Non-invasive impedance analysis: a new non-invasive test for graft surveillance

Detection of failing grafts with early reoperation is clearly associated with better long-term patency than intervention after graft failure. Duplex ultrasonography is more accurate than ankle:brachial index for graft surveillance, but is expensive, time consuming and technically demanding. Non-invasive estimation of graft impedance is now possible. The present study was undertaken to evaluate the utility of non-invasive impedance in detecting the failing vein graft. Sixty-nine grafts in 51 patients were followed over a period of 12 months (April 1992–March 1993). High risk infrainguinal arterial vein bypass patients were entered into a graft surveillance program. Ankle:brachial index, non-invasive impedance and duplex ultrasonography were performed upon discharge, 1 month after surgery and then at 3-monthly intervals. Non-invasive impedance was measured using a mean Doppler flow signal obtained from both upper and lower ends of the graft paired with the mean pulse volume recording obtained from the distal arterial bed. The mean pulse volume recording and flow signals were digitized by discrete Fourier transform and an impedance index generated. An impedance index ⩾ 0.5 was considered abnormal. Impedance results were compared with ankle:brachial index, duplex ultrasonography and angiography when appropriate, and detected 28 failing and five failed grafts. Non-invasive impedance achieved a sensitivity of 91 % and a specificity of 94%. Similarly, duplex ultrasonography was 91% sensitive and 97% specific, while ankle:brachial index was 58% sensitive and 94% specific. Non-invasive impedance is a simple, inexpensive and effective test which detects the failing graft and is an appropriate first-line alternative to duplex ultrasonography for postoperative graft surveillance.     

Operative transluminal laser angioplasty as the sole treatment for late stenoses of femorodistal artery bypass graft: Experimental and clinical studies

To determine the role of Nd:YAG laser thermal angioplasty as the sole treatment for late stenoses of femorodistal artery bypass graft, the lasing effect of a larger size of hot-tip probe (3, 4, and 5 mm) was experimentally studied in vitro. For an adequate lasing effect, 30 watts of laser power output for 3 seconds was needed for the 3 mm probe, 40 watts for the 4 mm probe, and 50 watts for the 5 mm probe, respectively. Based on these results, we used Nd:YAG laser thermal angioplasty alone for 25 grafts, including 16 polytetrafluoroethylene (PTFE) grafts, eight saphenous vein grafts, and one externally supported (EXS) Dacron graft in which the stenotic lesions were detected by deterioration of the Doppler flow waveform pattern or a significant fall in the ankle/brachial pressure index (ABPI). Follow-up was from 3 to 24 months (average of 9 months) for PTFE grafts, from 5 to 21 months (average of 11 months) for saphenous vein grafts, and 13 months for the EXS Dacron graft following femorodistal artery reconstructions. Stenotic lesions were most common in the distal anastomotic sites: 11 PTFE grafts, three saphenous vein grafts, and one EXS Dacron graft. Among these, 13 grafts showed a type II flow waveform pattern at the time of surgery. Clinical success was achieved in 12 of the PTFE grafts (75%), in five of the vein grafts (62.5%), and in the single EXS Dacron graft. Four PTFE and three saphenous vein grafts failed subsequent to repeat intraoperative balloon angioplasty in three and graft extension in three and one graft interposition. Perforation occurred in only one vein graft. Continuing patency has now been maintained for up to 25 months after lasing. Nd:YAG laser thermal angioplasty using a 3 to 5 mm hot-tip probe is effective as the sole procedure for widening a stenotic lesion and improving patency after femorodistal artery reconstruction.     

Femorodistal vein grafts: The utility of graft surveillance criteria

Purpose: This retrospective review of femorodistal vein grafts was analyzed to determine the usefulness of various graft surveillance criteria.Method: The surveillance schedule involved evaluations at 1 month, every 3 months the first year, and then every 6 months. Salvage intervention or graft occlusion occurring within the next follow-up interval defined surveillance end points. One hundred two grafts (329 surveillance visits) had an ankle/brachial index (ABI). A duplex scanning – determined midgraft peak systolic flow velocity (PSFV) was available for 81 grafts (262 visits). Forty-eight grafts (137 visits) had both a PSFV and entire graft duplex scanning (EGDS) to determine stenosis greater than 50%, whereas 40 grafts (91 visits) had simultaneous ABI and EGDS.Results: When a greater than 15% decrease in ABI denoted an abnormal surveillance study result, a positive predictive value (PPV) of 24.3% and negative predictive value of 94.5% were noted. Similarly, a PSFV cutoff of less than 35 cm/sec demonstrated values of 26.3% and 94.2%, respectively. When an EGDS of greater than 50% stenosis or a PSFV of less than 35 cm/sec were the cutoff criteria, the PPV was 36.7% and negative predictive value 99.1%, whereas characterizing abnormal results further with ABI (>15%↓) increased the PPV to 83.3%.Conclusion: The combination of an EGDS, midgraft PSFV, and ABI provides optimal follow-up for our patients with a femorodistal vein graft. (J V ASC S URG 1995; 21:127-34.)     

Haemodynamic effect of intermittent pneumatic compression of the leg after infrainguinal arterial bypass grafting

BACKGROUND: Intermittent pneumatic compression (IPC) may increase blood flow through infrainguinal arterial grafts, and has potential clinical application as blood flow velocity attenuation often precedes graft failure. The present study examined the immediate effects of IPC applied to the foot (IPC(foot)), the calf (IPC(calf)) and to both simultaneously (IPC(foot+calf)) on the haemodynamics of infrainguinal bypass grafts. METHODS: Eighteen femoropopliteal and 18 femorodistal autologous vein grafts were studied; all had a resting ankle : brachial pressure index of 0.9 or more. Clinical examination, graft surveillance and measurement of graft haemodynamics were conducted at rest and within 5 s of IPC in each mode using duplex imaging. Outcome measures included peak systolic (PSV), mean (MV) and end diastolic (EDV) velocities, pulsatility index (PI) and volume flow in the graft. RESULTS: All IPC modes significantly enhanced MV, PSV, EDV and volume flow in both graft types; IPC(foot+calf) was the most effective. IPC(foot+calf) enhanced median volume flow, MV and PSV in femoropopliteal grafts by 182, 236 and 49 per cent, respectively, and attenuated PI by 61 per cent. Enhancement in femorodistal grafts was 273, 179 and 53 per cent respectively, and PI attenuation was 63 per cent. CONCLUSION: IPC was effective in improving infrainguinal graft flow velocity, probably by reducing peripheral resistance. IPC has the potential to reduce the risk of bypass graft thrombosis.     

Intra-operative Doppler Flow Measurement do not Predict ‘At-risk’ Status of Infrainguinal Bypass Grafts

AIMS: Patients undergoing infrainguinal arterial reconstruction using vein conduits, frequently undergo intra-operative Doppler flow measurements to determine technical adequacy. The aim of this study was to determine the proportion of vein grafts with normal intra-operative haemodynamic parameters that were subsequently discovered to be 'at risk' on post-operative duplex surveillance scanning. METHODS: We prospectively collected data on 82, primary infrainguinal vein bypass grafts. Post papaverine graft flow and peripheral resistance were measured using the Scimed Opdop intra-operative Doppler machine. All grafts were determined to be technically adequate on the basis of measured peripheral resistance units (mPRU) being < or =1. At 1 week, a post-operative duplex surveillance scan was performed. At risk status was determined and compared to the intra-operative Doppler flow measurement. Statistical analysis was performed using the Mann-Whitney U-test. RESULTS: The post-operative duplex scan demonstrated that 53 (65%) of the 82 vein bypass grafts were diagnosed as being 'not at risk'; and 29 (35%) were regarded as at risk. When the groups were compared, there was no significant difference in intra-operative haemodynamic parameters between those not at risk and those at risk (P=0.19, Mann-Whitney U-test). The 1 month primary patency rate was 79% with a secondary patency rate of 100%. CONCLUSION: Despite normal intra-operative Doppler flow measurements, 35% of vein grafts were regarded as being at risk at the 1 week post-operative duplex surveillance scan. No single value may be universally applicable for identifying at risk grafts intraoperatively. Indeed, graft failure appears to be a multifactorial process.     

The correlation of early flow disturbances with the development of infrainguinal graft stenosis: A 10-year study of 341 autogenous vein grafts

Purpose: Although duplex surveillance of infrainguinal bypass grafts is widely accepted, the optimal frequency and intensity of graft surveillance remains controversial. Earlier reports have suggested that grafts can be stratified into high-risk and low-risk groups based on the presence or absence of early graft flow disturbances. The purpose of this study was to provide long-term data in determining whether early graft flow disturbances detected by means of duplex scanning can predict the development of intrinsic vein graft stenosis. Methods: We reviewed a series of patients undergoing prospective duplex graft surveillance after autogenous infrainguinal bypass grafting procedures from 1987 to 1997. Patients included in the study underwent at least one duplex scan within 3 months of graft implantation and were observed for a minimum of 6 months. Grafts were categorized as abnormal when a focal flow disturbance with a peak systolic velocity greater than 150 cm/s was identified within 3 months of graft implantation. Results: Of 341 vein grafts in 296 patients who met inclusion criteria, 89 grafts (26%) required revision for intrinsic stenosis; the mean follow-up period was 35 months (range, 6 months to 10 years). Early flow disturbances were detected in 84 (25%) grafts. Grafts with early flow disturbances were more likely to ultimately require revision (43% vs 21%; P = .0001) and required initial revision earlier (8 months vs 16 months; P = .019). Eighty-two percent of initial graft revisions occurred in the first 2 postoperative years; 69% occurred in the first year. However, an annual 2% to 4% incidence of late-appearing graft stenosis persisted during long-term follow-up. An additional 24 patients (7% of grafts) required an inflow or outflow reconstruction. Conclusion: Grafts with early postoperative flow disturbances detected by means of duplex scanning have nearly three times the incidence of graft-threatening stenosis and an earlier requirement for revision, when compared with normal grafts. This suggests that the biology and etiology of these lesions may differ. These data support not only aggressive efforts to detect early graft lesions to stratify grafts at highest risk, but also continued lifelong graft surveillance to detect late-appearing lesions, inflow and outflow disease progression, and maximize graft patency. (J Vasc Surg 1999;30:8-15.)     

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.     

Detection and grading of femorodistal vein graft stenoses: duplex velocity measurements compared with angiography

Increasing recognition of the importance of vein graft stenoses in precipitating failure of femorodistal bypass procedures has stimulated an increasing interest in noninvasive postoperative surveillance. We have used duplex scanning, measuring relative changes in velocity throughout the entire length of the graft, to detect nonhemodynamic stenoses (i.e., stenoses without a significant change in ankle-brachial pressure indexes) as well as more severe lesions during the postoperative period. Seventy-five in situ vein grafts were assessed at three monthly intervals from operation with duplex scanning and intravenous digital subtraction angiography. Nineteen grafts (25%) had angiographically documented stenoses at a mean follow-up of 12 months. All 19 stenoses were detected independently by duplex velocity ratio criteria and 15 were correctly graded as mild, moderate, or severe. The results suggest that duplex-derived velocity ratio criteria are appropriate for graft surveillance and for determining the natural history of even minor stenoses to identify the optimal time of surgical intervention.     

The importance of routine surveillance of distal bypass grafts with duplex scanning: a study of 379 reversed vein grafts

To assess the utility of routine duplex surveillance, 379 infrainguinal reversed vein grafts performed at two independent teaching hospitals were prospectively entered into a surveillance protocol from March 1986 through August 1989. An average of 3.2 postoperative duplex graft flow velocity (GFV) measurements per graft was obtained during a mean follow-up interval of 21 1/2 months. Only 2.1% of 280 grafts with GFV measurements greater than 45 cm/sec failed within 6 months of a normal surveillance examination. GFV measurements less than 45 cm/sec in 99 grafts led to arteriography in 75 grafts, identifying 50 stenotic lesions in 48 bypasses (12.6% of series). Inflow lesions were present in 5%, outflow stenoses in 2%, and intrinsic graft stenoses in only 6% of bypasses. Only 29% of grafts identified as failing by duplex scan were associated with a reduction in ankle-brachial index of greater than 0.15. Secondary reconstructions were performed in 48 grafts based on detection of a reduced GFV measurement; all such reconstructions are patent after a mean follow-up of 5 months. Duplex surveillance is more reliable in identification of failing vein grafts than is determination of ankle-brachial index.     

Incidence of stenoses in femorodistal bypass vein grafts in a multicentre study.

OBJECTIVES: To establish the incidence of graft stenosis in a large population of patients undergoing femorodistal bypass procedures and to investigate the differences in incidence between individual surgical centres and other subpopulations. PATIENTS AND METHODS: A total of 277 patients with femorodistal bypasses underwent duplex scanning of vein grafts for 12 months for the detection of graft stenoses. A standard definition of a significant stenosis was used in all twenty participating centres. RESULTS: Overall stenosis rate was 27%. Stenoses were more common in composite vein grafts (43%) than in single segment vein grafts (25%) p=0.05. Stenoses were more common in female patients (38%) than males (22%) p=0.02. Stenosis rates in individual centres entering more than 20 patients varied from 9% to 56%. In a multiple regression analysis only aspirin use, sex and centre were significant factors predicting the likelihood of graft stenosis. CONCLUSION: Female patients, those taking aspirin and patients with composite vein grafts appear to be more at risk of graft stenosis, but this does not fully explain wide variations in the incidence of stenoses reported by individual centres.     

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.     

Value and limitations of secondary femoropopliteal bypasses with polytetrafluoroethylene

Secondary femoropopliteal bypasses with polytetrafluoroethylene (PTFE) grafts are widely regarded to be of questionable value. This has prompted some to abandon all attempts at secondary revascularization with PTFE and others to recommend that primary femoropopliteal bypasses be performed preferentially with PTFE grafts so that vein may be used for secondary procedures. Because we questioned both of these views, we reviewed all femoropopliteal bypasses done at our institution in the past 12 years and identified 73 secondary PTFE femoropopliteal procedures performed after a failed ipsilateral infrainguinal bypass (69 failed femoropopliteal; 4 failed femorodistal). Seventy (96%) secondary bypasses were performed for limb salvage and 3 (4%) for severe disabling claudication. Insertion of grafts to the popliteal artery was above the knee in 26 (36%) and below the knee in 47 (64%). Primary life-table graft patency at 4 years was only 38%. Forty-eight reinterventions in 34 limbs were required to restore or maintain graft patency in thrombosed or failing grafts. For thrombosed grafts, 20 interventions consisted of 9 simple thrombectomies and 11 thrombectomies with additional revision procedures (5 distal or proximal extensions, 6 patch angioplasties). Twenty-eight lesions threatening graft patency were treated by percutaneous transluminal angioplasty in 3, proximal or distal extensions in 20, and patch angioplasty in 5. As a result of these reinterventions, the overall secondary patency rate was 55% at 4 years, and the limb salvage rate was 74% at 4 years. Although aggressive follow-up and reintervention may be required, the use of secondary PTFE conduits in the femoropopliteal position is a viable option in patients undergoing limb salvage procedures who are at high risk.(ABSTRACT TRUNCATED AT 250 WORDS)     

Significance of the early postoperative duplex result in infrainguinal vein bypass surveillance.

BACKGROUND: Duplex surveillance of infrainguinal vein grafts may not be efficient. METHODS: Consecutive patients who had received infrainguinal vein grafts were enrolled in a duplex surveillance program. A first scan at 6 weeks after surgery categorized grafts into four groups: (a) low risk grafts, (b) mild flow disturbance, (c) intermediate stenosis and (d) critical stenosis. Disease progression was assessed over time. RESULTS: Of 364 grafts followed-up for a median of 23 months, 236 (65%) had no flow abnormality at 6-weeks, and had a 40-month cumulative patency rate of 82%. The remaining 128 (35%) grafts had a flow disturbance. Of 29 critical stenoses, 15 were repaired, 11 occluded and three did not change. Of 57 intermediate lesions, 32 progressed to critical, nine occluded, two were repaired and 14 did not change or improved. Of 42 mild lesions, 16 progressed to a higher grade, four occluded and 22 did not change or improved. There was no significant difference in graft patency between grafts with repaired stenoses and those without stenoses, but grafts with untreated critical stenoses were associated with lower patency (p<0.001). CONCLUSIONS: A duplex scan 6 weeks after operation can predict those patients who require continuing duplex surveillance.     

Infrapopliteal bypass for established gangrene of the forefoot or toes

This study was undertaken to assess factors affecting limb salvage after femorodistal bypass in patients with established gangrene. From January 1977 through June 1983, 361 patients underwent infrapopliteal bypasses; 58 patients (59 limbs) had forefoot and/or toe gangrene. There were 33 men and 25 women (mean age 67.6 years), and 40 patients (69%) were diabetic. A total of 71 femorodistal bypass procedures were performed in these patients: a single bypass in 49, repeat procedure in eight, and multiple bypasses in two patients. Graft material was autogenous saphenous vein in 22 cases, polytetrafluoroethylene (PTFE) in 39 cases, and a composite graft in 10 procedures. After bypass 50 patients underwent limited toe or forefoot amputation with uncomplicated healing. Limb salvage by life-table analysis was 70% at 1 year, 60% at 3 years, and 28% at 5 years. The graft patency at 3 years was 65% for vein grafts and 30% for PTFE grafts. In the entire series the operative mortality rate was 1.7%. Age, sex, hypertension, or diabetes mellitus did not influence the result of surgery. Similarly, failure of a previous femoropopliteal or tibial graft did not reduce the likelihood of limb salvage. Graft patency, however, is prerequisite for limb salvage, and graft patency can be maintained by thrombectomy or repetitive bypass. The present study suggests that limb salvage is possible in as many as two thirds of limbs with established gangrene. Although saphenous vein remains the graft material of choice, its absence should not preclude attempts at limb salvage. Repetitive grafting did not jeopardize patient safety but contributed significantly to extended limb survival.     

THE VALUE OF DUPLEX SCANNING IN SURVEILLANCE OF INFRA-INGUINAL VEIN AND SYNTHETIC GRAFTS

The contribution of duplex scanning to improving early diagnosis of graft stenosis was evaluated in 195 patients after infra-inguinal bypass procedures. Over a 31 month period, 406 duplex scans were obtained on 232 limbs with 191 vein and 41 polytetrafluoroethylene (PTFE) grafts. Peak systolic velocities > 200cm/s with spectral broadening and lumen reduction on B-mode image were the criteria adopted for identification of a haemodynamically significant (> 50%) stenosis. Sixty-one stenoses were identified in 55 of the grafted limbs. Thirty-three of the 55 limbs had a subsequent angiogram. The angiogram showed graft occlusion in six limbs, graft stenosis in 18, and native artery stenosis in four. Twenty-one of the grafts had the angiogram within 1 month after the duplex had detected graft stenosis, and one (4.76%) became occluded in this interval. Seven had an angiogram more than 1 month after the duplex study, and five (71.4%) had become occluded. The angiographic study did not confirm a graft stenosis in five limbs. Three were submitted to operation and stenosis was confirmed. Seventeen graft thromboses were detected by duplex scanning. Graft thrombosis was demonstrated following a previous negative duplex scan in one of the 106 vein grafts (0.94%), and in four of 30 PTFE grafts (13.3%). Duplex scanning is effective in the detection of graft stenosis. The precise anatomical location is less accurate when in the region of an anastomosis. Early attention should be taken when duplex studies suggest critical graft stenosis because there is a high risk of occlusion. Polytetrafluoroethylene grafts tend to thrombose without a precursory focal stenosis.     

Comparison of duplex ultrasound with digital subtraction angiography in the assessment of infra-inguinal autologous vein bypass grafts

BACKGROUND: Postoperative surveillance of infra-inguinal vein grafts has arisen because of the high incidence of vein graft stenoses, which frequently progress to vein graft occlusion. The use of duplex ultrasound as the primary imaging method for graft surveillance is well established. This study aims to compare the accuracy of duplex ultrasound with the reference standard of digital subtraction angiography in the assessment of infra-inguinal vein grafts. METHODS: Sixty patients underwent routine postoperative duplex ultrasound as part of the local graft surveillance programme. Angiography was subsequently carried out on 18 grafts. Each lower limb arterial tree was divided into three segments (native arteries proximal to the graft, the graft itself and native arteries distal to the graft) resulting in a total of 42 comparisons. Degree of diameter stenosis on ultrasound was compared with angiography findings to determine concordance. Agreement was also expressed as a kappa value. RESULTS: Overall accuracy of duplex ultrasound was 88% (37/42). A kappa value of 0.80 indicates good agreement. In three of the five discordant cases, ultrasound correctly identified a stenosis, but overestimated the degree of stenosis compared with angiography. In each of the remaining two discordant cases, ultrasound identified a focal stenosis that was not apparent on angiography. In both cases, the area of duplex described abnormality responded to balloon angioplasty. CONCLUSION: Duplex ultrasound as part of the local vein graft surveillance programme is a reliable and accurate method in the detection of failing grafts and in some instances may be more sensitive.     

The effect of anticoagulation therapy and graft selection on the ischemic consequences of femoropopliteal bypass graft occlusion: results from a multicenter randomized clinical trial

OBJECTIVE: A recent retrospective study showed that the ischemic consequences of femoropopliteal bypass graft occlusion were more severe with polytetrafluoroethylene (PTFE) than with vein. This study examines this conclusion and whether oral anticoagulation therapy reduces the degree of ischemia after occlusion of PTFE and vein femoropopliteal bypass grafts. METHODS: Four hundred two patients who underwent femoropopliteal bypass grafting (233 PTFE and 169 vein) were randomized to a postoperative regimen of either warfarin (international normalized ratio, 1.4 to 2.8) and aspirin (WASA; 325 mg daily) therapy or aspirin alone (ASA) therapy. The grade of acute ischemia at the time of graft occlusion was assessed with the Society of Vascular Surgery recommended reporting standards (I, viable; II, threatened). Early graft occlusions (<30 days) were excluded. RESULTS: There were 100 graft occlusions (67 PTFE and 33 vein) during a mean follow-up period of 36 months (PTFE) and 39 months (vein). Forty-eight patients were randomized to WASA therapy, and 52 were randomized to ASA therapy. The patients were well matched for age, atherosclerotic risk factors, operative indication, and preoperative ankle-brachial index. Overall, a greater percentage of the PTFE occlusions caused grade II ischemia than did the vein graft occlusions (48% versus 18%; P =.005). The ankle-brachial index at the time of graft occlusion was significantly lower in the PTFE grafts than in the vein grafts (0.28 versus 0.45; P =.001). The patients with PTFE who were undergoing WASA therapy at the time of graft occlusion had less grade II ischemia than did those patients who were undergoing ASA therapy (28% versus 55%; P =.057). However, the incidence rate of severe ischemia after graft occlusion remained greater with PTFE grafts and WASA therapy as compared with all the vein grafts (28% versus 18%). The vein graft occlusions had the same incidence rate of grade II ischemia with WASA therapy as with ASA therapy (20% versus 17%; P = 1.0). CONCLUSION: The ischemic consequences of femoropopliteal bypass graft occlusion are worse with PTFE than with vein. Treatment with WASA therapy lessens the severity of acute ischemia after the occlusion of PTFE graft as compared with ASA therapy but not to the degree seen with vein graft occlusion. Occlusion of femoropopliteal vein grafts is seldom accompanied by severe ischemia and is not improved with WASA therapy.     

Balloon angioplasty as a treatment of failing infrainguinal autologous vein bypass grafts

PURPOSE: The purpose of this study was to evaluate the role of balloon angioplasty in the treatment of failing infrainguinal vein bypass (IVB) grafts. METHODS: A retrospective chart review of patients undergoing revision of a failing IVB graft by vascular surgeons at a tertiary care center from 1990 to 2001 was performed. Failing bypass grafts were identified by routine duplex scan surveillance and physical examination. The criteria for endovascular intervention varied on the basis of surgeon preferences and time period; factors considered when choosing balloon angioplasty included significant comorbidities that precluded operative intervention, the lack of adequate conduit for surgical revision, or poor accessibility of the stenotic lesion. Data recorded included demographic patient data, type of IVB graft, patency status, further procedures performed, and all complications and mortalities. Cumulative primary and assisted patency rates were calculated by using Kaplan-Meier life-table analysis. RESULTS: A total of 45 balloon angioplasties were performed in 36 patients. There were 36 angioplasties of vein bypass grafts, and additional balloon angioplasties were performed on nine of these patients. Locations of IVB grafts included femoropopliteal (13 patients), femorodistal (13), and popliteal to distal (10). Initial success was achieved in 33 of 36 vein bypass grafts (91.7%). In these bypass grafts, the stenotic lesions were identified and treated at the proximal anastomosis (3 patients), mid-bypass graft (6 patients), and distal anastomosis (27 patients). Autogenous vein was used for all bypass grafts. Cumulative vein bypass graft (life-table analysis) primary patency rates (those free of occlusion or bypass graft threatening stenosis) were 74.2% at 6 months, 62.7% at 12 months, and 58.2% at 24 months. Repeat interventions included surgical thrombectomy with vein patch angioplasty or bypass graft revision, as well as repeat balloon angioplasty with or without thrombolysis. Cumulative assisted vein bypass graft patency rates (those free of occlusion or bypass graft threatening stenosis) were 87.0%, 83.2%, and 78.9% at 6, 12, and 24 months, respectively. Two patients (4%) developed thigh hematomas; no other procedure-related complications were noted, and there were no deaths in the perioperative period. CONCLUSION: Balloon angioplasty of failing infrainguinal vein bypass grafts can be successfully performed with a low rate of complications. Acceptable short-term patency can be achieved. This procedure should be considered as an initial option in failing IVB grafts.     

The origin of infrainguinal vein graft stenosis: A prospective study based on duplex surveillance

Purpose: The purpose of this study was to determine the origin of vein graft lesions and their propensity for progression based on prospective duplex surveillance of 135 infrainguinal vein bypasses.Methods: One hundred sixteen greater saphenous, 13 spliced, five cephalic, and one superficial femoral vein grafts were evaluated by color duplex imaging at surgical procedure, 1 and 6 weeks, 3 and 6 months, and every 3 to 6 months thereafter. Duplex-identified lesions were graded by peak systolic velocity and velocity ratio criteria and were either followed or subjected to revision.Results: Early postoperative duplex surveillance allowed stratification of infrainguinal grafts into two subsets. Of 91 (67%) grafts with normal early scans (at 3 months), only two (2.2%) developed de novo stenoses (at 6 and 8 months) that required revision. Forty-four grafts with abnormal duplex scans had a focal flow abnormality (peak systolic velocity >150 cm/sec, velocity ratio >1.5) in the graft body ( n = 24) or anastomotic region ( n = 20). In 14 grafts the flow abnormality (mean peak systolic velocity = 217 cm/sec, velocity ratio = 2.3) normalized. Ten additional grafts exhibited a moderate, persistent graft stenosis (mean peak systolic velocity 248 cm/sec, velocity ratio = 3.3) that was not repaired. All 20 grafts with lesions that progressed to high-grade stenosis (mean peak systolic velocity = 362 cm/sec, velocity ratio = 7.2) and were revised had a residual flow abnormality confirmed at operation, or it appeared by 6 weeks. In the entire series six (4.4%) grafts failed during the mean 12-month follow-up interval (range 3 to 30 months), 4 with unrepaired defects and two after revision.Conclusions: Prospective duplex surveillance verified that de novo graft stenosis was uncommon (<2.2%) after reversed and in situ saphenous vein bypass grafting. Graft stenoses developed at sites of unrepaired defects or early appearing conduit abnormalities. An early appearing duplex focal flow abnormality warranted careful surveillance, because one half of such sites progressed to a high-grade stenosis. Grafts with normal early duplex scans exhibited a low incidence of stenosis development or occlusion, and thus less intense postoperative surveillance can be recommended. (J VASC SURG 1995;21:16-25.)     

Transfer function index: is it a reliable method for vein graft surveillance?

Introduction: Duplex ultrasound scanning is currently the best available non‐invasive method for vein graft surveillance. However, it is expensive and its results are highly operator dependent. The aim of the present study is to compare, another non‐invasive method of graft surveillance, the transfer function index (TFI), with duplex ultrasound scanning in identifying significant stenoses in infrainguinal saphenous vein bypass grafts. Methods: Initially a retrospective pilot study was carried out between 1 January and 30 June 2002. Patients were identified from the vascular surgical operation database. The ultrasound report and TFI result of each patient were reviewed. Then a prospective comparative study was carried out between 1 July and 31 December 2002. Duplex ultrasound and TFI studies were undertaken at the 3 month interval. Comparisons were made between the accuracy and predictive value of ultrasound versus TFI in assessing significant graft stenosis. Results: In the present retrospective study TFI measurement was significantly lower in the at‐risk grafts than in the normal grafts (P = 0.001). In the prospective group TFI was again found to be significantly lower in the at‐risk group (mean TFI 0.86) than in the normal group (mean TFI 1.064, P = 0.001). The sensitivity and specificity of the TFI were 92% and 97%, respectively. The accuracy of TFI was calculated to be 98%. Conclusion: TFI is an accurate non‐invasive method of vascular graft surveillance. TFI can be carried out in the vascular clinic and is quick and inexpensive. Normally TFI could replace duplex ultrasound surveillance, with ultrasound being reserved for those with an abnormal TFI.