Development of a Decision Tree to Streamline Infrainguinal Vein Graft Surveillance.

BACKGROUND: Duplex ultrasound (DU) remains the gold standard for identification and grading of infrainguinal vein graft stenosis. However, DU-based graft surveillance remains controversial. The aim of this study was to develop a decision tree to identify high-risk grafts which would benefit from DU-based surveillance. METHODS: Consecutive patients undergoing infrainguinal vein graft bypass were enrolled in a DU surveillance program. An early postoperative DU was performed at a median of 6 weeks (range 4-9). Based on the findings of this scan and 4 established risk factors for graft failure (diabetes, smoking, infragenicular distal anastomosis, revision bypass surgery), a classification and regression tree (CART) was created to stratify grafts into grafts which are at high and low risk of developing severe stenosis or occlusion. The accuracy of the CART model was evaluated using area under receiver operator characteristic curve (ROC). RESULTS: Of 796 vein graft bypasses performed (760 patients), 64 grafts were occluded by the first surveillance visit and 732 vein grafts were entered into surveillance program. The CART model stratified 299 grafts (40.8%) as low-risk and 433 (59.2%) as high-risk grafts. One hundred twenty-six (17.2%) developed critical vein graft stenosis. Overall, 30-month primary patency, primary-assisted and secondary patency rates were 76.2%, 83.6%, and 85.3%, respectively. The area under ROC curve for the CART model was 0.88 (95% confidence interval 0.81-0.94). Primary graft patency rates were higher in low-risk versus high-risk grafts (log rank 186, P < 0.0001). Amputation rates were significantly higher in the high-risk grafts compared with low-risk ones (log rank 118, P < 0.0001). CONCLUSION: A clinical decision rule based on readily available clinical data and the findings of significant flow abnormalities on an early postoperative DU scan successfully identifies grafts at high risk of failure and will contribute to safely improving the efficacy of infrainguinal vein graft surveillance services.

Spiral laminar flow prosthetic bypass graft: medium-term results from a first-in-man structured registry study.

BACKGROUND: A number of surgical strategies and graft enhancements have been trialled to improve the performance of prosthetic grafts. Neointimal hyperplasia may, in part, be a normal cellular response to an abnormal (turbulent) flow environment. This first-in-many study assesses the safety and medium-term patency performance of a new graft designed to induce stable laminar flow through the distal anastomosis. METHOD: Forty patients who required an infrainguinal bypass graft were recruited/registered from a number of centers in Belgium and The Netherlands. Thirty-nine received a Spiral Laminar Flow graft as part of a standard treatment protocol (23 above-the-knee and 16 below-the-knee bypasses). Kaplan-Meier analyses were used to calculate primary and secondary patency rates. RESULTS: The 12-, 24-, and 30-month primary patency rates were 86%, 81%, and 81% for above-the-knee bypasses and 73%, 57%, and 57% for below-the-knee bypasses, respectively. In the case of secondary patency rates, numbers were unchanged for above-the-knee bypasses and were 86%, 64%, and 64%, respectively, for below-the-knee bypasses. There were no amputations in the study population. CONCLUSION: This first-in-man series shows potential for the idea of spiral flow-enhanced prosthetic grafts. As always, randomized studies are required to explore the role of different enhanced prosthetic grafts.

Left ventricular hypertrophy is present in one-half of newly-diagnosed peripheral arterial disease patients.

OBJECTIVES: Peripheral arterial disease (PAD) patients are at high risk of cardiac death. Coincidental but silent coronary disease is obviously a major contributor but left ventricular hypertrophy (LVH) could be a second major contributor. METHODS: To investigate whether LVH could really be making a large contribution to cardiac death in PAD, we assessed the prevalence of LVH when PAD was first diagnosed. RESULTS: The prevalence of echo LVH when left ventricular mass was indexed to body surface area was 50%. Although office blood pressure and 24-h blood pressure were both significantly higher in those with LVH, in clinical practice, a contemporaneous blood pressure measurement (office or 24 h) at the time of PAD diagnosis would only partially identify those with LVH. For example, an office blood pressure cut-off of < 140/90 mmHg was found in 27% of all LVH cases and a 24-h blood pressure cut-off of < 125/80 mmHg was found in 24% of all LVH cases. CONCLUSION: In conclusion, there is already a high prevalence of LVH in patients at first diagnosis of PAD. LVH is therefore common enough in PAD patients to potentially make a major contribution to cardiac death, which means that future research should now investigate whether screening for and regressing LVH when present would actually reduce cardiac deaths over and above merely achieving target blood pressure.

Comparison of vortical structures induced by arteriovenous grafts using vector Doppler ultrasound.

Arteriovenous prosthetic grafts are used in hemodialysis. Stenosis in the venous anastomosis is the main cause of occlusion and the role of local hemodynamics in this is considered significant. A new spiral graft design has been proposed to stabilize the flow phenomena in the host vein. Cross-flow vortical structures in the outflow of this graft were compared with those from a control device. Both grafts were integrated in identical in-house ultrasound-compatible flow phantoms with realistic surgical configurations. Constant flow rates were applied. In-plane 2-D velocity and vorticity mapping was developed using a vector Doppler technique. One or two vortices were detected for the spiral graft and two to four for the control, along with reduced stagnation points for the former. The in-plane peak velocity and circulation were calculated and found to be greater for the spiral device, implying increased in-plane mixing, which is believed to inhibit thrombosis and neo-intimal hyperplasia.

Secondary flow in peripheral vascular prosthetic grafts using vector Doppler imaging.

Prosthetic grafts are used for the treatment of peripheral arterial disease. Re-stenosis in the distal anastomosis of these grafts is a common reason for graft occlusion. The role of local hemodynamics in development of neo-intimal hyperplasia is well known. A new graft design has been proposed for the induction of optimized spiral flow in the host vessel. The secondary flow motions induced by this graft were compared with those of a control device. Both types of grafts were connected with vessel mimic and positioned in ultrasound flow phantoms with identical geometry. Constant flow rates were applied. Data collected in the cross-sectional view distal from the graft outflow and dual-beam vector Doppler was applied to create 2-D velocity maps. A single-spiral flow pattern was found for the flow-modified graft, and double or triple spirals for the control graft. In-plane maximum velocity was greater for the flow-modified graft than for the control device.

Hemodynamic effects of spiral ePTFE prosthesis compared with standard arteriovenous graft in a carotid to jugular vein porcine model.

INTRODUCTION: The primary patency rate of arteriovenous (AV) grafts is limited by distal venous anastomosis stenosis or occlusion due to intimal hyperplasia associated with distal graft turbulence. The normal blood flow in native arteries is spiral laminar flow. Standard vascular grafts do not produce spiral laminar flow at the distal anastomosis. Vascular grafts which induce a spiral laminar flow distally result in lower turbulence, particularly near the vessel wall. This initial study compares the hemodynamic effects of a spiral flow-inducing graft and a standard graft in a new AV carotid to jugular vein crossover graft porcine model. METHODS: Four spiral flow grafts and 4 control grafts were implanted from the carotid artery to the contralateral jugular vein in 4 pigs. Two animals were terminated after 48 hours and 2 at 14 days. Graft patency was assessed by selective catheter digital angiography, and the flow pattern was assessed by intraoperative flow probe and color Doppler ultrasound (CDU) measurements. The spiral grafts were also assessed at enhanced flow rates using an external roller pump to simulate increased flow rates that may occur during dialysis using a standard dialysis needle cannulation. The method increased the flow rate through the graft by 660 ml/min. The graft distal anastomotic appearances were evaluated by explant histopathology. RESULTS: All grafts were patent at explantation with no complications. All anastomoses were found to be wide open and showed no significant angiographic stenosis at the distal anastomosis in both spiral and control grafts. CDU examinations showed a spiral flow pattern in the spiral graft and double helix pattern in the control graft. No gross histopathological effects were seen in either spiral or control grafts. CONCLUSION: This porcine model is robust and allows hemodynamic flow assessment up to 14 days postimplantation. The spiral flow-inducing grafts produced and maintained spiral flow at baseline and enhanced flow rates during dialysis needle cannulation, whereas control grafts did not produce spiral flow through the distal anastomosis. There was no deleterious effect of the spiral flow-inducing graft on macroscopic and histological examination. The reducing effect of spiral flow on intima hyperplasia formation will be the subject of further study using the same AV graft model at a longer period of implantation.

An animal paired crossover ePTFE arteriovenous graft model.

PURPOSE: Previously, we developed a porcine model for Arterio Venous Graft (AVG) failure to allow assessment of new access strategies. This model was limited concerning graft length. In the present technical report, we describe a modification of our model allowing the assessment of long AVGs. TECHNIQUE: In 4 pigs, AVGs of 15 cm length were created bilaterally in a cross-over fashion between the carotid artery and the contralateral jugular vein. Two days (2 pigs) and two weeks (2 pigs) after AV shunting, graft patency was evaluated by angiography, showing all four grafts to be patent, with no sign of angiographic or macroscopic narrowing at the anastomoses sites. CONCLUSIONS: In this modified pig AVG failure model, implantation of a bilateral cross-over long AVG is a feasible approach. The present model offers a suitable tool to study local interventions or compare various long graft designs aimed at improvement of AVG patency.

Long-term results after placement of aortic bifurcation self-expanding stents: 10 year mortality, stent restenosis, and distal disease progression.

PURPOSE: To retrospectively evaluate the 10 year follow-up results in patients who had "kissing" self-expanding stent aortic bifurcation reconstruction. METHODS: Forty-three patients were treated with "kissing" self-expanding stents for aortoiliac occlusive disease. Early follow-up with clinical and ankle brachial pressure indices (ABPI) was performed at 3, 6, 12, and 24 months and with intra-arterial digital subtraction angiography at 12-24 months; clinical and angiographic follow-up was performed for symptom recurrence up to 10 years after treatment. Retrospective record review was performed to assess mortality, clinical patency, angiographic patency, and secondary assisted patency of both stents and downstream peripheral vessels at 5 and 10 years follow-up. RESULTS: The 2 year primary angiographic and secondary assisted stent patencies were 89% and 93%, respectively. At 10 years follow-up in 40 patients the mortality was 38% (due to myocardial infarction, stroke, chronic renal failure, malignancy, and liver failure). At 5 and 10 years follow-up the primary clinical stent patency was 82% and 68%, and the secondary assisted stent patency 93% and 86%, respectively. At 5 and 10 years, the distal vessel patency was 86% and 72%, and the secondary assisted distal vessel patency treated by surgical or endovascular techniques was 94% and 88%, respectively. At 10 years there was no limb loss. CONCLUSION: The long-term (10 year) results of aortic bifurcation arterial self-expanding stent placement in patients with arterial occlusive disease show a 10 year primary stent patency rate of 68% but a secondary assisted patency rate of 86%. In addition there is a high overall mortality due to other cardiovascular causes and the rate of distal disease progression and loss of patency is similar to the loss of stent patency rate.

Cutting balloon angioplasty versus standard balloon angioplasty for failing infra-inguinal vein grafts: comparative study of short- and mid-term primary patency rates.

PURPOSE: To evaluate the results of a recent change in practice in our institution using cutting balloon angioplasty instead of standard balloon angioplasty as the primary treatment for failing infra-inguinal vein bypass grafts. METHODS: In this nonrandomized cohort study with a historical control, failing infra-inguinal vein grafts were identified at duplex surveillance or clinical examination. Patients had confirmatory arteriography and balloon angioplasty at the same attendance. Interventions proximal or distal to the graft itself and prosthetic grafts were not included. Patients were entered into a duplex graft surveillance program. Initial assessment of technical success was duplex or improvement 4-6 weeks after the primary angioplasty. RESULTS: Twenty-seven consecutive patients were treated with standard balloon angioplasty, then 11 consecutive patients were treated with cutting balloon angioplasty. Initial technical success was 74% for the standard balloon versus 82% for the cutting balloon. The primary patency rate at 6 months was 16/26 (62%) for standard balloon angioplasty and 8/10 (80%) for cutting balloon angioplasty (p = 0.44). The primary patency rate at 12 months was 9/25 (36%) for standard balloon angioplasty and 5/10 (50%) for cutting balloon angioplasty (p = 0.47). CONCLUSION: The use of cutting balloons for primary angioplasty of infra-inguinal vein grafts offers no definite advantage over standard balloon angioplasty in this institution or compared with patency rates after standard balloon angioplasty reported elsewhere. Larger multicenter studies would be required to demonstrate whether there was any real difference between the two techniques.

Spiral laminar flow in the abdominal aorta: a predictor of renal impairment deterioration in patients with renal artery stenosis?

BACKGROUND: Spiral or helical arterial blood flow patterns have been widely observed in both animals and humans. The absence of spiral flow has been associated with carotid arterial disease. The aim of this study was to detect the presence of aortic spiral flow using magnetic resonance imaging (MRI) and to evaluate the relationship of the presence of spiral aortic flow with renal arterial disease and renal function in the follow-up of patients with suspected renal atheromatous disease. METHODS: Prospective study of 100 patients with suspected renal arterial disease and 44 patient controls. Using a 1.5 T MRI unit (Siemens Symphony), phase contrast flow quantification and three-dimensional contrast enhanced MR angiography of the abdominal aorta were performed. Renal arterial stenoses (RAS) were classified minimal, moderate or severe. Renal function was followed at 3 months before and 6 months after MRI. RESULTS: Non-spiral flow was more prevalent in patients with more severe RAS. Renal impairment progressed significantly in severe RAS without spiral flow (P = 0.0065), but did not progress significantly in severe RAS with spiral flow (P = 0.12). In minimal or moderate RAS with or without spiral flow there was no significant progression (P = 0.16, 0.13, 0.47, 0.092, respectively). CONCLUSIONS: Aortic spiral blood flow can be assessed with MRI. Lack of aortic spiral blood flow in patients with severe RAS is associated with significant short-term renal function deterioration. Determination of blood flow patterns may be a useful indicator of renal impairment progression in patients with suspected renal artery stenosis.

Two-dimensional flow quantitative MRI of aortic arch blood flow patterns: Effect of age, sex, and presence of carotid atheromatous disease on prevalence of spiral blood flow.

PURPOSE: To determine the effect of age, sex, and presence of carotid atheromatous disease on the presence of aortic spiral blood flow pattern using two-dimensional flow quantitative magnetic resonance imaging (MRI). MATERIALS AND METHODS: Sixty subjects (37 women, 23 men) were examined. Prospective phase contrast flow quantitative MRI (1.5 T, Siemens Symphony) sequences in the plane of the aortic arch, and three-dimensional contrast-enhanced MR angiography of the vessels from the aortic arch to the circle of Willis, were performed. Flow quantitative analysis, using circular regions of interest, in the root, apex, and descending aortic arch to determine the presence of a spiral blood flow pattern was undertaken. The results were correlated with the subjects age, sex, and presence of significant carotid arterial disease. RESULTS: A spiral blood flow pattern was seen during diastole in 43 of 50 (86%), 42 of 48 (88%), and in 26 of 28 (93%) subjects in the root, apex, and descending aortic arch, respectively. Spiral flow was seen during systole in 14 of 35 (40%), 20 of 47 (42%), and 11 of 31 (35%) subjects in the root, apex, and descending aortic arch, respectively. There was no clear effect of age or sex on the presence of spiral flow. Carotid disease was associated with a significant reduction in the prevalence of systolic spiral flow from 51%-19% subjects (P < 0.05). CONCLUSION: Spiral flow pattern can be seen in the arch of the aorta in clinical practice using flow quantitative MRI. The prevalence of spiral flow pattern does not appear affected by subject age or sex. Carotid atheromatous disease is associated with a reduction in prevalence of systolic spiral flow pattern in the aortic arch.