Vein graft surveillance: is graft revision without angiography justified and what criteria should be used?

The Fate of Unrevised Stenoses in Infrainguinal Autologous Vein Grafts as Detected by Intraoperative Duplex Scanning

Intraoperative infrainguinal autologous vein graft stenoses are common, and some authors advise revision of these stenoses. But the natural history of these lesions is not clear. This study was undertaken to determine the natural history of duplex-detected intraoperative stenoses with a nonrevision policy. Intraoperative duplex scanning was performed in 46 infrainguinal autologous vein bypasses. The surgeon was blinded for the results of the intraoperative duplex scan and no intraoperative graft revision or modification of the routine postoperative protocol was performed after the duplex scan. Intraoperative duplex parameters and patient and bypass characteristics were correlated with the occurrence of an early graft event (occlusion or revision of a patent graft within 6 weeks postoperatively), which was the study's primary endpoint. Early graft event rate was 37% (17/46). PSV ratio and PSV-max were the only parameters with a significant correlation with the occurrence of an early graft event. An intraoperatively measured PSV ratio of =3.0 was the best predictor of an early graft failure with a sensitivity of 71% (95% CI: 50–83%) and a specificity of 90% (95% CI: 78–97%). In 12 of the 15 (80%) grafts matching this criterion an early graft event occurred, while only 5 (16%) early graft events occurred in the remaining 31 grafts (ie, a negative predictive value of 84%). When a PSV ratio of =3.0 was used as a cutoff value to predict early postoperative graft events, the likelihood ratios for a positive and negative test result were respectively 6.82 (95% CI: 2.23–20.8) and 0.33 (95% CI: 0.16–0.69). Unrevised intraoperative duplex-detected stenoses in infrainguinal autologous vein graft stenoses are a serious threat to early graft patency. The presence of an intraoperatively detected graft stenosis with a PSV ratio =3.0 is a strong predictor of early graft failure.

Hemodynamic changes associated with bypass stenosis regression

OBJECTIVE

Ultrasound scanning is used to detect velocity increases indicative of a bypass stenosis. Subsequent examinations have shown regression of some stenotic lesions. This study examined hemodynamic changes that coincided with stenosis regression.

METHODS

Duplex ultrasound scans were used to record the peak systolic velocity (PSV) and volume flow from proximal and distal segments of infrainguinal bypasses. Valve remnants or other image defects were also noted. The PSV ratio (Vr) was calculated as the PSV at a stenosis divided by the PSV proximal to the lesion. A stenosis was defined as Vr >/=2.0.

RESULTS

An initial ultrasound scan performed 31 +/- 6 days after surgery revealed a stenosis in 68 of 565 bypasses. In six bypasses, the increased PSV (272 +/- 61 cm/s) and Vr (3.4 +/- 1.3) were sustained during the follow-up period of 8 +/- 3 months. In 27 bypasses with a PSV of 335 +/- 63 cm/s and a Vr of 4.0 +/- 1.6, the stenosis was repaired. In 35 bypasses with a PSV of 261 +/- 82 cm/s and Vr of 3.2 +/- 1.2, stenosis regression occurred with no increases in PSV observed on later scans. In this group, proximal bypass flow decreased during the follow-up interval from 247 +/- 130 mL/min to 151 +/- 135 mL/min and distal flow from 180 +/- 102 mL/min to 103 +/- 54 mL/min ( P < .05, paired t test). Ultrasound image abnormalities were noted in 4 bypasses (67%) with persistent stenoses, 14 with repaired stenoses (52%), and 10 with resolved stenoses (29%).

CONCLUSION

These data indicate early postoperative hyperemia is present in bypasses, demonstrating focal velocity increases. Such velocity increases may be the result of the bypass conduit acting as a flow-limiting lesion until the hyperemia subsides. As the blood flow decreases so does the PSV, giving the appearance of stenosis regression.

Magnetic Resonance Angiography in the Follow-up of Distal Lower-Extremity Bypass Surgery: Comparison with Duplex Ultrasound and Digital Subtraction Angiography

PURPOSE

The danger of limb loss as a consequence of acute occlusion of infrapopliteal bypasses underscores the requirement for careful patient follow-up. The objective of this study was to determine the agreement and accuracy of contrast material-enhanced moving-table magnetic resonance (MR) angiography and duplex ultrasonography (US) in the assessment of failing bypass grafts. In cases of discrepancy, digital subtraction angiography (DSA) served as the reference standard.

MATERIALS AND METHODS

MR angiography was performed in 24 consecutive patients with 26 femorotibial or femoropedal bypass grafts. Each revascularized limb was divided into five segments--(i) native arteries proximal to the graft; (ii) proximal anastomosis; (iii) graft course; (iv) distal anastomosis; and (v) native arteries distal to the graft-resulting in 130 vascular segments. Three readers evaluated all MR angiograms for image quality and the presence of failing grafts. The degree of stenosis was compared to the findings of duplex US, and in case of discrepancy, to DSA findings. Two separate analyses were performed with use of DSA only and a combined diagnostic endpoint as the reference standard.

RESULTS

Image quality was rated excellent or intermediate in 119 of 130 vascular segments (92%). Venous overlay was encountered in 26 of 130 segments (20%). In only two segments was evaluation of the outflow region not feasible. One hundred seventeen of 130 vascular segments were available for quantitative analysis. In 109 of 117 segments (93%), MR angiography and duplex US showed concordant findings. In the eight discordant segments in seven patients, duplex US overlooked four high-grade stenoses that were correctly identified by MR angiography and confirmed by DSA. Percutaneous transluminal angioplasty was performed in these cases. In no case did MR angiography miss an area of stenosis of sufficient severity to require treatment. Total accuracy for duplex US ranged from 0.90 to 0.97 depending on the reference standard used, whereas MR angiography was completely accurate (1.00) regardless of the standard definition.

CONCLUSION

Our data strongly suggest that the accuracy of MR angiography for identifying failing grafts in the infrapopliteal circulation is equal to that of duplex US and superior to that of duplex US in cases of complex revascularization. MR angiography should be included in routine follow-up of patients undergoing infrapopliteal bypass surgery.

Evaluation of Peripheral Arterial Bypass Grafts with Multi–Detector Row CT Angiography: Comparison with Duplex US and Digital Subtraction Angiography

PURPOSE

To assess the technical feasibility of multi-detector row computed tomographic (CT) angiography in the assessment of peripheral arterial bypass grafts and to evaluate its accuracy and reliability in the detection of graft-related complications, including graft stenosis, aneurysmal changes, and arteriovenous fistulas.

MATERIALS AND METHODS

Four-channel multi-detector row CT angiography was performed in 65 consecutive patients with 85 peripheral arterial bypass grafts. Each bypass graft was divided into three segments (proximal anastomosis, course of the graft body, and distal anastomosis), resulting in 255 segments. Two readers evaluated all CT angiograms with regard to image quality and the presence of bypass graft-related abnormalities, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. The results were compared with McNemar test with Bonferroni correction. CT attenuation values were recorded at five different locations from the inflow artery to the outflow artery of the bypass graft. These findings were compared with the findings at duplex ultrasonography (US) in 65 patients and the findings at conventional digital subtraction angiography (DSA) in 27.

RESULTS

Image quality was rated as good or excellent in 250 (98%) and in 252 (99%) of 255 bypass segments, respectively. There was excellent agreement both between readers and between CT angiography and duplex US in the detection of graft stenosis, aneurysmal changes, and arteriovenous fistulas (kappa = 0.86-0.99). CT angiography and duplex US were compared with conventional DSA, and there was no statistically significant difference (P >.25) in sensitivity or specificity between CT angiography and duplex US for both readers for detection of hemodynamically significant bypass stenosis or occlusion, aneurysmal changes, or arteriovenous fistulas. Mean CT attenuation values ranged from 232 HU in the inflow artery to 281 HU in the outflow artery of the bypass graft.

CONCLUSION

Multi-detector row CT angiography may be an accurate and reliable technique after duplex US in the assessment of peripheral arterial bypass grafts and detection of graft-related complications, including stenosis, aneurysmal changes, and arteriovenous fistulas.

Contrast Material–enhanced, Moving-Table MR Angiography versus Digital Subtraction Angiography for Surveillance of Peripheral Arterial Bypass Grafts

PURPOSE

To assess the accuracy of moving-table MR angiography (MRA) in the evaluation of peripheral bypass grafts.

MATERIALS AND METHODS

There were 39 patients who had had peripheral bypass graft surgery and then subsequently underwent digital subtraction angiography (DSA) and contrast material-enhanced MRA, which was performed with moving-table software on a 1.0-T system before and during administration of 40 mL gadolinium. For evaluation, every bypass graft was divided into three parts and every leg into 14 segments. Disease severity was scored in four categories (0%-29%, 30%-69%, 70%-99%, 100%). Results were compared with those of the DSA. A total of 147 bypass graft segments and 938 vessel segments were classified.

RESULTS

In 132 of the assessable 147 bypass segments, disease gradings with both methods were congruent; however, 13 stenoses were misinterpreted by MRA for one grade and two additional lesions by two grades, leading to an accuracy in precise stenoses detection of 89.9%. The sensitivity and specificity values in the detection of bypass graft stenoses >69% (grade 3 + 4 lesions) reached 90.0% and 98.3%, respectively. In 821 of 938 vessel segments the accuracy of MRA in stenoses detection reached 87.5%. The sensitivity and specificity values in the detection of grade 3 + 4 lesions were 95.6% and 94.0% for the native vessels, respectively.

CONCLUSION

Moving-table MRA was as accurate in assessing bypass grafts as it was for the native arteries and showed a great accuracy in stenosis detection compared with DSA. Therefore, MRA is a promising modality for bypass graft surveillance and might be a noninvasive alternative to DSA in this regard.

Peripheral MR angiography

Peripheral arterial occlusive disease is a chronic and progressive disease with a reported incidence rate from 4.5% to 8.8% in men over 55 years of age. The diagnosis is usually made clinically, but for treatment planning and control, imaging of the peripheral arteries is required. Since its introduction in 1994, contrast-enhanced MR angiography has demonstrated a high diagnostic confidence and has replaced the invasive intra-arterial DSA, which is still the current gold standard for many different indications. For the peripheral arteries, clinical use of MR angiography was hampered for some years by the unsolved problem of the large imaging volume and the small diameter of the distal arteries. However, since the availability of ultra-fast high-gradient sequences and the possibility of moving-bed imaging, contrast-enhanced MR angiography, over the last few years, has shown its enormous potential and high accuracy in the diagnosis and follow-up of patients suffering from peripheral arterial occlusive disease. Exciting innovations in hardware and software allows very fast, very accurate, and very robust noninvasive imaging of the peripheral arteries, and both treatment planning as well as follow-up can be performed using contrast-enhanced MR angiography. The following review introduces the basic concepts of peripheral MR angiography--focusing on contrast enhanced imaging--and presents the different techniques as well as some potential limitations and how they could be solved. Finally, this article provides a look into the already-begun future of peripheral contrast-enhanced MR angiography with hybrid and combination techniques.

Interobserver variation in duplex scanning of infrainguinal arterial bypass grafts

OBJECTIVE

to determine the degree of interobserver variation of color-flow duplex scanning of infrainguinal arterial bypass grafts.

METHODS

two experienced vascular technologists randomly assessed bypass grafts in 32 consecutive patients, using a color-flow duplex scan. In pre-defined segments the highest peak systolic velocity (PSV(max)) and end-diastolic velocity (EDV) were measured and a peak systolic velocity ratio (PSV ratio) was calculated. Results were analyzed as continuous variables (Bland and Altman plots and Intraclass Correlation Coefficient=ICC) and also as categorical data (weighted Kappa coefficient) for the PSV ratio 1-2.5, > or =2.5-4, > or =4.0.

RESULTS

the ICC for the PSV(max), PSV ratio and EDV indicated "almost perfect" agreement for all three parameters. However, the Bland and Altman plots showed impressive interobserver variation for the higher values of all three parameters. For the PSV ratio categories a weighted kappa of 0.31 was calculated, indicating only fair agreement. Substantial variation was found for the categories with PSV ratios > or =2.5-4.0 and > or =4.0.

CONCLUSION

though performing accurately for the lower values of the assessed parameters, duplex scanning shows considerable interobserver variation for the clinically significant higher values. Particularly in the PSV ratio interval > or =2.5-4.0, most relevant for clinical decision-making, the interobserver variability is unacceptable.

Modifiable patient factors are associated with reverse vein graft occlusion in the era of duplex scan surveillance

OBJECTIVE

Modifiable patient factors that contribute to graft occlusion may be addressed after surgery. To determine risk factors associated with reverse vein graft (RVG) occlusion, we examined the characteristics and duplex scan surveillance (DS) patterns of patients with RVGs.

METHODS

Patients treated with RVG from January 1996 through December 2000 were identified from a prospective registry. The study population consisted of all patients with RVGs performed during the study period with grafts that subsequently occluded. Patients whose grafts remained patent served as age-matched and gender-matched control subjects. The prescribed DS regimen was every 3 months for the first postoperative year and every 6 months thereafter. Early DS failure was defined as having no DS within the first 3 months. Cox proportional hazards analysis was used to compare the two groups. Hazard ratios were calculated.

RESULTS

During the study period, 674 patients underwent RVG. Fifty-five patients with occluded RVGs were compared with 118 with patent RVGs. The follow-up period for occluded grafts was 13.40 +/- 12.59 months and for patent grafts was 32.40 +/- 15.61 months. Dialysis therapy, a known hypercoagulable state, continued smoking, and DS failure were independent factors associated with RVG occlusion. The hazards ratio for dialysis was 6.45 (95% CI, 3.07 to 13.51; P <.001), for current smoking was 4.72 (95% CI, 2.5 to 8.85; P <.001), for hypercoagulable state was 2.99 (95% CI, 1.47 to 6.10; P =.003), and for early DS failure was 2.43 (95% CI, 1.29 to 4.59; P =.006).

CONCLUSION

Continued smoking and failure to undergo DS within the first three postoperative months are modifiable factors associated with RVG occlusion. Smoking cessation and graft surveillance must be stressed to optimize patency of infrainguinal RVGs.

The vascular laboratory in practice: a national survey in the Netherlands

OBJECTIVES

to overview Dutch vascular laboratory practice and specifically the variation in duplex criteria.

METHODS

a questionnaire was sent to all vascular laboratories in The Netherlands (n=140).

RESULTS

the response rate of the inquiry was 64% (n=89). There is no consensus on interpretation of outcome. In 22% of the clinics (n=20) a diagnostic angiography will be omitted when a percutaneous angioplasty is advised on account of duplex ultrasound. Only 5% (n=4) relies upon duplex ultrasound for operation without diagnostic angiography. In 44% (n=39) a PSV (peak systolic velocity) of 125 cm/s is used to identify a>70% or internal carotid artery stenosis. In 44% (n=39) a PSV of 210 cm/s and 10% (n=9) a PSV > or =150 cm/s is used. For grading a relevant stenosis in the femoro-politeal arteries a PSV ratio > or =2.5 is chosen in 75% (n=67). Criteria used for graft surveillance shows also a wide variation.

CONCLUSIONS

a commission for the accreditation of vascular laboratories should be established with the goal of creating standards and performing quality control.

Repeat surgery without preoperative angiography in limbs with patent infrainguinal bypass grafts

The aim of this study was to assess the feasibility and results of repeat surgery without preoperative angiography in limbs with patent infrainguinal bypass grafts. Between January 1995 and December 1999, 73 surgical interventions were performed for correction of inflow, graft, or runoff-related lesions in limbs with patent infrainguinal bypass grafts. Fifty-six of the 73 cases were operated on based on the findings obtained from duplex scanning alone. There were 53 vein and 3 prosthetic grafts in the series. The indications for intervention without angiography were stenotic or occlusive lesions in 35, graft aneurysm in 7, and arteriovenous fistulae in 14. There were no deviations from the preoperatively planned surgical strategy in patients undergoing surgery without preoperative angiography. Cumulative life table primary, (stenosis free) and primary-assisted patency rates, at 12 months following graft revisions (excluding arteriovenous fistulae ligatures) without preoperative angiography, were 64% and 85%, respectively. The corresponding figures for revisions performed with preoperative angiography were 58% and 84%, respectively. There were no significant differences between patients undergoing surgery with or without preoperative diagnostic angiography with regard to patency rates. Surgical interventions for correction of infrainguinal graft-related stenotic or aneurysmal lesions can be safely performed based on findings obtained from duplex scanning.

Intraoperative angioscopy may improve the outcome of in situ saphenous vein bypass grafting: a prospective study

OBJECTIVE

To find out whether intraoperative angioscopic assistance has any effect on graft outcome in patients with critical leg ischemia.

MATERIAL AND METHODS

One hundred one patients requiring a below-knee bypass were assigned to undergo in situ saphenous vein bypass with or without intraoperative angioscopic assistance; otherwise treated similarly including preoperative duplex vein mapping, intraoperative graft flow measurements, and angiography. Data on operative details, morbidity, hospital stay, and graft patency were collected prospectively and compared. All patients were followed up for 12 months.

RESULTS

The group that underwent angioscopy (A) and the control group (B) were similar in all respects, except for the number of patients enrolled in the groups (32 and 69, respectively). Angioscopy revealed incompletely destructed valves in 34 patients (range, 0 to 5; mean 1), undiagnosed vein branches in 111 patients (mean 4.3), and partly occluding thrombus in 5 patients. The number of postoperative arteriovenous fistulas with signs of failing graft and a need for angiographic or surgical reintervention were significantly higher in group B (P <.0001). The 1-year primary patency rate was significantly better in group A (P <.01), but the primary assisted and secondary patency rates did not differ between the groups.

CONCLUSIONS

Angioscopic assistance has an impact on primary graft patency, minimizes the risk for graft failure and thus reduces the need for reintervention by allowing identification of persistent saphenous vein branches, incomplete valve destruction, and partly occluding graft thrombus without adding extra operative time.

Lower extremity bypass graft revision in diabetics

Revision of lower extremity bypass graft stenoses identified by surveillance duplex scanning is frequently required in diabetic patients. The authors evaluated (1) the value of routine angiography before graft revision in diabetics, (2) factors that predict patients in whom angiography alters management, and (3) the incidence of recurrent stenosis and factors that might predict it. Forty-two infrainguinal primary vein bypasses undergoing primary revision were retrospectively studied. The initial graft stenosis was detected at a mean of 11.5 +/-3.6 months after the original bypass. Angiograms were obtained in 38 cases, revealing additional findings in 29 of 38 cases (76%), with a resultant alteration of the operative plan in 27 cases (71%). The most frequent additional angiographic finding was the identification or localization of a lesion in the inflow or outflow tracts (18 of 27 cases). Cases where the angiogram altered the management plan had a mean systolic velocity ratio across the stenosis (Vr) of 7.3 +/-6.1, versus a Vr of 4.8 +/-1.3 for cases where the angiogram did not alter the management plan (p<0.04). Duplex scanning identified 4 lesions that were not seen on angiography; 3 of 4 were confirmed as webs at surgery. Twenty of 42 grafts (48%) developed recurrent stenoses at a mean of 4.9 +/-3.8 months from initial revision. Restenosis occurred in 69% of female limbs as compared to 38% of male limbs (p=0.06). Recurrent stenosis was not a predictor of ultimate graft failure, unless left untreated. Four of 10 untreated grafts ultimately failed. A total of 9 of the 42 grafts eventually failed (21%), leading to 3 amputations (7%). The authors conclude that failing infrainguinal bypass grafts identified by duplex in diabetics should undergo a detailed angiographic evaluation. This frequently leads to an alteration in the management plan, especially in the presence of a high Vr across stenoses. High rates of limb salvage (93%) and assisted primary graft patency (79%) despite a high recurrent stenoses rate (48%) justify routine duplex surveillance, preoperative angiography, and aggressive graft revision in diabetic patients with infrainguinal grafts.

Transfer function index of pulse volume recordings: a new method for vein graft surveillance

OBJECTIVE

Color flow duplex scanning is currently the best method available for vein graft surveillance. However, it puts a considerable strain on the workload of a vascular unit and requires a highly trained operator. The aim of this study was to develop and validate a new, noninvasive tool for graft surveillance. The utility of transfer function index (TFI) of pulse volume recordings is tested for this purpose.

METHODS

The design of the study was a blind comparative study that involved 70 testing procedures that were performed on 58 different infrainguinal vein bypass grafts. The TFI was measured with a portable vascular laboratory multi-cuff unit. Ankle/brachial indexes were obtained with the same device. Color flow duplex scanning was used as a diagnostic standard. A graft was defined as at risk, according to duplex scanning, if a local stenosis with a V2/V1 more than 2 was found or if peak systolic velocity remained less than 45 cm/s throughout the graft. The repeatability of the method was tested on 30 grafts.

RESULTS

A total of 63 tests were available for analysis. Seven tests were excluded. Four were excluded because they had unreliable TFI measurement due to cardiac arrhythmias, and in three tests, the whole graft could not be visualized in the duplex scan. Forty normal and 22 at-risk grafts were found. One graft was occluded. The TFI was significantly lower for at-risk grafts (0.89) versus normal grafts (1.09; P =.005). A TFI of 1.02 or less correctly detected 21 of 22 at-risk grafts. The sensitivity, specificity, and accuracy were 96%, 65%, and 76%, respectively. The ability of the ankle/brachial index to detect the at-risk grafts was clearly inferior to the TFI. The repeatability of the method at proximal thigh, distal thigh, and proximal calf was +/- 0.21, +/- 0.07, and +/- 0.14, respectively.

CONCLUSION

The TFI is a sensitive and reliable method to detect an at-risk graft. The examination is noninvasive, simple, quick to perform, and well tolerated by the patients. We suggest that the TFI could be the first-line screening method in vein graft surveillance.

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.

Duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery: costs and clinical outcomes compared with other surveillance programs

PURPOSE

In this study we assessed the costs and clinical outcomes of duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery and compared duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up.

METHODS

In a clinical study, 293 patients (mean age, 70.1 years; 58.7% men) with peripheral arterial disease were observed in a duplex scan surveillance program after infrainguinal autologous vein bypass grafting surgery. Costs were calculated from the health care perspective for surveillance and subsequent interventions from 30 days to 1 year postoperatively. All costs are presented in 1995 US dollars per patient. In a simulation model, we estimated the costs and amputations of duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up conditional on the indication for surgery. The main outcome measure was the incremental cost per major amputation per patient avoided during the first postoperative year.

RESULTS

Duplex scan surveillance was the least expensive ($2823) and resulted in the fewest major amputations (17 per 1000 patients examined), compared with ankle-brachial index surveillance ($5411 and 77 amputations per 1000 patients) and clinical follow-up ($5072 and 77 amputations per 1000 patients). In patients treated for critical limb ischemia, duplex scan surveillance was the least expensive ($2974) and resulted in the fewest major amputations (19 per 1000 patients). Under all surveillance programs, 13 major amputations per 1000 patients treated for intermittent claudication were performed, and clinical follow-up had the lowest costs ($1577). In a sensitivity analysis that assumed that duplex scan surveillance could have avoided six major amputations per 1000 patients treated for intermittent claudication compared with the other programs, duplex scan surveillance had an incremental cost of $80,708 per major amputation per patient avoided compared with clinical follow-up.

CONCLUSION

Duplex scan surveillance is highly effective for patients treated for critical limb ischemia, leading to a reduction of major amputations and consequently to a reduction in costs compared with other surveillance programs. In patients treated for intermittent claudication, the evidence supporting duplex scan surveillance is less firm, but if duplex scan can avoid six major amputations per 1000 patients examined, the incremental costs are justified.

Identification of factors predictive of lower extremity vein graft thrombosis

OBJECTIVE

The objective of this study was to assess the prognostic value of hemodynamic parameters measured with duplex ultrasound scan, together with other important graft and patient characteristics, in predicting lower extremity vein graft thrombosis.

METHODS

A total of 165 lower extremity vein grafts were entered prospectively into a postoperative duplex ultrasound scan surveillance program with examinations performed at 1, 2, 3, 4, 6, 9, 12, 18, and 24 months, and annually thereafter. Duplex scan-derived blood flow velocity measurements were recorded at 1562 patient visits over 7 years. Graft patency was determined after each visit, and an analysis of factors predictive of vein graft thrombosis was performed with Poisson regression.

RESULTS

Thirty-two episodes of first-time graft thrombosis occurred, 23 of which were permanent. One-, 3-, and 5-year secondary graft patency rates were 90%, 86%, and 79%, respectively. In multivariate analyses, duplex scan velocity measurements predictive of lower extremity graft thrombosis included the maximum velocity ratio (Vr) in association with a graft stenosis and the mean graft peak systolic velocity (MGV) within nonstenotic portions of the body of the graft. The incidence of graft thrombosis among grafts without inflow/outflow stenoses, with Vr less than 3.5, and with MGV 50 cm/s or more, was 2.9% per year. Incidence rates were considerably higher among grafts with a of Vr of 3.5 or more (incidence rate ratio = 7.0; 95% CI, 3.4-14.6) or an MGV less than 50 cm/s (incidence rate ratio = 6.5; 95% CI, 3.3-13.1). In grafts without identifiable inflow, outflow, or graft stenoses, there was no association between MGV and the risk of graft thrombosis.

CONCLUSION

Duplex scan velocity measurements are valid predictors of impending graft thrombosis. A Vr of 3.5 or more and an MGV less than 50 cm/s are the best predictive measures. Repair of correctable graft lesions with a Vr of 3.5 or more, or inflow, outflow, or graft lesions associated with an MGV less than 50 cm/s are recommended. Grafts without detectable inflow, outflow, or graft stenoses, regardless of MGV, may be safely followed.

Serial measurement of cross-sectional area in peripheral vein grafts using three-dimensional ultrasound

Frequent surveillance of bypass grafts placed in the lower limbs can provide early detection of stenoses. A three-dimensional (3-D) ultrasound (US) imaging system has been used to produce serial surface reconstructions of regions of interest in vein grafts in the lower extremities. Using anatomical reference points, data sets from serial studies are registered in a common 3-D coordinate system. Cross-sectional area measurements are extracted from the surface reconstructions in planes normal to the vessel center axis. These measurements are compared at matched sites over time to track changes in the vessel configuration. The quantitative measurements are paired with surface displays of the vessels for a complete depiction of the changing geometry. Example studies from three patients are shown, for time periods up to 38 weeks. The cross-sectional area measurements highlight regions of remodeling and developing stenoses within the grafts.

Surveillance of peripheral arterial bypass grafts with three-dimensional MR angiography: comparison with digital subtraction angiography

OBJECTIVE

The purpose of this study was to use contrast-enhanced three-dimensional MR angiography to assess the patency of peripheral arterial bypass grafts of the lower extremity.

SUBJECTS AND METHODS

The study included 39 patients with 45 lower limb grafts. Twenty-eight were saphenous vein grafts, 13 were expanded polytetrafluoroethylene, and two were Dacron grafts. Digital subtraction angiography correlation was available for 30 patients (31 grafts). MR angiography was performed on a 1.5-T system with a multichannel quadrature phased array peripheral vascular coil. The scanning delay was determined with a test bolus technique, using half-time to maximum signal intensity in the graft. Arterial imaging was accomplished with two three-dimensional MR angiography acquisitions with gadopentetate dimeglumine administered using an automated injector. The pelvic and femoral arteries were imaged, the MR table was repositioned, and the lower limb arteries were imaged. The three-dimensional MR angiography sequence used the following parameters: TR/TE, 5.2/1.5 msec; inversion time, 28 msec; flip angle, 30 degrees. The proximal anastomosis, graft, and distal anastomosis were characterized as normal, stenosed, occluded, or ectatic or aneurysmatic.

RESULTS

Sensitivity and specificity values for MR angiography regarding the assessment of grafts were 100% for 87 evaluable segments for which digital subtraction angiography correlation was available: stenosis (n = 10), occlusions (n = 9), ectasia or aneurysms (n = 8). Six segments could not be assessed because of the presence of intravascular stents or metallic clips.

CONCLUSION

Contrast-enhanced three-dimensional MR angiography is well suited for the characterization of arterial grafts, for planning subsequent vascular interventions, and for excluding further lesions.

Incidentally detected stenoses proximal to grafts originating below the common femoral artery: do they affect graft patency or warrant repair in asymptomatic patients?

OBJECTIVE

Stenoses in infrageniculate arteries proximal to a lower extremity vein graft may reduce flow velocity through the bypass graft and are thought to predispose to graft occlusion. Repair of these lesions has been recommended to preserve graft function. This study was undertaken to better define the natural history of grafts below inflow lesions and to evaluate the necessity of repair to preserve graft patency.

METHODS

From 1994 through 1999, patients undergoing lower extremity vein grafts by a single surgeon at a university hospital and an affiliated teaching hospital were placed in a prospective protocol for proximal infrageniculate native artery and graft surveillance through use of duplex scanning. The records of those patients with grafts originating distal to the common femoral artery were evaluated; they form the basis for this report. Arteriograms were obtained before bypass grafting, and no patient had a stenosis greater than 50% diameter reduction proximal to the graft origin. Follow-up scans were obtained from the common femoral artery through the graft and outflow artery. The peak systolic velocity and velocity ratio in an infrageniculate native artery proximal to the graft origin were recorded, as were the location and the time interval since the bypass graft. Repair of these proximal lesions was not performed during the course of this study. Revision of the bypass graft or its anastomoses was undertaken according to preestablished duplex scan criteria.

RESULTS

During this time, 288 autogenous infrainguinal bypass grafts were performed, of which 159 originated below the common femoral artery; of these, 74 were from the superficial femoral artery, 29 from the profunda femoris artery, 49 from the popliteal artery, and 7 from a tibial artery. The maximum peak systolic velocity proximal to the graft origin was more than 250 in 38 arteries (25%) and more than 300 in 26 arteries (16%). The velocity ratio was 3.0 or more in 32 arteries at the same location as the peak systolic velocity and 3.5 or more in 23 arteries (15%), confirming hemodynamically significant stenoses at these sites. The location of peak systolic velocity was the common femoral artery in 81 patients (51%), the superficial femoral artery in 50 (31%), the popliteal artery in 22 (14%), and a tibial artery in 6 (4%). Follow-up ranged from 8 to 60 months (mean, 35 months). During follow-up, 19 patients died, 18 with patent grafts. Overall, nine grafts occluded. One of the occluded grafts had a velocity ratio greater than 3.0; this may have contributed to graft thrombosis. The other occlusions resulted from an unrepaired graft lesion in 2 patients, graft infection in 2 patients, and graft ligation necessitated by below-knee amputation in 2 patients. No cause for the occlusion could be identified in two of the grafts (neither had evidence of proximal arterial stenosis). Assisted primary patency rates were 95% and 91% at 3 and 5 years, respectively.

CONCLUSIONS

For grafts originating distal to the common femoral artery, stenoses proximal to the graft do not affect bypass graft patency and do not require repair to prevent graft occlusion. Surveillance of these lesions may therefore be unnecessary, inasmuch as the repair of proximal lesions should not be undertaken to preserve graft function.

Interobserver agreement in duplex scanning for vein grafts

BACKGROUND

although the precision of duplex scanning is of utmost importance in vein-graft surveillance, it has not been properly assessed. This study aims to analyse interobserver agreement on duplex scanning.

METHODS

a blinded comparative trial of 69 infrainguinal vein bypass reconstructions. Two consecutive duplex scans were performed by different examiners and duplex ultrasound machines on the same patient. The duplex examinations were also compared with angiography, when available, and clinical follow-up.

RESULTS

interobserver agreement in Kappa statistics was 0.69, signifying "good" agreement between the examinations in detecting haemodynamically significant changes in the grafts. The sensitivity, specificity and accuracy figures compared with a combination of angiography and follow-up data for the two scans were 80%, 91%, 88% and 85%, 93%, 91%, respectively. The limits of agreement were, however, wide for Doppler-derived velocity characteristics.

CONCLUSION

duplex scanning is an accurate and reproducible method for detecting haemodynamically significant changes in infrainguinal vein grafts.

Do residual arteriovenous fistulae after in situ saphenous vein bypass grafting influence patency?

PURPOSE

The purpose of this study was to evaluate the influence on patency of residual arteriovenous fistulae (AVF) after in situ saphenous vein bypass grafting.

METHODS

Between January 1, 1994, and December 31, 1996, 98 in situ saphenous vein bypass grafting procedures were performed in 94 patients. Patency was evaluated with duplex scanning after operation and at 1, 3, 6, 9, and 12 months.

RESULTS

The indications for operation were intermittent claudication in two patients and critical leg ischemia in 92 patients. Two above-knee and 48 below-knee femoropopliteal and 48 femorocrural in situ saphenous vein bypass grafting procedures were performed. The median follow-up period was 9 months (range, 1.5 to 12.5 months). There were no residual AVF in 45 veins (44%; group 1), but 110 residual AVF were found in 53 veins (56%; group 2). In group 2, 36 AVF in 18 veins were surgically or radiologically occluded mainly as a result of a flow velocity decrease distal to the AVF, but the remaining 74 AVF were treated conservatively. The 1-year cumulative primary patency rates were 68% in group 1 and 74% in group 2 (log-rank test, 0.47; degree of freedom = 1; P =.52). The 1-year cumulative assisted primary patency rates were 68% in group 1 and 81% in group 2 (log-rank test, 2.19; degree of freedom = 1; P =. 14).

CONCLUSION

Residual AVF after in situ bypass grafting without influence on bypass graft hemodynamics do not compromise patency and thrombose spontaneously.

Effect of outflow level and maximum graft diameter on the velocity parameters of reversed vein bypass grafts

OBJECTIVE

The objective of this study was to define a normal range of distal graft velocity (DGV) and peak systolic velocity (PSV) on the basis of outflow level and maximum graft diameter for infrainguinal reversed vein bypass grafting (RVG).

METHODS

This study was designed as a prospective study of consecutive patients who underwent infrainguinal RVG from 1994 to 1997 in a university hospital and university-affiliated teaching hospital. All patients who underwent infrainguinal bypass grafting from 1994 to 1997 were placed in a prospective protocol with duplex scanning to better define the hemodynamics of normally functioning RVG. Graft revisions were performed for patients with velocity ratios of more than 2.5. One hundred twenty-one patients were entered into this protocol, and 114 were followed more than 3 months after RVG. Seven patients were excluded: five for death within 3 months, one for graft infection, and one for graft occlusion before the baseline duplex scanning. DGV and PSV were determined for each type of outflow (popliteal, crural, and pedal) and for ranges of maximum graft diameter. These then were correlated with subsequent graft occlusion or graft revision (graft failure).

RESULTS

Grafts with larger diameters were associated with lower DGVs (P <.001), and more proximal outflow arteries were associated with higher DGVs (popliteal, 75 cm/s; crural, 50 cm/s; and pedal, 40 cm/s; P <.01). The mean PSVs were 150, 140, and 122 cm/s for popliteal, crural, and pedal grafts, respectively, but the difference was not statistically significant. The assisted primary patency rates for the grafts in this series were 99%, 92%, and 92% at 1, 2, and 3 years.

CONCLUSION

Graft diameter and location of the distal anastomosis significantly affect the flow velocity in RVG. Other variables did not influence these parameters. Currently established criteria for arteriography or graft repair on the basis of graft velocity parameters may be improved if they can be modified depending on diameter and outflow.

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.

Surgical and endovascular intervention for infrainguinal vein graft stenosis

PURPOSE

The purpose of this study was to evaluate the stenosis-free patency of open repair (vein-patch angioplasty, interposition, jump grafting) and percutaneous transluminal balloon angioplasty (PTA) of 144 vein graft stenoses that were detected during duplex scan surveillance after infrainguinal vein bypass grafting.

METHODS

Patients who underwent revision of an infrainguinal vein bypass graft were analyzed for type of vein conduit, vascular laboratory findings leading to revision, repair techniques, assisted graft patency rate, procedure mortality rate, and restenosis of the repair site.

RESULTS

The time of postoperative revision ranged from 1 day to 133 months (mean, 13 months). One hundred eighteen primary and 26 recurrent stenoses (peak systolic velocity, >300 cm/s) in 52 tibial and 35 popliteal vein bypass grafts were identified by means of duplex scanning. The repairs consisted of 77 open procedures (vein-patch angioplasty, 28; vein interposition, 33; jump graft, 9; primary repair, 3) and 67 PTAs. No patient died as a result of intervention. Cumulative assisted graft patency rate (life-table analysis) was 91% at 1 year and 80% at 3 years. At 2 years, cumulative assisted graft patency rate was comparable for saphenous vein grafts (reversed, 94%; in situ, 88%; nonreversed, 63%) and alternative vein grafts (89%). Stenosis-free patency rate at 2 years was identical (P =.55) for surgical intervention (63%) and endovascular intervention (63%) but varied with type of surgical revision (P =.04) and time of intervention (<4 months, 45%; >4 months, 71%; P =.006). The use of duplex scan-monitored PTA to treat focal stenoses (<2 cm) and late-appearing stenoses (>3 months) was associated with a stenosis-free patency rate that was 89% at 1 year. After intervention, the alternative vein bypass grafts necessitated twice the reinterventions per month of graft survival (P =.01). Bypass graft to the popliteal versus infrageniculate arteries, site of graft stenosis (vein conduit, anastomotic region), and repair of a primary versus a recurrent stenosis did not influence the outcome after intervention.

CONCLUSION

The revision of duplex scan-detected vein graft stenosis with surgical or endovascular techniques was associated with an excellent patency rate, including when intervention on alternative vein conduits or treatment of restenosis was necessary. When PTA was selected on the basis of clinical and duplex scan selection criteria, the endovascular treatment of focal vein graft stenosis was effective, durable, and comparable with the surgical revision of more extensive lesions.