Serious Failure Modes After EVAR Are Device Specific.

OBJECTIVES: Type I and III endoleaks following endovascular aneurysm repair (EVAR) can lead to catastrophic events that require major re-interventions. We reviewed our experience with aortic endograft re-interventions for type I and III endoleaks and other serious failures among different devices. METHODS: We retrospectively reviewed patients with a prior EVAR who underwent open conversion (OC) or major endovascular intervention (MEI) (re-lining, cuff/limb extension, parallel graft) for type I/III endoleaks at our institution from 2002 to 2019. Baseline characteristics, procedural details, re-interventions, and outcomes were collected. RESULTS: A total of 229 patients (194 men) underwent re-interventions for type I and III endoleaks after EVAR (90 OC, 139 MEI) for devices implanted between 1997 and 2019. Average age at re-intervention was 78±8.5 years. A total of 135 (59%) were implanted at our institution, whereas 93 (41%) were referred. Median time to re-intervention was 4 years with 25% to 75% interquartile range (IQR) of 2.2-6.6 years. There was no significant difference in baseline demographics or type of re-interventions (OC/MEI) between device types. 42/229 (18%) presented with ruptured aneurysms, 20/229 (9%) were symptomatic, whereas the rest presented with asymptomatic radiographic findings. Type 1A endoleak was present in 146/229 (63.8%-72 with proximal migration), type IB in 46/229 (20.1%), type IIIA in 37/229 (16.6%), type IIIB in 15/229 (6.5%), and persistent aneurysm sac growth with no radiographic evidence of an endoleak in 6/229 (2.6%). Devices included most commercial products: AFX, Excluder, AneuRx, Ancure, Endurant, and Zenith. A smaller number of investigational devices accounted for the rest. Type 1A endoleak was the most common indication for re-intervention among all devices except for AFX and ancure devices, proximal migration was a frequent presentation with AneuRx. AFX devices more frequently presented with a type III and ancure devices more frequently presented with a type IB endoleak. CONCLUSIONS: Serious failure modes after EVAR differ between endografts and occur throughout the follow-up period. This is important to guide targeted interrogation of surveillance studies and follow-up schedules, even for discontinued devices, as well as comparisons between various series and estimation of EVAR failure rates. CLINICAL IMPACT: Surveillance after EVAR is critical for long term success of the repair, understanding of the differential modes of failure of every graft available is important in the longitudinal evaluation of these endografts. Equally important is the understanding of the modes of failure of legacy endografts that are no longer on the market but still being followed, in order to be able to tailor a surveillance regiemn and the evntual repair if needed.

Choosing the correct treatment for acute aortic type B dissection.

Acute type B aortic dissection is a life threatening disease process, which remains a clinical dilemma despite advances in technology, surgical technique and postoperative management. The variability of presenting symptoms, lack of a consensus on indications for treatment and differing opinions about the optimal timing for repair have added to the management confusion. Medical management has been the standard of care for acute uncomplicated type B dissection. Surgical repair and endovascular intervention are reserved for those who present with, or subsequently develop, dissection-related complications. Complicated dissections occur in 25% of cases and may include organ malperfusion, aortic rupture, periaortic hematoma, and uncontrolled hypertension. In the past decade thoracic endovascular aortic repair (TEVAR) has gained widespread acceptance as the modality of choice for the treatment of complicated type B dissection. This transition is representative of advances in technology, physician experience with aortic endografts and lower morbidity and mortality rates associated with TEVAR. The best medical therapy remains the standard of care for uncomplicated dissection, however this strategy fails to prevent long-term aortic-related morbidity and mortality. Recent data suggest that early TEVAR lowers aortic-related events and improves long-term aortic specific survival by covering the entry tear, promoting false lumen thrombosis and inducing aortic wall remodeling. The paucity of supporting data has created controversy surrounding the optimal treatment strategy for acute type B dissection. Nonetheless, recent healthcare trends show a paradigm shift towards the utilization of early TEVAR in acute type B dissection.

Ruptured abdominal aortic aneurysms: is open surgery an outdated operation?

The advent of endovascular aneurysm repair (EVAR) has revolutionized the treatment of abdominal aortic aneurysms. EVAR has evolved into the preferred treatment for abdominal aortic aneurysms with suitable anatomy. Several randomized clinical trials have confirmed that EVAR reduces short-term morbidity and mortality. Despite vast improvements in diagnostic imaging, open surgical repair techniques and the care of critically ill patients over the past two decades rupture of abdominal aortic aneurysms still carries an extremely high morbidity and mortality. To improve outcomes in treatment of rAAA a movement has occurred away from open repair and toward EVAR as a paradigm shift that may help to improve otherwise dismal results. In the past 10 years, numerous studies including meta-analyses, administrative databases and randomized control trials have investigated the presumed advantages of EVAR over open repair. This review summarizes the world wide experience for ruptured AAA repair and addresses the role for standardization of care with the use of aortic aneurysm protocols.

Technical and patient-related characteristics associated with challenging retrieval of inferior vena cava filters.

OBJECTIVE: To identify patient-related and device-specific predictors of challenging and failed inferior vena cava (IVC) filter retrievals. METHODS: Retrospective single center review of consecutive retrievable IVC filters placed between 2004 and 2009. Retrieval was defined as challenging when it was unsuccessful owing to reported technical failure or when adjunctive endovascular maneuvers or access sites were recruited. Data regarding patient- and filter-specific information were collected. Logistic regression models were used to identify predictors of the reported outcomes. Statistical significance was set at p < .05. RESULTS: Four hundred and one patients underwent retrievable IVC filter placement-the majority indicated for prophylaxis (67%). Two hundred and fifty-nine retrievals were attempted and 237 filters were successfully retrieved (overall retrieval rate: 59.1%). Eleven out of 259 (4.2%) attempts were aborted owing to significant thrombus within the filter and 11 (4.2%) were technically unsuccessful. In 142 patients no attempt for filter retrieval was made-the major reason being physician oversight (44.3%). Thirty-eight out of 248 (15.3%) non-aborted filter retrievals were recorded as challenging. Failed retrievals were predicted by prolonged dwell time (96.9 ± 111.9 vs. 29.5 ± 25.1 days, odds ratio [OR] 1.034, 95% confidence interval [CI] 1.016-1.053, p < .001), therapeutic indication (OR 5.197, 95% CI 1.200-22.511, p = .028), and filter wall apposition (OR 11.857, 95% CI 2.069-67.968, p = .006). Challenging retrievals were predicted by dwell time (51.1 ± 69.8 vs. 29.1 ± 24.5 days, OR 1.017, 95% CI 1.005-1.029, p = .007), filter tilt (OR 2.607, 95% CI 1.045-6.508, p = .040) and filter wall apposition (OR 6.149, 95% CI 2.398-15.763, p = <.001). CONCLUSIONS: Physician oversight leads to poor IVC filter retrieval rates. Retrievals can be challenging or fail when the dwell time is >50 days and >90 days, respectively, and when the filter hook apposes the caval wall. Filter tilt increases retrieval difficulty but not failure rates.

Cryoplasty offers no advantage over standard balloon angioplasty for the treatment of in-stent stenosis.

In-stent restenosis is the primary failure mode of endovascular treatment of occlusive disease in the femeropopliteal segment. Cryoplasty has been proposed to reduce intimal hyperplasia through induction of apoptosis. We sought to evaluate the efficacy of cryoplasty for treatment of in-stent restenosis compared to conventional balloon angioplasty (CBA). After IRB approval, a retrospective record review was performed of reinterventions for in-stent restenosis by a single vascular surgery group at a university hospital. Reinterventions involving cryoplasty and CBA were evaluated at 1, 3, 6 and 12 months after intervention with duplex imaging to identify significant recurrent stenosis utilizing established velocity criteria. Data collected included basic demographic information and comorbidities as well as time to restenosis. Statistical analysis was performed using Kaplan­Meier survival curves with the log rank test, Wilcoxon rank test, and Cox proportional hazards models. From December 2004 to November 2007, 76 reinterventions were performed using CBA (n = 39) or cryoplasty (n = 37) for in-stent restenosis without placement of additional stents. Periprocedural technical success (>30% residual stenosis) was 100% for both groups, with no complications. The two cohorts were statistically similar in mean age, gender, comorbidities, tobacco use and use of statins, aspirin and Plavix. However, the mean lesion length was significantly longer in the cryoplasty cohort (CBA: 140.9 mm, Cyro: 191.7 mm; P = 0.032). The mean time to recurrent stenosis or need for additional secondary intervention was significantly shorter for the cyroplasty cohort than for the CBA, 4.09 and 10.79 months, respectively (P = .0001). Recurrent stenosis-free survival was significantly lower in the cyroplasty cohort at 3 months (CBA: 96.9%, Cyro: 88.9%) and 6 months (CBA: 84.0%, Cyro: 43.8%; P = .0089). Cyroplasty as a modality for treatment of in-stent stenosis in the femoropopliteal segment offers no benefit over CBA.

Carotid artery stenosis: what is left to surgery.

While carotid angioplasty and stenting has been clearly established as a minimally invasive alternative to endarterectomy for patients with carotid occlusive disease, its indications continue to evolve, being refined as more controlled data of large studies are being accumulated. The purpose of this article is to review the current evidence supporting the application of either technique in certain subsets of patients, and the relative contraindications for their use.

The Gore Excluder endograft device for the treatment of abdominal aortic aneurysms.

UNLABELLED: Open surgical repair on abdominal aortic aneurysms has been performed for many years with good RESULTS: Despite the many advances in medical care, the procedure is still associated with many complications. The Gore Excluder endograft is a third-generation endograft that became the third commercially available endograft approved in the United States. Data from multiple trials have compared the use of the Excluder endograft to open repair and have shown favorable RESULTS: This review shall summarize the clinical use of the Excluder endograft from its initial clinical trial in 1998 to its current commercial use.

Natural history of claudication: long-term serial follow-up study of 1244 claudicants.

OBJECTIVE: The purpose of this study was to delineate the natural history of claudication and determine risk factors for ischemic rest pain (IRP) and ischemic ulceration (IU) among patients with claudication. METHODS: We prospectively collected data on 1244 men with claudication during a 15-year period, including demographics, clinical risk factors, and ankle-brachial index (ABI). We followed these patients serially with ABIs, self-reported walking distance (WalkDist), and monitoring for IRP and IU. We used Kaplan-Meier and proportional hazards modeling to find independent predictors of IRP and IU. RESULTS: Mean follow-up was 45 months; statistically valid follow-up could be carried out for as long as 12 years. ABI declined an average of 0.014 per year. WalkDist declined at an average rate of 9.2 yards per year. The cumulative 10-year risks of development of IU and IRP were 23% and 30%, respectively. In multivariate analysis using several clinical risk factors, we found that only DM (relative risk [RR], 1.8) and ABI (RR, 2.2 for 0.1 decrease in ABI) predicted the development of IRP. Similarly, only DM (RR, 3.0) and ABI (RR, 1.9 for 0.1 decrease in ABI) were significant predictors of IU. CONCLUSION: This large serial study of claudication is, to our knowledge, the longest of its kind. We documented an average rate of ABI decline of 0.014 per year and a decline in WalkDist of 9.2 yards per year. Two clinical factors, ABI and DM, were found to be associated with the development of IRP and IU. Our findings may be useful in predicting the clinical course of claudication.

Exclusion of accessory renal arteries during endovascular repair of abdominal aortic aneurysms.

OBJECTIVE: Adequate proximal neck length is important for proper endovascular treatment of abdominal aortic aneurysms (AAAs). Placement of endografts in AAAs with relatively short proximal necks may require covering the origin of accessory renal arteries. Exclusion of these arteries carries the theoretical concern of regional renal ischemia associated with loss of parenchyma or worsening hypertension. We reviewed our experience with accessory renal exclusions during endovascular AAA repair to determine the frequency and severity of complications. METHODS: Complete records were available for review on 311 of 325 consecutive patients treated with endovascular grafts for AAAs from February 6, 1996, to March 15, 2001. The presence of accessory renal arteries was ascertained from preoperative/intraoperative aortography or from computed tomographic scanning. Sizes of the accessories were measured by using the main renal arteries as a reference. Considerations for excluding the accessory renal arteries were based on the likelihood of successful proximal attachment to healthy aorta, an accessory vessel whose size does not exceed the diameter of the main renal artery, and the absence of renal disease. RESULTS: The mean follow-up was 11.5 months. Fifty-two accessory renal arteries were documented in 37 patients (12%), ranging from 1 to > or =3 per patient. Of these, 26 accessory renal arteries were covered in 24 patients. Patients ranged in age from 57 to 85 years (mean, 74.1 years), with 20 men and 4 women. The Ancure device was used in 23 patients and the Excluder device in one. Of the accessories excluded, 22 originated above the aneurysm and 4 originated directly from the aneurysm itself. There were no perioperative mortalities. One patient died 5 months after surgery from an unrelated condition. There was one type I (distal) endoleak and no type II endoleaks. Five patients (21%) had segmental renal infarction associated with the side of accessory renal artery exclusion. Only one patient with segmental infarction had significant postoperative hypertension that resulted in changes in blood pressure medication. The blood pressure reverted to normal 3 months later. One patient with a stenotic left main renal artery required exclusion of the accessory renal artery for successful proximal attachment. Serum creatinine levels remained unchanged throughout follow-up in all but one patient, in whom progressive postoperative renal failure developed despite normal renal flow scan, presumably from intraoperative manipulation and contrast nephropathy. CONCLUSION: Exclusion of accessory renal arteries to facilitate endovascular AAA repair appears to be well tolerated. Long-term sequelae seem infrequent and mild.

Quality of life assessment in patients undergoing endovascular or conventional AAA repair.

PURPOSE: To compare health-related quality of life outcomes in a cohort of abdominal aortic aneurysm (AAA) patients treated concurrently with either a conventional or endoluminal intervention. METHODS: Between December 1997 and April 1999, 51 AAA patients treated by either open or endovascular techniques were enrolled in this prospective study. Conventional therapy was performed in 26 patients (19 men; mean age 70.4 +/- 6.0 years) with anatomical features unsuitable for the endovascular approach. Twenty-five patients (23 men; mean age 70.7 +/- 7.2 years) underwent endoluminal AAA exclusion using either the Ancure or bifurcated Enduring stent-grafts. The Medical Outcomes Study Short-Form 36-item health survey was administered preoperatively and at 1, 4, 8, and > or = 52 weeks after discharge. RESULTS: At 1 week, both groups showed significant reductions (p < 0.001) in mean scores compared to baseline in 4 dimensions (physical function, social function, role-physical, and vitality), but the decline was more pronounced in patients having open repair. Endoluminal patients returned to their baseline scores by the 4th postoperative week, whereas complete recovery to baseline in the conventional patients was delayed to the 8th week. CONCLUSIONS: Patients treated endoluminally exhibit better physical and functional scores as early as 1 week after discharge; they also return to baseline status significantly earlier than the conventional group. These findings document the perceived advantage of endovascular therapy over conventional AAA treatment.

Association of intraluminal thrombus in abdominal aortic aneurysm with local hypoxia and wall weakening.

PURPOSE: Our previous computer models suggested that intraluminal thrombus (ILT) within an abdominal aortic aneurysm (AAA) attenuates oxygen diffusion to the AAA wall, possibly causing localized hypoxia and contributing to wall weakening. The purpose of this work was to investigate this possibility. METHODS: In one arm of this study, patients with AAA were placed in one of two groups: (1) those with an ILT of 4-mm or greater thickness on the anterior surface or (2) those with little (< 4 mm) or no ILT at this site. During surgical resection but before aortic cross-clamping, a needle-type polarographic partial pressure of oxygen (PO2) electrode was inserted into the wall of the exposed AAA, and the PO2 was measured. The probe was advanced, and measurements were made midway through the thrombus and in the lumen. Mural and mid-ILT PO2 measurements were normalized by the intraluminal PO2 measurement to account for patient variability. In the second arm of this study, two AAA wall specimens were obtained from two different sites of the same aneurysm at the time of surgical resection: group I specimens had thick adherent ILT, and group II specimens had thinner or no adherent ILT. Nonaneurysmal tissue was also obtained from the infrarenal aorta of organ donors. Specimens were subjected to histologic, immunohistochemical, and tensile strength analyses to provide data on degree of inflammation (% area inflammatory cells), neovascularization (number of capillaries per high-power field), and tensile strength (peak attainable load). Additional specimens were subjected to Western blotting and immunohistochemistry for qualitative evaluation of expression of the cellular hypoxia marker oxygen-regulated protein. RESULTS: The PO2 measured within the AAA wall in group I (n = 4) and group II (n = 7) patients was 18% +/- 9% luminal value versus 60% +/- 6% (mean +/- SEM; P <.01). The normalized PO2 within the ILT of group I patients was 39% +/- 10% (P =.08 with respect to the group I wall value). Group I tissue specimens showed greater inflammation (P <.05) compared with both group II specimens and nonaneurysmal tissue: 2.9% +/- 0.6% area (n = 7) versus 1.7% +/- 0.3% area (n = 7) versus 0.2% +/- 0.1% area (n = 3), respectively. We found similar differences for neovascularization (number of vessels/high-power field), but only group I versus control was significantly different (P <.05): 16.9 +/- 1.6 (n = 7) vs 13.0 +/- 2.3 (n = 7) vs 8.7 +/- 2.0 (n = 3), respectively. Both Western blotting and immunohistochemistry results suggest that oxygen-regulated protein is more abundantly expressed in group I versus group II specimens. Tensile strength of group I specimens was significantly less (P <.05) than that for group II specimens: 138 +/- 19 N/cm2 (n = 7) versus 216 +/- 34 N/cm2 (n = 7), respectively. CONCLUSION: Our results suggest that localized hypoxia occurs in regions of thicker ILT in AAA. This may lead to increased, localized mural neovascularization and inflammation, as well as regional wall weakening. We conclude that ILT may play an important role in the pathology and natural history of AAA.

Adenovirus-mediated gene transfer of human inducible nitric oxide synthase in porcine vein grafts inhibits intimal hyperplasia.

OBJECTIVE: The aim of this study is to determine whether adenoviral inducible nitric oxide synthase (iNOS) gene transfer could inhibit intimal hyperplasia (IH) in porcine internal jugular veins interposed into the carotid artery circulation. METHODS: Porcine internal jugular veins were transduced passively with 1 x 10(11) particles of an adenoviral vector carrying either the human iNOS (AdiNOS) or beta-galactosidase (AdlacZ) cDNA for 30 minutes and then interposed into the carotid artery circulation. Segments of each vein graft were maintained in an ex vivo organ culture to measure nitrite accumulation, a marker of nitric oxide synthesis. The grafts were analyzed immunohistochemically for the presence of neutrophils, macrophages, and leukocytes by staining for myeloperoxidase, ED1, and CD45, respectively, at 3 (n = 4) and 7 (n = 4) days. Morphometric analyses and cellular proliferation (Ki67 staining) were assessed at 3 (n = 4), 7 (n = 4), and 21 days (n = 8). RESULTS: AdlacZ-treated vein grafts demonstrated high levels of beta-galactosidase expression at 3 days with a gradual decline thereafter. Nitrite production from AdiNOS-treated vein grafts was approximately fivefold greater than AdlacZ-treated grafts (P =.00001). AdiNOS or AdlacZ treatment was associated with minimal graft inflammation. Cellular proliferation rates were significantly reduced in AdiNOS-treated grafts as compared with controls at both 3 (41%, P =.000004) and 7 days (32%, P =.0001) after bypass. This early antiproliferative effect was most pronounced at the distal anastomosis (65%, P =.0005). The iNOS gene transfer reduced the intimal/medial area ratio in vein grafts at 7 (36%, P =.009) and 21 days (30%, P =.007) versus controls. This inhibition of IH was again more prominent in the distal segments of the grafts (P =.01). CONCLUSION: Adenovirus-mediated iNOS gene transfer to porcine internal jugular vein grafts effectively reduced cellular proliferation and IH. Although iNOS gene transfer reduced IH throughout the entire vein graft, the most pronounced effect was measured at the distal anastomosis. These results suggest potential for iNOS-based genetic modification of vein grafts to prolong graft patency.

Outcome events in patients with claudication: a 15-year study in 2777 patients.

OBJECTIVE: The purpose of this study was to delineate the natural history of claudication and determine risk factors for death. METHODS: We reviewed the key outcomes (death, revascularization, amputation) in 2777 male patients with claudication identified over 15 years at a Veterans Administration hospital with both clinical and noninvasive criteria. Patients with rest pain or ulcers were excluded. Data were analyzed with life-table and Cox hazard models. RESULTS: The mean follow-up was 47 months. The cohort exhibited a mortality rate of 12% per year, which was significantly (P <.05) more than the age-adjusted US male population. Among the deaths in which the cause was known, 66% were due to heart disease. We examined several baseline risk factors in a multivariate Cox model. Four were significant (P <.01) independent predictors of death: older age (relative risk [RR] = 1.3 per decade), lower ankle-brachial index (RR = 1.2 for 0.2 change), diabetes requiring medication (RR = 1.4), and stroke (RR = 1.4). The model can be used to estimate the mortality rate for specific patients. Surprisingly, a history of angina and myocardial infarction was not a significant predictor. Major and minor amputations had a 10-year cumulative rate less than 10%. Revascularization procedures occurred with a 10-year cumulative rate of 18%. CONCLUSIONS: We found a high mortality rate in this large cohort and four independent risk factors that have a large impact on survival. Risk stratification with our model may be useful in determining an overall therapeutic plan for claudicants. A history of angina and myocardial infarction was not a useful predictor of death, suggesting that many patients in our cohort presented with claudication before having coronary artery symptoms. Our data also indicate that claudicants have a low risk of major amputation at 10-year follow-up.

Is proximal aortic neck dilatation after endovascular aneurysm exclusion a cause for concern?

PURPOSE: The purpose of this study was to evaluate the extent and frequency of dilatation of the proximal aortic neck over time after endovascular exclusion of abdominal aortic aneurysms and the effect on the continued integrity of the repair. METHODS: Patients enrolled in the multicenter tube and bifurcated trials of the Guidant-Endovascular Technologies Ancure endografting system and at least 1 year of follow-up were reviewed. Neck diameter measurements were obtained from computed tomography scans that were obtained with and without contrast by an independent core laboratory facility. The diameter was considered to be the minor axis of the first slice at which point at least one half of the proximal attachment frame was located. A change exceeding 2.5 mm was considered to be significant. RESULTS: At 1 year, 13% of the patients (42/314 patients) showed evidence of proximal neck dilatation, with a mean diameter increase of 4.8 +/- 2.4 mm. The proportion of patients with dilatation increased to 21% at 2 years (48/226 patients) and 19% at 3 years (11/59 patients). The initial presence of an endoleak, the neck length, and the aneurysm size had no clear effect on the development of neck enlargement. Initial neck diameter was inversely related to and the strongest predictor of later dilatation. Graft oversizing was not an independent predictor of neck dilatation on multivariate analysis. Only one migration of the proximal attachment system was observed during follow-up. CONCLUSION: Most proximal aortic necks remain stable, but approximately 20% of necks increase in diameter by 2 years. Smaller necks dilate more often than larger ones. This effect is independent from the frequent oversizing of grafts in smaller necks. The integrity of the repair remains good at 3 years of follow-up.

The Ancure endografting system: an update.

The Ancure endografting system (Guidant Cardiac and Vascular Division, Menlo Park, Calif) features a unibody, nonsupported woven polyester graft designed to treat abdominal aortic aneurysms. It is constructed in tube, bifurcated, and aortoiliac configurations. The attachment system consists of a frame with four independent V-shaped double hooks that penetrate the arterial wall for fixation. There are separate attachment systems at the proximal and distal ends of the endoprosthesis. In September 1999, the Food and Drug Administration (FDA) approved the tube and bifurcated devices for general use. The aortoiliac device is under present consideration of the FDA. Phase II and III clinical trials of the system enrolled over 870 patients from the end of 1995 to the summer of 1999. The device was deployed successfully in 90% to 96% of cases, depending on the configuration and the phase of the trial. Mortality rates were similar to those of concurrent open surgical control rates, but serious morbidity was reduced. Long-term follow-up of the bifurcated group from phase II showed only one migration and no ruptures. Aneurysm size reduction in this group was noted in 51.3% of patients at 1 year and 68.5% at 2 years. In the same subset, type I endoleaks were noted in 2.7% at 1 year and 1.3% at 2 years. All postoperative imaging studies were reviewed by a core laboratory facility. The advantages of the ancure system include solid fixation, flexibility in accommodating morphologic changes, and excellent long-term clinical performance. The disadvantages include a large introducer system and the potential for limb obstruction by compression or angulation. However, limb compromise responds well to intraluminal stenting. The expected FDA approval of the aortoiliac device and a larger variety of graft sizes should expand the number of patients who can be treated with this system.

Mechanical properties and microstructure of intraluminal thrombus from abdominal aortic aneurysm.

Accurate estimation of the wall stress distribution in an abdominal aortic aneurysm (AAA) may prove clinically useful by predicting when a particular aneurysm will rupture. Appropriate constitutive models for both the wall and the intraluminal thrombus (ILT) found in most AAA are necessary for this task. The purpose of this work was to determine the mechanical properties of ILT within AAA and to derive a more suitable constitutive model for this material. Uniaxial tensile testing was carried out on 50 specimens, including 14 longitudinally oriented and 14 circumferentially oriented specimens from the luminal region of the ILT, and 11 longitudinally oriented and 11 circumferentially oriented specimens from the medial region. A two-parameter, large-strain, hyperelastic constitutive model was developed and used to fit the uniaxial tensile testing data for determination of the material parameters. Maximum stiffness and strength were also determined from the data for each specimen. Scanning electron microscopy (SEM) was conducted to study the regional microstructural difference. Our results indicate that the microstructure of ILT differs between the luminal, medial, and abluminal regions, with the luminal region stronger and stiffer than the medial region. In all cases, the constitutive model fit the experimental data very well (R2>0.98). No significant difference was found for either of the two material parameters between longitudinal and circumferential directions, but a significant difference in material parameters, stiffness, and strength between the laminal and medial regions was determined (p<0.01). Therefore, our results suggest that ILT is an inhomogeneous and possibly isotropic material. The two-parameter, hyperelastic, isotropic, incompressible material model derived here for ILT can be easily incorporated into finite element models for simulation of wall stress distribution in AAA.

Is color-flow duplex a good diagnostic test for detection of isolated calf vein thrombosis in high-risk patients?

Color-flow duplex scanning (CDS) is a good diagnostic test for lower extremity proximal deep vein thrombosis (DVT). This report aims to evaluate the diagnostic accuracy of CDS in detecting isolated calf DVT in two in-hospital populations. A total of 166 patients had routine DVT testing with both CDS and venography: 99 total joint arthroplasty patients and 67 symptomatic in-hospital patients. Isolated calf DVT was noted in 34% of arthroplasty patients and 12% of symptomatic in-hospital patients. Peroneal DVT was most common. The sensitivity, specificity, positive predictive value, and negative predictive value (with 95% confidence interval [CI]) of CDS in detecting isolated calf DVT in the symptomatic in-hospital group was 39% (16%-62%), 98% (94%-99%), 88% (65%-99%), and 81% (71%-91%), respectively. In the arthroplasty patients these values were 13% (3%-23%), 92% (85%-99%), 60% (30%-90%), and 55% (45%-65%), respectively. CDS has a low sensitivity in detecting isolated calf DVT among hospitalized patients and cannot be deemed an effective tool for identifying clots limited to only one or two tibial vessels.

Is routine use of the intensive care unit after elective infrarenal abdominal aortic aneurysm repair necessary?

INTRODUCTION: Postoperative care after infrarenal abdominal aortic aneurysm (AAA) repair has traditionally involved admission to the intensive care unit (ICU). With the advent of endovascular AAA repair, the management of open procedures has received increased scrutiny. We recently modified our AAA clinical pathway to include selective use of the ICU. METHODS: Consecutive elective infrarenal AAA repairs performed by members of the vascular surgery division at a university medical center from 1994 to 1999 were analyzed retrospectively with a computerized database, the Medical Archival Retrieval System. Group I consisted of 245 patients who were treated in the ICU for 1 or more days, and Group II included 69 patients admitted directly to the floor. Ruptured, symptomatic, suprarenal, endovascular, and reoperative repairs were excluded. Outcome variables were compared over the 6-year period. RESULTS: Floor admissions increased over the study period with 0%, 0%, 3.3%, 16.3%, 48.6%, and 43.6% of patients admitted directly to the surgery ward from 1994 to 1999. The average ICU length of stay declined from 4.6 to 1.2 days, whereas the hospital length of stay decreased from 12.5 to 6.8 days from 1994 to 1999. The change in ICU use had no effect on death (2.4% in Group I vs 0% in Group II). Major and minor morbidity was comparable. Hospital charges were significantly lower for patients in Group II. CONCLUSION: A policy of selective utilization of the ICU after elective infrarenal AAA repair is safe. It can reduce resource use without a negative impact on the quality of care.

Long-term fate of the aneurysmal sac after endoluminal exclusion of abdominal aortic aneurysms.

PURPOSE: Shrinkage of an abdominal aortic aneurysm (AAA) is the hallmark of successful endoluminal treatment. Our goal was to prospectively assess the midterm to long-term shrinkage of the AAA sac after endovascular repair. METHODS: A total of 123 patients with AAA underwent endoluminal treatment with the Ancure device at our institution between February 1996 and February 2000. At least a 1-year follow-up was available for 70 of the 123 patients. AAA sac size, presence of endoleaks, calcifications, and outcome data were collected on these patients at 6, 12, 24, and 36 months after repair and compared with the preoperative AAA size and characteristics. All endoleaks found at the 6-month follow-up visit were treated aggressively with embolotherapy. An AAA sac regression of 0.5 cm or more was considered the minimum measurable decrease. Regression of the sac diameter to 3.5 cm or less was considered a complete collapse of the sac. RESULTS: Successful endoluminal repair was accomplished in 119 of 123 patients. The mortality rate was 0.8% (1/123). There was a steady decrease in AAA sac size from baseline (5.56 +/- 0.1 cm), to 6 months (5.0 +/- 0.14 cm, P =.0006), to 12 months (4.65 +/- 0.13 cm, P =.04), and to 24 months (4.26 +/- 0.16 cm, P =.03). At 24 months, 74% (29/39) had a decrease in sac size of 0.5 cm or more, with 28% (11/39) complete collapse. Patients with initial endoleaks had the same likelihood of regression of sac size (> or = 0.5 cm) when compared with the group of patients with no endoleaks at the 24-month evaluation (64% vs 76%, P =.09). CONCLUSION: Endoluminal AAA repair resulted in a significant reduction in sac size that continues up to 2 years. Significant shrinkage occurs as early as 6 months after placement. The initial presence of endoleaks does not predict the lack of sac regression.