Biomedical subjects

Asterios N Katsamouris

Publications and source records attributed to Asterios N Katsamouris.

7 recordsLinked to original sources

PubMed2006

Flow dynamics in expansions characterizing abdominal aorta aneurysms.

Our purpose was to identify and quantify hemodynamic factors contributing to the generation, proliferation, and rupturing of abdominal aorta aneurysms (AAAs) using a computational investigation of steady laminar and turbulent flow in AAA models. Steady laminar and turbulent flows were computed using the incompressible Navier-Stokes equations. Flow fields in symmetric shapes of different extents and degrees of expansion are presented first. Two representative cases of asymmetric AAAs are considered next: an aneurysm with an elliptic cross section and an aneurysm with preferential expansion in one direction. For symmetric aneurysms, parametric studies are presented. For asymmetric aneurysms, flow fields are computed only for high flow rates representative of systolic flow. For all cases, a recirculating flow region was found in the expanded part of the AAA. Recirculation is accompanied by a minor increase in pressure but a significant increase in wall shear stress. For cases where turbulent flow was considered, it was found that the recirculation zone diminishes but the computed wall shear stress reaches levels higher than laminar flow. The levels of wall shear stress reached in turbulent flow may cause lesions of the aneurysmal wall. The minor variation of pressure within the aneurysms with smooth expansions indicates that the structural properties of the arterial wall tissue may play a significant role for the generation and subsequent proliferation of the aneurysm. However, the high values of the wall shear stress in AAAs appear to be an important hemodynamic factor that may contribute to wall degeneration and eventual rupturing. The recirculating flow in AAAs may explain the generation of intraluminal thrombi. Furthermore, the asymmetry and complexity of the flow in asymmetric AAAs may explain the frequently observed asymmetric thrombi distribution.

Aorta, Abdominal↗

PubMed2006

A decoupled fluid structure approach for estimating wall stress in abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is a localized dilatation of the aortic wall. The lack of an accurate AAA rupture risk index remains an important problem in the clinical management of the disease. To accurately estimate AAA rupture risk, detailed information on patient-specific wall stress distribution and aortic wall tissue yield stress is required. A complete fluid structure interaction (FSI) study is currently impractical and thus of limited clinical value. On the other hand, isolated static structural stress analysis based on a uniform wall loading is a widely used approach for AAA rupture risk estimation that, however, neglects the flow-induced wall stress variation. The aim of this study was to assess the merit of a decoupled fluid structure analysis of AAA wall stress. Anatomically correct, patient specific AAA wall models were created by 3D reconstruction of computed tomography images. Flow simulations were carried out with inflow and outflow boundary conditions obtained from patient extracted data. Static structural stress analysis was performed applying both a uniform pressure wall loading and a flow induced non-uniform pressure distribution obtained during early systolic deceleration. For the structural analysis, a hyperelastic arterial wall model and an elastic intraluminal thrombus model were assumed. The results of this study demonstrate that although the isolated static structural stress analysis approach captures the gross features of the stress distribution it underestimates the magnitude of the peak wall stress by as much as 12.5% compared to the proposed decoupled fluid structure approach. Furthermore, the decoupled approach provides potentially useful information on the nature of the aneurysmal sac flow.

Aged, 80 and over↗

PubMed2005

Peripheral arterial embolism due to a left ventricular diverticulum in a young adult.

A 32-year-old man was admitted to the emergency department of our hospital after experiencing a peripheral arterial embolism. Investigation of the possible embolic sources in an otherwise asymptomatic patient revealed the existence of a left ventricular diverticulum. The left ventricular diverticulum is a rare congenital anomaly, either isolated or as a part of a syndrome including other congenital malformations. The treatment of choice, especially in symptomatic patients, is surgical resection, while in asymptomatic patients anticoagulation therapy is indicated.

Adult↗

PubMed2003

Suspected acute deep vein thrombosis of the lower limb in outpatients: considerations for optimal diagnostic approach.

The objective of this study was to review our diagnostic approach using color duplex scanning (CDS) in the management of symptomatic outpatients with suspected lower limb deep venous thrombosis (DVT). CDS was carried out in 315 consecutive outpatients with unilateral symptoms consistent with DVT. Both limbs were assessed in 205 patients. Other pathology was routinely sought when the symptomatic limb was free of thrombosis. Acute DVT was present in 25% (76/315) of the symptomatic limbs, and in only 8% it was confined to calf veins. Other pathology was detected in 90 limbs (28%). Swelling with or without pain was associated with DVT in 44% and 10%, respectively. The time elapsed between the onset of symptoms and CDS was 3 days (range 1-6 days). DVT in the contralateral asymptomatic limb was present in 5 (9%) of the 56 patients with DVT in the symptomatic limb. In the absence of DVT in the symptomatic limb, the contralateral asymptomatic limb was free of thrombosis. Clinical diagnosis of DVT in outpatients was unreliable. CDS revealed that only one-fourth of the symptomatic limbs had DVT, and other pathology mimicking DVT was present in 28%. CDS is a useful tool that offers a prompt, efficient diagnosis. Investigation of the contralateral asymptomatic limb seems to be necessary only when DVT is found in the symptomatic limb.

Adult↗

PubMed2003

Potential benefits from heating the high-dose rtPA boluses used in catheter-directed thrombolysis for acute/subacute lower limb ischemia.

PURPOSE: To explore the potential benefits from heating recombinant tissue plasminogen activator (rtPA) before catheter-directed thrombolysis in patients with lower-limb ischemia of <30 days' duration. METHODS: Over a 2-year period, 34 patients (26 men; mean age 63.5 years, range 39-80) with 10 iliac and 24 infrainguinal arterial occlusions (5 embolic and 29 thrombotic) were treated with two 5-mg boluses of rtPA injected into the proximal clot, followed by 2 additional 5-mg boluses of rtPA. In the first 18 patients (group A), room temperature rtPA was administered, whereas in the last 16 patients (group B), the rtPA boluses were heated to 38 degrees C for 30 minutes before injection. Residual thrombus was treated with a continuous infusion of 2.5 mg/h of rtPA for 4 hours then at a reduced dose (1 mg/h). RESULTS: Successful thrombolysis was achieved in 28 (82%) arteries. Unmasked lesions were treated with balloon angioplasty/stenting in 17 cases and with surgery in 4. One fatal retroperitoneal hematoma occurred in group A. Heating the rtPA did not significantly alter the outcome of thrombolysis. However, a statistically significant reduction in the total rtPA dose was observed in group B (24.28 mg versus 27.9 mg in group A, p=0.05), as well as quicker lysis (2 hours, 42 minutes versus 6 hours, 12 minutes in group A, p=0.001). There was no statistical difference in the amputation-free survival at 30 days between the groups. CONCLUSIONS: In patients with acute or subacute lower limb ischemia treated with catheter-directed thrombolysis, heating the rtPA results in faster lysis with a considerable reduction in the total dose of the lytic agent.

Acute Disease↗

PubMed2002

Vibrational angioplasty in the treatment of chronic infrapopliteal arterial occlusions: preliminary experience.

PURPOSE: To evaluate the safety and efficacy of vibrational angioplasty in chronic infrapopliteal arterial occlusions. METHODS: Twelve patients (9 men, aged 54 to 90 years) with 13 below-knee arterial chronic total occlusions were treated percutaneously using vibrational angioplasty. The occlusions were located in the anterior tibial artery (n=5), the tibioperoneal trunk (n=4), the peroneal artery (n=1), the posterior tibial artery (n=1), and in both the tibioperoneal trunk and peroneal artery (n=2). The length of the lesions ranged from 5 to 14 cm. RESULTS: Recanalization was successful in 12 (92.3%) lesions. In 1 case, the wire perforated the arterial wall; the procedure was abandoned without clinical sequelae. The time to cross the occlusions with the wire ranged from 6 to 19 minutes. No other complications were observed. Clinical follow-up ranged to 18 months. Ten patients with ulceration or gangrene demonstrated good wound healing, and pain was alleviated in all successfully treated patients. CONCLUSIONS: Vibrational angioplasty appears feasible as a means of safely recanalizing chronic total occlusions of the infrapopliteal arteries. Further experience should be acquired to assess its short- and long-term effects on this vascular territory.

Aged↗

PubMedDate not supplied

Use of the Trellis Peripheral Infusion System for enhancement of rt-PA thrombolysis in acute lower limb ischemia.

The Trellis Peripheral Infusion System is an over-the-wire 0.035" guidewire compatible device, designed to isolate a region of the peripheral vasculature to allow for lytic drug infusion and dispersion. We used it successfully through a percutaneous approach in two cases of acute thrombosis of a native lower limb artery. The total amount of rt-PA used was 12 and 9 mg, respectively and was delivered through bolus injections obviating the need for a supplementary continuous infusion of the agent. The time for dissolution of thrombus was 45 and 35 minutes, respectively. No complications were observed.

Acute Disease↗