Local and global distensibility assessment of abdominal aortic aneurysms in vivo from probe tracked 2D ultrasound images.

Rupture risk estimation of abdominal aortic aneurysm (AAA) patients is currently based on the maximum diameter of the AAA. Mechanical properties that characterize the mechanical state of the vessel may serve as a better rupture risk predictor. Non-electrocardiogram-gated (non-ECG-gated) freehand 2D ultrasound imaging is a fast approach from which a reconstructed volumetric image of the aorta can be obtained. From this 3D image, the geometry, volume, and maximum diameter can be obtained. The distortion caused by the pulsatility of the vessel during the acquisition is usually neglected, while it could provide additional quantitative parameters of the vessel wall. In this study, a framework was established to semi-automatically segment probe tracked images of healthy aortas (N = 10) and AAAs (N = 16), after which patient-specific geometries of the vessel at end diastole (ED), end systole (ES), and at the mean arterial pressure (MAP) state were automatically assessed using heart frequency detection and envelope detection. After registration AAA geometries were compared to the gold standard computed tomography (CT). Local mechanical properties, i.e., compliance, distensibility and circumferential strain, were computed from the assessed ED and ES geometries for healthy aortas and AAAs, and by using measured brachial pulse pressure values. Globally, volume, compliance, and distensibility were computed. Geometries were in good agreement with CT geometries, with a median similarity index and interquartile range of 0.91 [0.90-0.92] and mean Hausdorff distance and interquartile range of 4.7 [3.9-5.6] mm. As expected, distensibility (Healthy aortas: 80 ± 15·10-3 kPa-1; AAAs: 29 ± 9.6·10-3 kPa-1) and circumferential strain (Healthy aortas: 0.25 ± 0.03; AAAs: 0.15 ± 0.03) were larger in healthy vessels compared to AAAs. Circumferential strain values were in accordance with literature. Global healthy aorta distensibility was significantly different from AAAs, as was demonstrated with a Wilcoxon test (p-value = 2·10-5). Improved image contrast and lateral resolution could help to further improve segmentation to improve mechanical characterization. The presented work has demonstrated how besides accurate geometrical assessment freehand 2D ultrasound imaging is a promising tool for additional mechanical property characterization of AAAs.

Endovascular Revascularization Plus Supervised Exercise Versus Supervised Exercise Only for Intermittent Claudication: A Cost-Effectiveness Analysis.

[Figure: see text].

A Generalized Approach for Automatic 3-D Geometry Assessment of Blood Vessels in Transverse Ultrasound Images Using Convolutional Neural Networks.

Accurate 3-D geometries of arteries and veins are important clinical data for diagnosis of arterial disease and intervention planning. Automatic segmentation of vessels in the transverse view suffers from the low lateral resolution and contrast. Convolutional neural networks are a promising tool for automatic segmentation of medical images, outperforming the traditional segmentation methods with high robustness. In this study, we aim to create a general, robust, and accurate method to segment the lumen-wall boundary of healthy central and peripheral vessels in large field-of-view freehand ultrasound (US) datasets. Data were acquired using the freehand US, in combination with a probe tracker. A total of ±36 000 cross-sectional images, acquired in the common, internal, and external carotid artery ( N = 37 ), in the radial, ulnar artery, and cephalic vein ( N = 12 ), and in the femoral artery ( N = 5 ) were included. To create masks (of the lumen) for training data, a conventional automatic segmentation method was used. The neural networks were trained on: 1) data of all vessels and 2) the carotid artery only. The performance was compared and tested using an open-access dataset. The recall, precision, DICE, and intersection over union (IoU) were calculated. Overall, segmentation was successful in the carotid and peripheral arteries. The Multires U-net architecture performs best overall with DICE = 0.93 when trained on the total dataset. Future studies will focus on the inclusion of vascular pathologies.

Reproducibility assessment of ultrasound-based aortic stiffness quantification and verification using Bi-axial tensile testing.

Current guidelines for abdominal aortic aneurysm (AAA) repair are primarily based on the maximum diameter. Since these methods lack robustness in decision making, new image-based methods for mechanical characterization have been proposed. Recently, time-resolved 3D ultrasound (4D US) in combination with finite element analysis was shown to provide additional risk estimators such as patient-specific peak wall stresses and wall stiffness in a non-invasive way. The aim of this study is to: 1) assess the reproducibility of this US-based stiffness measurement in vitro and in vivo, and 2) verify this 4D US stiffness using the gold standard: bi-axial tensile testing of the excised aortic tissue. For the in vitro study, 4D US data were acquired in an idealized inflation experiment using porcine aortas. The full aortic geometry was segmented and tracked over the cardiac cycle, and afterwards finite element analysis was performed by calibrating the finite element model to the measured US displacements to find the global aortic wall stiffness. For verification purposes, the porcine tissue was subjected to bi-axial tensile testing. Secondly, four AAA patients were included and 4D US data were acquired before open aortic surgery was performed. Similar to the experimental approach, the 4D US data were analyzed using the iterative finite element approach. During surgery, aortic tissue was harvested and the resulting tissue specimens were analyzed using bi-axial tensile testing. Finally, reproducibility was quantified for both methods. A high reproducibility was observed for the wall stiffness measurements using 4D US, i.e., an ICC of 0.91 (95% CI: 0.78-0.98) for the porcine aortas and an ICC of 0.98 (95% CI: 0.84-1.00) for the AAA samples. Verification with bi-axial tensile testing revealed a good agreement for the inflation experiment and a moderate agreement for the AAA patients, partially caused by the diseased state and inhomogeneities of the tissue. The performance of aortic stiffness characterization using 4D US revealed overall a high reproducibility and a moderate agreement with ex vivo mechanical testing. Future research should include more patient samples, to statistically assess the accuracy of the current in vivo method, which is not trivial due to the low number of open surgical interventions.

Overstenting the hypogastric artery during endovascular aneurysm repair with and without prior coil embolization: A comparative analysis from the ENGAGE Registry.

BACKGROUND: Endovascular aneurysm repair of aortoiliac or iliac aneurysms is often performed with stent graft coverage of the origin of the hypogastric artery (HA) to ensure adequate distal seal. It is considered common practice to perform adjunctive coiling of the HA to prevent a type II endoleak. Our objective was to question the necessity of pre-emptive coiling by comparing the outcomes of HA coverage with and without prior coil embolization. METHODS: Data from the Endurant Stent Graft Natural Selection Global Postmarket Registry (ENGAGE), which prospectively enrolled 1263 endovascular aneurysm repair patients between March 2009 and April 2011 from multiple centers worldwide, were used for this study. We identified patients in whom the Endurant stent graft (Medtronic Vascular, Santa Rosa, Calif) covered one or both HAs and grouped them into cases in which prior HA embolization-coils or plugs-was performed (CE) and cases in which HA embolization was not performed (NE). The occurrence of covered HA-related endoleak and secondary interventions were compared between groups. RESULTS: In 197 patients, 225 HAs were covered. Ninety-one HAs were covered after coil embolization (CE group), and 134 HAs were covered without prior coil embolization (NE group). Both groups were similar at baseline and had comparable length of follow-up to last image (665.2 ± 321.7 days for CE patients; 641.6 ± 327.6 days for NE patients; P = .464). Importantly, both groups showed equivalent iliac morphology concerning common iliac artery proximal, mid, and distal dimensions and tortuosity, making them suitable for comparative analysis. During follow-up, HA-related endoleaks were sparse and occurred equally often in both groups (CE 5.5% vs NE 3.0%; P = .346). Secondary intervention to resolve an HA-related endoleak was performed twice in the CE group and three times in the NE group. Late non-HA-related endoleaks occurred more often in the CE group compared with the NE group, (25.0% vs 15.0%; P = .080). Secondary interventions for other reasons than HA-related endoleaks occurred in 7.5% of NE cases and 15.4% of CE cases (P = .057), mostly for occlusions in the ipsilateral iliac limb. During follow-up, 19 NE patients and 9 CE patients died, which is not significantly different (P = .225), and no deaths were related directly or indirectly to HA coverage. Also, no reports of gluteal necrosis and bowel ischemia were made. CONCLUSIONS: This study shows that HA coverage with the Endurant endograft without prior coil embolization does not increase the incidence of endoleak or related secondary interventions. These findings together with the already available evidence suggest that omission of coil embolization may be a more resource-effective strategy whenever HA coverage is required.

Supervised Exercise Therapy for Intermittent Claudication Is Increasingly Endorsed by Dutch Vascular Surgeons.

BACKGROUND: Although supervised exercise therapy (SET) is generally accepted as an effective noninvasive treatment for intermittent claudication (IC), Dutch vascular surgeons were initially somewhat hesitant as reported by a 2011 questionnaire study. Later on, a nationwide multidisciplinary network for SET was introduced in the Netherlands. The aim of this questionnaire study was to determine possible trends in conceptions among Dutch vascular surgeons regarding the prescription of SET. METHODS: In the year of 2015, Dutch vascular surgeons, fellows, and senior residents were asked to complete a 26-item questionnaire including issues that were considered relevant for prescribing SET such as patient selection criteria and comorbidity. Outcome was compared to the 2011 survey. RESULTS: Data of 124 respondents (82% males; mean age 46 years; 64% response rate) were analyzed. SET referral rate of new IC patients was not different over time (2015: 81% vs. 2011: 75%; P = 0.295). However, respondents were more willing to prescribe SET in IC patients with chronic obstructive pulmonary disease (2015: 86% vs. 2011: 69%; P = 0.002). Nevertheless, a smaller portion of respondents found that SET was also indicated for aortoiliac disease (2015: 63% vs. 2011: 76%; P = 0.049). Insufficient health insurance coverage and/or personal financial resources were the most important presumed barriers preventing patients from initiating SET (80% of respondents). Moreover, 94% of respondents judged that SET should be fully reimbursed by all Dutch basic health insurances. CONCLUSIONS: The concept of SET for IC is nowadays generally embraced by the vast majority of Dutch vascular surgeons. SET may have gained in popularity in IC patients with cardiopulmonary comorbidity. However, SET remains underutilized for aortoiliac disease. Reimbursement is considered crucial for a successful SET implementation.

Gender differences following supervised exercise therapy in patients with intermittent claudication.

OBJECTIVE: Prevalence of peripheral arterial disease is equal in men and women. However, women seem to suffer more from the burden of disease. Current studies on gender-related outcomes following supervised exercise therapy (SET) for intermittent claudication (IC) yield conflicting results. METHODS: A follow-up analysis was performed on data from the 2010 Exercise Therapy in Peripheral Arterial Disease (EXITPAD) study, a multicenter randomized controlled trial including IC patients receiving SET or a walking advice. The SET program was supervised by physiotherapists and included interval-based treadmill walking approximating maximal pain combined with activities such as cycling and rowing. Patients usually started with three 30-minute sessions a week. Training frequency was adapted during the following year on the basis of individual needs. The primary outcome was gender differences regarding the change in absolute claudication distance (ACD) after SET. ACD was defined as the number of meters that a patient had covered just before he or she was forced to stop walking because of intolerable pain. Secondary outcomes were gender differences in change of functional walking distance, quality of life, and walking (dis)ability after SET. Walking distances were obtained by standardized treadmill testing according to the Gardner-Skinner protocol. Quality of life was measured by the 36-Item Short Form Health Survey, and walking (dis)ability was determined by the Walking Impairment Questionnaire (WIQ). Measurements were performed at baseline and after 3, 6, 9, and 12 months. Only patients who met the 12-month follow-up measure were included in the analysis. RESULTS: A total of 113 men and 56 women were available for analysis. At baseline, groups were similar in terms of clinical characteristics and ACD walking distances (men, 250 meters; women, 270 meters; P = .45). ACD improved for both sexes. However, ACD increase was significantly lower for women than for men during the first 3 months of SET (Δ 280 meters for men vs Δ 220 meters for women; P = .04). Moreover, absolute walking distance was significantly shorter for women compared with men after 1 year (565 meters vs 660 meters; P = .032). Women also reported less on several WIQ subdomains, although total WIQ score was similar (0.69 for men vs 0.61 for women; P = .592). No differences in quality of life after SET were observed. CONCLUSIONS: Women with IC benefit less during the first 3 months of SET and have lower absolute walking distances after 12 months of follow-up compared with men. More research is needed to determine whether gender-based IC treatment strategies are required.

Multicenter randomized controlled trial of the costs and effects of noninvasive diagnostic imaging in patients with peripheral arterial disease: the DIPAD trial.

OBJECTIVE: The purpose of our study was to compare the costs and effects of three noninvasive imaging tests as the initial imaging test in the diagnostic workup of patients with peripheral arterial disease. MATERIALS AND METHODS: Of 984 patients assessed for eligibility, 514 patients with peripheral arterial disease were randomized to MR angiography (MRA) or duplex sonography in three hospitals and to MRA or CT angiography (CTA) in one hospital. The outcome measures included the clinical utility, functional patient outcomes, quality of life, and actual diagnostic and therapeutic costs related to the initial imaging test during 6 months of follow-up. RESULTS: With adjustment for potentially predictive baseline variables, the learning curve, and hospital setting, a significantly higher confidence and less additional imaging were found for MRA and CTA compared with duplex sonography. No statistically significant differences were found in improvement in functional patient outcomes and quality of life among the groups. The total costs were significantly higher for MRA and duplex sonography than for CTA. CONCLUSION: The results suggest that both CTA and MRA are clinically more useful than duplex sonography and that CTA leads to cost savings compared with both MRA and duplex sonography in the initial imaging evaluation of peripheral arterial disease.

Vessel wall calcifications at multi-detector row CT angiography in patients with peripheral arterial disease: effect on clinical utility and clinical predictors.

PURPOSE: To evaluate retrospectively the effect of vessel wall calcifications on the clinical utility of multi-detector row computed tomographic (CT) angiography performed in patients with peripheral arterial disease and to identify clinical predictors for the presence of vessel wall calcifications. MATERIALS AND METHODS: The study was approved by the hospital institutional review board, and informed consent was obtained from all patients. For this study the authors included patients from two randomized controlled trials that measured the costs and effects of diagnostic imaging in patients with peripheral arterial disease. All patients underwent CT angiography and were followed up for 6 months. Clinical utility was measured on the basis of therapeutic confidence (rated on a 10-point scale) in the results of initial CT angiography and the need for additional vascular imaging. Univariable and multivariable logistic and linear regression analysis and the area under the receiver operating characteristic curve were used to evaluate the effect of vessel wall calcifications on the clinical utility of CT angiography and the use of patient characteristics to predict the number of calcified segments at CT angiography. RESULTS: A total of 145 patients were included (mean age, 64 years; 70% men). The authors found that the number of calcified segments was a significant predictor of the need for additional imaging (P = .001) and of the confidence scores (P < .001). The number of calcified segments discriminated between patients who required additional imaging after CT angiography and those who did not (area under the receiver operating characteristic curve, 0.66; 95% confidence interval: 0.54, 0.77). Age, diabetes mellitus, and cardiac disease were significant predictors of the number of calcified segments in both the univariable and multivariable analyses (P < .05). CONCLUSION: Vessel wall calcifications decrease the clinical utility of CT angiography in patients with peripheral arterial disease. Diabetes mellitus, cardiac disease, and elderly age (older than 84 years) are independently predictive for the presence of vessel wall calcifications.

Acute abdominal aortic aneurysms: cost analysis of endovascular repair and open surgery in hemodynamically stable patients with 1-year follow-up.

PURPOSE: To retrospectively assess the in-hospital and 1-year follow-up costs of endovascular aneurysm repair and conventional open surgery in patients with acute infrarenal abdominal aortic aneurysm (AAA) by using a resource-use approach. MATERIALS AND METHODS: Institutional Review Board approval was obtained, and informed consent was waived. In-hospital costs for all consecutive patients (61 men, six women; mean age, 72.0 years) who underwent endovascular repair (n = 32) or open surgery (n = 35) for acute infrarenal AAA from January 1, 2001, to December 31, 2004, were assessed by using a resource-use approach. Patients who did not undergo computed tomography before the procedure were excluded from analysis. One-year follow-up costs were complete for 30 patients who underwent endovascular repair and for 34 patients who underwent open surgery. Costs were assessed from a health care perspective. Mean costs were calculated for each treatment group and were compared by using the Mann-Whitney U test (alpha = .05). The influence of clinical variables on the total in-hospital cost was investigated by using univariate and multivariate analyses. Costs were expressed in euros for the year 2003. RESULTS: Sex, age, and comorbidity did not differ between treatment groups (P > .05). The mean total in-hospital costs were lower for patients who underwent endovascular repair than for those who underwent open surgery (euro20 767 vs euro35 470, respectively; P = .004). The total costs, including those for 1-year follow-up, were euro23 588 for patients who underwent endovascular repair and euro36 448 for those who underwent open surgery (P = .05). The results of multivariate analysis indicated that complications had a significant influence on total in-hospital cost; patients who had complications incurred total in-hospital costs that were 2.27 times higher than those for patients who had no complications. CONCLUSION: Total in-hospital costs and total overall costs, which included 1-year follow-up costs, were lower in patients with acute AAA who underwent endovascular repair than in those who underwent open surgery.

DSA versus multi-detector row CT angiography in peripheral arterial disease: randomized controlled trial.

PURPOSE: To prospectively compare therapeutic confidence in, patient outcomes (in terms of quality of life) after, and the costs of digital subtraction angiography (DSA) with those of multi-detector row computed tomographic (CT) angiography as the initial diagnostic imaging test in patients with peripheral arterial disease (PAD). MATERIALS AND METHODS: Institutional medical ethics committee approval and patient informed consent were obtained. Between April 2000 and August 2001, patients with PAD were randomly assigned to undergo either DSA or multi-detector row CT angiography as the initial diagnostic imaging test. Outcomes were the therapeutic confidence assessed by physicians (on a scale from 0 to 10), the need for additional imaging, the health-related quality of life at 6-month follow-up, diagnostic and therapeutic costs, and the costs for a hospital stay. Costs were computed from a hospital perspective according to Dutch guidelines for cost calculations in health care. Mean outcomes were compared between groups with unpaired t testing and were adjusted for predictive baseline characteristics with multivariable regression analysis. RESULTS: Among the 145 patients, 72 were randomly allocated to the DSA group and 73 to the CT angiography group. One patient in the DSA group had to be excluded. Mean age was 63 years in the DSA group and 64 years in the CT angiography group. There were 47 men in the DSA group and 58 men in the CT angiography group. Physician confidence in making a correct therapeutic choice was significantly higher at DSA (mean confidence score, 8.2) than at CT angiography (mean score, 7.2; P < .001). During 6-month follow-up, 14% less additional imaging was performed in the DSA group than in the CT angiography group (P = .3). No significant quality-of-life differences were found between groups. The diagnostic cost associated with DSA (564 +/- 210 euro [standard deviation]) was significantly higher than that associated with CT angiography (363 +/- 273 euro), a difference of -201 euro (95% confidence interval: -281 euro, -120 euro; P < .001). Therapeutic and hospitalization costs were similar for both strategies. CONCLUSION: These results suggest that use of noninvasive multi-detector row CT angiography instead of DSA as the initial diagnostic imaging test for PAD provides sufficient information for therapeutic decision making and reduces imaging costs.

Imaging peripheral arterial disease: a randomized controlled trial comparing contrast-enhanced MR angiography and multi-detector row CT angiography.

PURPOSE: To prospectively evaluate clinical utility, patient outcomes, and costs of contrast material-enhanced magnetic resonance (MR) angiography compared with multi-detector row computed tomographic (CT) angiography for initial imaging in the diagnostic work-up of patients with peripheral arterial disease. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Patients referred for diagnostic imaging work-up to evaluate the feasibility of a revascularization procedure were randomly assigned to undergo either MR angiography or CT angiography. Clinical utility was assessed with therapeutic confidence (scale of 0-10) at initial imaging and with the need for additional imaging. Patient outcomes included ankle-brachial index, maximum walking distance, change in clinical status, and health-related quality of life. Actual diagnostic and therapeutic costs were calculated from the hospital perspective. Differences between group means were calculated with unpaired t tests and 95% confidence intervals. RESULTS: A total of 157 consecutive patients with peripheral arterial disease were prospectively randomized to undergo MR angiography (51 men, 27 women; mean age, 63 years) or CT angiography (50 men, 29 women; mean age, 64 years). For one of the 78 patients in the MR group, no data were available. Mean confidence for MR angiography (7.7) was slightly lower than that for CT angiography (8.0, P = .8). During 6 months of follow-up, 13 patients in the MR group compared with 10 patients in the CT group underwent additional vascular imaging (P = .5). Although not statistically significant, there was a consistent trend of less improvement in the MR group across all patient outcomes. The average cost for diagnostic imaging was 359 ($438) higher in the MR group than in the CT group (95% confidence interval: 209, 511 [$255, $623]; P < .001). Therapeutic costs were higher in the MR group, but the difference was not significant. CONCLUSION: The results suggest that CT angiography has some advantages over MR angiography in the initial evaluation of peripheral arterial disease.