Natural history of infrainguinal vein graft stenosis relative to bypass grafting technique

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.

Pseudoaneurysm Development after Drug-Eluting Balloon (DEB) Angioplasty of a Venous Femoropopliteal Bypass Graft

Endovascular recanalization of occluded venous femoropopliteal bypass grafts is widely used because of easy access. This case report describes pseudoaneurysm developing 4 weeks after endovascular recanalization of an occluded in situ venous femoropopliteal graft. The patient was treated for a popliteal aneurysm with a venous femoropopliteal bypass graft, which subsequently occluded. Four weeks after DEB PTA, the occluded graft developed 3 pseudoaneurysms. Impaired vessel wall healing after intraluminal paclitaxel administration could have contributed to this. This case adds a perspective to the choice of treatment of occluded venous femoropopliteal bypass grafts.

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.

Comparison of the Resistive Properties of Reversed and Nonreversed Saphenous Veins at Arterial Pressure and Flow: Implications for Optimal Graft Configuration

Clinicians continue to debate the hemodynamic advantages of reversed vs nonreversed vein grafts in infrainguinal arterial reconstructions. Vein grafts placed in the reversed configuration do not require valve lysis but have the theoretical drawback of being smaller in caliber at the inflow end than the outflow end. The purpose of this study was to objectively determine the effect of vein valve lysis and flow direction on vein graft hemodynamics by using physiologic levels of pulsatile flow (Q), pressure gradient (AP), outflow resistance (Ro), and longitudinal impedance (ZL).

Nine cryopreserved human greater saphenous veins (length=23 ±1 cm) were perfused via an in vitro circuit utilizing a variable pulsatile perfusion pump, Windkessel, and clamp resistor. Levels of Q and AP were chosen to simulate the known physiologic conditions of infrainguinal bypass grafting while holding Reynolds numbers <2,400. Veins were studied in the reversed configuration prior to valve lysis, after valve lysis by use of a catheter-directed valvulotome with 3 mm cutting head, and in the nonreversed configuration. Ultrasonic transit-time flow and proximal and distal intraluminal pressure were continuously recorded while Ro and pump rate were varied. Waveforms were digitally stored at 200 Hz at pump rates of 60, 100, 140, and 180 beats per minute at a Q of 154 ± 1 and 253 ± 1 mL/min while Pprox was maintained at 100 mmHg. Veins were perfusion fixed at 100 mmHg, sectioned at 2 cm intervals, and analyzed morphometrically. Inner diameter (id) and outer diameter (od) were determined by light microscopy after correction for shrinkage artifact by comparing to outer diameter measured by digital calipers at 2 cm intervals at the time of perfusion. Percent vein taper was calculated as (idmax7idmin)/idmax and wall thickness (t) as (od-id)/2. After Fourier transformation, ZL was calculated as AP/Q at each harmonic and the curves compared by use of Wilcoxon signed-ranks test.

There were one to four valves per vein (idmean=3.6 ±0.3 mm; range 2.3-6.2) with an average taper of -8 + 12% (range: -46-36%) and mean wall thickness of 0.51 ±0.03 mm (range 0.42-0.68 mm). ZL curves were smooth and reproducible over the measured frequency range. Neither valve lysis nor flow direction had an effect on ZL at any level of Q or Ro, even in veins with a taper >25%. Mean wall thickness correlated with ZL (r2=0.43; p=0.05).

In this in vitro system, saphenous vein graft impedance (ZL) was independent of valve lysis, flow direction, and the degree of vein taper but was weakly dependent on wall thickness. In veins of adequate size, hemodynamic considerations should not influence the decision to use the reversed vs nonreversed configuration.

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.

Open surgical revision provides a more durable repair than endovascular treatment for unfavorable vein graft lesions

OBJECTIVE

Lower extremity bypass grafts that develop stenoses are commonly treated with either open surgical or endovascular revision. Vein graft stenoses with unfavorable lesions (multiple lesions, lesions >2 cm in length, lesions in grafts <3 months old, lesions in grafts <3 mm in diameter) fare worse than those with favorable lesions when treated with endovascular therapy. However, it is not known if unfavorable lesions fare better with surgical revision than with endovascular treatment or than favorable lesions treated with surgery.

METHODS

We performed a retrospective review of 175 vein graft revisions performed at a single institution from 2000 to 2010. Characteristics of lesions treated with surgical and endovascular revision were identified. Cox proportional hazard models were used to identify predictors of revision failure (restenosis >75%, revision, or amputation).

RESULTS

Ninety-one failing vein grafts (52%) were treated with surgical revision and 84 with endovascular treatment (48%), with a median follow-up of 30 months. Favorable lesions fared better than unfavorable lesions after endovascular treatment, with 12-month freedom from failure of 59% vs 34% (P < .01), but not after surgical revision (66% vs 62%; P = .90). Unfavorable lesions had better freedom from failure after surgery than endovascular treatment (62% vs 34%; P < .01), and results in favorable lesions were similar (66% vs 59%; P = .57).

CONCLUSIONS

For the treatment of failing vein grafts, endovascular therapy appears adequate for favorable lesions and surgical revision is more durable for unfavorable lesions.

Interpretation of arterial duplex testing of lower-extremity arteries and interventions

Arterial duplex testing is used to evaluate patients with lower-limb arterial occlusive or aneurysmal disease to provide clinicians with detailed information on location, extent, and severity of disease. It is possible to detect disease from the visceral aorta to the tibial arteries. Duplex testing is interpreted in conjunction with limb-pressure measurements to accurately categorize arterial hemodynamics and functional impairment. Understanding the features of duplex-acquired velocity spectra recordings is fundamental to accurate diagnostic testing, including the characteristic spectral features of "normal" versus "abnormal" lower-limb arterial flow, hemodynamic changes associated with stenosis or occlusion, and the status of distal limb or foot perfusion. Scanning can provide an arterial map of occlusive or aneurysm lesions analogous to an angiogram. Testing is accurate before and after intervention for the detection of stenosis; a common failure mode after bypass grafting or peripheral angioplasty. The detection of high-grade stenosis in an arterial repair allows for pre-emptive treatment before thrombosis occurs and improves long-term patency.

Low levels of a natural IgM antibody are associated with vein graft stenosis and failure

BACKGROUND

All humans have natural, protective antibodies directed against phosphorylcholine (PC) epitopes, a common inflammatory danger signal appearing at sites of cell injury, oxidative stress, and on bacterial capsules. In large human cohorts, low levels of anti-PC IgM were associated with a significantly increased risk of stroke or myocardial infarction. However, it is not known if these antibodies protect against the premature closure of arterial reconstructions.

METHODS

A prospective, observational study of patients undergoing elective, infrainguinal, autogenous vein bypasses for atherosclerotic occlusive disease of the legs was conducted. Clinical data were recorded prospectively, and preoperative levels of anti-PC IgM measured with the CVDefine kit from Athera Biotechnologies (Solna, Sweden). The principal clinical end point was the loss of primary patency (loss of graft flow, or any intervention for stenosis). Patients were followed regularly by duplex ultrasound at 1, 3, 6, 12, 18 months, and yearly thereafter.

RESULTS

Fifty-six patients were studied, for an average of 1.3 years. Indications for surgery were claudication (33.9%), ischemic rest pain (17.9%), and ischemia with ulceration or gangrene (48.2%). Seventeen (30.4%) patients experienced loss of primary patency (10 graft occlusions, seven surgical or endovascular revisions of graft stenoses). Kaplan-Meier survival analysis showed that the quartile of patients with the lowest anti-PC IgM levels had significantly worse primary graft patency (log-rank test, P = .0085). Uni- and multivariate Cox proportional hazards analysis revealed that the preoperative anti-PC IgM level was an important predictor of graft failure. Patients with IgM values in the lowest quartile had a 3.6-fold increased risk of graft failure (95% confidence interval: 1.1-12.1), even after accounting for other significant clinical or technical factors such as indication for surgery, site of distal anastomosis, or vein graft diameter.

CONCLUSIONS

A naturally occurring IgM antibody directed against the proinflammatory epitope PC may be protective against vein graft stenosis and failure, through anti-inflammatory mechanisms. Measurement of this antibody may be a useful prognostic indicator, although larger studies of more diverse populations will be needed to confirm these results. The biological actions of anti-PC IgM suggest it may be useful in developing immunotherapies to improve bypass longevity.

Circulating inflammatory cells are associated with vein graft stenosis

OBJECTIVE

Infrainguinal autogenous vein grafts are especially prone to narrowing and failure, and both inflammatory and thrombotic pathways are implicated. Platelets and monocytes are the key thrombo-inflammatory cells that arrive first at sites of vascular injury. These cells have potent interactions that recruit and activate one another, propagating thrombotic and inflammatory responses within the vessel wall. We therefore hypothesized that elevated levels of platelet-monocyte aggregates (PMA) might be associated with stenosis, and could possibly discriminate between patients with or without vein graft stenosis.

METHODS

Thirty-six vascular surgery patients were studied, in a stable quiescent period after infrainguinal autogenous vein graft bypasses for occlusive disease. Eighteen patients had hemodynamically significant graft stenoses confirmed by imaging, and 18 were free from stenosis. The level of PMA in whole blood was quantified after blood draw using two-color flow cytometry. Three measurements were made per sample: the basal, in-vivo level of aggregates (baseline PMA); the predisposition to spontaneously generate PMA (spontaneous PMA); and PMA generation by the addition of exogenous thrombin receptor-activating peptide (stimulated PMA). The baseline, in-vivo level of PMA was estimated by immediate flow analysis. The predisposition to spontaneously generate PMA was measured after in vitro incubation. Responsiveness to thrombin stimulation of the blood was quantified by the in vitro dose response to an exogenous thrombin receptor-activating peptide (sfllrn).

RESULTS

Baseline PMA levels were similar in patients with vein graft stenosis vs nonstenosis (14.8% ± 3.2 vs 10.1% ± 1.5, respectively, mean ± SEM). However, patients with stenosis showed higher spontaneous PMA levels (58.5% ± 4.5 vs 28.3% ± 4.3; P < .001) and higher stimulated PMA levels (P < .001; analysis of variance). Covariables of smoking, diabetes, statin, or antithrombotic therapy could not account for these differences.

CONCLUSIONS

Platelet-monocyte reactivity may play a role in the development of vein graft stenoses. Those with/without stenosis differed primarily in their threshold, or predisposition to form aggregates (spontaneous PMA), while their basal circulating levels of PMA (baseline PMA) were similar. These measurements may unmask pathologic differences in thrombo-inflammatory responsiveness that are not apparent in basal measurements. Understanding the causes and mechanisms leading to abnormal platelet-monocyte responses may improve approaches to predicting or preventing vein graft stenosis.

[What are the guidelines for using a venous segment for an arterial bypass? General review]

Since the first femoropopliteal bypass, performed by J. Kunlin, in 1950, the saphenous vein has remained the material of choice for arterial bypass in a wide variety of localizations. Harvesting must be adapted to vein quality and the length necessary for the bypass. A thorough knowledge of the histological structure of the graft and the impact of the harvesting process on endothelial cells is needed to understand early and late complications related to saphenous harvesting. Several experimental studies and clinical series, particularly for aortocoronary bypass, have shown the role of atraumatic harvesting, removing the perivenous fat, and/or papaverine infusion in the perivascular tissues. A venous graft can be used in six localizations. For femoropopliteal bypass, the venous graft can be used reversed or in situ, after valvular section. For bypass to tibial vessels and bypass to the ankle and the foot, the graft can be the greater saphenous vein or the lesser saphenous vein, or veins from the arm. These bypasses can be done reversed or in situ or transposed reversed or after valvular disruption. This technique has the advantage of placing the largest portion of the vein at the level of the proximal anastomosis, but with the risk of endothelial cell desquamation during vein harvesting, which can lead to late fibrosis of the graft. For aorto-iliac bypass, new prosthetic grafts and the development of endovascular techniques have overshadowed the former advantages of the saphenous vein grafts. Surgical renal revascularisations have become less frequent since the development of endovascular techniques. Nevertheless, the venous graft remains useful for some revascularisations - hepatic-renal bypass, iliorenal bypass, difficult nephrologic situations (solitary kidney, chronic occlusion). For aortocoronary bypass, long-term outcome has been studied in many studies. It is recommended to use the grafts with a no touch technique, using a portion without valves. The carotid venous graft is a useful technique when endarterectomy is difficult or not satisfactory. The graft must be harvested from the calf, without valves, have a diameter of 5mm and be harvested without injury.

Is Infrainguinal Percutaneous Atherectomy Better Suited for Certain Arteries Than Others?

Objective: We analyzed our results with percutaneous rotational atherectomy catheters and specifically examined whether they were more likely to be associated with a successful outcome when used to treat smaller diameter vessels such as infrapopliteal (IP) arteries compared to larger diameter femoropopliteal (FP) arteries and infrainguinal arterial autogenous vein grafts (GRAFTS). Material and Methods: Between January 1, 2005, and December 31, 2006, athrectomies were performed on 32 patients for claudication (14), gangrene (9), rest pain (4), and failing GRAFTS (5). Treated vessels included 14 superficial femoral, 1 popliteal, 5 anterior tibial, 4 posterior tibial, and 3 peroneal arteries along with 5 failing GRAFTS. All procedures were performed by vascular surgeons in an endovascular operating suite using a mobile C-arm. Results for larger diameter vessels including FP arteries and GRAFTS were combined (FP + BYPASSES) and compared to results of IP artery lesions. Follow-up averaged 10 weeks (range, 0.5-34 weeks). Results: Length of treated lesions averaged 4.2 cm (range, 1—15 cm) for FP + GRAFT lesions (9 occlusions, 11 stenoses) versus 1.8 cm (1-4 cm) for IP lesions (6 occlusions, 6 stenoses; P = ns). Procedural success rate based on postoperative segmental pressures, pulse volume recordings, and duplex ultrasound was 70% (14/20) for FP + GRAFTS versus 83% (10/12) for IP lesions (P = .03). Need for concomitant adjunctive balloon angioplasty to treat residual stenosis tended to be higher for FP + GRAFT lesions (40% [8/20]) compared to IP lesions (25% [3/12]; P = ns). During follow-up, 25% (5/20) of FP + GRAFTS lesions required reintervention (3 balloon angioplasties, 1 thrombectomy, 1 GRAFT pseudoaneurysm) versus none for the IP lesions (P = .03). Limb salvage rates were 90% (18/20) for FP + GRAFT lesions versus 100% (12/12) for IP lesions during this short follow-up. Conclusions: These preliminary results suggest that short segment IP arterial stenoses and occlusions can be successfully treated with atherectomy catheters with a lower rate of reintervention during short-term follow-up, less need for concomitant adjunctive balloon angioplasty and a lower complication rate compared to FP + graft lesions.

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.

Genomic and proteomic determinants of lower extremity revascularization failure: rationale and study design

This translational research program applies a working model of advanced functional genomics/proteomics and bioinformatics to human peripheral arterial occlusive disease (PAOD). It is a multidisciplinary collaborative effort of clinicians, scientists, and statisticians with an advisory panel consisting of experts in inflammation biology, vascular biology, molecular genetics, bioinformatics, clinical trial design, and epidemiology. The proposed human initiative is designed to study 300 symptomatic patients with PAOD undergoing medical management with or without vascular intervention by lower extremity angioplasty/stenting or vein graft bypass. The study aims to test the hypothesis that the systemic inflammatory response after vascular intervention influences the local milieu responsible for vascular repair and adaptation. The expectation is that this response is not uniform in all patients but, rather, is modulated by either preoperative genetic predisposition or postprocedure differential regulation of the innate immune response to injury that promotes a maladaptive phenotype leading to intervention failure. Therefore, some of these differences may be present and detectable before intervention and amenable to class prediction and prospective treatment strategies, whereas others may be detectable in the early postprocedural period, before the onset of clinical failure, permitting interventions to prevent an adverse outcome. The combination of genomic/proteomic data together with functional and quality-of-life outcome measures to define a critical model for class prediction and analysis should lead to new knowledge about failure mechanisms of vascular intervention and new strategies to improve existing approaches to lower extremity revascularization.

Primary revision of mid-vein stenoses in venous bypass conduits: venous patch versus interposition vein

PURPOSE

Patients after infrainguinal vein bypasses are a group at risk of graft stenosis and occlusion. Revision of failing grafts has been shown to significantly improve bypass patency and limb salvage. Options for surgical revision of mid bypass stenosis includes either patch angioplasty (PA) or interposition grafting (IG). We reviewed our experience with surgical revision of vein bypass stenosis.

METHODS

From April 1968 to March 2006, 7557 autogenous vein bypasses were performed at Albany Medical Center and its affiliated institutions, of these 316 required single or multiple revision of vein grafts with patch angioplasty or interposition vein grafting. Excluded were proximal and distal anastomotic revisions. Only 235 bypasses had single revisions as either patch angioplasty (n = 108) or interposition grafting (n = 127) and are the focus of this review. The initial bypass revisions in these two groups are analyzed for indications, clinical parameters, operative strategies, and long-term patencies and clinical outcomes.

RESULTS

There were no significant differences in mean age, gender, or frequency of comorbid conditions (coronary artery disease, pulmonary disease, hypertension, and diabetes) between the two patient groups. Secondary patency of patch angioplasty revision at 5 years was 79%. Patencies for interposition grafting revision at 5 years were equivalent to patch angioplasty group at 75%. When bypasses were evaluated on the basis of initial reconstructions (ie, in situ vs excised vein bypass), the results showed that in situ bypasses that required initial revision had similar 5-year patencies when interposition grafting was used as the first revision strategy vs patch angioplasty (80% vs 73%). Excised vein bypasses had similar patency when patch was their first revision strategy vs interposition grafting (4 year secondary patency 92% vs 75% respectively).

CONCLUSION

Autogenous vein bypasses are at risk for developing significant stenosis and occlusion with time. Bypass stenosis that develops in the main body of the graft can be effectively repaired using either patch angioplasty or interposition grafting. Depending on the host of other factors, such as availability of autogenous venous conduit, location of stenosis, accessibility for operative repair, and the patient's anatomic characteristics, either operative strategy is effective in prolonging the patency of the bypass.

Plaque excision with the Silverhawk catheter: Early results in patients with claudication or critical limb ischemia

OBJECTIVE

This study was conducted to detail the early experience after infrainguinal atherectomy using the Silverhawk plaque excision catheter for the treatment of symptomatic peripheral vascular disease.

METHODS

A prospective database was established in August 2004 in which data for operations, outcomes, and follow-up were recorded for patients undergoing percutaneous plaque excision for peripheral arterial occlusive disease. Society for Vascular Surgery (SVS) ischemia scores and femoropopliteal TransAtlantic Inter-Society Consensus (TASC) criteria were assigned. A follow-up protocol included duplex ultrasound surveillance at 1, 3, and 6 months and then yearly thereafter. Standard statistical analyses were performed.

RESULTS

During a 17-month period, 66 limbs of 60 patients (37 men [61.7%]) underwent 70 plaque excisions (four repeat procedures). Indications included tissue loss based on SVS ischemia at grades 5 and 6 (25/70), rest pain at grade 4 (22/70), and claudication at grades 2 to 3 (23/70). The mean lesion length was 8.8 +/- 0.7 cm. The technical success rate was 87.1% (61/70). Adjunctive treatment was required in 17 procedures (24.3%), consisting of 14 balloon angioplasties and three stents. Femoropopliteal TASC criteria included 5 TASC A lesions, 14 TASC B lesions, 32 TASC C lesions, and 19 TASC D lesions. Although 17 plaque excisions included a tibial vessel, no patient underwent isolated tibial atherectomy. The mean increase in ankle-brachial index was 0.27 +/- 0.04 and in toe pressure, 20.3 +/- 6.9 mm Hg. Mean duplex ultrasound follow-up was 5.2 months (range, 1 to 17 months). One-year primary, primary assisted, and secondary patency was 61.7%, 64.1%, and 76.4%, respectively. Restenosis or occlusion developed in 12 patients (16.7%) and was detected at a mean of 2.8 +/- 0.7 months. Restenosis or occlusion was significantly more common (P < .05) in patients with TASC C and D lesions compared with patients with TASC A and B lesions. Six (8.3%) of 12 patients underwent reintervention on the basis of duplex ultrasound surveillance results. Four (33.3%) of 12 patients experienced reocclusion during the same hospitalization, and amputation and open revascularization were required in two patients each.

CONCLUSIONS

Percutaneous plaque excision is a viable treatment option for lower extremity revascularization. Outcomes are related to ischemia and lesion severity. Patency and limb salvage rates are equivalent to other endovascular modalities.

Hemodynamic changes associated with bypass stenosis regression

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The value of duplex surveillance after open and endovascular popliteal aneurysm repair

OBJECTIVE

The objective of this study was to determine the clinical value of vascular laboratory surveillance after open or endovascular repair of popliteal aneurysm by analysis of the frequency and nature of secondary interventions performed.

METHODS

Over an 8-year period, 55 popliteal artery aneurysms were repaired in 46 men (mean age, 72 years) by aneurysm ligation and bypass grafting (vein, 37; prosthetic, 7), endoaneurysmorrhaphy and interposition grafting (prosthetic, 3; vein, 1), or endograft exclusion (n = 7). Indications for intervention included aneurysm thrombosis with critical limb ischemia (n = 8), symptomatic (n = 10) or asymptomatic (n = 37), >1.75 cm popliteal aneurysm with mural thrombus. Catheter-directed thrombolysis was used in three limbs to restore aneurysm and tibial artery patency before open repair. Duplex ultrasound surveillance was performed after repair to identify residual and acquired lesions. Life-table analysis was used to estimate repair site intervention-free (primary) and assisted-primary patency.

RESULTS

During a mean 20-month follow-up interval, 20 secondary procedures were performed in 18 (31%) limbs to repair duplex-detected graft stenosis (n = 10), repair site thrombosis (n = 5), vein graft aneurysm (n = 3), graft entrapment (n = 1), or type 1 endoleak (n = 1). Primary patency was 76% and 68% at 1 and 3 years, and was uninfluenced by tibial artery runoff status or type of bypass conduit. Open (n = 12) or endovascular (n = 8) secondary procedures were performed on 15 (12 vein, 3 prosthetic) bypass grafts, 2 endografts, and 1 interposition graft. Mean time to repair graft stenosis (11 months) was shorter than to repair of vein graft aneurysm (37 months). Assisted-primary patency was 93% and 88% at 1 and 3 years; redo bypass grafting was required and successful in five limbs. Limb salvage was 100%.

CONCLUSIONS

One third of popliteal artery aneurysms repaired by open or endovascular procedures required a secondary intervention within 2 years of repair. Repair-site surveillance using duplex ultrasound was able to identify lesions that threaten patency, which resulted in excellent assisted patency and limb preservation rates when corrected.

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.

Pedal arterial bypass for limb salvage in patients with diabetes mellitus

OBJECTIVE

to evaluate pedal bypass grafting in patients with diabetes mellitus with critical limb ischaemia.

PATIENTS AND METHOD

from 1994 to 1999, 49 consecutive pedal bypass grafts were performed in 46 patients with a median age of 69 years (range 37-85 years). The incidence of insulin-dependent diabetes mellitus was 87%. The distal anastomosis was located at the dorsalis pedis artery in 36, at the inframalleolar posterior tibial artery in 9 and at the plantar artery in 4 cases, respectively.

RESULTS

one patient died perioperatively. Two bypass occlusions and one major amputation accounted for a primary patency rate of 96% and a limb salvage rate of 98% at 30 days, respectively. During a median follow-up of 28 months (range 1-70 months), 21 patients died of nonrelated causes. Three additional graft occlusions and 4 major amputations were noted resulting in a primary patency rate of 89% and a limb salvage rate of 87% at 48 months, respectively.

CONCLUSION

Pedal bypass grafting utilising the greater saphenous vein with in-situ technique is a reliable and effective procedure to achieve durable limb salvage in patients with diabetes mellitus.

Early results of a prospective randomized trial of spliced vein versus polytetrafluoroethylene graft with a distal vein cuff for limb-threatening ischemia

OBJECTIVE

Single-piece vein remains the conduit of choice in patients who need bypass grafting for limb salvage. When this option is not available, two of the remaining options are prosthetic bypass graft or several segments of vein spliced together. In this study, we compare spliced vein bypass grafting versus polytetrafluoroethylene grafting with a distal vein cuff in patients with limb-threatening ischemia.

METHODS

Between 1996 and 2000, 39 bypass grafting procedures in 36 patients were performed for limb-threatening ischemia. These procedures were prospectively randomized to either spliced vein bypass grafting (spliced group, 19 bypass grafts) or polytetrafluoroethylene grafting with a distal vein cuff (cuff group, 20 bypass grafts). All the patients in the cuff group underwent anticoagulation therapy with warfarin sodium after surgery. The inclusion criteria included: no single-piece vein option for bypass grafting, adequate vein for splice, no composite sequential option, and limb-threatening ischemia. The demographics were similar between the two groups.

RESULTS

The primary patency rate at 2 years was 44% and 49% for the spliced and cuff groups, respectively. In the spliced group, seven of 19 bypass grafts underwent revision in the follow-up period, and two of 20 cuffed bypass grafts were successfully revised. The secondary patency rate was 87% and 59% (P <.05), with limb salvage rates of 94% and 85% for spliced and cuff groups, respectively. Four patients in the spliced vein group needed reoperation for wound complications related to vein harvest. One polytetrafluoroethylene graft needed removal for infection. Two early mortalities occurred in the spliced group, one from myocardial infarction and one from stroke. The overall survival rate at 2 years between the two groups was 67% and 100% for the spliced and cuff groups, respectively (P <.05).

CONCLUSION

Although this is a preliminary report, it appears that both spliced vein bypass grafting and polytetrafluoroethylene bypass grafting with a distal vein cuff produce acceptable limb salvage rates. The secondary patency rate for spliced vein is better, but these bypass grafts more often need revision or reoperation for wound complications.

The durability of endoscopic saphenous vein grafts: a 5-year observational study

BACKGROUND

Endoscopic saphenous vein harvest has been explored as a minimally invasive alternative to a long continuous leg incision for removal of the greater saphenous vein. The endoscopic technique uses limited incisions (2-4) with extended "skin bridges" and videoscopic equipment for the dissection and removal of the greater saphenous vein. This study was undertaken to evaluate the long-term durability of saphenous vein grafts harvested by an endoscopic technique and used for lower extremity arterial revascularization.

METHODS

All patients who underwent endoscopic saphenous vein harvesting for lower extremity arterial bypass grafting were prospectively followed for graft patency and risk factors. Grafts were surveyed with serial duplex scans at 3- to 6-month intervals over this 5-year study. Life-table methods were used to assess graft survival. A computerized registry and medical records were reviewed to determine graft patency and patient survival.

RESULTS

From September 1994 to August 2000, 164 lower extremity arterial saphenous vein grafts harvested by an endoscopic technique were used for lower extremity arterial bypass grafting in 150 patients. The patient population included 111 males (75%) and 112 smokers (75%), but also included a high-risk cohort of 65 diabetic patients (43%) and 15 patients undergoing dialysis/renal transplant (10%). Twenty-eight patients (19%) died within the study period. With life-table methods, 1-, 3-, and 5-year secondary patency rates were 85% (+/- 3.2%), 74% (+/- 5.7%), and 68% (+/- 11.6%). Of the 30 failed grafts, 7 (4%) failed in the first month related to inadequate runoff (4), cardiac instability (2), and an additional surgical procedure (1). Twenty-three grafts (14%) failed between 1 and 42 months. Twenty-two (16%) of these 134 patent grafts underwent a second procedure to maintain patency (13 as primary-assisted patency and 9 as secondary patency).

CONCLUSIONS

Endoscopic saphenous vein harvest for lower extremity arterial reconstruction provides a satisfactory conduit for lower extremity bypass grafting. Although increased manipulation from this limited access technique may incite an injury response in the vein, these vein grafts can maintain an adequate patency for lower extremity bypass grafting.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Predictors of outcome when reoperating for early infrainguinal bypass occlusion

The purpose of this study is to identify factors that predict outcome after intervention for early (<30 days) infrainguinal graft thrombosis. We reviewed the medical records, arteriograms, and follow-up studies of patients who underwent infrainguinal bypass for limb salvage between 8/91 and 9/98 and whose graft failed <30 days from the index procedure. Five factors were analyzed: (1) conduit: single segment saphenous vein versus alternative vein or composite conduit (20 vs. 13 patients); (2) repair modality: construction of a new graft at the time of the initial take-back procedure versus local revision and/or thrombectomy alone (12 vs. 21 patients); (3) run-off: good run-off versus poor run-off (20 vs. 13 patients); (4) operative findings: the presence of a correctable problem versus noncorrectable problem (20 vs. 13 patients); and (5) surgical history: previous versus no previous ipsilateral bypass (16 vs. 17 patients). These variables are statistically significant risk factors that can be used in combination to predict outcome. Unless a focal lesion clearly responsible for graft occlusion is found, complete graft replacement should be considered even if the new bypass must be prosthetic. The costs and morbidity of repeated procedures argue for primary amputation when adverse risk factors exist.

Effective hemodynamic diameter: an intrinsic property of vein grafts with predictive value for patency

INTRODUCTION

Conduit size and quality are major determinants of the long-term success of infrainguinal autologous vein grafting. However, accurate measurement of the internal diameter of vein grafts is difficult given their variable wall thickness and taper. The purpose of this study was to define the "effective" internal diameter of a vein graft according to its hemodynamic properties and to determine its significance for graft patency.

METHODS

Sixty infrainguinal bypass grafts performed on 57 patients were evaluated intraoperatively. Proximal and distal graft pressure and blood flow (Q(meas)) were measured with fluid-filled catheter transduction and ultrasonic transit-time flowimetry, respectively, after unclamping. Waveforms were recorded digitally at 200 Hz under baseline conditions and after stimulation with 60 mg of papaverine. According to Fourier transformation of the measured pressure gradient (DeltaP), the Womersley solution for fluid flow in a straight rigid tube was used to calculate theoretical flow waveforms (Q(calc)) for a range of graft diameters. The theoretical waveforms were then compared with the measured flow waveforms and the best-fit diameter chosen as the "effective hemodynamic diameter" (EHD). Only grafts in which the correlation coefficient of Q(calc) versus Q(meas) was more than 0.90 were accepted (n = 47) to assure validity of the hemodynamic model. After a mean follow-up of 12.5 months (range, 0.1-43.9 months), patency was determined by the life table method. Hemodynamic and clinical variables were tabulated, and their effect on patency determined the use of univariate and multivariate Cox regression.

RESULTS

Mean EHD was 4.1 +/- 0.1 mm with a range of 2.5 to 5.7 mm. Administration of papaverine caused profound changes in DeltaP (+78% +/- 17%) and Q(meas) (+71% +/- 12%) as expected, but had no effect on EHD (+0.05% +/- 0.1%). Univariate regression identified five variables associated with decreased secondary patency (P <.10): low EHD, conduit source other than the greater saphenous vein, high baseline DeltaP(mean), female sex, and redo operation. Of these, only low EHD was significant after multivariate analysis (P =.03). Patency of small diameter grafts (EHD < 3.6 mm; n = 11) was compared with patency of larger grafts (EHD > 3.6 mm; n = 36) to test a frequently espoused clinical guideline. Grafts with an EHD less than 3.6 mm exhibited significantly lower secondary patency compared with larger grafts (P =.0001). The positive and negative predictive values for an EHD less than 3.6 mm for secondary graft failure for grafts with at least 1 year follow-up were 86% and 88%, respectively.

CONCLUSION

An EHD is a unique parameter that quantifies conduit size and has a significant impact on vein graft patency. An EHD less than 3.6 mm portends graft failure.

Intraoperative duplex monitoring of infrainguinal vein bypass procedures

PURPOSE

The purpose of this study was to evaluate intraoperative duplex scanning of infrainguinal vein bypass grafts to detect technical and hemodynamic problems, monitor their repair, and correlate findings with the incidence of thrombosis and stenosis repair rates within 90 days of operation.

METHODS

Color duplex scanning was used at operation to assess vein/anastomotic patency and velocity spectra waveforms of 626 infrainguinal vein bypass grafts (in situ saphenous, 228 grafts; nonreversed translocated saphenous, 170 grafts; reversed saphenous, 147 grafts; alternative [arm, lesser saphenous], 81 grafts) to the popliteal (n = 267 grafts), infrageniculate (n = 323 grafts), or pedal artery (n = 36 grafts). The entire bypass graft was scanned after intragraft injection of papaverine hydrochloride (30-60 mg) to augment graft flow. Vein/anastomotic/artery segments with velocity spectra that indicate highly disturbed flow (peak systolic velocity, >180 cm/sec; spectral broadening; velocity ratio at site, >3) were revised. Grafts with a low peak systolic velocity less than 30 to 40 cm/s and high outflow resistance (absent diastolic flow) underwent procedures (distal arteriovenous fistula, sequential bypass grafting) to augment flow; if this was not possible, the grafts were treated with an antithrombotic regimen, including heparin, dextran, and antiplatelet therapy.

RESULTS

Duplex scanning prompted revision of 104 lesions in 96 (15%) bypass grafts, including 82 vein/anastomotic stenoses, 17 vein segments with platelet thrombus, and 5 low-flow grafts. Revision rate was highest (P <.01) for alternative vein bypass grafts (27%) compared with the other grafting methods (reversed vein bypass grafts, 10%; nonreversed translocated, 13%; in situ, 16%). A normal intraoperative scan on initial imaging (n = 464 scans) or after revision (n = 67 scans) was associated with a 30-day thrombosis rate of 0.2% and a revision rate of 0.8% for duplex-detected stenosis (peak systolic velocity, >300 cm/s; velocity ratio, >3.5). By comparison, 20 of 95 bypass grafts (21%) with a residual (n = 29 grafts) or unrepaired duplex stenosis (n = 53 grafts) or low flow (n = 13 grafts) had a corrective procedure for graft thrombosis (n = eight grafts) or stenosis (n = 12 grafts; P <.001). Overall, 8% of patients with bypass grafts underwent a corrective procedure within 90 days of operation. Secondary graft patency was 99.4% at 30 days and 98.8% at 90 days (eight graft failures).

CONCLUSION

The observed 15% intraoperative revision rate coupled with a low 90-day failure/revision rate (2.5%) for bypasses with normal papaverine-augmented duplex scans supports the routine use of this diagnostic modality to enhance the precision and early results of infrainguinal vein bypass procedures.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The effect of 'non-critical' (<50%) stenosis on vein graft longitudinal resistance and impedance

OBJECTIVE

vein graft stenoses <50% cause minimal flow impairment, velocity elevation, or symptomatology and are therefore usually assumed to be "non-critical". The purpose of this study was to assess the effect of <50% vein graft stenosis on vein graft longitudinal impedance, as elevated impedance has been found to correlate with clinical graft failure.

METHODS

eight segments of non-reversed cryopreserved vein (mean length 23+/-1 cm; mean outer diameter 4.7+/-0.2 mm) were saline-perfused in vitro utilising a variable pulsatile perfusion pump, Windkessel, and clamp resistor simulating the haemodynamic conditions of arterial bypass. Proximal (Pprox) and distal (Pdist) pressure were continuously measured by fluid-filled catheter transduction, and flow (Q) by ultrasonic transit-time flowmetry. Waveforms were digitally recorded at 200 Hz at pulse rates ranging from 60-180 b.p.m. with mean flow (Q) of 154 ml/min and mean proximal pressure (Pprox) of 100 mmHg (max/min 120/90). Graded mid-graft stenoses of <50% were created using an inflatable vascular occluder and measured by the corresponding changes in mean pressure gradient (DeltaP=Pprox-Pdist) and Q (%stenosis=1-{DeltaPbaselineQstenosis/Delta PstenosisQbaseline}1/4). Vein graft longitudinal resistance (RL) was calculated as DeltaP/Q. After Fourier transformation, vein graft longitudinal impedance (ZL) was calculated as DeltaP/Q at each harmonic, with ZL determined by integration over 0-4 Hz. Results are reported as mean+/-S.E.M.

RESULTS

the desired levels of pressure and flow were established in all vein segments. Graded inflation of the occluder resulted in vein graft stenosis of 23+/-3% and 39+/-3%. This was accompanied by a mild reduction in Q (12% and 30%) and considerable increases in both RL (180% and 710%) and ZL (140% and 430%).

CONCLUSIONS

"non-critical" vein graft stenosis (<50%) causes minimal change in mean flow, but substantial elevations in longitudinal resistance and impedance. The contribution of "non-critical" stenosis to vein graft failure may be under-appreciated.

Economising vein-graft surveillance programs

OBJECTIVES

To investigate the effectiveness of two alternative vein-graft surveillance strategies. In the first strategy surveillance was restricted to patients with a possible higher risk of significant stenosis development, i.e., those with a moderate stenosis identified early after the operation. In the second strategy the effects of reducing the number of duplex tests per patient was examined.

PATIENTS AND METHODS

In a prospective study in three vascular surgical departments 300 patients (300 femoropopliteal or distal grafts) underwent duplex surveillance during the first year after the operation. The duplex-derived PSV-ratio was considered to represent the degree of stenosis. Arteriographic confirmation of suspected stenoses was routinely obtained, and patients without a suspected graft stenosis underwent a consented arteriogram during the first postoperative year. The decision to perform a graft revision was taken on the basis of an arteriographic stenosis of at least 70% diameter reduction. In the first strategy graft categories were defined on the basis of the first postoperative duplex examination: grafts with a PSV-ratio < 1.5, grafts with a PSV-ratio < 1.5-2.0, grafts with a PSV-ratio of 2.0-2.5, grafts with PSV-ratios 2.5-3.0, and grafts with PSV-ratios > 3.0. The primary patency rate at 12 months was compared for these categories. In the second alternative strategy the number of examinations and the percentage of event causing de novo stenoses were analysed per surveillance interval.

RESULTS

The presence of moderate abnormalities at the initial duplex scan did not identify patients with a high risk of an event, as initial PSV-ratios of 1.5-2.0 and 2.0-2.5 (early mild-moderate lesions) had comparable 12-month primary patencies to patients with a PSV-ratio < 1.5 (completely normal grafts): (63%, 73%, and 71%, respectively). The interval incidence of event causing de novo stenoses was 8% of the total number of duplex tests performed at 3 months, and 8% at 6 months after the operation. In patients who had no previous intervention for stenosis and had a normal bypass during the first 6 months postoperatively, a sharp drop in this incidence was seen at 9 and 12 months, with event causing de novo stenoses observed in only 2% and 1% of all duplex tests.

CONCLUSIONS

All patients should be included in a surveillance program, as the presence of a normal vein graft at the first duplex examination does not rule out the subsequent development of graft stenosis. The duration of the surveillance period may be restricted to the first 6 months after operation in patients who have a normal bypass during that time period, as only few stenoses will be missed by this policy.