In vivo transluminal microvascular endothelial cell seeding on balloon injured rabbit arteries

AIM

Seeding venous endothelial cells (EC) onto damaged vascular surfaces attenuates the development of intimal hyperplasia. Unlike venous EC, fat derived microvascular endothelial cells (MVEC) do not require a culture step to increase the yield. The authors investigated whether fat derived MVEC are suitable to reduce intimal hyperplasia after PTA.

METHODS

Five rabbits were subjected to percutaneous transluminal angioplasty (PTA) of both iliac arteries. One side was seeded transluminally with autologous perirenal fat derived MVEC, using a double balloon catheter. The contralateral side was sham seeded, and served as a control. Follow-up was 4 weeks. Another rabbit was used for a feasibility experiment. This rabbit was subjected to a 1-sided seeding procedure and was sacrificed after 1 week. In a 7th rabbit, a 1-sided PTA was transformed, and autologous labelled cells were injected in the distal aorta instead of seeded, follow-up was 1 week. Histological investigation was per-formed.

RESULTS

The MVEC seeded artery of the pilot experiment was patent. All sham seeded arteries (5) except for 1 were patent. The patent ones showed moderate intimal hyperplasia. MVEC seeding (5) resulted in occlusion twice. In the patent MVEC seeded arteries intimal hyperplasia was present in more extended form than in the sham seeded arteries. Both the patent MVEC- and sham-seeded arteries were covered with an EC layer. Injected labelled MVEC were not found again on the de-endothelialized artery.

CONCLUSION

In this study seeding of fat derived MVEC on damaged native arteries results in an increased development of intimal hyperplasia and a decreased patency. One of the reasons may be the presence of non-EC in the seeded cell population.

Quality of Life after Endovascular and Open AAA Repair. Results of a Randomised Triala

AIM

To compare the quality of life (QoL) in the first postoperative year after elective endovascular abdominal aortic aneurysm repair (EVAR) and open repair (OR) in a randomised study.

METHODS

In the Dutch Randomised Endovascular Aneurysm Management (DREAM) trial, patients are randomly allocated to EVAR or OR. QoL questionnaires (SF-36 and EuroQoL-5D) were sent to all patients preoperatively (PREOP) and at five time points in the first postoperative year (3W, 6W, 3M, 6M and 12M). Between November 1999 and August 2002, 153 patients (141 male; 12 female) were randomised (78 EVAR and 75 OR; one crossover from OR to EVAR). The EuroQoL-5D scores and the eight domains of the SF-36 for the two groups were compared using the Mann-Whitney test. Changes over time were analysed using the Wilcoxon sign test.

RESULTS

There were no statistically significant differences in baseline characteristics (age, gender and SVS risk factors). The preoperative QoL scores of the study group were similar to the QoL scores of the general population of the same age. After 3W the OR group showed a significant decrease on the EuroQol-5D (p=0.022) and in six of the eight SF-36 domains. The EVAR group also showed a significant decrease on the EuroQol-5D (p=0.004) and in 5 of the 8 domains of the SF-36. At 6W the EuroQol-5D had recovered to baseline in the OR group and the decreased domains of the SF-36 had partially recovered. In the EVAR group the EuroQol-5D and three of the five decreased SF-36 domains, had returned to baseline. From 6M on, the OR group reported a significantly higher score on the EuroQoL-5D than the EVAR group (p=0.045 (6M) and p=0.001 (12M)).

CONCLUSION

In the early postoperative period there is a small, yet significant QoL advantage for EVAR compared to OR. At 6 months and beyond, patients reported better QoL after OR than after EVAR.

[Endovascular treatment of 4 patients with a traumatic rupture of the thoracic aorta]

OBJECTIVE

To present our initial results with the endovascular treatment of traumatic rupture of the thoracic aorta.

DESIGN

Retrospective.

METHOD

Between April and October, 2002, 4 men between the ages of 22 and 46 were treated endovascularly for a traumatic rupture of the thoracic aorta. The diagnosis 'rupture of the thoracic aorta' was made on the basis of CT-angiography in all cases. In the first case, a thoracic Gore TAG-endoprosthesis (Gore & Associates; Den Bosch) was used, and in 3 cases a Talent-endoprosthesis (Medtronic AVG; Heerlen).

RESULTS

There was an average of 2.5 days (limits: 0-5 days) between admission and the placement of the endoprosthesis. There was one intra-operative complication in the form of a dissection of the right femoral artery when the endoprosthesis was inserted. In 3 cases, the left subclavian artery was occluded by the prosthesis. This had no negative consequences for the patients during the follow-up period (limits: 4-12 months). The CT-angiogram taken 3 months after the operation consistently showed a good position of the endoprosthesis with no signs of leakage.

CONCLUSION

For a limited follow-up period, the endovascular treatment of a traumatic rupture of the thoracic aorta has been shown to be safe and effective. The long term results must be awaited.

Decision-making in follow-up after endovascular aneurysm repair based on diameter and volume measurements: a blinded comparison

OBJECTIVE

to assess whether volume, in addition to diameter, measurements facilitate decision-making after endovascular aneurysm repair (EVAR).

MATERIAL/METHODS

patients (n = 82) with an immediately post-EVAR, and at least one follow-up (3-60 months), computed tomographic angiogram (CTA) were studied. The actual and all preceding proportional sac size changes were recorded. The resulting 347 diameter and 347 volume data were placed in random order and reviewed by three blinded observers who then recommended one of three treatment policies: "good/wait", "uncertain/intensify follow-up" or "not good/further diagnostics (Dx) or intervention (Rx)". The observers were instructed to consider changes of 10% relevant. One observer reviewed the graphs twice.

RESULTS

the interobserver agreements (kappa) for the diameter were 0.92, 0.81 and 0.76 and for volumes 0.91, 0.88 and 0.86. The intra-observer agreement was 0.93 for both diameter and volume. Volume data resulted in significantly more "good/wait" decisions out to 36 months. Diameter data resulted in more "not good/Dx or Rx"-decisions out to 36 months (all p < 50.005).

CONCLUSION

post-EVAR aneurysm sac volume data appears to provide earlier reassurance, reduce unnecessary interventions and to be more sensitive to secondary problems than diameter data alone.

Rapid, arteriovenous graft failure due to intimal hyperplasia: a porcine, bilateral, carotid arteriovenous graft model

BACKGROUND

The loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future.

MATERIALS AND METHODS

In 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis.

RESULTS

From 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation.

CONCLUSIONS

Implantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.

Screening for asymptomatic internal carotid artery stenosis and aneurysm of the abdominal aorta: comparing the yield between patients with manifest atherosclerosis and patients with risk factors for atherosclerosis only

OBJECTIVE

The purpose of this study was to investigate whether screening for internal carotid artery stenosis (ICAS) and aneurysm of the abdominal aorta (AAA) is indicated in patients with either manifest atherosclerotic disease or with only risk factors for atherosclerosis.

STUDY DESIGN

Data were obtained for 2274 patients enrolled in the SMART study, an ongoing single-center, prospective cohort study of patients referred to our vascular center with manifest atherosclerotic disease (peripheral atherosclerotic disease [PAD]; transient ischemic attack [TIA], stroke, or ICAS; AAA; angina pectoris; or myocardial infarction [MI]) or with only risk factors for atherosclerosis (diabetes mellitus, hypertension, hyperlipidemia). The presence of ICAS or AAA was determined with duplex scanning and ultrasonography.

RESULTS

The prevalence of ICAS 70% or greater is low in patients with risk factors for atherosclerosis only (1.8%-2.3%), intermediate in patients with angina pectoris or MI (3.1%), and highest in patients with PAD (12.5%) or AAA (8.8%). The prevalence of AAA 3 cm or larger is low in patients with risk factors for atherosclerosis only (0.4-1.6%), intermediate in patients with angina pectoris or MI (2.6%), and highest in patients with PAD (6.5%) or TIA, stroke, or ICAS (6.5%). The prevalence of AAA larger than 5 cm is low in all of the considered patient groups. The yield of screening can be optimized through selection on the basis of simple patient characteristics. In patients with PAD, selecting those with advanced age (>54 years) increased the prevalence of ICAS to 21.8%. Selecting patients with lower diastolic blood pressure (<83 mm Hg) increased the prevalence of ICAS to 17.9%. In patients with both advanced age and lower diastolic blood pressure, the prevalence of ICAS increased to 34.7%. Selecting patients with advanced age increased the prevalence of AAA 3 cm or larger to 9.6%. In patients with TIA, stroke, or ICAS, selecting those with advanced age increased the prevalence of AAA 3 cm or larger to 8.2%. Selecting patients with taller stature (>169 cm) increased the prevalence of AAA 3 cm or larger to 9.3%. In patients with advanced age and taller stature, the prevalence of AAA 3 cm or larger increased to 13.1%.

CONCLUSIONS

Screening for ICAS should be limited to patients referred with PAD or AAA, especially those with advanced age or with low diastolic blood pressure. Screening for AAA should be limited to patients referred with PAD or with TIA, stroke, or ICAS, particularly those with advanced age or tall stature. In patients referred with angina pectoris or MI and those referred with only risk factors for atherosclerosis, screening cannot be endorsed.

[Treatment of abdominal aortic aneurysms]

Three treatment options are available for an asymptomatic abdominal aortic aneurysm (AAA): an expectant approach with ultrasonographic check-ups, reconstruction of the abdominal aorta via the conventional ('open') approach and endovascular repair. For aneurysms less than 5.5 cm in diameter the annual rupture risk is less than 1%. For these patients a better alternative to the expectant approach does not seem to exist. The risk of rupture needs to be weighed up against the risks of a conventional operation. The operation mortality of patients with a non-ruptured AAA is about 7% while other serious complications occur in about 10%. The short to medium-term results of endovascular aneurysm repair are characterized by high reintervention rates, material fatigue and device failure. The three treatment options described are currently being investigated in several large-scale randomised studies for AAAs greater than 5.5 cm in diameter.

The Dutch Randomised Endovascular Aneurysm Management (DREAM) trial. Background, design and methods

After the introduction of endovascular repair of abdominal aortic aneurysms (AAA), both benefits and drawbacks of this new technique have been reported. To assess whether the new technique is an adequate substitute of conventional AAA repair, a randomised study is due. The Dutch Randomised Endovascular Aneurysm Management (DREAM) trial is a randomised multicenter trial enrolling patients eligible for elective treatment of infrarenal AAAs. In this study, the cost-effectiveness of endovascular aneurysm repair (EAR) is compared with that of conventional transabdominal surgery, in patients that are considered suitable for both types of treatment. The primary endpoint is combined operative mortality and morbidity. Secondary endpoints and additional assessments include event free survival, quality of life, length of hospital stay and costs. It is expected that the DREAM-trial will lead to a safe and controlled introduction of a new technology. Also, the medical community will obtain valid scientific evidence of the merits of endovascular AAA repair. Finally, policy makers will be provided with accurate cost-effectiveness data for the Dutch healthcare system. The aim of the present paper is to describe the background, methods and design of the DREAM-trial.

Reduction of non-endothelial cell contamination of microvascular endothelial cell seeded grafts decreases thrombogenicity and intimal hyperplasia

INTRODUCTION

fat derived microvascular endothelial cells (MVEC) seeded on prosthetic vascular grafts, improve patency in animals. Results in humans were disappointing, due to thrombogenicity and progressive intimal hyperplasia. Also in animals intimal hyperplasia was found. We postulate that contaminating cells present in the transplant are involved in the intimal hyperplasia. We developed a method to further purify human MVEC from 40-90%. Here we tested the effects of enrichment upon thrombogenicity and seeding-related intimal hyperplasia.

METHODS

liposuction fat was enzymatically digested and centrifuged. To enrich MVEC, contaminating macrophages and fibroblasts were removed with dynabeads coated with macrophage- and fibroblast-specific antibodies. Thrombogenicity was assessed by measuring tissue factor and thrombomodulin activity, presence of endothelial nitric oxide synthase and via perfusion of the cells with whole blood. To investigate seeding-related intimal hyperplasia, PTFE grafts were seeded with the cells and cultured for 3 weeks.

RESULTS

tissue factor activity of purified cells was reduced compared to nonpurified cells. Purified cells showed thrombomodulin activity and eNOS expression. Fragment 1+2 and Fibrinopeptide A generation after perfusion of purified cells were significantly lower than after perfusion of nonpurified cells, and only nonpurified cells were covered with platelets and fibrin. Prostheses seeded with nonpurified cells showed an EC monolayer above a multilayer of myofibroblasts, prostheses seeded with purified cells only showed a single EC monolayer. Mixing experiments with human umbilical cord EC (HUVEC) and fibroblasts showed that when more than 25% HUVEC were present a confluent EC layer was formed. When the amount of fibroblasts was 25% or less, no development of a subendothelial multilayer of myofibroblasts was found within 3 weeks.

CONCLUSION

reduction of non-endothelial cell contamination of microvascular endothelial cell seeded grafts decreases thrombogenicity and might prevent seeding-related intimal hyperplasia.

The sac shrinking process after EAR does not start immediately in most patients

OBJECTIVE

the aim of this study was to determine the pattern of shrinkage after endovascular aneurysm repair (EAR) using logarithmic, exponential and linear models and to calculate a lag time is present.

PATIENTS AND METHODS

patients with a complete CTA follow-up of 2 years and a primary shrinking aneurysm were included, resulting in a study group of 29 patients. Six functions, logarithmic, exponential and linear, all with and without lag time, were fitted to the thrombus volume obtained from measurements postoperative and after 6, 12 and 24 months. The correlation coefficient was used to determine the association between the calculated and measured values. A correlation coefficient >0.95 was considered a good fit.

RESULTS

a logarithmic model produced the best fits. From the 29 patients, two patients could not be described by any model. The remaining 27 patients could be fitted using a logarithmic function with a correlation coefficient of >0.95 (median 0.99, range 0.95-1.00). Twenty-two of these patients had a lag time (median 63.4 days, range 5.8-252.3). Only five of the initial 44 patients (11%) showed immediate sac shrinkage.

CONCLUSION

almost all shrinkage processes could be described by a logarithmic function. In over 75% of patients a lag time to shrinkage could be calculated. In only a small proportion did the shrinking process start immediately after EAR.

Contaminants from the transplant contribute to intimal hyperplasia associated with microvascular endothelial cell seeding

OBJECTIVES

seeding prosthetic grafts with fat-derived microvascular endothelial cells (MVEC) results not only in a non-thrombogenic EC layer, but also in intimal hyperplasia. Here we investigated incidence, composition, progression, and cause of this intimal hyperplasia.

DESIGN

EPTFE grafts with MVEC were implanted as carotid interpositions in six dogs with 1 month, and in three dogs with 4, 8 and 12 months follow-up. Grafts seeded without cells, implanted in the contralateral carotid, served as a control. In another three dogs labelled cells were seeded to investigate the contribution of the seeded cells (2-3 weeks).

MATERIALS AND METHODS

MVEC were isolated from the falciform ligament. Cells were pressure seeded on ePTFE grafts. Labelling was performed using retroviral gene transduction. The grafts were analysed with immunohistochemical techniques.

RESULTS

after 1 month, all patent non-seeded grafts (5/6) showed fibrin and platelet deposition, and all patent seeded grafts (5/6) were covered with a confluent endothelial monolayer on top of a multilayer of myofibroblasts, elastin and collagen. After long term follow-up, all non-seeded grafts were occluded, all patent seeded grafts (4 and 12 months) were covered with an EC-layer with intimal hyperplasia underneath. The thickness of the intima did not progress after 1 month. Transduced cells were found in the endothelial monolayer, hyperplastic intima and luminal part of the prosthesis.

CONCLUSIONS

MVEC seeding in dogs results in intimal hyperplasia in all patent grafts, which contains myofibroblasts. Contaminants from the transplant contribute to this intimal hyperplasia.

[Spiral computed tomographic angiography as a substitute for intra-arterial angiography of aorta and its branches]

Until recently, intra-arterial angiography was the diagnostic method of first choice when pathology of the aorta or its branches was suspected. A disadvantage of this technique is that only the lumen of spaces with blood flow can be visualised and that the soft tissue surroundings remain (partly) invisible. Spiral computer tomographic angiography (CTA) has some major advantages compared with conventional angiography. The technique is less invasive and faster. Also, the soft tissue is imaged by CTA. In addition, computer reconstructions allow viewing from all directions without the limitations of overprojection. Spiral CTA is a suitable technique for imaging the thoracic part of the aorta: in case of dissection if transoesophageal echography is not available, in case of an aneurysm to determine the diameter and in case of rupture as a highly sensitive but not very specific examination technique. For imaging of the abdominal part of the aorta, spiral CTA may be considered. In case of an aneurysm or a possible rupture of this part of the aorta it is then possible to visualize the operation area and to choose the optimal approach. For the exclusion of stenoses in mesenteric arteries or in renal arteries, spiral CTA offers the advantage of non-invasivity. The technique is less suitable for demonstration of these stenoses and does not allow immediate intervention.

Cerebral Blood Flow in Relation to Contralateral Carotid Disease an MRA and TCD Study

OBJECTIVE

to describe redistribution of cerebral blood flow in patients with severe internal carotid artery (ICA) stenoses in relation to contralateral ICA disease.

METHODS

sixty-six patients scheduled for carotid endarterectomy (CEA) were grouped according to severity of contralateral stenosis (<30% [group I]; 30-69% [group II]; 70-99% [group III]; occlusion [group IV]. Transcranial Doppler (TCD) and magnetic resonance angiography (MRA) investigations were performed preoperatively.

RESULTS

TCD demonstrated a reversed flow in the contralateral anterior cerebral artery (A(1)segment) and ophthalmic artery in three-quarters of group IV patients (p <0.0001). Group IV patients also exhibited decreased blood flow velocity in the contralateral middle cerebral artery (p =0.001). MRA showed increased ipsilateral ICA and basilar artery (BA) blood flow volumes (Q-flows) in group IV patients when compared to the other groups (p <0.001). No changes in total Q-flow (ICAs+BA) were found.

CONCLUSIONS

in patients considered for CEA, the severity of the contralateral ICA disease is an important determinant of the pattern of blood flow redistribution through the anterior communicating pathway and ophthalmic artery. Significant flow redistribution through the posterior communicating pathway occurs especially in patients with contralateral ICA occlusion.

Concerns for the durability of the proximal abdominal aortic aneurysm endograft fixation from a 2-year and 3-year longitudinal computed tomography angiography study

OBJECTIVE

To provide a long-term perspective on the durability of the proximal abdominal aortic aneurysm endograft fixation from a single device series with perpendicular neck measurements in two groups of patients with complete 2- and 3-year follow-up.

DESIGN

This was a prospective study of postoperative, radiologic images.

SETTING

The study used a referral center, institutional practice, and ambulatory patients.

SUBJECTS

From January 1994 until May 1998, 37 endografts were implanted for abdominal aortic aneurysm. In the first postoperative year, there were four unrelated deaths and six conversions, leaving 27 patients with complete 24-month data and 13 with complete 36-month data.

MAIN OUTCOME MEASURE

Computed tomography angiograms were processed on a work station to measure the neck perpendicular to the central lumen line of the aorta. The surface area at the proximal endovascular anastomosis was recorded at each follow-up interval and related to the postoperative size at the same level.

RESULTS

Significant dilatation of the surface area was found: 20% (16% to 27%) at 24 months (c2 = 30; P < .001, Friedman) and 23% (18% to 28%) at 36 months (c2 = 27; P < .001, Friedman). This increase in neck size was continuous and linear, with a yearly rate of approximately 10% surface area; translated into diameter, this approximates 1 mm/y.

CONCLUSION

A continuous aortic enlargement of approximately 1 mm/y at the level of the proximal endovascular anastomosis was found. Because of the practice of oversizing the endograft relative to the infrarenal aortic neck, a loss of the endovascular seal may not become apparent until several years after endovascular abdominal aortic aneurysm repair is performed.

Early experience with intravascular ultrasound in evaluating the effect of statins on femoropopliteal arterial disease: hypothesis-generating observations in humans

The purpose of this study was to compare the vascular response seen with intravascular ultrasound (IVUS) at 1-year follow-up between statin-treated and non-statin-treated patients. Patients (n = 10) undergoing percutaneous transluminal angioplasty (PTA) of the femoropopliteal artery were studied with IVUS immediately after PTA and at 1-year follow-up. In nondilated matched vascular segments, the change in lumen, vessel, and plaque volume was assessed. In balloon-dilated matched vascular segments, the change in lumen, vessel, and plaque area was assessed. A comparison was made between statintreated (n = 5) and non-statin-treated patients (n = 5) in lumen, vessel, and plaque changes. At follow-up, both statin-treated and non-statin-treated patients showed a similar increase in plaque volume at the nondilated segment (+4% and +2%, respectively). In statin-treated patients the plaque volume increase was compensated by an increase in vessel volume (+2%), resulting in an increase in lumen volume (+1%). In non-statin-treated patients, on the other hand, the increase in plaque volume was associated with a decrease in vessel volume (-2%), resulting in a decrease in lumen volume (-4%). At the balloon-dilated segment a similar trend in changes of lumen, vessel, and plaque was encountered. Differences between both groups of patients were not statistically significant. Despite the nonsignificant nature of the observation, this small retrospective IVUS study may generate the hypothesis that statin therapy may contribute to superior long-term lumen dimensions by inducing positive vascular remodeling both in nondilated and balloon-dilated vascular segments.

Preoperative MRA flow quantification in CEA patients: flow differences between patients who develop cerebral ischemia and patients who do not develop cerebral ischemia during cross-clamping of the carotid artery

BACKGROUND AND PURPOSE

We sought to investigate whether preoperative volume flow in the internal carotid arteries (ICAs), the basilar artery (BA), and the middle cerebral arteries (MCAs) and collateral flow via the circle of Willis differ between patients who do and patients who do not develop cerebral ischemia during clamping of the carotid artery in carotid endarterectomy (CEA).

METHODS

Quantitative volume flow in the ICAs, BA, and MCAs and directional flow in the circle of Willis were measured preoperatively with 2-dimensional phase-contrast MR angiography in 86 CEA patients. During the operation, electroencephalographic (EEG) recordings were obtained that were monitored by a clinical neurophysiologist. Reference volume flow values were assessed in 24 control subjects.

RESULTS

In patients with an ICA stenosis without contralateral ICA occlusion (n=62), of whom 16% developed ischemic EEG changes during clamping, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (mean, 278 versus 160 mL/min; P:<0.05). Flow in the contralateral ICA (156 versus 273 mL/min; P:<0.01), flow in the BA (116 versus 165 mL/min; P:<0.05), and presence of collateral flow via the circle of Willis to the clamped ICA (0% versus 37%; P:<0.05) were significantly lower. MCA flow did not differ significantly between groups. Additionally, in patients with an ICA stenosis and a contralateral ICA occlusion (n=24), of whom 42% developed cerebral ischemia, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (309 versus 239 mL/min; P:<0.05). BA flow, MCA flow, and presence of willisian collateral flow (0% versus 14%) did not differ significantly between groups.

CONCLUSIONS

Preoperative volume flow in the clamped ICA is significantly higher in CEA patients with ischemic EEG changes during clamping than in CEA patients without such changes. The latter patients probably have better developed collateral pathways preoperatively.

Inter- and intraobserver variability of CT measurements obtained after endovascular repair of abdominal aortic aneurysms

OBJECTIVE

Important decisions are made on the basis of CT angiographic measurements of aneurysm size obtained after endovascular abdominal aortic aneurysm repair; however, little is known about the variability of these measurements. We evaluated the variability of CT angiographic measurements of aneurysm size obtained after endovascular abdominal aortic aneurysm repair.

MATERIALS AND METHODS

Thirty CT angiographic data sets were randomly chosen from 91 sets, including preoperative, postoperative, and follow-up CT images. All images were obtained according to a standardized acquisition protocol. On a workstation, three parameters were measured: maximum aneurysm diameter, maximum aneurysm cross-sectional area, and aneurysm volume. All data sets were measured twice by two investigators in a random order. The difference of each pair of measurements was plotted against the mean value. The mean difference and its standard deviation were calculated with a repeatability coefficient.

RESULTS

The intraobserver repeatability coefficient for observer 1 was 3.8 mm for diameter, 201.7 mm(2) for cross-sectional area, and 5.6 mL for volume. For observer 2, these figures were 3.0 mm, 219.0 mm(2), and 8.1 mL, respectively. The interobserver repeatability coefficients were 3.9 mm, 236.2 mm(2), and 10.3 mL.

CONCLUSION

Determination of the repeatability coefficient of aneurysm size measurements obtained after endovascular abdominal aortic aneurysm repair provides a good description of precision.

Three-dimensional intravascular ultrasound assessment of abdominal aortic aneurysm necks

PURPOSE

To document the accuracy of an automated analysis system for measuring lumen diameter and neck lengths of abdominal aortic aneurysms (AAAs) from intravascular ultrasound (IVUS) images and to describe additional features associated with 3-dimensional (3D) IVUS imaging.

METHODS

Twenty-two aortic aneurysms were studied with IVUS. Lumen diameters obtained using the automated analysis system were compared with manual measurements from axial IVUS scans, as were neck lengths obtained using automated analysis versus those measured with the aid of a displacement sensing device. Automated analyses were repeated by a second observer. Agreement was expressed as the coefficient of variation (CV).

RESULTS

Twenty proximal aortic, 6 distal aortic, and 3 iliac necks were available for analysis. Comparison between automated analysis and manual measurements for lumen diameter revealed a difference of 0.45 +/- 0.42 mm (mean +/- SD, Pearson's r = 0.99, p < 0.001, CV = 2.1%) and a difference of 0.05 +/- 0.12 cm (r = 0.99, p = 0.04, CV = 4.1%) for neck length. Interobserver difference for lumen diameter was 0.13 +/- 0.66 mm (r = 0.99, p < 0.001, CV = 3.4%) and 0.05 +/- 0.11 cm for length measurements (r = 0.99, p = 0.02, CV = 3.5%). The 3D IVUS imaging facilitated the identification of neck configuration.

CONCLUSIONS

Automated analysis of IVUS images allows accurate measurement of the lumen diameter of proximal and distal AAA necks and gives length measurements comparable to those of manual analysis. Longitudinal display of IVUS images aids in the elucidation of neck anatomy.

A simple technique to improve the accuracy of proximal AAA endograft deployment

PURPOSE

To report a technique for overcoming the positioning errors caused by angulation and rotation of the proximal aortic neck when anteroposterior fluoroscopic imaging is used during endograft deployment.

TECHNIQUE

Aortic neck angulation and rotation were measured preoperatively using spiral computed tomographic angiography in sagittal and axial projections. Before proximal graft deployment, the proximal end of the endograft was centered in the field of view, and the position of the C-arm was adjusted to the aortic neck angulation. Using this technique, optimal positioning of the endograft relative to the true position of the renal arteries can be achieved.

CONCLUSIONS

C-arm angulation and rotation is helpful in facilitating perfect positioning for an optimal seal between the endograft and the infrarenal aortic neck.

Maximal aneurysm diameter follow-up is inadequate after endovascular abdominal aortic aneurysm repair

BACKGROUND

follow-up after endovascular abdominal aortic aneurysm repair (EAR) generally consists of serial diameter measurements. A size change after EAR, however, is the consequence of alterations of the excluded aneurysm sac volume.

OBJECTIVE

to assess the agreement between diameter measurements and volume measurements after endovascular aneurysm repair.

PATIENTS AND METHODS

from 53 consecutive patients scheduled for EAR, follow-up of at least 6 months was available in 35 patients. CTA was performed on all patients at discharge, at 6 months and yearly thereafter. The resulting 113 datasets were processed on a workstation in a blinded and random order. Maximal aneurysm diameter (DMAX) was measured along the central lumen line. Total aneurysm volume was measured by manual segmentation. All measurements of an individual patient were compared with each other, resulting in 149 comparisons. The significance of individual size changes was classified based on the 95% confidence limits of the intra-observer variability, using difference-of-means analysis. DMAX changes were compared to volume changes.

RESULTS

in 37% of the comparisons, discordance was found between DMAX and volume measurements. A decrease in aneurysm size was missed using DMAX in 14% of cases and an increase in 19% of cases.

CONCLUSION

aneurysm size changes after EAR are not noticed using maximal diameter measurements in over one-third of cases.

Mortality and morbidity rates after conventional abdominal aortic aneurysm repair

AIM

To grade and analyse by levels of evidence the mortality and morbidity rates of elective abdominal aortic aneurysm (AAA) surgery as reported over the past 12 years.

METHODS

Articles on elective AAA surgery published between 1985 and 1996 were retrieved and classified into 5 levels of evidence. Level 1 contains prospective studies and is subdivided into population-based (Level 1a) and hospital-based (Level 1b) studies. Level 2 includes retrospective studies, subdivided into population-based (Level 2a), hospital-based (Level 2b), and hospital-based studies concerning a specified group of selected patients (Level 2c). Operative mortality and systemic and local/vascular complication rates and 95% confidence intervals were calculated per level of evidence.

RESULTS

Seventy-two articles describing a total of 37,654 patients could be included: 2 level 1a studies (patient total: 692), 9 Level 1b studies (patient total: 1,677), 13 Level 2a studies (patient total 21,409), 32 Level 2b studies (patient total: 12,019), and 16 Level 2c studies (patient total: 1,857). The mean 30-day mortality rates of the two population-based levels were similar: 8.2% (6.4%-10.6%) for the prospective (1a) and 7.4% (7.0%-7.7%) for the retrospective series (2a). These figures were significantly higher than the remarkably similar hospital-based mortality rates: 3.8% (3.0%-4.8%) for the prospective (1b), 3.8% (3.5%-4.2%) for the retrospective (2b), and 3.5% (2.8%-4.4%) for selected patient group studies (2c). The most frequent complication was of cardiac origin. In the population-based series the cardiac complication rate was 10.6% (8.5%-13.2%) and 11.1% (9.1%-13.6%) for Levels 1a and 2a respectively. This compared well with the 12.0% (10.5%-13.9%) for the prospective, hospital-based series (Level 1b). The cardiac complication rates in the retrospective, hospital-based studies was significantly lower: 8.9% (8.4%-9.5%) and 6.1% (4.9%-7.6%) for Levels 2b and 2c respectively.

CONCLUSION

There is a clear and consistent disagreement in reported mortality rates between hospital-based and population-based studies of elective AAA-surgery. Prospective studies give the best documentation of postoperative morbidity.

Dilatation of the proximal neck of infrarenal aortic aneurysms after endovascular AAA repair

OBJECTIVES

to assess size changes of the proximal aortic neck after endograft placement.

METHODS

since 1994, 54 consecutive patients have undergone abdominal aortic aneurysm (AAA) repair with the Endovascular Technologies (EVT) endograft. The study group comprised the 33 patients who had completed at least six months of the prospective follow-up protocol. The pre-, postoperative and follow-up helical computed tomography (CT) angiograms (CTAs) were processed on a workstation. The proximal neck dimensions were measured perpendicular to the central lumen line of the aortic neck. The cross-sectional area was measured at the proximal attachment system and at 1 cm proximal to the renal arteries.

RESULTS

while the dimensions of suprarenal aorta did not change, a significant dilatation of the proximal neck was found. The median increase was 10.3% at 6 months and 15.5% at 12 months. No correlation could be found between the amount of dilatation and pre- or postoperative neck-size, graft diameter and amount of graft-oversizing.

CONCLUSION

the infrarenal aortic neck demonstrates continued dilatation during follow-up after endograft placement.

The effect of bisoprolol on perioperative mortality and myocardial infarction in high-risk patients undergoing vascular surgery. Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography Study Group

BACKGROUND

Cardiovascular complications are the most important causes of perioperative morbidity and mortality among patients undergoing major vascular surgery.

METHODS

We performed a randomized, multicenter trial to assess the effect of perioperative blockade of beta-adrenergic receptors on the incidence of death from cardiac causes and nonfatal myocardial infarction within 30 days after major vascular surgery in patients at high risk for these events. High-risk patients were identified by the presence of both clinical risk factors and positive results on dobutamine echocardiography. Eligible patients were randomly assigned to receive standard perioperative care or standard care plus perioperative beta-blockade with bisoprolol.

RESULTS

A total of 1351 patients were screened, and 846 were found to have one or more cardiac risk factors. Of these 846 patients, 173 had positive results on dobutamine echocardiography. Fifty-nine patients were randomly assigned to receive bisoprolol, and 53 to receive standard care. Fifty-three patients were excluded from randomization because they were already taking a beta-blocker, and eight were excluded because they had extensive wall-motion abnormalities either at rest or during stress testing. Two patients in the bisoprolol group died of cardiac causes (3.4 percent), as compared with nine patients in the standard-care group (17 percent, P=0.02). Nonfatal myocardial infarction occurred in nine patients given standard care only (17 percent) and in none of those given standard care plus bisoprolol (P<0.001). Thus, the primary study end point of death from cardiac causes or nonfatal myocardial infarction occurred in 2 patients in the bisoprolol group (3.4 percent) and 18 patients in the standard-care group (34 percent, P<0.001).

CONCLUSIONS

Bisoprolol reduces the perioperative incidence of death from cardiac causes and nonfatal myocardial infarction in high-risk patients who are undergoing major vascular surgery.