Studying the expansion of small abdominal aortic aneurysms: is there a role for peak wall stress?

AIM: The aim of this paper was to study the characteristics of three distending small abdominal aortic aneurysms (AAAs), with an increase in maximal diameter from 5 to 5.5 cm or above. METHODS: Peak Wall Stress (PWS) in the presence and absence of intraluminal thrombus (ILT) was evaluated in 3 cases of small AAAs (5 cm), at initial presentation and after their expansion, at maximum diameters ≥5.5 cm using finite element analysis. Furthermore, AAA sac volume (Vsac), the percentage volume of ILT (ILT%) and the percentage change of Vsac (ΔV%) and ILT (ILT%) were estimated and the location of PWS was recorded. RESULTS: Two AAA expanded from 5cm to 5.5 cm in a period of 6 months after initial presentation, with increase of sac volume by 20% and 30%, respectively. The third AAA expanded to a diameter of 6.5 cm after a follow-up period of 13 months, with a subsequent increase in sac volume of 78%. The expansion of AAA max diameter did not correlate with differences in peak wall stress (PWS) values at the initial presentation, ranging from 20.5 to 21.3 Nt/cm2. CONCLUSION: PWS values cannot solely serve as a predictive tool for small AAA expansion. Small AAA expansion seem to be a multifactorial process, not solely described by PWS values but rather by a combination of mechanical, hemodynamic and biological factors.

External jugular vein aneurysm: a source of thrombotic complications.

Superficial venous aneurysms are rare and usually are uneventful. We present a case in which a 40-year old female presenting with a thrombosed external jugular vein aneurysm which previously caused an undetected pulmonary embolism. The aneurysm was excised and the external jugular vein was ligated under local anesthesia and anticoagulation was initiated. In conclusion aneurysms of the superficial venous system should be considered as a possible source of pulmonary emboli. These sites can safely be excised and ligated under local anesthesia offering long term protection from its possible complications.

The role of geometric parameters in the prediction of abdominal aortic aneurysm wall stress.

OBJECTIVE: To study the correlation between peak wall stress (PWS) and abdominal aorta aneurysm (AAA) geometric parameters in the presence of intraluminal thrombus (ILT). DESIGN: Computational study using finite element analysis. MATERIAL: AAA models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 19 patients. METHODS: PWS was evaluated in the presence and absence of ILT. DeltaPWS% represents the percentage change in PWS in the presence of ILT. The 3D lumen centrelines were extracted, and the values of torsion, tortuosity and mean curvature were estimated. RESULTS: A positive correlation was observed between DeltaPWS% and relative ILT volume (P=0.03). PWS in the presence of ILT significantly correlated only with the degree of centerline tortuosity (P=0.003) and maximum diameter (P<0.0001). The optimal predictive model for PWS in the presence of ILT was estimated to contain both maximum diameter and centreline tortuosity. CONCLUSIONS: Specific geometric parameters in AAA models in the presence of ILT could serve as potential predictors of elevated PWS. PWS correlated significantly with the maximum diameter and the degree of centreline tortuosity. Centreline tortuosity may become a useful addition to maximum diameter in the decision-making process of AAA treatment.

Peak wall stress does not necessarily predict the location of rupture in abdominal aortic aneurysms.

UNLABELLED: Using finite element analysis, we evaluated if the site of an aortic bleb, known to be prone to rupture, coincides with the location of peak wall stress (PWS) in a patient-specific abdominal aortic aneurysm (AAA) model. REPORT: PWS was not located at the bleb site, even when stress values were estimated for different bleb wall thicknesses (0.5-2.0 mm) while the rest of the AAA wall was considered constant (2 mm). DISCUSSION: The sites of PWS in AAAs should not always be considered as the sites most prone to rupture since other factors, such as wall strength, may play a role in rupture-risk prediction, depicting the need for further investigation of these parameters.

Combined simultaneous basilic and brachial vein transposition. A new technique to create an autologous vascular access.

In this report, we present a technique to extend the function of an antecubital arteriovenous fistula in which both the basilic and the brachial veins were simultaneously transposed to create an autologous graft in the arm. This procedure may particularly be applicable for patients in whom, although a brachio-cephalic fistula, anastomosing the brachial artery and the perforating antecubital vein, has been previously performed and has remained patent arterialising the deep arm veins, the cephalic vein has failed to mature or has been thrombosed after multiple punctures. Our preliminary experience in eight patients has shown satisfactory outcome.

Caval migration of a ureteral J-stent after simultaneous ureter and iliac vein perforation during its placement for obstructive pyelonephritis.

A variety of indications have made the use of double pigtail ureteral catheters routine in urological practice. Although side effects are frequent they are usually mild. We report a case of intravenous stent migration after simultaneous perforation of the left ureter and left common iliac vein during retrograde J-stent placement. To the authors' knowledge such a potentially severe complication of a J-stent has not been previously described. A postprocedural plain abdominal radiograph is a helpful tool which may suggest possible misplacement of the pigtail stent especially if urine fails to return from the distal opening and, if verified, advocate immediate intervention in order to avoid any further devastating complications.

The influence of intraluminal thrombus on abdominal aortic aneurysm wall stress.

AIM: The aim of this study was to examine the effect of intraluminal thrombus (ILT) on the peak wall stress (PWS) in abdominal aorta aneurysm models (AAA). METHODS: Anatomically correct patient specific AAA models were created by 3D reconstruction of in vivo acquired computed tomography images from 19 male patients. Patients were divided in two groups according to aneurysm peak transverse diameter, 5-7 cm (10 patients, ''intermediate'' group) and >7 cm (9 patients, ''large'' group), respectively. PWS was evaluated in the presence and absence of ILT. The percentage of PWS reduction (Delta PWS %) was estimated as a percentage of PWS value in the absence of ILT. Finite element analysis was used to numerically compute the wall stress distribution assuming a 2-mm thick hyperelastic AAA wall material model and a 120 mmHg systolic uniform wall loading. The thrombus was modeled as an isotropic, elastic, homogenous and incompressible material. The volume of ILT was estimated as a percentage of the AAA sac volume. RESULTS: The ILT volume was 49.9%+/-10.6% in the ''large'' group and 58.6%+/-13.2% in the ''intermediate'' group (t-test P=0.14). The ''large'' AAAs have higher PWS values than the ''intermediate'' group, both in the presence of ILT (36.9+/-5.8 vs. 23.5+/-6.2 Nt/cm(2), P=0.0001) as well as in the absence of ILT (52.6+/-15.4 vs. 35.0+/-10.5 Nt/cm(2), P=0.01). The presence of ILT resulted in a decrease of PWS (Delta PWS) in all cases. There was no statistical difference between the two groups in the mean PWS reduction, in the presence of ILT (26.9+/-12.5 Nt/cm(2) in the ''large'' group and 31.0+/-11.7 Nt/cm2 in the ''intermediate'' group, t-test P=0.48). However, a strong correlation between the ILT relative volume (ILT%) and the degree of PWS reduction was found only in the ''intermediate'' AAA group (Pearson correlation 0.86, P<0.001), whereas no correlation was observed in the ''large'' AAA group (Pearson correlation 0.05, P=0.9). CONCLUSIONS: The presence of ILT reduced the PWS in all cases. In the ''intermediate'' AAAs our results showed a linear correlation between ILT relative volume and cents PWS. However, in ''large'' aneurysms no such correlation was found. This indicates that the degree of ILT influence on the reduction of PWS in ''large'' AAAs may be related to other factors such as the geometric configurations of the AAA.

Recurrent varicose veins after surgery: a new appraisal of a common and complex problem in vascular surgery.

OBJECTIVE: To assess the true incidence, the reflux patterns and the mechanisms responsible for recurrent varicose vein disease according to current definitions and guidelines. PATIENTS AND METHODS: Ninety-three patients (69 female, 24 male, mean age: 48 years) were prospectively evaluated pre- and postoperatively (1 month and 5 years), using clinical and colour duplex examination of both lower limbs. The CEAP score and its modification for recurrence (REVAS) were used for classification. RESULTS: In 113 operated lower limbs, 28 (25%) were found to have a recurrence, 20 of which were symptomatic (20/28, 72%). However, in this group, the mean severity score decreased significantly from 6.5 (SD 3.1) to 5.2 (SD 2.8) (p<0.001, paired t-test). The correlation between the type and cause of recurrence revealed: (1) true recurrent varices in eight limbs (8/28, 29%), primarily caused by neovascularisation, (2) new varicose veins as a consequence of disease progression in seven limbs (7/28, 25%), (3) residual veins in three limbs (3/28, 11%) mainly due to tactical errors (e.g. failure to strip the GSV), (4) complex patterns in 10 limbs (10/28, 36%). In the limbs with recurrence, 42 sources of venous reflux were identified: (1) 19 new sites of venous reflux were due to disease progression (15% of the operated limbs), (2) 13 were caused by neovascularisation (11.5% of the operated limbs), (3) six resulted from tactical failures (5.3% of the operated limbs) and (4) four were due to technical failures (3.5% of the operated limbs). CONCLUSIONS: This study shows that the recurrence of varicose veins after surgery is not uncommon. However, the clinical condition of most affected limbs remains improved. Progression of the disease and neovascularisation are responsible for more than half of the recurrences. Rigorous evaluation of patients and assiduous surgical technique might reduce recurrence due to technical and tactical failures.

Translation and validation of a quality of life questionnaire for chronic lower limb venous insufficiency into greek.

AIM: In order to provide a practical instrument for quality of life measures, for researchers and primary care physicians in Greece, we decided to translate and validate the published postal questionnaire CIVIQ (Chronic Venous Insufficiency Questionnaire) into the Greek language. METHODS: The study took place in 2 vascular surgical clinics. Fifty patients with known chronic venous insufficiency (CVI) were asked to complete the questionnaire. A debriefing method was used for the cultural adaptation. To measure test-retest reliability, 50 patients with known CVI disease, were asked to complete the questionnaire. RESULTS: The adaptation of CIVIQ questionnaire in the Greek language demonstrated its good validity (Cronbach's alpha=0.92) and reproducibility (coefficient = 0.98). CONCLUSIONS: CIVIQ seems to be a reliable tool in helping to assess the health status of the Greek general population and could be used to contribute to the identification of the magnitude of the problem of CVI in the Greek setting.

Hemodynamics induced after acute reduction of proximal thoracic aorta compliance.

OBJECTIVE: to investigate the affect of reduced aortic compliance on cardiovascular hemodynamics. MATERIALS AND METHOD: fourteen Yucatan miniature swine were divided into two equal groups, a Sham Operated Group and a Banding Group. A Teflon prosthesis was wrapped around the aortic arc in order to limit proximal aortic compliance (Banding Group). Data were recorded operatively (after implantation of a pressure sensor and a flow probe in the ascending aorta), after banding (only in the Banding Group) and at 2 days postoperatively. RESULTS: after banding, compliance decreased by 52 +/- 13% ((-)X +/- SEM) (p < 0.01) while systolic and pulse pressure increased by 37 +/- 8% (p < 0.05) and 87 +/- 31% (p < 0.01), respectively. Diastolic pressure, mean blood pressure, cardiac output and systemic vascular resistance did not change significantly. Aortic characteristic impedance increased nearly 2.5 times. Amplitudes of forward and reflected pressure waves (derived from the aortic pressure wave) increased by 96 +/- 41% and 174 +/- 46%, respectively (p < 0.05), while the time delay between the two decreased by 36 +/- 7% (p < 0.05). CONCLUSIONS: about half of the total arterial compliance is located in the proximal thoracic aorta. Arterial reconstruction of the proximal aorta with a non-compliant graft results in a significant decrease in systemic arterial compliance, which in turn increases systolic and pulse pressure. The development of more compliant prosthesis, which matches the host artery compliance, is expected to reduce the hemodynamic changes induced after their implantation.

Clinical presentation and anatomic distribution of chronic venous insufficiency of the lower limb in a typical Mediterranean population.

BACKGROUND: The aim of this study was to demonstrate the characteristics of lower limb chronic venous insufficiency (CVI) in a homogeneous Mediterranean population. METHODS: Investigation of 694 patients with uni- or bilateral symptoms and signs of lower limb CVI using colour duplex scanning. Limbs with previous venous surgery were excluded. The limbs were classified according to history and ultrasonic findings into those with post-thrombotic and those with primary CVI. The clinical presentation according to the CEAP classification was correlated to the anatomic distribution of venous reflux. RESULTS: Most of the symptomatic limbs (537/656, 81.5%) with primary CVI belonged to classes 1 to 3. In these limbs reflux confined to superficial veins was very common (64.5%, 424/656) whereas the prevalence of deep and perforator vein reflux was 18.5 and 25.5%, respectively. In contrast most of the limbs (69.5%) with post-thrombotic CVI belonged to classes 4 to 6, had a complex pattern of reflux, and involvement of deep and perforator veins was common (86.5 and 48%, respectively). In about a quarter (24%) of patients with suspected primary CVI no reflux was found in either limb on duplex scanning. Most of them (48%) had telangiectasis. Bilateral reflux was found in 71% of the patients with primary CVI. CONCLUSIONS: The clinical presentation was worse in limbs with post-thrombotic CVI than in those with a primary disease. Post-thrombotic CVI was associated with a complex pattern of reflux, affecting mostly the deep and perforator veins, whereas superficial reflux was the most common pattern in limbs with primary CVI. Therefore, surgery aiming to eliminate superficial reflux would confer only a minimal benefit in limbs with post-thrombotic CVI but would treat the majority of the limbs with the primary CVI. The high prevalence of bilateral reflux found in patients with primary CVI suggests a bilateral predisposition, which supports the hypothesis of the existence of a generalised venous disease.

Chronic venous insufficiency. A common health problem in general practice in Greece.

BACKGROUND: A study was carried out in Greece with the aim of assessing the prevalence of chronic venous insufficiency (CVI) in Greece and to discuss the role of general practice in the epidemiology, early diagnosis, and initial management of this disease. DESIGN: a prevalence study was carried out in rural Greece between January 17 and December 30, 1997. SETTING: 13 GPs, 11 of those working in 13 rural primary health centers, 1 in the University Hospital of Heraklion and 1 private sector from different Greek districts were invited to participate in the study. PARTICIPANTS AND METHODS: patients with the following criteria were entered into the study: weight, pain, cramps, burning, itching, formication and swelling. Complete information about patients' history was collected by the general practitioners (GPs) who used a semi-structured questionnaire. The diagnosis of CVI was established with Doppler ultrasound. RESULTS: Data were based on 6,119 questionnaires and GPs observed 4,502 randomly selected patients. The diagnosis of CVI was established in 993 patients and its prevalence was found to be 11.9% in males and 39.8% in females. Varicose veins were the most frequent clinical finding in patients with vein reflux and diabetes mellitus was the most common co-existing disease in males and hypertension in females. CONCLUSIONS: The prevalence of venous insufficiency (VI) appears to be a frequent health problem in general practice in Greece. It requires further investigation in order to explore the observed differences between various groups.

The importance of communication between physicians and patients. Special considerations in the era of endovascular therapy.

Most of the lawsuits in medical practice are the result of inadequate communication between doctors and patients and litigation has very little to do with errors. In the era of the technological development and the implementation of new techniques such as endovascular therapy, good communication between physicians and patients is essential. The purpose of this review is to elicit important considerations on challenging issues relating to the art of communication between physicians and patients and to provide information on what the vascular surgeon or interventionalist should bear in mind in obtaining an adequate informed consent from the patients.

Artificial neural networks for discriminating pathologic from normal peripheral vascular tissue.

The identification of the state of human peripheral vascular tissue by using artificial neural networks is discussed in this paper. Two different laser emission lines (He-Cd, Ar+) are used to excite the chromophores of tissue samples. The fluorescence spectrum obtained, is passed through a nonlinear filter based on a high-order (HO) neural network neural network (NN) [HONN] whose weights are updated by stable learning laws, to perform feature extraction. The values of the feature vector reveal information regarding the tissue state. Then a classical multilayer perceptron is employed to serve as a classifier of the feature vector, giving 100% successful results for the specific data set considered. Our method achieves not only the discrimination between normal and pathologic human tissue, but also the successful discrimination between the different types of pathologic tissue (fibrous, calcified). Furthermore, the small time needed to acquire and analyze the fluorescence spectra together with the high rates of success, proves our method very attractive for real-time applications.

Upper extremities deep venous thrombosis: comparison of light reflection rheography and colour duplex ultrasonography for diagnosis and follow-up.

BACKGROUND: Non-invasive diagnosis of axillary-subclavian vein thrombosis or documentation of the post-thrombotic syndrome performing methods currently in use is not definitive. The purpose of this prospective study was to compare two methods for the diagnosis and follow-up of patients with primary and secondary axillary-subclavian vein thrombosis: light reflection rheography (LLR) which is a reflection of venous pressure changes in the extremity as record from the subdermal capillary plexus, and colour duplex ultrasonography (CDUS). METHODS: In 36 patients with primary and secondary axillary-subclavian vein thrombosis were used a 4006 GE (Milwaukee, USA) colour duplex ultrasonography and an AV-1000 Hemodynamics instrument for the light reflection rheography for diagnosis and follow-up. The LLR methodology that applied was simple, involving testing of the venous outflow in the upper extremities in response to exercise, and with normally respiratory variations of an open venous system that was also assessed by the non-invasive modalities. In the LLR application of venous congesting pressure, and measurement of the rate of venous outflow when the congesting pressure is released was also performed. RESULTS: Both methods were able to diagnose the axillary-subclavian thrombosis in the initial acute state. There were no cases of false-positive results in either method. The CDUS presented a lower sensitivity in comparison to LLR in the follow-up period of the patients. A positive study was confirmed by phlebography in each instance. CONCLUSIONS: The tracing obtained by LLR is easy to interpret and provides objective evidence of proximal venous occlusion. The test is easy to apply and the instrumentation is relatively inexpensive. Both LLR and CDUS, could prove to be an exciting development among non invasive diagnostic techniques for axillary-subclavian vein thrombosis, with major sensitivity of LLR in the follow-up.