Postoperative duplex scan surveillance of axillofemoral bypass grafts

OBJECTIVE: Duplex scan surveillance (DS) for axillofemoral bypass grafts (AxFBGs) has not been extensively studied. The intent of this study was twofold: 1, to characterize the flow velocities within AxFBGs; and 2, to determine whether postoperative DS is useful in assessment of future patency of AxFBGs. METHODS: We identified all patients who underwent AxFBG procedures between January 1996 and January 2001 at our combined university and Veterans Affairs hospital vascular surgical service. All grafts were performed with ringed 8-mm polytetrafluoroethylene with the distal limb of the axillofemoral component anastomosed to the hood of the femoral-femoral graft. DS was every 3 months for 1 year and every 6 months thereafter. Duplex scan results were compared in primarily patent grafts with grafts that thrombosed. Graft failures from infection were excluded. Influences of ankle-brachial index, blood pressure, outflow patency, operative indication, and comorbidities on graft patency were analyzed. RESULTS: One hundred twenty patients underwent AxFBG procedures. Twenty-eight were excluded because of infection or death before surveillance examination. Fourteen were lost to follow-up, 23 had failed grafts from occlusion, and 55 had grafts that remained patent. In the 78 patients evaluated during long-term follow-up period, the mean peak systolic velocities (PSVs) at the proximal (axillary) anastomosis during the first postoperative year ranged from 153 to 194 cm/s. Mean PSVs at the mid portion of the axillofemoral graft during the first postoperative year ranged from 100 to 125 cm/s, whereas those for the distal axillofemoral anastomosis ranged from 93 to 129 cm/s. Mean midgraft and distal anastomotic velocities obtained before thrombosis were significantly lower in the thrombosed grafts compared with the last recorded velocities at the same sites in the patent grafts (mean PSV, 84 versus 112 cm/s; P =.015; mean PSV, 89 versus 127 cm/s; P =.024, respectively). Forty-eight percent of occluded grafts had a mean midgraft PSV at last observation of less than 80 cm/s. Blood pressure correlated with midgraft velocity (r = 0.415; P <.05). With multivariate logistic regression analysis, a mean midgraft velocity less than 80 cm/s was the sole independent factor associated with graft failure (P <.01). No patients with midgraft velocities greater than 155 cm/s had occlusion. CONCLUSION: Flow velocity varies widely within and among AxFBGs. Patency of AxFBGs is associated with higher midgraft PSV, and thrombosis with midgraft velocities less than 80 cm/s.     

Duplex surveillance of abdominal aortic stent grafts

Aortic stent grafting is gaining acceptance rapidly as a durable and effective alternative to open surgery for abdominal aortic aneurysms (AAA). Unlike follow-up after open surgical procedures, postplacement surveillance protocols are necessary to ensure long-term freedom from device failure or aneurysm rupture. Surveillance protocols incorporating duplex scanning are effective and may reduce overall postplacement expenses. Specific device or patient anatomic features may be prone to failure, and familiarity with each approved device is a prerequisite to the performance of effective device surveillance studies. Mechanisms of failure of aneurysm exclusion after device placement, or "endoleak," have been described and categorized. Endoleak significance is directly related to location, duration, and influence on AAA diameter. Endoleak type also determines when and whether additional interventions are indicated. Future progress in endovascular AAA exclusion will depend in large part on the reliability and utility of cost-effective postprocedure surveillance protocols incorporating duplex ultrasound imaging.     

Duplex guided balloon angioplasty of failing infrainguinal bypass grafts.

OBJECTIVE: To assess the results of angioplasty and stent placement under duplex guidance for failing grafts. METHODS: Over 22 months, 25 patients (72% males) with a mean age of 74+/-10 years presented to our institution with a failing infrainguinal bypass. The site of the most significant stenotic lesion was in the inflow in four cases, conduit in 18 cases and at the outflow in 11 cases. All arterial (20) or graft (13) entry sites cannulations were performed under direct duplex visualization. Duplex scanning was the sole imaging modality used to manipulate the guide wire and directional catheters from the ipsilateral CFA to a site beyond the most distal stenotic lesion. Selection and placement of balloons and stents were also guided by duplex. In 11 cases (33%), the contralateral CFA was used as the entry site and a standard approach (fluoroscopy and contrast material) was employed. Completion duplex exams were obtained in all cases. RESULTS: The overall technical success was 97% (32/33 cases). In only one case, the outflow stenotic lesion in the plantar artery could not be traversed with the guidewire due to extreme tortuosity. Overall local complications rate was 6% (two cases). One vein bypass pseudoaneurysm caused by rupture with a cutting balloon was repaired by patch angioplasty and one SFA pseudoaneurysm at the puncture site required open repair. Overall 30-day survival rate was 100%. Overall 6-month limb salvage and primary patency rates were 100 and 69%, respectively. CONCLUSIONS: Duplex guided endovascular therapy is an effective modality for the treatment of failing infrainguinal arterial bypasses.     

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.     

Duplex sonographic monitoring of infra-inguinal arterial reconstructions: can a threatened bypass occlusion be detected by this method?]

In our institution, 95 infrainguinal arterial reconstructions were prospectively entered into a graft surveillance programme which consisted of a postoperative i.a. DSA and routine assessment of graft flow velocity (GFV) and ankle pressure indices (ABI) during the first postoperative year. An average of 4.1 GFV measurements was obtained during a mean follow-up period of 8.2 months. Abnormal GFV led to arteriography in 29 bypasses identifying--aside from three false positive findings--two graft occlusions and 24 severe (> 70%) graft stenoses. Of the latter, in only 7 cases a significant decrease in ABI was found. Unheralded graft occlusion occurred in 6 patients. Including the corrections of the above mentioned lesions, secondary patency rates were 97% at 30 days and 89% at one year.     

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.     

Duplex scan surveillance after carotid angioplasty and stenting: a rational definition of stent stenosis

OBJECTIVE: A duplex ultrasound (DUS) surveillance algorithm used after carotid endarterectomy (CEA) was applied to patients after carotid stenting and angioplasty (CAS) to determine the incidence of high-grade stent stenosis, its relationship to clinical symptoms, and the outcome of reintervention. METHODS: In 111 patients who underwent 114 CAS procedures for symptomatic (n = 62) or asymptomatic (n = 52) atherosclerotic or recurrent stenosis after CEA involving the internal carotid artery (ICA), DUS surveillance was performed 300 cm/s, diastolic velocity >125 cm/s, internal carotid artery stent/proximal common carotid artery ratio >4) involving the stented arterial segment prompted diagnostic angiography and repair when >75% diameter-reduction stenosis was confirmed. Criteria for >50% CAS stenosis was a PSV >150 cm/s with a PSV stent ratio >2. RESULTS: All 114 carotid stents were patent on initial DUS imaging, including 90 (79%) with PSV <150 cm/s (94 +/- 24 cm/s), 23 (20%) with PSV >150 cm/s (183 +/- 34 cm/s), and one with high-grade, residual stenosis (PSV = 355). During subsequent surveillance, 81 CAS sites (71%) exhibited no change in stenosis severity, nine sites demonstrated stenosis regression to <50% diameter reduction, and five sites developed velocity spectra of a high-grade stenosis. Angiography confirmed >75% diameter reduction in all six CASs with DUS-detected high-grade stenosis, all patients were asymptomatic, and treatment consisted of endovascular (n = 5) or surgical (n = 1) repair. During the mean 33-month follow-up period, three patients experienced ipsilateral, reversible neurologic events at 30, 45, and 120 days after CAS; none was associated with severe stent stenosis. No stent occlusions occurred, and no patient with >50% CAS stenosis on initial or subsequent testing developed a permanent ipsilateral permanent neurologic deficit or stroke-related death. CONCLUSION: DUS surveillance after CAS identified a 5% procedural failure rate due to the development of high-grade in-stent stenosis. Both progression and regression of stent stenosis severity was observed on serial testing, but 70% of CAS sites demonstrated velocity spectra consistent with <50% diameter reduction. The surveillance algorithm used, including reintervention for asymptomatic high-grade CAS stenosis, was associated with stent patency and the absence of disabling stroke.     

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.     

Duplex imaging of in situ saphenous vein bypass grafts and late failure reduction

Duplex ultrasonic scanning was applied prospectively to 20 consecutive cases of in situ saphenous vein infrainguinal bypass 1, 3, 6, and 12 months postoperatively. All 20 (100 percent) and 17 of 19 (90 percent) of the proximal and distal anastomoses, respectively, could be imaged satisfactorily. Graft velocity ranged from 30 to 100 cm/s. Of three grafts with low velocity, one had impending graft failure and two had inherently low velocity but remained patent. Five defects in three grafts were detected. In three cases, intervention prevented graft failure. The primary patency rate was 80 percent, but was improved to 95 percent as a result of graft surveillance and simple revisions. Duplex scanning is a superior method for postoperative in situ saphenous vein bypass surveillance. We recommend that patients be studied 1 month postoperatively and every 3 to 6 months thereafter.     

Axillofemoral arterial bypass grafts.

The results of 24 axillofemoral arterial bypass grafts performed over a five-year period are presented. This extraanatomical technique of arterial reconstruction is valuable following removal of an infected aortic Dacron graft and for limb salvage or severe intermittent claudication in selected poor-risk patients with aortoiliac occlusive disease. There were few early patency rate was excellent, but the long-term success of the operation is uncertain.     

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.     

Blood flow surveillance of hemodialysis grafts: insights from two case reports

It is widely recommended that all hemodialysis grafts undergo blood flow ( Q _a) surveillance, and that stenosis be corrected when accompanied by a low Q _a or decrease in Q _a (Δ Q _a). This recommendation has, however, become increasingly controversial. Studies have shown that although there is an association between Q _a and thrombosis, the accuracy of Q _a in predicting thrombosis within individual patients is poor. We describe two cases that demonstrate common causes of poor predictive accuracy. These cases also show that application of Q _a surveillance algorithms is often complex and ambiguous. Most studies reporting that surveillance with intervention reduces thrombosis or prolongs graft life have used historical or sequential control groups, or have been retrospective. Accurate assessment of the benefit of graft surveillance must await studies that are fully prospective and randomized with concurrent control groups. Until such studies have demonstrated sufficient benefit, we do not recommend periodic Q _a surveillance with intervention of all hemodialysis grafts.     

The role of simple non-invasive testing in infra-inguinal vein graft surveillance

A prospective vein graft screening programme was established in order to improve graft patency in the period 1-12 months after operation. Patient assessment consisted of ankle:brachial pressure index (ABPI) measurement before and after exercise, and Duplex scanning. Thirty-nine grafts have been followed up, with 19 stenoses detected in 18 grafts (46%) using Duplex. Of these 18 grafts, six had a serial fall in resting ABPI, median 0.14 (range 0.11-0.33), and nine had a post-exercise ABPI fall, median 0.19 (range 0.13-0.4). The remaining three had a normal ABPI but were unable to exercise. Fifteen grafts have been treated, 12 by percutaneous transluminal angioplasty (PTA), and three by surgery. One stenosis treated with PTA recurred within 3 months and was repaired with a vein patch. Since screening was implemented no grafts in the programme have occluded. This study indicates that simple ABPI measurements can be used to screen "at risk" grafts for evaluation with Duplex scanning, without jeopardising graft patency.     

The tandem bypass: subclavian artery-to-middle cerebral artery bypass with dacron and saphenous vein grafts. Technical case report

BACKGROUND: Fusiform or dolichoectatic intracranial aneurysms often cannot be managed with conventional surgical or endovascular techniques, and instead require trapping and revascularization techniques. On rare occasions in elderly patients, extracranial sites used for anastomosing the bypass have been previously repaired with synthetic vascular prostheses. This circumstance in an elderly subarachnoid hemorrhage patient led to a novel bypass procedure, the tandem bypass: a long extracranial-to-intracranial bypass with two grafts of different materials assembled in series. CASE DESCRIPTION: A 71-year-old man with carotid artery atherosclerotic disease and a previous vascular reconstruction (subclavian artery-to-internal carotid artery Dacron interposition graft) presented with a subarachnoid hemorrhage from a dolichoectatic supraclinoid ICA aneurysm. The aneurysm was treated with trapping and distal revascularization. The final construct was a subclavian artery-to-middle cerebral artery bypass, with the graft being the previous Dacron prosthesis and a long saphenous vein. The vein graft was anastomosed end-to-side to the Dacron graft proximally, and end-to side to the middle cerebral artery distally. Subsequently, inflow to the aneurysm was occluded with clips on the Dacron graft beyond the proximal anastomosis of the vein graft, and outflow from the aneurysm was occluded with clips on the supraclinoid ICA. CONCLUSIONS: The tandem bypass, which uses prosthetic graft material and saphenous vein in succession, is a technically straightforward technique in patients who need extracranial-to-intracranial bypasses and who also have pre-existing carotid reconstructions or lack sufficient saphenous vein to complete a long bypass.