval of 8.5 (1-39) months. Restenosis occurred more frequently in the distal third of a graft (P = 0.002) compared with that in the proximal or mid-grafts, and restenosis was more common in in situ than reversed vein grafts (P = 0.03). It is concluded that infrainguinal vein graft stenoses were successfully treated by single PTA. There was, however, a high restenosis rate after angioplasty of stenosis in the distal third of a vein graft and, while approximately one third of such stenoses can be treated by a single PTA, the optimal management of recurrent stenosis requires further investigation.

Doppler spectral characteristics of infrainguinal vein bypasses

With the aim of assessing the velocity profile of femoropopliteal and femorocrural vein bypasses, 128 patients undergoing infrainguinal vein bypass surgery entered a postoperative Duplex surveillance protocol, which included clinical assessment and Duplex scanning, using Doppler spectral analysis. Doppler spectra were obtained at three sites in each graft and the following waveform parameters recorded: maximum systolic velocity, minimum diastolic velocity and resistance index. In patent reconstructions systolic velocity decreased by 30% during the first 6 months after surgery. In the absence of arteriovenous fistulas the initially antegrade diastolic velocity was replaced by a retrograde flow within 3 months, whereas a forward flow in diastole was sustained in grafts with patent fistulas. Abnormal Duplex findings in 31 patients led to angiography and revision in 13 cases. Four revised grafts failed, while nine remained patent at follow-up 1-12 months later. Ten (56%) of 18 non-revised bypasses with abnormal Duplex findings failed within 9 months compared to 1 (1%) of 76 bypasses with a normal velocity profile (p < 0.00001). In conclusion, Ultrasound Duplex scanning with spectral analysis provides valuable information concerning haemodynamics of infrainguinal vein bypasses and identifies grafts at risk of thrombosis. Inclusion of low resistance index (< 0.75) as an additional criteria for detection of stenoses appears to improve the sensitivity of Duplex scanning.

Infrainguinal vein graft stenosis

Although knowledge of the biological processes involved in the development of intimal hyperplasia has increased markedly in recent years, the precise aetiology of infrainguinal vein graft stenosis remains undetermined. Current therapy is therefore directed at treatment of the established lesion rather than its prevention. There seems little doubt, however, that recent advances in understanding of the vascular biology of normal and pathological saphenous vein will eventually lead to specific targeted therapy that will allow the prevention of vein graft stenosis.