Intraoperative duplex monitoring of infrainguinal vein bypass procedures

Trends in Utilization of Completion Imaging after Lower Extremity Bypass and Its Association with Major Adverse Limb Events and Loss of Primary Patency

BACKGROUND

Failure following lower extremity bypasses (LEBs) isoften secondary to technical defects. Despite traditional teachings, routine use of completion imaging (CI) in LEB has been debated. This study assesses national trends of CI following LEBs and the association of routine CI with 1-year major adverse limb events (MALE) and 1-year loss of primary patency (LPP).

METHODS

The Vascular Quality Initiative (VQI) LEB dataset from 2003-2020 was queried for patients who underwent elective bypass for occlusive disease. The cohort was divided based on surgeons' CI strategy at time of LEB, categorized as routine (≥80% of cases/year), selective (<80% of cases/year), or never. The cohort was further stratified by surgeon volume category [low (<25th percentile), medium (25th-75th percentile), or high (>75th percentile)]. The primary outcomes were 1-year MALE-free survival and 1-year loss of primary patency (LPP)-free survival. Our secondary outcomes were temporal trends in CI use and temporal trends in 1-year MALE rates. Standard statistical methods were utilized.

RESULTS

We identified 37,919 LEBs; 7,143 in routine CI strategy cohort, 22,157 selective CI and 8,619 in never CI. Patients in the 3 cohorts had comparable baseline demographics and indications for bypass. There was a significant decrease in CI utilization from 77.2% in 2003 to 32.0% in 2020 (P < 0.001). Similar trends in CI use were observed in patients who underwent bypass to tibial outflows (86.0% in 2003 vs. 36.9% in 2020; P < 0.001). While the use of CI has decreased over time, 1-year MALE rates have increased from 44.4% in 2003 to 50.4% in 2020 (P < 0.001). On multivariate COX regression, however, no significant associations between CI use or CI strategy and risk of 1-year MALE or LPP was found. Procedures performed by high-volume surgeons carried a lower risk of 1-year MALE (HR: 0.84; 95% CI [0.75-0.95]; P = 0.006) and LPP (HR:0.83; 95% CI [0.71-0.97]; P < 0.001) compared to low-volume surgeons. Repeat adjusted analyses showed no association between CI (use or strategy) and our primary outcomes when the subgroups with tibial outflows were analyzed. Similarly, no associations were found between CI (use or strategy) and our primary outcomes when the subgroups based on surgeons' CI volume were evaluated.

CONCLUSIONS

The use of CI, for both proximal and distal target bypasses, has decreased over time while 1-year MALE rates have increased. Adjusted analyses indicate no association between CI use and improved MALE or LPP survival at 1 year and all CI strategies were found to have equivalent outcomes.

Comparative analysis of patients undergoing lower extremity bypass using in-situ and reversed great saphenous vein graft techniques

OBJECTIVE

Autologous great saphenous vein (GSV) is considered the conduit of choice for lower extremity bypass (LEB). However, the optimal configuration remains the source of debate. We compared outcomes of patients undergoing LEB using in-situ and reversed techniques.

METHODS

The Vascular Quality Initiative database was queried for patients undergoing LEB with a single-segment GSV in in-situ (ISGSV) and reversed (RGSV) configurations for symptomatic occlusive disease from 2003 to 2021. Patient demographics, procedural detail, and in-hospital and follow-up outcomes were collected. The primary outcome measures included primary patency at discharge or 30 days and one year. Secondary outcomes were secondary patency, and reinterventions at discharge or 30 days and one year. Cox proportional hazards models were created to determine the association between bypass techniques and outcomes of interest.

RESULTS

Of 8234 patients undergoing LEBs, in-situ and reversed techniques were used in 3546 and 4688 patients, respectively. The indication for LEBs was similar between the two cohorts. ISGSV was performed more frequently from the common femoral artery and to more distal targets. RGSV bypass was associated with higher intraoperative blood loss and longer operative time. Perioperatively, ISGSV cohort had higher rates of reinterventions (13.2 vs 11.1%; p = 0.004), surgical site infection (4.2 vs 3%; p = 0.003), and lower primary patency (93.5 vs 95%; p = 0.004) but a comparable rate of secondary patency (99 vs 99.1%; p = 0.675). At 1 year, in-situ bypasses had a lower rate of reinterventions (19.4% vs 21.6%; p=0.02), with similar rates of primary (82.6 vs 81.8%; p = 0.237) and secondary patency (88.7 vs 88.9%; p = 0.625). After adjusting for significant baseline differences and potential confounders, in-situ bypass was independently associated with decreased risks of primary patency loss (HR 0.9; 95% CI, 0.82-0.98; p = 0.016) and reinterventions (HR 0.88; 95% CI, 0.8-0.97; p = 0.014) but a similar risk of secondary patency loss (HR 0.99; 95% CI, 0.86-1.16; p = 0.985) at follow-up, compared to reversed bypass. A subgroup analysis of bypasses to crural targets showed that in-situ and reversed bypasses had similar rates of primary patency loss and reinterventions at 1 year. Among patients with chronic limb-threatening ischemia, in-situ bypass was associated with a decreased risk of reinterventions but similar rates of primary and secondary patency and major amputations at 1 year.

CONCLUSIONS

In patients undergoing LEBs using the GSV, in-situ configuration was associated with more perioperative reinterventions and lower primary patency rate. However, this was offset by decreased risks of loss of primary patency and reinterventions at 1 year. A thorough intraoperative graft assessment with adjunctive imaging may be performed to detect abnormalities in patients undergoing in-situ bypasses to prevent early failures. Furthermore, closer surveillance of reversed bypass grafts is warranted given the higher rates of reinterventions.

Routine Completion Angiography For Infrainguinal Bypasses Using Prosthetic Conduit: No Effect On Postoperative Patency

INTRODUCTION

Recent studies have demonstrated increased postoperative patency with the use of routine completion angiography for bypass using venous conduit. Compared to vein conduits however, prosthetic conduits are less plagued by technical issues such as unlysed valves or arteriovenous fistulae. The effect of routine completion angiography on bypass patency in prosthetic bypasses has yet to be compared to the more traditional selective use of completion imaging.

METHODS

A retrospective review of all infrainguinal bypass procedures using prosthetic conduit completed at a single hospital system from 2001 to 2018 was performed. Demographics, comorbidities, intraoperative reintervention rates and 30-day rates of graft thrombosis were analyzed. Statistical analysis included t-tests, chi square tests and cox regression.

RESULTS

Four hundred and ninety-eight bypasses that were performed in 426 patients met inclusion criteria. Fifty-six (11.2%) bypasses were classified into the routine completion angiogram group compared to 442 (88.8%) into the no completion angiogram group. Patients who underwent routine completion angiograms had a rate of intraoperative reintervention of 21.4%. When comparing bypasses that underwent routine completion angiography versus no completion angiography, there were no significant differences in rates of reintervention (3.5% vs. 4.5%, P=0.74) or graft occlusion (3.5% vs. 4.7%, P=0.69) at 30-days postoperatively.

CONCLUSION

Almost one-quarter of lower extremity bypasses using prosthetic conduit that undergo routine completion angiography undergo post-angiogram bypass revision, however this is not associated with an increased graft patency at 30-days postoperatively.

Impact of Bypass Flow Assessment on Long-Term Outcomes in Patients with Chronic Limb-Threatening Ischemia

BACKGROUND

Transit time flow meter (TTFM) allows quick and accurate intraoperative graft assessment. The main study goal is to evaluate the influence of graft flow measurements on long-term clinical outcomes in patients with chronic limb-threatening ischemia (CLTI) undergoing bellow the knee (BTK) vein bypass surgery.

METHODS

Between January 1st, 1999 and January 1st, 2006, 976 CLTI consecutive patients underwent lower extremity bypass surgery. When applying the exclusion criteria, 249 patients were included in the final analysis. Control measurements were performed at the end of the procedure. Patients were divided according to the mean (more/less than 100 ml/min) and diastolic graft flow (more/less than 40 ml/min) values in four groups. The primary endpoints were a major adverse limb event (male) and primary graft patency.

RESULTS

After the median follow-up of 68 months, a group with the mean graft flow below 100 ml/min and the diastolic graft flow below 40 ml/min had the highest rates of male (χ² = 36.60, DF = 1, P < 0.01, log-rank test) and the worst primary graft patency (χ² = 53.05, DF = 1, P < 0.01, log-rank test).

CONCLUSION

In patients with CLTI undergoing BTK vein bypass surgery, TTFM parameters, especially combined impact of mean graft flow less than 100 ml/min and diastolic graft flow less than 40 ml/min, were associated with an increased risk of poor long-term male and primary graft patency.

Factors associated with infrainguinal bypass graft patency at 1-year; a retrospective analysis of a single centre experience

INTRODUCTION

The aim of this study was to identify factors associated with primary graft patency 1 year following open lower limb revascularisation (LLR) at a tertiary referral vascular service.

METHODS

A retrospective analysis of patients undergoing infra-inguinal bypass surgery between January 2016 and May 2017 at a tertiary vascular centre (St Mary's Hospital, London) was performed. Data regarding patient demographics, comorbidities, type of operation and post-operative anti-thrombotic strategy were collected. Quality of run-off score was assessed from pre-operative imaging.

RESULTS

Seventy-seven cases were included in the analysis. Overall, the primary patency rate at 1-year was 63.6% (n = 49/77) and the secondary patency rate was 67.5% (n = 52/77). Independent variables with statistically significant inferior patency rates at 1-year were (1) bypasses with below knee targets (p = 0.0096), (2) chronic limb threatening ischaemia indication (p = 0.038), (3) previous ipsilateral revascularisation (p < 0.001) and (4) absence of hypertension history (p = 0.041). There was also a trend towards significance for American Society of Anesthesiologists (ASA) grade (p = 0.06). Independent variables with log-rank test p values of <0.1 were included in a Cox proportional hazards model. The only variable with a statistically significant impact on primary patency rates was previous open or endovascular ipsilateral revascularisation (HR 2.44 (1.04-5.7), p = 0.04).

CONCLUSION

At 1-year follow-up, previous ipsilateral revascularisation was the most significant factor in affecting patency rates. Patients in this subgroup should therefore be deemed high-risk, which should be reflected in the informed consent and peri-operative management.

Applications of intraoperative Duplex ultrasound in vascular surgery: a systematic review

Objective

This review aims to summarise the contemporary uses of intraoperative completion Duplex ultrasound (IODUS) for the assessment of lower extremity bypass surgery (LEB) and carotid artery endarterectomy (CEA).

Methods

We performed a systematic literature search using the databases of MEDLINE. Eligible studies evaluated the use of IODUS during LEB or CEA.

Results

We found 22 eligible studies; 16 considered the use of IODUS in CEA and 6 in LEB. There was considerable heterogeneity between studies in terms of intervention, outcome measures and follow-up. In the assessment of CEA, there is conflicting evidence regarding the benefits of completion imaging. However, analysis from the largest study suggests a modest reduction in adjusted risk of stroke/mortality when using IODUS selectively (RR 0.74, CI 0.63–0.88, p = 0.001). Evidence also suggests that uncorrected residual flow abnormalities detected on IODUS are associated with higher rates of restenosis (range 2.1% to 20%). In the assessment of LEB, we found a paucity of evidence when considering the benefit of IODUS on patency rates or when considering its utility as compared to other imaging modalities. However, the available evidence suggests higher rates of thrombosis or secondary intervention in grafts with uncorrected residual flow abnormalities (up to 36% at 3 months).

Conclusions

IODUS can be used to detect defects in both CEA and LEB procedures. However, there is a need for more robust prospective studies to determine the best scanning strategy, criteria for intervention and the impact on clinical outcomes.

Systematic review and meta-analysis of saphenous vein harvesting and grafting for lower extremity arterial bypass

OBJECTIVE

In the present systematic review and meta-analysis, we compared the short- and long-term outcomes of different harvesting and grafting techniques in patients undergoing lower extremity arterial bypass.

METHODS

We searched multiple electronic databases (up to December 1, 2019) for comparative trials investigating different harvesting and bypass grafting techniques.

RESULTS

We identified a total of 37 studies for our review. Skip incision harvesting showed a similar high primary patency rate (Peto odds ratio [OR], 0.93; 95% confidence interval [CI], 0.83-1.04; P = .20) with continuous incision harvesting and comparable low wound complication rates (relative risk, 1.55; 95% CI, 0.91-2.66; P = .11) with endoscopic harvesting. In situ bypass grafting a long-term patency similar to that of reversed grafting (Peto OR, 1.01; 95% CI, 0.75-1.37; P = .93). However, for femoropopliteal bypass, the reversed bypass grafting group had significantly lower 2-year (Peto OR, 0.63; 95% CI, 0.52-0.78; P < .001) and 5-year (Peto OR, 0.70; 95% CI, 0.50-0.98; P = .04) failure rates compared with the in situ bypass grafting group. For infrapopliteal bypass, the in situ bypass grafting group had significantly lower 1-year (Peto OR, 1.54; 95% CI, 1.04-2.28; P = .03), 2-year (Peto OR, 1.52; 95% CI, 1.15-2.02; P = .003), and 3-year (Peto OR, 2.14; 95% CI, 1.13-4.05; P = .02) failure rates.

CONCLUSIONS

Skip incision harvesting can be considered the first-line harvesting strategy. For patients undergoing femoropopliteal bypass, reversed bypass grafting seems to result in better long-term patency. In contrast, for those undergoing infrapopliteal bypass, in situ bypass grafting resulted in superior long-term patency.

The Impact of a Simplified Hydrostatic Bypass Flow Technique on Error Detection during Surgical Limb Revascularization

Technical errors have an impact on the results of surgical lower limb revascularization. Use of ultrasound scanning or angiography on the operating table is inconvenient and, in case of angiography, carries a certain risk of radiation and contrast exposure. A simpler method of screening for errors is required. This study assessed the accuracy of a new simple hydrostatic bypass flow technique during surgical limb revascularization. In all, 885 patients were included in the retrospective study. All were treated for Chronic Limb-Threatening Ischemia (CLTI) with a femoropopliteal bypass. Preoperatively, the radiological Vascular Surgery/International Society of Cardiovascular Surgery (SVS/ISCVS) score was used to assess the complexity of the anatomical changes. The surgeon made a subjective runoff assessment for every surgery. In 267 cases, the hydrostatic bypass flow (HBF) technique was used, and, in 66 cases, a digital subtraction angiography (DSA) was used. In each case, a postoperative Doppler ultrasound (DUS) examination was performed following the HBF. Good early results were achieved in 89.46%, and 154 errors (17.4%) were detected (85 were detected on the operating table, including 57 technical errors). Independent efficacy in error detection was proven with a postoperative Doppler examination (Aera Under Curve (AUC) = 0.89; criterion mid-graft peak systolic velocity (PSV) <24 cm/s, p = 0.00001) and hydrostatic bypass flow (AUC = 0.71, criterion HBF < 53 mL/min, p = 0.00001) during surgery. The hydrostatic bypass flow technique is an effective intraoperative screening method in bypass surgery. Algorithmic use of HBF, DSA if needed, and DUS postoperatively improves the outcome. HBF sufficiently reduced the need for on-table angiography.

[Intraoperative completion diagnostics in open vascular surgery]

Intraoperative imaging diagnostics during open vascular surgical procedures aim to enhance diagnostic certainty during the operation, ensure quality control documentation and reduce avoidable complications; however, the evidence for the various diagnostic imaging procedures with respect to improvement of perioperative outcome is not confirmed for carotid endarterectomy or for infrainguinal bypass surgery. Nevertheless, an intraoperative diagnostic control is principally recommended. The advantage of intraoperative imaging is confirmed and essential for the surgical reconstruction of bypass occlusions and acute thromboembolic occlusions.

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.

Outcomes of completion imaging for lower extremity bypass in the Vascular Quality Initiative

OBJECTIVE

The objective of this study was to determine the association of intraoperative completion imaging (CI) for lower extremity vein bypass to a below-knee target with primary patency in the Vascular Quality Initiative.

METHODS

The Vascular Quality Initiative database was queried from January 2003 to October 2013 for lower extremity bypass (LEB) procedures that were elective, had an indication of occlusive disease, used a single-segment greater saphenous vein conduit, and had a below-knee target. LEBs with inflow arteries above the knee and below the knee were included. LEBs with concomitant endovascular procedures were excluded. CI was defined as completion angiography, completion duplex ultrasound, or both. The end points were primary patency at discharge and at 1 year. Multivariable analysis was performed controlling for patient demographics, comorbidities, bypass characteristics, and center.

RESULTS

Of 14,284 LEBs that were performed during the study period, 3147 satisfied the inclusion and exclusion criteria. Of 1457 (46%) that underwent CI, 287 (20%) underwent duplex ultrasound, 1116 (77%) underwent angiography, and 54 (3.7%) underwent both duplex ultrasound and angiography. There were more patients in the CI group with a history of smoking and a bypass graft crossing the knee. There was no difference in primary patency at discharge between the two groups (CI, 93.2% vs no CI, 93.8%; P = .52). Of the patients who underwent CI, the discharge primary patency was 95.1% for completion duplex ultrasound vs 92.8% for completion angiography (P = .17). On multivariable analysis, there was no significant association of CI with discharge primary patency (P = .69). The 1-year primary patency was 63% in the CI group vs 68% in the no CI group (P = .051). The 1-year primary patency was 60% for the duplex ultrasound group vs 65% for the angiography group (P = .61). On multivariable analysis, there was no significant association of CI with 1-year primary patency (P = .69).

CONCLUSIONS

In electively performed LEBs using single-segment saphenous vein to a below-knee target artery for occlusive disease, CI does not influence primary graft patency at discharge or at 1 year.

Use of completion imaging during infrainguinal bypass in the Vascular Quality Initiative

OBJECTIVE

The purpose of this study was to examine the practice patterns of intraoperative completion imaging (CI) for lower extremity bypass (LEB) in the Vascular Quality Initiative (VQI).

METHODS

A retrospective review of all LEB procedures in the VQI database from January 2003 to October 2013 was performed. Regions with fewer than 200 LEB procedures were excluded from the regional analysis. The modality of CI was defined as duplex ultrasound, angiography, or both.

RESULTS

A total of 14,140 LEBs were captured, with the rate of CI being 43%. After exclusion of three regions for insufficient volume (<200 LEBs), 13,945 LEB operations across 13 regions were available for regional analysis. Use of any type of intraoperative CI varied across regions from a low of 8% to a high of 70%, with angiography being performed most frequently. When CI was performed, the type of imaging modality varied between regions from a high of 99% for angiography to a high of 75% for duplex ultrasound. CI was more common in male patients (44% of male patients vs 42% of female patients; P = .032), diabetics (44% of diabetic patients vs 42% of nondiabetic patients; P = .026), and patients with coronary artery disease (45% of patients with coronary artery disease vs 42% of patients with no coronary artery disease; P = .0015). CI was performed less frequently in LEB using single-segment great saphenous vein vs LEB using lesser saphenous, arm, or composite vein (48% vs 57%; P < .0001). CI was used in 51% of LEBs with a tibial or pedal target vessel vs 38% of LEBs with a more proximal target vessel (P < .0001). Patients with an indication of critical limb ischemia underwent CI in 45% of LEBs vs 39% with an indication other than critical limb ischemia (P < .0001).

CONCLUSIONS

Within the VQI database, considerable practice pattern variation exists in the use of CI. Currently, CI is most commonly employed for patients with critical limb ischemia, infrageniculate target vessel, and disadvantaged venous conduit. Further study is required to standardize and to define the appropriate use of CI for LEBs.

Challenges of distal bypass surgery in patients with diabetes: patient selection, techniques, and outcomes

Surgical revascularization of the lower extremity using bypass grafts to distal target arteries is an established, effective therapy for advanced ischemia. Recent multicenter data confirm the primacy of autogenous vein bypass grafting, yet there remains significant heterogeneity in the utilization, techniques, and outcomes associated with these procedures in current practice. Experienced clinical judgment, creativity, technical precision, and fastidious postoperative care are required to optimize long-term results. The diabetic patient with a critically ischemic limb offers some specific challenges; however, numerous studies demonstrate that the outcomes of vein bypass surgery in this population are excellent and define the standard of care. Technical factors, such as conduit and inflow/outflow artery selection, play a dominant role in determining clinical success. An adequate-caliber, good-quality great saphenous vein is the optimal graft for distal bypass in the leg. Alternative veins perform acceptably in the absence of the great saphenous vein, whereas prosthetic and other nonautogenous conduits have markedly inferior outcomes. Graft configuration (reversed, nonreversed, or in situ) seems to have little effect on outcome. Shorter grafts have improved patency. Inflow can be improved by surgical or endovascular means if necessary, and distal-origin grafts (eg, those arising from the superficial femoral or popliteal arteries) can perform as well as those originating from the common femoral artery. The selected outflow vessel should supply unimpeded runoff to the foot, conserve conduit length, and allow for adequate soft-tissue coverage of the graft and simplified surgical exposure. This review summarizes the available data linking patient selection and technical factors to outcomes and highlights the importance of surgical judgment and operative planning in the current practice of infrainguinal bypass surgery.

Transit-Time Volume Flow Measurements in Autogenous Femorodistal Bypass Surgery for Intraoperative Quality Control

The aim of this study was to assess intraoperative transit-time volume flow measurements (VFMs) as a tool for intraoperative evaluation of lower extremity arterial bypass grafts and to predict their patency. We analyzed 273 consecutive patients who had an infrainguinal bypass procedure using the great saphenous vein from 1998 until 2008; 103 had an intraoperative VFM. All intraoperative revisions were recorded and analyzed. Patency and revision rates were compared between those receiving and those not receiving intraoperative VFM. Cox regression was used for analysis of predictors of patency. Primary patency at 1 and 2 years was 75 and 67%, respectively, in patients receiving intraoperative VFM versus 72 and 69% in those without VFM ( p = .79). In the VFM group, 12% had an immediate revision versus 6% without VFM ( p = .06). In the VFM group, 4% underwent revision to salvage the bypass within the first postoperative 30 days versus 6% without VFM ( p = .32). Patency was not associated with the use of VFM. Receiver operating characteristic curve was significant for occlusion at 30 days postoperatively but with a low predictive value ( p = .019,area under the curve 0.648). VFM may be helpful in selecting bypasses requiring immediate revision to prevent postoperative occlusion. The use of VFM is not significantly associated with patency.

Early duplex scanning after infrainguinal endovascular therapy

OBJECTIVES

Duplex ultrasound scanning (DUS) has benefit for intraoperative and subsequent evaluation of surgical bypasses in the lower extremities. The utility of DUS after endovascular revascularizations is not established. This study was performed to evaluate whether DUS findings after infrainguinal endovascular interventions for critical limb ischemia (CLI) were predictive of need for reintervention or amputation.

METHODS

To identify the study cohort, peripheral interventions for CLI (Rutherford grades 4, 5, 6) over a 24-month period (2006-2007) were reviewed. DUS findings were considered indicative of hemodynamic stenosis if the peak systolic velocity (PSV) was ≥ 180 cm/s or the PSV velocity ratio was ≥ 2.0. Demographic, clinical, procedural, and outcomes were examined. SVS and TASC II classifications and reporting standards were used. Arteriograms were reviewed and treated segments were categorized as patent (<30% residual stenosis) or abnormal (≥ 30% residual stenosis).

RESULTS

There were 122 infrainguinal interventions for CLI in 113 patients (53% male; mean age 71 years). Risk factors included diabetes: 61%; renal failure: 20%; and smoking (within 1 year): 40%. DUS was performed within 30 days of the index procedure in 90 cases. Fifty patients had an abnormal early duplex and 40 patients had a normal duplex. In patients with a normal duplex ultrasound the amputation rate was 5% vs 20% in the group with an abnormal duplex (P = .04). Primary patency was 56% in the normal duplex group and 46% in the abnormal duplex group (P = .18). Early duplex ultrasound was able to identify a residual stenosis not seen on completion angiography in 56% of cases.

CONCLUSIONS

Duplex scanning detects residual stenosis missed with conventional angiography after infrainguinal interventions. An abnormal DUS in the first 30 days after an intervention is associated with an increased risk of amputation. This suggests a possible role for intraprocedural DUS, as well as routine postprocedure DUS, close clinical follow-up, and consideration of reintervention for residual abnormalities in patients treated for CLI.

Technical factors in lower-extremity vein bypass surgery: how can we improve outcomes?

Lower-extremity vein bypass surgery has been a standard operation in the armamentarium of vascular surgeons for more than 4 decades. Yet there remains surprising heterogeneity in the utilization, techniques, and outcomes associated with this procedure in current practice. Despite improvements in surgical technique and careful postoperative surveillance, vein graft failure remains a significant clinical problem affecting up to 50% of patients within 5 years. Experience, clinical judgment, creativity, and technical precision are required to optimize long-term results. Many factors, including patient-specific comorbidities, and variable biologic responses in the venous conduit, influence the ultimate outcome. Technical factors, however, play a dominant role in determining clinical success. Multiple single-center reports, and more recent multicenter trials, have clearly demonstrated that conduit selection and quality is the most critical element. An adequate caliber (>/=3.5 mm), good quality great saphenous vein is the optimal graft for infrainguinal bypass. Contralateral great saphenous vein, arm vein, and lesser saphenous vein are the next most desirable conduits. Graft configuration (reversed, nonreversed, or in situ) appears to have little influence on outcomes per se. Shorter grafts have improved patency. Inflow can be improved by surgical or endovascular means if necessary, and distal-origin grafts perform as well as those originating from the common femoral artery. The selected outflow vessel should supply unimpeded runoff to the foot, conserve conduit length, and allow for adequate soft-tissue coverage of the graft and a simplified surgical exposure. This review summarizes the data linking technical factors with graft patency, highlighting the importance of surgical judgment and operative planning in the current practice of infrainguinal bypass surgery.

Efficacy of duplex ultrasound surveillance after infrainguinal vein bypass may be enhanced by identification of characteristics predictive of graft stenosis development

OBJECTIVE

Controversy regarding the efficacy of duplex ultrasound surveillance after infrainguinal vein bypass led to an analysis of patient and bypass graft characteristics predictive for development of graft stenosis and a decision of secondary intervention.

METHODS

Retrospective analysis of a contemporary, consecutive series of 353 clinically successful infrainguinal vein bypasses performed in 329 patients for critical (n = 284; 80%) or noncritical (n = 69; 20%) limb ischemia enrolled in a surveillance program to identify and repair duplex-detected graft stenosis. Variables correlated with graft stenosis and bypass repair included: procedure indication, conduit type (saphenous vs nonsaphenous vein; reversed vs nonreversed orientation), prior bypass graft failure, postoperative ankle-brachial index (ABI) < 0.85, and interpretation of the first duplex surveillance study as "normal" or "abnormal" based on peak systolic velocity (PSV) and velocity ratio (Vr) criteria.

RESULTS

Overall, 126 (36%) of the 353 infrainguinal bypasses had 174 secondary interventions (endovascular, 100; surgery, 74) based on duplex surveillance; resulting in 3-year Kaplan-Meier primary (46%), assisted-primary (80%), and secondary (81%) patency rates. Characteristics predictive of duplex-detected stenosis leading to intervention (PSV: 443 +/- 94 cm/s; Vr: 8.6 +/- 9) were: "abnormal" initial duplex testing indicating moderate (PSV: 180-300 cm/s, Vr: 2-3.5) stenosis (P < .0001), non-single segment saphenous vein conduit (P < .01), warfarin drug therapy (P < .01), and redo bypass grafting (P < .001). Procedure indication, postoperative ABI level, statin drug therapy, and vein conduit orientation were not predictive of graft revision. The natural history of 141 (40%) bypasses with an abnormal first duplex scan differed from "normal" grafts by more frequent (51% vs 24%, P < .001) and earlier (7 months vs 11 months) graft revision for severe stenosis and a lower 3-year assisted primary patency (68% vs 87%; P < .001). In 52 (15%) limbs, the bypass graft failed and 20 (6%) limbs required amputation.

CONCLUSIONS

The efficacy of duplex surveillance after infrainguinal vein bypass may be enhanced by modifying testing protocols, eg, rigorous surveillance for "higher risk" bypasses, based on the initial duplex scan results and other characteristics (warfarin therapy, non- single segment saphenous vein conduit, redo bypass) predictive for stenosis development.

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.

Pre-Clinical Validation of a New Intra-Operative "Dual Beam Doppler" Blood Flowmeter in an Artificial Circuit

BACKGROUND

Intra-operative flow measurement during coronary or peripheral bypass operations is helpful for ruling out technical failures and for prediction of complication and patency rates. Preclinical validation of the flowmeters is required in order to rely on the intra-operatively measured results. The aim of this study is to evaluate a new "dual beam Doppler" blood flowmeter before clinical application and to compare it with the established "transit time flow measure-ment" technique in an artificial circuit.

METHODS

Measurements were performed in an experimental flow model using pig blood and pig arteries. Three different flowmeters were used: Quantix OR (dual beam doppler flowmeter), CardioMed (transit time flowmeter), and Transonic (transit time flowmeter). Three validation tests were performed to assess correlation, precision, and repeatability of devices. (1) Correlation and agreement analysis was performed with various flow amounts (10-350 mL/min) (n = 160). (2) Device reproducibility and measurement stability were tested with a constant flow (flow amount = 300 mL/min) (n = 30). (3) A user accuracy test (intra- and inter-observer variability) was performed by 5 different observers with a constant flow (flow amount = 205 mL/min) (n = 75). Time collected true flow was used as a reference method in all steps and all tests were performed in a blind manner. Results are shown as mean values +/- standard deviations. Pear-son's correlation and Bland-Altman plot analyses were used to compare measurements.

RESULTS

The mean flow was 167 +/- 98 mL/min for true flow and 162 +/- 94 mL/min, 165 +/- 94 mL/min, and 166 +/- 100 mL/min for Quantix OR, CardioMed, and Transonic, respectively. Correlation coefficients between Quantix OR, Medi-Stim, Transonic, and time collected true flow were over 0.98 (P = .01). Most of the measured results ( > 90%) were between +/- 1.96 SD agreement limits in Bland and Altman plot analysis. All devices showed good results in the reproducibility test. During the user accuracy test, larger variance changes were observed between intra- and inter-observer results with the dual beam Doppler flowmeter compared to the 2 used transit time flowmeters when used for single sided vessel access without stabilization device (available from the manufacturer).

CONCLUSION

All 3 tested flowmeters showed an excellent correlation to the true flow in an artificial circuit and the accuracy of the tested devices was within agreement limits. Reproducibility of all devices was good and linear. The new dual beam Doppler flow measurement technique compares favorably to the classic transit time method. Clinical use may depend on operator, location, and condition, thus more studies may be required to ensure uniform results using the currently available blood flow measurement devices.

Surgical Management of Critical Limb Ischemia

At the present time, infrainguinal bypass using autogenous vein is the most effective and durable treatment for chronic limb ischemia caused by long-segment, diffuse, atherosclerotic occlusive disease. Quality of the vein conduit is the most important factor that determines operative success. Preoperative vein mapping is useful to identify an optimal vein conduit as well as to suggest vein segments that should not be explored due to occlusion, significant calcification, poor caliber, or sclerosis. Reversed, nonreversed, and in situ vein bypass grafts all perform equally well, and the choice of technique depends on anatomic considerations and surgeon preference. Bypass grafts originating from inflow sources distal to the common femoral artery may be appropriate in selected cases without compromising graft patency. All vein graft patients should be followed by postoperative, duplex-based graft surveillance. Antiplatelet therapy is indicated in all infrainguinal bypass patients; oral anticoagulation may be worthwhile in selected, high-risk patients, but hemorrhagic risks are significantly increased.

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.

Interpretation of the Results of Doppler Ultrasound Flow Volume Measurements of Infrainguinal Vein Bypasses

OBJECTIVES

To evaluate a pattern for the interpretation of the results of intraoperative Doppler ultrasound flow volume measurement of infrainguinal vein bypasses.

DESIGN

Retrospective analysis of prospective data.

MATERIALS

91 consecutively performed infrainguinal non-reversed free vein bypasses.

METHODS

Using preoperative angiograms, the run-off, which can be expected after the reconstruction, was evaluated by means of a point score. A first measurement of the flow volume was taken after the release of the blood flow and a second after administration of 20 mg Alprostadil into the bypass. From these two results, we calculated an average value, which was set in relation to the run-off score. From this we computed a relative flow, i.e. the flow per open crural vessel = per run-off score unit (quotient:flow/score).

RESULTS

The median relative flow of angiographically perfect reconstructions was 86 ml/min. In 14 reconstructions, the control angiogram showed stenoses: median relative flow 59 ml/min, range between 20 and a maximum of 75 ml/min. The practical application of the flow measurement requires a minimum relative flow guideline for stenosis-free reconstructions. A guideline of 80 ml/min would yield a sensitivity of 100% and a specificity of 68%.

CONCLUSIONS

Measurement of flow volume could be used as a screen, in order to filter out reconstructions, which must be further clarified with an angiogram. A further prospective evaluation of the value of volume flow is needed before any conclusive recommendations can be drawn.

Optimizing infrainguinal arm vein bypass patency with duplex ultrasound surveillance and endovascular therapy

OBJECTIVE

Infrainguinal bypass grafting with arm vein is associated with lower patency rates compared with saphenous vein conduits. In this study the effect of a duplex ultrasound surveillance program to enable identification and treat graft lesions with open or endovascular repair on patency was analyzed.

METHODS

Over 9 years 89 infrainguinal arm vein (26% spliced vein) bypasses were performed to treat critical lower limb ischemia in 89 patients without adequate saphenous vein conduits. Seventy-six (85%) of the bypasses were repeat procedures. Grafts were assessed at operation with duplex ultrasound scanning, then enrolled in a surveillance program. Graft stenoses with peak systolic velocity greater than 300 cm/s and velocity ratio greater than 3.5, detected at duplex ultrasound scanning, were repaired with percutaneous transluminal balloon angioplasty (PTA) if specific criteria were met, including greater than 3 months since primary procedure, lesion length less than 2 cm, and graft diameter greater than 3.5 mm, or with open surgical repair for early appearing or extensive graft lesions.

RESULTS

During a mean 26-month follow-up, duplex surveillance resulted in a 48% (43 bypasses) intervention rate. Primary patency rate was 43% at 3 years. Twenty-six (43%) of 61 lesions identified and repaired met criteria for PTA; the remaining 35 graft lesions (stenosis, n = 30; vein graft aneurysm, n = 5) were surgically corrected with vein patch angioplasty (n = 15), interposition grafting (n = 13), jump graft bypass (n = 6), or open repair (n = 1). At 3 years the assisted primary patency rate was 91% (7 graft failures). Multiple interventions were performed in 18 (42%) revised grafts because of metachronous (n = 6) or repair site stenosis (n = 12). In 18 graft interventions (PTA, n = 9; surgery, n = 9) recurrent stenosis developed, and endovascular therapy was used in one third (n = 6). At 3 years the stenosis-free patency rate for PTA (48%) and surgically repaired (53%) graft lesions was similar.

CONCLUSIONS

Arm veins used in lower limb bypass procedures are prone to development of stenosis and aneurysm, lesions easily detected with a life-long duplex ultrasound surveillance program. Excellent long-term patency (91%) was achieved despite graft intervention being performed in nearly half of all bypasses and one third of revised grafts. Endovascular treatment was possible in half of all graft stenosis, with outcomes similar to those with surgical repair.

What's new in vascular ultrasound

Duplex ultrasound has long been the method of choice in the diagnosis and evaluation of deep venous thrombosis and carotid artery stenosis and in monitoring lower extremity bypasses. In recent years, innovative procedures and technology have fostered new applications for duplex ultrasound, such as detection of in-stent stenosis and endoleaks, intraoperative evaluation of in situ vein bypasses and monitoring of endovenous procedures, and treatment of common femoral pseudoaneurysms. The low cost and noninvasiveness of duplex ultrasound make it ideal for such studies,as well as for screening for asymptomatic vascular disease.

Intraoperative duplex ultrasound of visceral revascularizations: optimizing technical success and outcome

PURPOSE

The purpose of this study was to evaluate the use of intraoperative duplex ultrasound scanning (IOUS) during visceral revascularizations and correlate its results with clinical outcome.

METHODS

We studied 68 patients (15 men and 53 women, mean age 66.5 years, range 27-86 years) who underwent visceral revascularization with concomitant IOUS examination of 120 visceral arteries (52 celiac, 60 superior mesenteric, and 8 inferior mesenteric arteries) from 1992 to 2002. Patients were divided into two groups on the basis of ultrasound findings: normal and abnormal IOUS. The incidence of early and late graft-related complications (thrombosis, restenosis, recurrent symptoms, reintervention) and graft-related death was compared in both groups.

RESULTS

One-hundred and two (85%) arteries had normal IOUS. Eight (6.6%) arteries had minor defects, including small kinks (4), mild residual stenoses (3), and small intimal flap (1). Ten (8.4%) arteries had major defects, consisting of hemodynamically significant residual stenoses (4), thrombus (2), kinks (2), bidirectional flow (1), and intimal flap (1). Major defects were successfully revised in all except three cases: two persistent mild stenoses and one bidirectional flow. Patients with abnormal IOUS at the end of the operation had increased incidence of graft-related complications and/or death (55.5% vs 7.8%; P =.004), early graft thrombosis (14.2% vs 1.0; P =.04), reintervention (21.4% vs 3.2%; P =.03), and graft-related death (33.3% vs 1.9%; P =.02), compared with patients with normal IOUS.

CONCLUSION

This study supports the routine use of IOUS during visceral revascularizations to optimize technical success and outcome. Persistent ultrasound scanning abnormalities are associated with risk of early graft failure, reintervention, and death. Patients with normal ultrasound scans can expect excellent results.

Blinded comparison of preoperative duplex ultrasound scanning and contrast arteriography for planning revascularization at the level of the tibia

PURPOSE

We examined whether preoperative duplex ultrasound scanning (DU) could replace contrast material-enhanced arteriography (CA) in selecting the recipient artery of tibial or peroneal artery bypass grafts.

METHODS

In patients who underwent tibial or peroneal artery bypass grafting because of critical ischemia, images were obtained of the lower extremity arterial circulation with both DU and CA. Vascular surgeons, blinded to the operation performed, reviewed either DU or CA images for arterial visualization and patency. The tibial or peroneal artery best suited to receive the bypass graft was selected by surgeons using only data from either DU or CA images. This selection was compared with the artery actually used at bypass surgery.

RESULTS

Preoperative DU and CA data for 40 lower extremities in 38 patients undergoing bypass grafting at the level of the tibia provided 110 arteries: 38 anterior tibial arteries, 32 peroneal arteries, and 40 posterior tibial arteries. Ten arteries (8 peroneal, 2 anterior tibial) were not identified with DU, and 1 artery (anterior tibial) was not identified with CA. DU enabled prediction of the artery actually used in 88% of patients (35 of 40), whereas CA enabled prediction of the artery actually used in 93% of patients (37 of 40; P =.59). Duplicate findings at DU and CA enabled selection of 85% of arteries actually used (95% confidence interval, 71%-93%). Arteries used for bypass grafting had significantly higher peak systolic velocity (35 cm/s vs 25 cm/s; P =.04), higher end-diastolic velocity (15 cm/s vs 9 cm/s; P =.005), and greater diameter (2.4 mm vs 1.7 mm; P =.003) compared with arteries not selected for bypass grafting.

CONCLUSION

Findings at DU and CA typically agree when used to select tibial or peroneal arteries for bypass grafting. With DU there is occasional difficulty in identification of the peroneal artery, but selection of the actual artery used is accurate. Peak systolic velocity, end-diastolic velocity, and diameter characteristics correlate with arteriographic criteria for tibial bypass target artery selection. If DU enables adequate identification of a target artery for bypass grafting, and especially if the peroneal artery is seen, findings at CA are not likely to alter bypass execution.

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.

Prospective Comparison of Intraoperative Angiography with Duplex Scanning in Evaluating Lower-Extremity Bypass Grafts in a Community Hospital

The gold standard for intraoperative evaluation of lower-extremity bypass grafts has been angiography. Limitations of this technique include inability to measure flow dynamics, violation of graft integrity, cost, and length of assessment time. The goal of this study was to evaluate duplex scanning as an alternative modality for intraoperative graft assessment. Our study group comprised of 19 consecutive patients undergoing infrainguinal bypass procedures at our institution between March 1999 and March 2000. Intraoperative angiography was compared with duplex scanning by evaluating parameters of assessment time, graft flow velocities, serum creatinine levels, and 30-day graft patency rates. Mean study times were the following: cut-film angiography, 22 ± 1.8 minutes; real-time fluoroscopy, 17 ± 2.5 minutes; and duplex imaging, 10.4 ± 1.1 minutes. As noted duplex imaging times as compared with radiographic modalities were significantly shorter ( P < 0.05). There was a substantial cost difference between angiography ($650) and duplex scanning ($350). A100 per cent correlation of study findings was noted between angiography and duplex scanning. No significant change in pre- versus postoperative creatinine levels was found. We conclude that duplex scanning is an effective modality and provides reliable intraoperative vascular graft assessment data in a community hospital setting. Advantages include a shorter study time, lower cost, flow dynamic data acquisition, and avoidance of mechanical graft trauma.