Open conversion after endovascular aortic aneurysm repair with the Ovation Prime™ endograft.

Advances in abdominal aortic aneurysm (AAA) endograft device technology have contributed to improved outcomes and durability of endovascular aortic aneurysm repair (EVAR), even in complex infrarenal aortic anatomies. However, stent graft failure secondary to endoleaks, migration, endotension and sac enlargement are persistent problems that can result in aneurysm rupture following EVAR.A symptomatic infrarenal AAA (4mm proximal neck) was treated initially with an Ovation Prime™ device (TriVascular, Inc., Santa Rosa, CA) in an off-label fashion, leading to type Ia endoleak moderately reduced by additional proximal neck ballooning. A failed Chimney technique to the single patent, but severely stenosed, right renal artery preceded the use of this device. A large type Ia endoleak was evident at 6-month follow-up, but following a failed supplementary endovascular intervention with coils to seal the endoleak, the patient presented with hemorrhagic shock from AAA rupture, requiring urgent open conversion. Intraoperatively it was impossible to explant this new type of endograft. Circumferential tying of the infrarenal aorta with a Teflon band was unable to stop the bleeding. However, after dividing the body of the stent-graft below the two proximal polymer rings, the endoleak was successfully treated by suturing the graft with the proximal aortic neck. The procedure was completed with extension of the stump to the common femoral arteries using a bifurcated Dacron prosthesis.The body of an Ovation Prime™ endograft may be impossible to explant in open conversion conditions. Large prospective studies with longer follow-up are required to adequately reflect the behavior of this particular device.

Impact of long-term warfarin treatment on EVAR durability: a meta-analysis.

PURPOSE: To evaluate whether postoperative long-term oral anticoagulation affects the durability of endovascular aneurysm repair (EVAR) and whether it is associated with an increased incidence of endoleak and subsequent need for reintervention. METHODS: A literature search was performed to identify studies of abdominal aortic aneurysm patients undergoing EVAR including an arm receiving warfarin postoperatively and reporting the frequency of any endoleaks and/or persistent type II endoleaks and reinterventions. The search identified 81 articles, of which 5 observational cohort studies ultimately met the inclusion criteria. RESULTS: Postoperative anticoagulation was required in 219 (14.6%) of the 1499 patients in the selected studies. The pooled effects analysis found that EVAR patients receiving long-term warfarin postoperatively had significantly more endoleaks of any type (OR 1.77, 95% CI 1.26 to 2.48, p=0.001) as well as persistent type II endoleaks (OR 1.58, 95% CI 1.05 to 2.37, p=0.03) compared with patients not on anticoagulation; however, there was no statistically significant difference in the reintervention rate between the groups. CONCLUSION: Long-term anticoagulation in EVAR patients was associated with a statistically significant increase in any endoleak and persisting type II endoleaks, although it was not linked to an increased risk of reintervention. Close monitoring for EVAR patients who require long-term oral anticoagulation is advised.

Clinical outcomes after crossed-limb vs. conventional endograft configuration in endovascular AAA repair.

PURPOSE: To report a case controlled analysis of endovascular aneurysm repair (EVAR) outcomes using the crossed-limb (CxL) endovascular configuration vs. the straight-limb configuration (SLC). METHODS: From January 2007 to July 2012, 27 patients (25 men; mean age 73.7±7.2 years, range 53-82) were treated by EVAR with the CxL technique. These patients were matched anatomically with 27 patients (27 men; mean age 72.4±7.4 years, range 52-86) who underwent EVAR using the same endograft and the standard SLC within a ±6-month period. Primary outcome measures included technical and clinical success and freedom from graft limb thrombosis, any type of endoleak, early or late secondary interventions, and aneurysm-related death estimated using the Kaplan-Meier method. RESULTS: The median follow-up periods for the CxL and SLC groups were 29.9 (range 6-54) and 33.5 (range 6-59) months, respectively (p=0.81). The technical success rate was 100% in both groups, but mean procedure times were significantly longer in the CxL group (116.3 vs. 90.7 minutes, p=0.035). Twelve intraoperative endoleaks (3 each for types Ia, Ib, II, and IV) occurred but without any difference between groups (p=0.51). One CxL group patient died in the early postoperative period (aneurysm-related) and another had an early graft limb thrombosis. One late type Ib intraoperative endoleak was recorded in the SLC group (p=0.51). For the CxL vs. SLC groups, the 1-year rates for freedom from endograft limb thrombosis (94% vs. 96%), any type of endoleak (96% vs. 96%), early or late reintervention (94% vs. 96%), and aneurysm-related death (94% vs. 96%) were not significantly different. Respective values at 36 months were 82% vs. 82%, 85% vs. 84%, 81% vs. 78%, and 83% vs. 84% (p>0.05). Clinical success rates at 12 months for the CxL and SLC groups were 91% and 100% (p>0.05), respectively, whereas at 36 months, the rates were 83% and 90% (p>0.05). CONCLUSION: No difference was found between the crossed-limb technique and the conventional endograft position as regards short- or midterm clinical outcomes.

Single-trocar transumbilical laparoscopy-assisted management of complicated jejunal diverticula.

Small-intestinal nonmeckelian diverticula are very uncommon and are considered to be acquired pulsion diverticula. Most of these diverticula are asymptomatic and are simply incidental findings. Complicated-acquired diverticular disease of the jejunum and ileum is a diagnostic dilemma. Small-bowel diverticulum is diagnosed with the aid of radiography techniques, such as small-bowel contrast series or enteroclysis. Laparotomy remains the gold standard for a definite diagnosis of asymptomatic and complicated diverticula, but laparoscopy is also very useful in the diagnosis and treatment of this condition. A surgical approach is the best form of treatment for complicated jejunoileal diverticula. The current report is about a patient who presented with iron deficiency anemia caused by a complicated jejunal diverticulum and managed with single-trocar transumbilical laparoscopy.

Thromboprophylaxis practices following varicose veins surgery.

OBJECTIVE: It is not clear whether patients undergoing varicose veins operations should receive thromboprophylaxis. A nationwide survey was conducted to assess thromboprophylaxis practice patterns in patients undergoing conventional vein surgery or endovenous procedures. METHODS: A questionnaire was e-mailed to all members of the Greek Society of Vascular and Endovascular Surgery (n = 163). RESULTS: In all, 68 members (42%) returned the survey, and 53% reported that they were not performing endovenous procedures. Thromboprophylaxis was used routinely by 52% after conventional surgery and 58% after endovenous procedures. Low-molecular-weight heparin was the preferred type of prophylaxis. Risk factors justifying thromboprophylaxis varied considerably among respondents. Postoperative duplex was performed routinely by 48% following stripping and by 76% following endovascular procedures. CONCLUSION: Thromboprophylaxis practices following varicose veins procedures vary among vascular surgeons in Greece. This reflects the uncertainty regarding the exact incidence of thromboembolic events in the existing literature as well as the absence of specific guidelines.

Oxidative stress contributes to methamphetamine-induced left ventricular dysfunction.

AIMS: Our aim was to test the hypothesis that the repeated, binge administration of methamphetamine would produce oxidative stress in the myocardium leading to structural remodeling and impaired left ventricular function. METHODS AND RESULTS: Echocardiography and Millar pressure-volume catheters were used to monitor left ventricular structure and function in rats subjected to four methamphetamine binges (3 mg/kg, iv for 4 days, separated by a 10-day drug-free period). Hearts from treated and control rats were used for histological or proteomic analysis. When compared with saline treatment, four methamphetamine binges produced eccentric left ventricular hypertrophy. The drug also significantly impaired systolic function (decreased fractional shortening, ejection fraction, and adjusted maximal power) and produced significant diastolic dysfunction (increased -dP/dt and tau). Dihydroethedium staining showed that methamphetamine significantly increased (285%) the levels of reactive oxygen species in the left ventricle. Treatment with methamphetamine also resulted in the tyrosine nitration of myofilament (desmin, myosin light chain) and mitochondrial (ATP synthase, NADH dehydrogenase, cytochrome c oxidase, prohibitin) proteins. Treatment with the superoxide dismutase mimetic, tempol in the drinking water prevented methamphetamine-induced left ventricular dilation and systolic dysfunction; however, tempol (2.5 mM) did not prevent the diastolic dysfunction. Tempol significantly reduced, but did not eliminate dihydroethedium staining in the left ventricle, nor did it prevent the tyrosine nitration of mitochondrial and contractile proteins. CONCLUSION: This study shows that oxidative stress plays a significant role in mediating methamphetamine-induced eccentric left ventricular dilation and systolic dysfunction.

Steerable weighted median filters.

A filter is steerable if transformed (i.e., rotated, scaled, etc.) versions of its impulse response can be expressed as linear combinations of a fixed set of basis functions. Steerability is important for numerous image processing applications. However, it is a property presently shared only by a specific class of linear filters. On the other hand, several classes of nonlinear filters, such as weighted median filters (WMFs), may offer certain advantages over linear filters such as robustness and edge preserving capabilities. In this paper, the concept of steerability is extended to encompass WMFs. It will be shown that, in general, a steerable WMF design technique needs to be capable of handling negative weights. Although methods that allow the design of WMFs admitting negative weights have already been proposed, such methods do not necessarily produce filters that are steerable, as opposed to the approach presented in this work. Experimental results illustrate the applicability of steerable WMFs in two applications, namely edge detection and orientation analysis.

Assessment of ischemia-induced microvascular remodeling using contrast-enhanced ultrasound vascular anatomic mapping.

Our aim was to apply novel contrast-enhanced ultrasound (CEU) techniques to characterize remodeling in different vascular compartments during ischemia-mediated angiogenesis. Hind limb ischemia was produced by ligation of an external iliac artery in 60 rats, half of which were treated with intramuscular fibroblast growth factor (FGF)-2 (5 microg). The proximal adductor muscles of the ischemic and control hind limb were studied immediately after ligation and at days 4, 7, or 14. Low-power maximum intensity projection imaging was performed to assess large intramuscular vessels to the fourth branch order. CEU data were analyzed to measure capillary perfusion and functional noncapillary microvascular blood volume. Resting capillary perfusion was reduced by 30% after arterial ligation and recovered earlier in FGF-2-treated versus nontreated rats (day 4 vs. 14). Changes in perfusion were temporally related to expansion of noncapillary microvascular blood volume on CEU, which was associated with an arteriogenic response on histology. Expansion of and organization (fractal distribution) of large collateral vessels occurred gradually over 2 weeks and was slightly more rapid with FGF-2 treatment. We conclude that CEU can separately assess collateral development, more distal arteriogenesis, and secondary changes in capillary perfusion that occur differentially with ischemia and growth factor therapy.

Anatomy and flow in normal and ischemic microvasculature based on a novel temporal fractal dimension analysis algorithm using contrast enhanced ultrasound.

Strategies for improvement of blood flow by promoting new vessel growth in ischemic tissue are being developed. Recently, contrast-enhanced ultrasound (CEU) imaging has been used to assess tissue perfusion in models of ischemia-related angiogenesis, growth-factor mediated angiogenesis, and tumor angiogenesis. In these studies, microvascular flow is measured in order to assess the total impact of adaptations at different vascular levels. High-resolution methods for imaging larger vessels have been developed in order to derive "angiograms" of arteries, veins, and medium to large microvessels. We describe a novel method of vascular bed (microvessel and arterial) characterization of vessel anatomy and flow simultaneously, using serial measurement of the fractal dimension (FD) of a temporal sequence of CEU images. This method is proposed as an experimental methodology to distinguish ischemic from nonischemic tissue. Moreover, an improved approach for extracting the FD unique to this application is introduced.

Texture synthesis: textons revisited.

This paper introduces a technique for synthesizing natural textures, with emphasis on quasiperiodic and structural textures. Textures are assumed to be composed of three components, namely illumination, structure, and stochastic. The contribution of this work is that, in contrast to previous techniques, it proposes a joint approach for handling the texture's global illumination, irregular structure, and stochastic component which may be correlated to the other two components. Furthermore, the proposed technique does not produce verbatim copies in the synthesized texture. More specifically, a top-down approach is used for extraction of texture elements (textons) in which, in contrast to previous texton-based approaches, no assumptions regarding perfect periodicity are made. The structure itself can be modeled as a stochastic process. Consequently, textons are allowed to have irregular and nonidentical shapes. In the synthesis stage, a new nonregular textural structure is designed from the original one that defines the place holders for textons. We call such place holders empty textons (e-textons). The e-textons are filled in by a representative texton. Since e-textons do not have identical shapes, a texton shape-matching procedure is required. After adding the illumination to the structural component, a strictly localized version of a block sampling technique is applied to add the stochastic component. The block sampling technique combined with the addition of the illumination component provides a significant improvement in the appearance of synthesized textures. Results show that the proposed method is successful in synthesizing structural textures visually indistinguishable to the original. Moreover, the method is successful in synthesizing a variety of stochastic textures.

A modified K-means algorithm for circular invariant clustering.

Several important pattern recognition applications are based on feature vector extraction and vector clustering. Directional patterns are commonly represented by rotation-variant vectors Fd formed from features uniformly extracted in M directions. It is often desirable that pattern recognition algorithms are invariant under pattern rotation. This paper introduces a distance measure and a K-means-based algorithm, namely, Circular K-means (CK-means) to cluster vectors containing directional information, such as Fd, in a circular-shift invariant manner. A circular shift of Fd corresponds to pattern rotation, thus, the algorithm is rotation invariant. An efficient Fourier domain representation of the proposed measure is presented to reduce computational complexity. A split and merge approach (SMCK-means), suited to the proposed CK-means technique, is proposed to reduce the possibility of converging at local minima and to estimate the correct number of clusters. Experiments performed for textural images illustrate the superior performance of the proposed algorithm for clustering directional vectors Fd, compared to the alternative approach that uses the original K-means and rotation-invariant feature vectors transformed from Fd.

Wavelet-based rotational invariant roughness features for texture classification and segmentation.

In this paper, we introduce a rotational invariant feature set for texture segmentation and classification, based on an extension of fractal dimension (FD) features. The FD extracts roughness information from images considering all available scales at once. In this work, a single scale is considered at a time so that textures with scale-dependent properties are satisfactorily characterized. Single-scale features are combined with multiple-scale features for a more complete textural representation. Wavelets are employed for the computation of single- and multiple-scale roughness features because of their ability to extract information at different resolutions. Features are extracted in multiple directions using directional wavelets, and the feature vector is finally transformed to a rotational invariant feature vector that retains the texture directional information. An iterative K-means scheme is used for segmentation, and a simplified form of a Bayesian classifier is used for classification. The use of the roughness feature set results in high-quality segmentation performance. Furthermore, it is shown that the roughness feature set exhibits a higher classification rate than other feature vectors presented in this work. The feature set retains the important properties of FD-based features, namely insensitivity to absolute illumination and contrast.