Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) in Uncomplicated Type B Aortic Dissection: Study Design and Rationale

Purpose

To describe the design and methodological approach of a multicenter, retrospective study to externally validate a clinical and imaging-based model for predicting the risk of late adverse events in patients with initially uncomplicated type B aortic dissection (uTBAD).

Materials and Methods

The Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) is a collaboration between 10 academic aortic centers in North America and Europe. Two centers have previously developed and internally validated a recently developed risk prediction model. Clinical and imaging data from eight ROADMAP centers will be used for external validation. Patients with uTBAD who survived the initial hospitalization between January 1, 2001, and December 31, 2013, with follow-up until 2020, will be retrospectively identified. Clinical and imaging data from the index hospitalization and all follow-up encounters will be collected at each center and transferred to the coordinating center for analysis. Baseline and follow-up CT scans will be evaluated by cardiovascular imaging experts using a standardized technique.

Results

The primary end point is the occurrence of late adverse events, defined as aneurysm formation (≥6 cm), rapid expansion of the aorta (≥1 cm/y), fatal or nonfatal aortic rupture, new refractory pain, uncontrollable hypertension, and organ or limb malperfusion. The previously derived multivariable model will be externally validated by using Cox proportional hazards regression modeling.

Conclusion

This study will show whether a recent clinical and imaging-based risk prediction model for patients with uTBAD can be generalized to a larger population, which is an important step toward individualized risk stratification and therapy.Keywords: CT Angiography, Vascular, Aorta, Dissection, Outcomes Analysis, Aortic Dissection, MRI, TEVAR© RSNA, 2022See also the commentary by Rajiah in this issue.

Impact of the COVID-19 pandemic on surgical care in the Netherlands

BACKGROUND

The COVID-19 pandemic caused disruption of regular healthcare leading to reduced hospital attendances, repurposing of surgical facilities, and cancellation of cancer screening programmes. This study aimed to determine the impact of COVID-19 on surgical care in the Netherlands.

METHODS

A nationwide study was conducted in collaboration with the Dutch Institute for Clinical Auditing. Eight surgical audits were expanded with items regarding alterations in scheduling and treatment plans. Data on procedures performed in 2020 were compared with those from a historical cohort (2018-2019). Endpoints included total numbers of procedures performed and altered treatment plans. Secondary endpoints included complication, readmission, and mortality rates.

RESULTS

Some 12 154 procedures were performed in participating hospitals in 2020, representing a decrease of 13.6 per cent compared with 2018-2019. The largest reduction (29.2 per cent) was for non-cancer procedures during the first COVID-19 wave. Surgical treatment was postponed for 9.6 per cent of patients. Alterations in surgical treatment plans were observed in 1.7 per cent. Time from diagnosis to surgery decreased (to 28 days in 2020, from 34 days in 2019 and 36 days in 2018; P < 0.001). For cancer-related procedures, duration of hospital stay decreased (5 versus 6 days; P < 0.001). Audit-specific complications, readmission, and mortality rates were unchanged, but ICU admissions decreased (16.5 versus 16.8 per cent; P < 0.001).

CONCLUSION

The reduction in the number of surgical operations was greatest for those without cancer. Where surgery was undertaken, it appeared to be delivered safely, with similar complication and mortality rates, fewer admissions to ICU, and a shorter hospital stay.

Multicenter Experience of Upper Extremity Access in Complex Endovascular Aortic Aneurysm Repair

PURPOSE

Upper extremity access (UEA) for antegrade cannulation of aortic side branches is a relevant part of endovascular treatment of complex aortic aneurysms and can be achieved using several techniques, sites and sides. The purpose of this study was to evaluate different UEA strategies in a multicenter registry of complex endovascular aortic aneurysm repair (EVAR).

METHODS

In six aortic centers in the Netherlands, all endovascular aortic procedures from 2006 to 2019 were retrospectively reviewed. Patients who received upper extremity access during complex EVAR were included. Primary outcome was a composite endpoint of any access complication, excluding minor hematomas. Secondary outcomes were access characteristics, access complications considered individually, access reinterventions and incidence of ischemic cerebrovascular events.

RESULTS

417 patients underwent 437 UEA for 303 fenestrated/branched EVARs, and 114 chimney EVARs. Twenty patients had bilateral, 295 left-sided, and 102 right-sided UEA. 413 approaches were performed surgically and 24 percutaneously. Distal brachial access was used in 89 cases, medial brachial in 149, proximal brachial in 140 and axillary access in 59 cases. No significant differences regarding the composite endpoint of access complications were seen (DBA 11.3% vs. MBA 6.7% vs. PBA 13.6% vs. AA 10.2%; p=.29). Postoperative neuropathy occurred most after proximal brachial access (DBA 1.1% vs. MBA 1.3% vs. PBA 9.3 % vs. AA 5.1%; p=.003). There were no differences in cerebrovascular complications between access sides (right 5.9% vs. left 4.1% vs. bilateral 5%; p=.75). Significantly more overall access complications were seen after a percutaneous approach (29.2% vs. 6.8%; p=.002). In multivariate analysis the risk for access complications after open approach was decreased by male gender (OR 0.27; CI 95% 0.10 - 0.72; p= .009), while an increase in age per year (OR 1.08; CI 95% 1.004 - 1.179; p=.039) and diabetes mellitus type 2 (OR 3.70; CI 95% 1.20 - 11.41; p= .023) increased the risk.

CONCLUSION

Between the four access localizations, there were no differences in overall access complications. Female gender, diabetes mellitus type 2 and ageing increased the risk for access complications after surgical approach. Furthermore, a percutaneous upper extremity access resulted in higher complication rates than a surgical approach.

Magnetic resonance imaging contrast-enhancement with superparamagnetic iron oxide nanoparticles amplifies macrophage foam cell apoptosis in human and murine atherosclerosis

AIMS

(Ultra) Small superparamagnetic iron oxide nanoparticles, (U)SPIO, are widely used as magnetic resonance imaging contrast media and assumed to be safe for clinical applications in cardiovascular disease. As safety tests largely relied on normolipidaemic models, not fully representative of the clinical setting, we investigated the impact of (U)SPIOs on disease-relevant endpoints in hyperlipidaemic models of atherosclerosis.

METHODS AND RESULTS

RAW264.7 foam cells, exposed in vitro to ferumoxide (dextran-coated SPIO), ferumoxtran (dextran-coated USPIO), or ferumoxytol [carboxymethyl (CM) dextran-coated USPIO] (all 1 mg Fe/mL) showed increased apoptosis and reactive oxygen species accumulation for ferumoxide and ferumoxtran, whereas ferumoxytol was tolerated well. Pro-apoptotic (TUNEL+) and pro-oxidant activity of ferumoxide (0.3 mg Fe/kg) and ferumoxtran (1 mg Fe/kg) were confirmed in plaque, spleen, and liver of hyperlipidaemic ApoE-/- (n = 9/group) and LDLR-/- (n = 9-16/group) mice that had received single IV injections compared with saline-treated controls. Again, ferumoxytol treatment (1 mg Fe/kg) failed to induce apoptosis or oxidative stress in these tissues. Concomitant antioxidant treatment (EUK-8/EUK-134) largely prevented these effects in vitro (-68%, P < 0.05) and in plaques from LDLR-/- mice (-60%, P < 0.001, n = 8/group). Repeated ferumoxtran injections of LDLR-/- mice with pre-existing atherosclerosis enhanced plaque inflammation and apoptosis but did not alter plaque size. Strikingly, carotid artery plaques of endarterectomy patients who received ferumoxtran (2.6 mg Fe/kg) before surgery (n = 9) also showed five-fold increased apoptosis (18.2 vs. 3.7%, respectively; P = 0.004) compared with controls who did not receive ferumoxtran. Mechanistically, neither coating nor particle size seemed accountable for the observed cytotoxicity of ferumoxide and ferumoxtran.

CONCLUSIONS

Ferumoxide and ferumoxtran, but not ferumoxytol, induced apoptosis of lipid-laden macrophages in human and murine atherosclerosis, potentially impacting disease progression in patients with advanced atherosclerosis.

Association of Hospital Volume with Perioperative Mortality of Endovascular Repair of Complex Aortic Aneurysms: A Nationwide Cohort Study

OBJECTIVE

We evaluate nationwide perioperative outcomes of complex EVAR and assess the volume-outcome association of complex EVAR.

SUMMARY OF BACKGROUND DATA

Endovascular treatment with fenestrated (FEVAR) or branched (BEVAR) endografts is progressively used for excluding complex aortic aneurysms (complex AAs). It is unclear if a volume-outcome association exists in endovascular treatment of complex AAs (complex EVAR).

METHODS

All patients prospectively registered in the Dutch Surgical Aneurysm Audit who underwent complex EVAR (FEVAR or BEVAR) between January 2016 and January 2020 were included. The effect of annual hospital volume on perioperative mortality was examined using multivariable logistic regression analyses. Patients were stratified into quartiles based on annual hospital volume to determine hospital volume categories.

RESULTS

We included 694 patients (539 FEVAR patients, 155 BEVAR patients). Perioperative mortality following FEVAR was 4.5% and 5.2% following BEVAR. Postoperative complication rates were 30.1% and 48.7%, respectively. The first quartile hospitals performed <9 procedures/yr; second, third, and fourth quartile hospitals performed 9-12, 13-22, and ≥23 procedures/yr. The highest volume hospitals treated the significantly more complex patients. Perioperative mortality of complex EVAR was 9.1% in hospitals with a volume of < 9, and 2.5% in hospitals with a volume of ≥13 (P = 0.008). After adjustment for confounders, an annual volume of ≥13 was associated with less perioperative mortality compared to hospitals with a volume of < 9.

CONCLUSIONS

Data from this nationwide mandatory quality registry shows a significant effect of hospital volume on perioperative mortality following complex EVAR, with high volume complex EVAR centers demonstrating lower mortality rates.

Assessment of behavioral determinants influencing success of supervised exercise therapy in patients with intermittent claudication: A cross sectional survey

BACKGROUND

Supervised exercise therapy is the first step in treatment of intermittent claudication. However, adherence to supervised exercise therapy is low. Limited access and reimbursement issues are known reasons, though lack of motivation is often leading. Behavioral determinants influencing motivation and thus adherence to supervised exercise therapy remain to be investigated. In this study we sought to determine which behavioral determinants would be of influence on the long-term adherence of supervised exercise therapy.

METHODS

200 patients, newly diagnosed with peripheral arterial disease Rutherford classification II-III, were sent a questionnaire to assess motivation and behavior with regard to supervised exercise therapy. The questionnaire was constructed using the I-CHANGE model for explaining motivational and behavioral change. Baseline characteristics were acquired from medical records. Alpha Cronbach's was calculated to test reliability of the questionnaire.

RESULTS

108 (54%) patients returned their questionnaire. A total of 79% patients followed supervised exercise therapy. Patients who increased their walking distance after supervised exercise therapy have significantly greater knowledge (p = 0.05), positive attitude (p = 0.03) and lower negative attitude (p = 0.01). Patients with a higher self-efficacy remained significantly more active after participating in supervised exercise therapy (p = 0.05).

CONCLUSION

Increasing the determinants knowledge, attitude and self-efficacy will improve adherence to supervised exercise therapy and result in delayed claudication onset time.

Cerebrovascular Complications After Upper Extremity Access for Complex Aortic Interventions: A Systematic Review and Meta-Analysis

PURPOSE

The purpose of this study was to review the risk of developing cerebrovascular complications from upper extremity access during endovascular treatment of complex aortic aneurysms.

METHODS

A systematic review and meta-analysis were conducted according to the PRISMA guideline. An electronic search of the public domains Medline (PubMed), Embase (Ovid), Web of Science and Cochrane Library was performed to identify studies related to the treatment of aortic aneurysms involving upper extremity access. Meta-analysis was used to compare the rate of cerebrovascular event after left, right and bilateral upper extremity access. Results are presented as relative risk (RR) and 95% confidence intervals (CIs).

RESULTS

Thirteen studies including 1276 patients with complex endovascular treatment of aortic aneurysms using upper extremity access were included in the systematic review. Left upper extremity access (UEA) was used in 1028 procedures, right access in 148 and bilateral access in 100 procedures. The rate of cerebrovascular complications for patients treated through left UEA was 1.7%, through right UEA 4% and through bilateral UEA 5%. In the meta-analysis, we included seven studies involving 645 patients treated with a left upper extremity access, 87 patients through a right and 100 patients through a bilateral upper extremity access. Patients, who underwent right-sided (RR 5.01, 95% CI 1.51-16.58, P = 0.008) or bilateral UEA (RR 4.57, 95% CI 1.23-17.04, P = 0.02), had a significantly increased risk of cerebrovascular events compared to those who had a left-sided approach.

CONCLUSION

Left upper extremity access is associated with a significantly lower rate of cerebrovascular complications as compared to right or bilateral upper extremity access.

A Stopped Pilot Study of the ProGlide Closure Device After Transbrachial Endovascular Interventions

Purpose: To evaluate the feasibility and safety of the suture-mediated ProGlide device in closure of the brachial artery after endovascular interventions. Materials and Methods: From 2016 to 2017, a pilot study was performed using the ProGlide to achieve hemostasis after percutaneous access of distal brachial arteries >4 mm in diameter. In an interim analysis, the results were compared to a matched control group taken from a 60-patient historical cohort who underwent brachial artery access and manual compression to achieve hemostasis between 2014 and 2017. The primary outcome was access-related reintervention and the secondary outcome was the incidence of access-site complications. Results: Seven patients (mean age 67.9 years; 6 men) were enrolled in the study before it was stopped in 2017. Four patients experienced 6 access-site complications (neuropathy, hematoma, occlusion, and pseudoaneurysm). These resulted in 3 access-related reinterventions: surgical evacuation of a hematoma, thrombectomy of the occluded brachial artery, and surgical repair of the pseudoaneurysm. In the interim comparison to the 19 matched patients (mean age 61.9 years; 6 men), the ProGlide group had proportionally more patients experiencing access-related complications (57% vs 16% for manual compression, p=0.035) and resultant reinterventions (43% vs 11%, p=0.064). Based on this data the trial was stopped. Conclusion: Considering this experience, it is not advisable to use the ProGlide in transbrachial endovascular interventions due to the high incidence of complications and access-related reinterventions.

Quality of life from a randomized trial of open and endovascular repair for abdominal aortic aneurysm

Background

Long-term survival is similar after open or endovascular repair of abdominal aortic aneurysm. Few data exist on the effect of either procedure on long-term health-related quality of life (HRQoL) and health status.

Methods

Patients enrolled in a multicentre randomized clinical trial (DREAM trial; 2000–2003) in Europe of open repair versus endovascular repair (EVAR) of abdominal aortic aneurysm were asked to complete questionnaires on health status and HRQoL. HRQoL scores were assessed at baseline and at 13 time points thereafter, using generic tools, the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36®) and EuroQol 5D (EQ-5D™). Physical (PCS) and mental component summary scores were also calculated. Follow-up was 5 years.

Results

Some 332 of 351 patients enrolled in the trial returned questionnaires. More than 70 per cent of questionnaires were returned at each time point. Both surgical interventions had a short-term negative effect on HRQoL and health status. This was less severe in the EVAR group than in the open repair group. In the longer term the physical domains of SF-36® favoured open repair: mean difference in PCS score between open repair and EVAR −1·98 (95 per cent c.i. −3·56 to −0·41). EQ-5D™ descriptive and EQ-5D™ visual analogue scale scores for open repair were also superior to those for EVAR after the initial 6-week interval: mean difference −0·06 (−0·10 to −0·02) and −4·09 (−6·91 to −1·27) respectively.

Conclusion

In this study EVAR appeared to be associated with less severe disruption to HRQoL and health status in the short term. However, during longer-term follow-up to 5 years, patients receiving open repair appeared to have improved quality of life and health status.

Diagnostic algorithms and treatment strategies in primary aortic and aortic graft infections

Aortic infections and aortic graft infections are one of the most dreadful clinical entities that a vascular surgeon can face. Clinical presentation of the patient can vary greatly and diagnosis can be difficult to make. In this manuscript, diagnostic modalities are reviewed and a diagnostic algorithm suggested. Further, results of present treatment options are evaluated and treatment strategies for different clinical scenarios suggested.

Spinal cord function monitoring during endovascular treatment of thoracoabdominal aneurysms: implications for staged procedures

AIM

Spinal cord ischemia is a well-known complication in the treatment of thoracoabdominal aneurysms (TAAA). Despite the fact that endovascular treatment of TAAA is less invasive, spinal cord ischemia rate is not reduced if compared to open repair.

METHODS

We report the results of our experience of spinal cord function monitoring by measuring motor evoked potentials (MEP) during endovascular treatment of TAAA type II and III. Depending on the level of the MEPs the decision is made whether to stage the procedure or not. We treated ten patients according to this protocol.

RESULTS

In two patients, MEPs decreased 50% or more and procedures were staged. Both experienced no neurological complications after first and second procedure. No MEPs decrease was seen during the second procedures. One of the other eight patients had a temporary right lower leg pararesis.

CONCLUSION

In conclusion we state that our first experience demonstrates the value of assessing spinal cord function during extensive endovascular TAAA repair with subsequent strategies to prevent paraplegia.

Endothelial cells (ECs) for vascular tissue engineering: venous ECs are less thrombogenic than arterial ECs

Primary endothelial cells (ECs) are the preferred cellular source for luminal seeding of tissue-engineered (TE) vascular grafts. Research into the potential of ECs for vascular TE has focused particularly on venous rather than arterial ECs. In this study we evaluated the functional characteristics of arterial and venous ECs, relevant for vascular TE. Porcine ECs were isolated from femoral artery (PFAECs) and vein (PFVECs). The proliferation rate was comparable for both EC sources, whereas migration, determined through a wound-healing assay, was less profound for PFVECs. EC adhesion was lower for PFVECs on collagen I, measured after 10 min of arterial shear stress. Gene expression was analysed by qRT-PCR for ECs cultured under static conditions and after exposure to arterial shear stress and revealed differences in gene expression, with lower expression of EphrinB2 and VCAM-1 and higher levels of vWF and COUP-TFII in PFVECs than in PFAECs. PFVECs exhibited diminished platelet adhesion under flow and cell-based thrombin generation was delayed for PFVECs, indicating diminished tissue factor (TF) activity. After stimulation, prostacyclin secretion, but not nitric oxide (NO), was lower in PFVECs. Our data support the use of venous ECs for TE because of their beneficial antithrombogenic profile.

Coagulation on endothelial cells: the underexposed part of Virchow's Triad

The process of thrombin generation involves numerous plasma proteases and cofactors. Interaction with the vessel wall, in particular endothelial cells (ECs), influences this process but data on this interaction is limited. We evaluated thrombin generation on EA.hy926, human coronary arterial ECs (HCAECs) and patient-derived human venous ECs (HVECs) by means of a modified calibrated automated thrombogram (CAT) method and especially looked into contribution of the intrinsic and extrinsic pathways. Thrombin generation was measured in presence of confluent ECs with normal pooled and factor XII-deficient (FXII-deficient) platelet-poor plasma, with/without active site inhibited factor VIIa (ASIS) to block the extrinsic pathway and corn trypsin inhibitor for blocking contact activation (intrinsic pathway). Fetal bovine serum (FBS) was removed from culture conditions as FXIIa from the serum retained on ECs apparently, thereby inducing strong contact activation. In serum-free conditions, EA.hy926 and patient-derived HVECs induced thrombin generation mainly via the contact activation pathway with minor influence of ASIS on peak height and very low thrombin generation curves in FXII-deficient plasma. HVECs derived from coronary arterial bypass graft (CABG) patients showed increased thrombin generation compared to control patients, which could be ascribed to increased contact activation. Contribution of the extrinsic pathway on patient-derived ECs was limited. We conclude that the CAT method in combination with serum-free cultured ECs offers a valuable high-throughput method to evaluate endothelial influences on thrombin generation, which appears to involve predominantly contact activation on ECs. Contact activation-mediated thrombin generation was increased on ECs from CABG patients compared to controls.

Use of the reversed Zenith iliac limb extension in the treatment of iliac artery aneurysms and various aortoiliac pathologies: outcome in midterm follow-up

PURPOSE

To report the midterm follow-up after treatment of various aortoiliac pathologies in an acute setting using reversed Zenith iliac limb extensions when appropriately sized stent-grafts were not available.

METHODS

From 2005 to 2007, 12 patients (10 men; mean age 71.5 ± 7.3 years) were treated with reversed Zenith iliac limb extensions for solitary iliac artery aneurysms (n = 8), an abdominal aortic aneurysm (AAA) in a small caliber aorta (n = 1), an anastomotic pseudoaneurysm in an aortobi-iliac graft (n = 1), a hypogastric artery aneurysm (n = 1), and a ruptured AAA secondary to a late type Ib endoleak after Talent stent-graft implantation (n = 1). The Zenith iliac limb extensions were deployed on the back table and reloaded in a reversed manner to treat aneurysms and other lesions with a broad range of different diameter necks and landing zones.

RESULTS

The technical success rate was 100%, and no endoleaks were present at the end of the procedures. The endoleak patient with the ruptured AAA died owing to respiratory insufficiency. The other 11 patients have a mean follow-up of 29±9 months. In this period, 2 patients received a femorofemoral crossover bypass because of an occluded iliac limb extension. One patient had a type II endoleak without growth of the iliac aneurysm. Two patients died of a ruptured 4.4-cm AAA at 16 months and of respiratory insufficiency due to metastases at 47 months, respectively.

CONCLUSION

When necessary, it is feasible to use a revered Zenith limb extension to treat solitary iliac aneurysms and other aortoiliac pathologies, achieving satisfactory midterm outcomes.

Differential protein expression in serum of abdominal aortic aneurysm patients - a proteomic approach

OBJECTIVE

The aim of the study is to investigate the differential expression of proteins in serum of abdominal aortic aneurysm (AAA) patients in relation to aneurysm size (D(max)) and progression.

METHODS

Two-dimensional differential in-gel electrophoresis (2D-DIGE) together with tandem mass spectrometry (MS/MS) was used to analyse the serum proteome from patients with small (D(max) 30-54 mm) AAA, either stable (increase D(max) <5 mm year⁻¹; n = 8) or progressive (increase D(max) ≥5 mm year⁻¹; n = 8), and large (D(max) ≥ 55 mm; n = 8) AAA. The identified proteins were quantitatively validated in a larger population (n = 80).

RESULTS

Several proteins were differentially expressed in serum of small stable, small progressive and large AAA. Three validated proteins (immunoglobulin G (IgG), α1-antitrypsin (α1-AT) and Factor XII activity) showed strong correlation with D(max). Size combined with either Factor XII activity or α1-antitrypsin had minimal effect on the prognostic value in predicting aneurysm progression compared with size alone (area under the curve (AUC), 0.85; 95% confidence interval (CI), 0.73-0.97; p < 0.001 and AUC, 0.85; 95% CI, 0.72-0.98; p < 0.001 vs. AUC, 0.83; 95% CI, 0.71-0.96; p < 0.001, respectively).

CONCLUSION

The present study indicates that both Factor XII and α1-antitrypsin are found in increased amounts in the serum of patients with expanding AAA. However, combination of either Factor XII or α1-antitrypsin with aneurysm diameter had little effect on prediction of aneurysm progression versus diameter alone.

Initial stress and nonlinear material behavior in patient-specific AAA wall stress analysis

Rupture risk estimation of abdominal aortic aneurysms (AAA) is currently based on the maximum diameter of the AAA. A more critical approach is based on AAA wall stress analysis. For that, in most cases, the AAA geometry is obtained from CT-data and treated as a stress free geometry. However, during CT imaging, the AAA is subjected to a time-averaged blood pressure and is therefore not stress free. The aim of this study is to evaluate the effect of neglecting these initial stresses (IS) on the patient-specific AAA wall stress as computed by finite element analysis. Additionally, the contribution of the nonlinear material behavior of the AAA wall is evaluated. Thirty patients with maximum AAA diameters below the current surgery criterion were scanned with contrast-enhanced CT and the AAA's were segmented from the image data. The mean arterial blood pressure (MAP) was measured immediately after the CT-scan and used to compute the IS corresponding with the CT geometry and MAP. Comparisons were made between wall stress obtained with and without IS and with linear and nonlinear material properties. On average, AAA wall stresses as computed with IS were higher than without IS. This was also the case for the stresses computed with the nonlinear material model compared to the linear material model. However, omitting initial stress and material nonlinearity in AAA wall stress computations leads to different effects in the resulting wall stress for each AAA. Therefore, provided that other assumptions made are not predominant, IS cannot be discarded and a nonlinear material model should be used in future patient-specific AAA wall stress analyses.

Assessment of endoleak significance after endovascular repair of abdominal aortic aneurysms: A lumped parameter model

The outcome of endovascular repair of abdominal aortic aneurysms (AAAs) is greatly compromised by the possible occurrence of endoleak. Previously, the causes and effects of endoleak on a patient-specific basis have mainly been investigated in experimental studies. In order to both reconcile and physically substantiate the various experimental findings, a lumped parameter model of an incompletely excluded AAA was developed. After experimental validation, the model was applied to study the effects on the intrasac pressure of the degree of endoleak, the degree of stent-graft compliance, and the resistance of a possible outflow tract formed by a branching vessel. It is concluded that the presence of endoleak leads to elevated intrasac pressure, the mean of which is mainly governed by the outflow tract resistance, while the pulse pressure is governed by both the endoleak resistance and the stent-graft compliance. Based on the agreement of the current results with previous findings, it is further concluded that the lumped parameter modelling method provides a useful numerical tool for validating experimental endoleak studies.

[Peripheral artery disease: clinical and cost comparison between duplex ultrasonography and contrast-enhanced magnetic resonance angiography--a multicenter randomized trial]

OBJECTIVE

To determine the clinical and economic consequences of replacing duplex ultrasonography (DUS) by contrast-enhanced magnetic resonance angiography (CE-MRA) for the initial diagnostic work-up of patients with peripheral artery disease (PAD).

DESIGN

Randomised multicentre study.

METHOD

In the period from January 2002 to August 2003, consecutive patients with PAD were randomly assigned to CE-MRA or DUS. The primary outcome measure was the costs. Secondary outcome measures included the confidence with which the specialist could take a therapeutic decision on the basis of the imaging study, the change in disease severity, and the change in quality of life (QOL) assessed during 6 months of follow-up. In addition, all costs of imaging, therapeutic interventions and outpatient visits were calculated.

RESULTS

After 6 months of follow-up the data on 352 patients were analysed. Use of CE-MRA reduced the number of additional vascular-imaging procedures by 42% ((69-40)/69) and the specialists felt more confident about their therapeutic decisions. The diagnostic costs of all imaging studies taken together were Euro 167,- higher, on average, in the CE-MRA group (p < 0.001). However, after 6 months of follow-up, no statistically significant differences were found between the two groups with regard to the change in disease severity, the QOL, or the total costs (p > 0.05).

CONCLUSION

Based on these findings, a specialist that replaces DUS by CE-MRA will feel more confident about taking a therapeutic decision and will feel less need for additional imaging. However, the diagnostic costs were higher with CE-MRA.

[Findings in 67 patients with recurrent or persistent symptoms after implantation of a disc prosthesis for low back pain]

OBJECTIVE

To determine the symptoms in patients who presented with persistent or recurrent backache or leg pain after implantation of an artificial disc prosthesis.

DESIGN

Descriptive.

METHOD

During the past II years in the Maastricht University Hospital (n=65) and the Utrecht University Medical Centre (n=2), 67 patients were seen with persistent or recurrent backache or leg pain in whom, an average of 53 months previously, one or more SB Charité-III lumbar-disc prostheses had been implanted elsewhere. The results were evaluated.

RESULTS

The most prominent findings were: migration of the prosthesis (n=6); subsidence into the vertebra (n=35); disc degeneration at one or more neighbouring levels (n=34) and arthrosis of facet joints (n=24). In 9 cases, rupture of the metal wire around the polyethylene core was observed and in 5 cases there were radiological signs of polyethylene wear. Re-operation (spondylodesis) was generally unsatisfactory if the prosthesis was left in place. In 21 patients, the prosthesis was removed; all specimens showed polyethylene wear or rupture.

CONCLUSION

Published results are mostly case series and suffer from observer bias; moreover, the benefits are moderate. Given the uncertain role ofdisc degeneration in patients with chronic backache, the real risk of complications and the uncertain advantages, the implantation ofa disc prosthesis is difficult to defend.

Recipient hemodynamics during non-heart-beating donor kidney transplantation are major predictors of primary nonfunction

Non-heart-beating donor (NHBD) kidneys may substantially expand the donor pool, but many transplant centers are reluctant to use these kidneys because of the relatively high incidence of primary nonfunction (PNF). In heart-beating donor kidneys, intravascular fluid depletion during transplant surgery is associated with delayed graft function (DGF). Therefore, we studied the effect of the recipients' hemodynamic status on the outcome of 177 NHBD kidney transplantations. Independent statistically significant predictors of PNF were average central venous pressure (CVP) below 6 cmH(2)O (adjusted odds ratio (AOR) 3.1 (95% CI: 1.4-7.1), p=0.007), average systolic blood pressure below 110 mmHg (AOR 2.6 (95% CI: 1.1-5.9), p=0.03) and pre-operative diastolic blood pressure below 80 mmHg (AOR 2.4 (95% CI: 1.0-5.9), p=0.05). Donor characteristics were not independently associated with PNF (p>0.10). In a subgroup analysis of 56 paired kidneys, 29% of the recipients with the lower CVP of the pair experienced PNF compared with 11% of their counterparts with higher CVP (p=0.09). Our study indicates that recipient hemodynamics during transplant surgery are major predictors of PNF. Therefore, improving recipient hemodynamics by expansion of the intravascular volume is expected to enhance the results of NHBD kidney transplantations and may enlarge the donor pool by increasing the acceptance of NHBD kidneys.

Endovascular treatment of traumatic rupture of the thoracic aorta

Background

Traumatic rupture of the thoracic aorta is a life-threatening event. Open surgical repair is the ‘gold standard’, but is associated with high mortality and morbidity rates. Endovascular repair is emerging as a potentially safer alternative.

Methods

A systematic review was performed of all published literature on this subject, including the authors' own experience. Using Sumsearch, PubMed and cross-references, all published reports up to January 2006 were identified, and analysed for injuries, perioperative morbidity, mortality, operating time, hospital stay and follow-up.

Results

A total of 284 patients were identified. Reported mortality rates range from 0 to 6 per cent. The procedure-related mortality rate is about 1·5 per cent. Some 6·7 per cent of all procedures were complicated by endoleak and the overall procedure-related morbidity rate was 14·4 per cent. These results are promising compared with those of open repair, but individual experience is limited and there may be some publication bias.

Conclusion

Endovascular repair of traumatic rupture of the thoracic aorta seems to reduce morbidity and mortality in patients with multiple trauma. Ideally, both devices and experienced personnel should be available in trauma centres.

Surgical repair of thoracoabdominal aortic aneurysms

Morbidity and mortality following thoracoabdominal aortic aneurysm (TAAA) repair are tremendous. Preoperative assessment is essential in detecting cardiac and pulmonary risk factors in order to reduce cardiopulmonary complications. Paraplegia and renal failure are main determinants of postoperative mortality and therefore gained substantial attention during the last decades. Left heart bypass, cerebrospinal fluid (CSF) drainage and epidural cooling have significantly reduced paraplegia rate, however, this dreadful event still occurs in up to 25% of patients undergoing type II repair. Renal failure has been partly prevented by means of retrograde aortic perfusion and cooling but renal failure still remains a significant problem. We have evaluated the effects of protective measures aiming for reduction of paraplegia and renal failure. Monitoring motor evoked potentials (MEPs) is an accurate technique to assess spinal cord integrity during TAAA repair, guiding surgical strategies to prevent paraplegia. Selective volume- and pressure controlled perfusion is a technique to continuously perfuse the kidneys during aortic cross clamping and subsequent circulatory exclusion In patients with atherosclerotic thoracoabdominal aortic aneurysms, blood supply to the spinal cord depends on a highly variable collateral system. In our experience, monitoring MEPs allowed detection of cord ischemia, guiding aggressive surgical strategies to restore spinal cord blood supply and reduce neurologic deficit: overall paraplegia rate was less than 3%. We believe that these protective measures should be included in the surgical protocol of TAAA repair, especially in type II cases. Renal and visceral ischemia can be reduced significantly by continuous perfusion during aortic cross clamping in TAAA repair. Not only sufficient volume flow but also adequate arterial pressure appears to be essential in maintaining renal function.Obviously, endovascular modalities have been successfully applied in TAAA patients, the majority of which as part of hybrid procedures. Technological innovation will eventually cause a shift from open to minimal invasive surgical repair. At present, however, open surgery is considered the gold standard for TAAA repair, especially in (relatively) young patients and patients suffering from Marfan's disease.

A patient-specific computational model of fluid–structure interaction in abdominal aortic aneurysms

It is generally believed that knowledge of the wall stress distribution could help to find better rupture risk predictors of abdominal aortic aneurysms (AAAs). Although AAA wall stress results from combined action between blood, wall and intraluminal thrombus, previously published models for patient-specific assessment of the wall stress predominantly did not include fluid-dynamic effects. In order to facilitate the incorporation of fluid-structure interaction in the assessment of AAA wall stress, in this paper, a method for generating patient-specific hexahedral finite element meshes of the AAA lumen and wall is presented. The applicability of the meshes is illustrated by simulations of the wall stress, blood velocity distribution and wall shear stress in a characteristic AAA. The presented method yields a flexible, semi-automated approach for generating patient-specific hexahedral meshes of the AAA lumen and wall with predefined element distributions. The combined fluid/solid mesh allows for simulations of AAA blood dynamics and AAA wall mechanics and the interaction between the two. The mechanical quantities computed in these simulations need to be validated in a clinical setting, after which they could be included in clinical trials in search of risk factors for AAA rupture.

Systemic dilation diathesis in patients with abdominal aortic aneurysms: a role for matrix metalloproteinase-9?

INTRODUCTION

Accumulating evidence suggests that patients with abdominal aortic aneurysm (AAA) suffer from a systemic dilating condition affecting all arteries. Matrix metalloproteinases (MMPs) and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), appear to be involved in aneurysm formation, as evidenced by increased aortic tissue MMP activity and plasma MMP levels in patients with AAA. Hypothesizing that an imbalance in plasma MMP/TIMP level might be associated with a systemic dilation diathesis, we studied mechanical vessel wall properties of non-affected arteries of patients with either AAA or aorto-iliac obstructive lesions in association with plasma MMP-9 and TIMP-1 levels.

METHODS

Twenty-two patients with AAA and 12 with aorto-iliac occlusive disease (AOD) were included. Diastolic diameter (d) and distension (Deltad) were measured at the level of the common carotid artery (CCA) and suprarenal aorta (SA) using ultrasonography. Distensibility (DC) and compliance (CC) were calculated from d, Deltad and brachial pulse pressure. Plasma MMP-9 and TIMP-1 were determined with specific immunoassays.

RESULTS

The average (+/-SD) age was 72.3+/-5.6 and 65.0+/-8.2 years for the AAA and AOD patients, respectively, (P=0.005). CCA diameter was 9.1+/-1.3mm in AAA patients and AOD 7.8+/-1.4mm in AOD patients, P=0.009. This difference persisted after correction for age. Plasma MMP-9 and TIMP-1 did not differ significantly between AAA and AOD patients. In the total 34 patients, the MMP-9/TIMP-1 ratio was correlated inversely with distensibility (r=-0.74, P=0.002) and to compliance (r=-0.58, P=0.024) of the suprarenal aorta.

CONCLUSIONS

The CCA diameter was larger in AAA patients compared to AOD patients. MMP-9/TIMP-1 ratio was associated with decreased distensibility and compliance of the suprarenal aorta. These data support the idea that AAA patients exhibit a systemic dilation diathesis, which might be attributable to MMP/TIMP imbalances.

Secondary prevention of atherosclerosis through chlamydia pneumoniae eradication (SPACE Trial): a randomised clinical trial in patients with peripheral arterial disease

BACKGROUND

Sero-epidemiological and experimental studies suggest that Chlamydia pneumoniae infections play an important role in the development of atherosclerosis. Clinical trials have shown contradictory results regarding the efficacy of antibiotics to prevent atherosclerosis-related complications in patients with coronary artery disease. Our aim was to study the effect of a short course of azithromycin on the incidence of cardiovascular events and peripheral vascular function in patients with stable peripheral arterial disease (PAD).

PATIENTS AND METHODS

Five hundred and nine PAD-patients were randomised to receive either a 3-day course of azithromycin (500 mg daily) or placebo, with 2 years of follow-up. C. pneumoniae serology was determined at baseline. Clinical endpoints were death, coronary events (myocardial infarction, unstable angina, and/or coronary revascularization procedures), cerebral events (stroke, TIA, and/or carotid endarterectomy) and peripheral arterial complications (increased PAD-symptoms with decreased ankle-brachial index (ABPI, 0.1-point decrease after 12 months), and/or peripheral revascularization procedures).

RESULTS

Five hundred and nine patients (160 women) with an atherosclerotic risk factor profile were randomised, 257 patients to azithromycin and 252 to placebo. Four hundred and forty nine patients (88%) had intermittent claudication and 60 (12%) had critical limb ischemia. By 24-month follow up, 182 patients (36%) developed 252 complications (45 deaths, 34 coronary events, 34 cerebral events and 139 peripheral arterial complications). C. pneumoniae IgA-titres were associated with the development of cardiovascular events. Nevertheless, the number of complications (131 in the azithromycin group vs. 121 in the placebo group) and the number of patients that developed complications (98 (38%) in the azithromycin vs. 84 (33%) in the placebo group) was comparable in both treatment groups. Life table analysis showed no effect of azithromycin on survival or ABPI.

CONCLUSION

A short-term course of azithromycin offers no benefits for survival or ankle pressure in PAD-patients.

Assessment of spinal cord integrity during thoracoabdominal aortic aneurysm repair

BACKGROUND

Monitoring motor-evoked potentials (MEPs) is an accurate technique to assess spinal cord integrity during thoracoabdominal aortic aneurysm (TAAA) repair, guiding surgical strategies to prevent paraplegia.

METHODS

In 210 consecutive patients with type I (n = 75), type II (n = 103), and type III (n = 32) TAAA surgical repair was performed using left heart bypass, cerebrospinal fluid drainage, and MEPs monitoring.

RESULTS

Reliable MEPs were registered in all patients. The median total number of patent intercostal and lumbar arteries was five. After proximal aortic crossclamping, MEP decreased below 25% of base line in 72 patients (34%) indicating critical spinal cord ischemia, which could be corrected by increasing distal aortic pressure. By using sequential clamping it appeared that in 43% of type I and II cases spinal cord circulation was supplied between T5 and L1, and 57% between L1 and L5. In type II and III cases cord perfusion was dependent upon lower lumbar arteries in 16% and pelvic circulation in 8%, necessitating reattachment of these segmental arteries. In 9% of patients critical ischemic MEP changes occurred without visible arteries, requiring aortic endarterectomy and selective grafting. One patient suffered early paraplegia and 2 delayed, and 2 patients had temporary neurologic deficit (5 of 210; 2.4%).

CONCLUSIONS

In patients with TAAA, blood supply to the spinal cord depends upon a highly variable collateral system. Monitoring MEPs is an accurate technique for detecting cord ischemia, guiding surgical tactics to reduce neurologic deficit (2.4%).