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Biomedical subjects

K Ivancev

Publications and source records attributed to K Ivancev.

At least 73 records · Page 4Linked to original sources
PubMed1996

Endovascular stent-anchored aortic grafts: a comparison between self-expanding and balloon-expandable stents in minipigs.

PURPOSE: To study endovascular graft attachment with self-expanding Gianturco Z-stents and balloon-expanded Palmaz stents and the effect of these devices on the renal ostia. METHODS: Ten stent-grafts were constructed, 5 with Gianturco Z-stents and 5 with Palmaz stents. The endografts were implanted under fluoroscopic guidance into the abdominal aorta of 10 pigs so that the uncovered portion of the proximal stent extended over the renal artery orifices. Distal aortic blood pressure and flow were measured before and after graft placement and 1 hour postprocedure. The aorta was then exposed surgically, and the central portion of the stent-graft was inspected through an aortotomy to assess perigraft leakage. RESULTS: Stent-graft implantation was accurate and hemostatic in all cases, despite longitudinal folding of the graft due to oversizing. However, transverse folds produced pressure gradients (> 15 mmHg) between the ends of the graft in two cases. In another case, a pressure gradient resulted from partial thrombosis of the graft. In two cases, renal artery occlusion and thrombosis occurred due to coverage by the graft material. In two other animals, one of the renal arteries was entirely uncovered by a stent. The remaining 16 renal arteries were covered by the proximal stent but not the graft, as intended. One (6.25%) of these arteries thrombosed, but the remainder were grossly patent when the animals were sacrificed at 1 hour. CONCLUSIONS: Both Palmaz and Gianturco Z-stents produced hemostatic endovascular graft attachment, even in the presence of moderate graft oversizing. The risk of acute renal artery occlusion from juxtarenal stenting does not appear to be prohibitive, but longer term observations are needed.

Animals↗
PubMed1995

The YAG laser and Wallstent endoprosthesis for palliation of cancer in the esophagus or gastric cardia.

The need for frequent retreatment is a disadvantage of using endoscopic laser therapy (ELT) alone for palliative treatment of esophageal carcinoma. In this prospective study, therefore, we investigated the potential and feasibility of combining ELT with a self-expanding metallic stent (Wallstent). Twelve patients received ELT followed by stent placement (stent group) and were compared with 39 patients receiving ELT alone (ELT group). Swallowing ability was similar in the two groups. About one-third of the patients who had a short life expectancy, did not appear to benefit from stenting, whereas the interval between retreatments was prolonged by a factor of 2-4 in the remaining patients. Median survivals were 5.5 (range 1.0-23.5) months in patients with stents, and 4.5 (range 1.2-24.6) months in patients without stents. There were few complications related to stenting. In one patient, technical problems caused stent dislodgement into the stomach. Another stent patient died of hemorrhage from an untreated tumor in the stomach, but it was considered unlikely that the bleeding was caused by the stent. In conclusion, this preliminary trial suggests that a Wallstent endoprosthesis, used in combination with laser treatment, may become a valuable tool for prolonging the dysphagia-free interval in selected patients.

Aged↗
PubMed1995

In vivo microscopy of hepatic metastases: dynamic observation of tumor cell invasion and interaction with Kupffer cells.

In vivo microscopy was used in the study of the biological behavior of tumor cells and of the activity of Kupffer cells in hepatic tumors in situ. Three tumor models, Friend erythroleukemia inoculated into Dilute Brown Aguti (DBA)/2 mice, murine colon adenocarcinoma (CT)-26 in Bagg Albino inbred albino (BALB)/c mice, and mammary cancer 13762 NF in Fischer rats, were investigated. Tumor cells showed a strong tendency to adhere to the sinusoidal endothelium, most frequently in the sinusoids near the tumors. Mechanical trapping of tumor cells in the narrow portion of hepatic sinusoids, a phenomenon suggested by previous investigators as a predominant pattern for tumor cells to arrest in the liver, was not confirmed. Our study documented that in tumor-bearing livers, as compared with normal control livers, the population size and the phagocytic capacity of Kupffer cells are increased in nontumorous areas but are significantly decreased inside the tumors. In vivo microscopic images showed that Kupffer cells are not only attracted to tumor cells in the hepatic circulation but also have the ability to phagocytose those tumor cells. In vivo microscopy has been shown to be a useful tool for dynamic studies in tumor biology, pathology, and pharmacology.

Animals↗
PubMed1994

Peribiliary plexa--important pathways for shunting of iodized oil and silicon rubber solution from the hepatic artery to the portal vein. An experimental study in rats.

OBJECTIVES: Iodized oil is commonly used in chemoembolization of hepatic tumors, and silicon rubber solution is used for casting studies of hepatic tumor vasculature. Understanding the distribution patterns of iodized oil and silicon rubber solution is of significance in the refinement of iodized oil techniques and proper interpretation of hepatic tumor vascular studies. In this study, the location for iodized oil and silicon rubber solution shunting from the hepatic artery to the portal vein was identified. METHODS: Iodized oil and silicone rubber solution were injected into the hepatic artery in rats. The porta hepatis and the liver periphery were examined using in vivo microscopy. RESULTS: Iodized oil and silicone rubber solution had identical distribution patterns in the hepatic circulation. Both were shunted in large quantities from the hepatic artery into the portal vein through the peribiliary plexa. Other potential shunting sites did not contribute to the shunting. CONCLUSIONS: Though of different chemical natures, iodized oil and silicon rubber solution share similar distribution patterns in the liver. Hepatic arterioportal shunting of these substances occurs via the peribiliary plexa.

Animals↗
PubMed1994

Resection of primary hepatic malignant fibrous histiocytoma, fibrosarcoma, and leiomyosarcoma.

Four patients had resection for primary hepatic sarcoma: one with malignant fibrous histiocytoma (MFH), two with poorly differentiated fibrosarcoma, and one with leiomyosarcoma. Age ranged from 40 to 69 years. One patient had a cousin and a grandmother who had died of hepatic tumors. At presentation, all patients had pain; one had tumor rupture, and one had mental changes and hypoglycemia. None had hepatitis or cirrhosis. Results of laboratory evaluation were nonspecific, including normal carcinoembryonic antigen and alpha-fetoprotein levels. Computed tomography showed hypodense masses with enhancement. Angiography showed a hypervascular mass in three patients and an avascular mass in the patient with MFH. Despite large tumors (8 to 32 cm), portal and hepatic veins were not invaded. The pattern of vascularization and lack of venous invasion helps differentiate primary hepatic sarcomas from hepatocellular carcinoma, especially in noncirrhotic patients. All patients had extensive hepatic resections, with one operative death. Immunohistochemical stains of the tumors were positive for vimentin but negative for epithelial markers, differentiating these lesions from other hepatic tumors. The patient with MFH died with recurrence at 10 1/2 months. The patient with the ruptured fibrosarcoma had a second resection and chemotherapy, but died with recurrence at 3 years. The patient with the leiomyosarcoma had a second resection and was disease free at 4 years. Resection of primary hepatic sarcoma is warranted, with potential survival measured in years.

Adult↗
PubMed1993

Distribution and effect of iodized poppyseed oil in the liver after hepatic artery embolization: experimental study in several animal species.

To define the intrahepatic distribution of iodized poppyseed oil and its effect on the liver, hepatic artery embolization (HAE) was performed in five mice, 12 rats, four rabbits, and 21 pigs with the iodized oil alone or in combination with gelatin sponge powder (GSPow) in three rats or gelatin sponge particles (GSPs) in nine pigs. All mice, rats, and rabbits underwent radiography of the upper abdomen and in vivo microscopy of the hepatic periphery during and immediately after injection and 1, 4, and 24 hours later. All pigs underwent angiography before and after HAE as well as measurement of portal venous pressure before HAE and 15, 30, 45, and 60 minutes and 4 weeks after HAE. Follow-up radiographs were obtained in 18 pigs. HAE performed with the iodized oil only was well tolerated by the liver, even when high doses were used, likely because of continuous flushing of the sinusoids by high blood flow from peripheral arterioles. When HAE was performed with the iodized oil and GSPow, this blood flow ceased and necrosis developed. The degree of necrosis after HAE with the iodized oil in combination with GSPs was directly associated with the dose of iodized oil. HAE performed with GSPs only did not cause damage.

Animals↗
PubMed1993

In vivo microscopy of hepatic tumors in animal models: a dynamic investigation of blood supply to hepatic metastases.

The dynamics of blood circulation in three experimental animal models of hepatic metastasis were investigated with in vivo microscopy. It was demonstrated that the tumor vasculature communicated with the portal venules and hepatic sinusoids that surrounded the tumors. The hepatic artery was not seen to connect to the tumors directly. However, it was demonstrated that arterial blood entered tumors through the portal venules and that the hepatic arterial flow entered the tumor without resistance, while blood from the portal vein met great resistance at the tumor border, with only small amounts entering the tumor. Interruption of either the hepatic artery or the portal vein did not result in cessation of the blood circulation in hepatic tumors. A reciprocal relationship between the hepatic arterial and portal venous supplies to hepatic tumors was suggested, and it was hypothesized that arterioportal communications play an important role in the arterial and portal venous supply of blood to hepatic tumors. A comprehensive understanding of the blood supply of hepatic tumors is important for improving clinical treatment of hepatic tumors.

Adenocarcinoma↗
PubMed1992

Effective palliative treatment of metastatic carcinoid tumors with intra-arterial chemotherapy/chemoembolization combined with octreotide acetate.

Survival in patients with metastatic carcinoid tumors is dependent on control of tumor growth and adequate palliation of vasoactive amine-induced symptoms of flushing, diarrhea, wheezing, and valvular heart disease. Eight patients with carcinoid tumors metastatic to the liver were treated with long-term octreotide acetate therapy (100 to 500 micrograms three times a day), intra-arterial 5-fluorouracil infusion (2 g/day x 5 days), and hepatic tumor chemoembolization. All eight patients became asymptomatic and have remained so with a mean follow-up duration of 22 months from the time of first infusion. Following institution of subcutaneous octreotide acetate, intra-arterial infusion, and tumor chemoembolization, all patients are alive with a mean survival of 40 months from the time of diagnosis of carcinoid syndrome (range: 2 to 108 months). Four patients had greater than a 50% decrease in tumor size after therapy (mean follow-up duration: 10.6 months), and the other four patients have had stable disease after institution of therapy. It appears that combinations of long-term subcutaneous administration of octreotide acetate, intra-arterial 5-fluorouracil, and tumor chemoembolization effectively control progressive liver metastasis and provide excellent symptomatic palliation in patients with hepatic metastasis from functional carcinoid tumors.

Carcinoid Tumor↗
PubMed1992

Management of biliary complications after liver transplantation.

Biliary tract complications after liver transplantation are common, and the evaluation of newer treatment options compared with standard surgical treatment is important. In 62 liver transplants performed in 55 adult patients, the biliary tract was reconstructed with choledochocholedochostomy (CC) in 52 (84%) and Roux-en-Y choledochojejunostomy (RYCJ) in 10 (16%). Seventeen biliary tract complications occurred in 16 patients (29%). The incidence of complications was the same after CC and RYCJ. Eight complications (47%) occurred within the first month and nine (53%) thereafter. Only 6 of 17 (35%) biliary tract complications required operation. One patient died of a biliary tract complication. No other allografts were lost due to biliary tract complications. Four patients transplanted at other centers were also treated, for a total of 21 biliary tract complications. Overall, there were nine bile leaks, eight bile duct strictures, two Roux loop hemorrhages, one choledocholithiasis, and one ampullary dyskinesia. Temporary or permanent stents were used successfully in seven of eight strictures. Five bile leaks were managed without operation. Nonsurgical management is appropriate for a selected majority of patients with late bile leaks, biliary tract strictures, or choledocholithiasis after liver transplantation.

Biliary Tract Diseases↗
PubMed1992

Silicone-covered expandable metallic stents in the esophagus: an experimental study.

Modified silicone-covered Gianturco expandable metallic stents were placed in the normal esophagus of six young pigs. Following endoscopic examination, the stents were placed using endoscopic and fluoroscopic control. The animals were observed for eating behavior and weight gain. Stents appeared to be tolerated well based on these parameters. Three stents remained in position for the full study period, and three stents migrated into the stomach during the study. The pigs were sacrificed at four weeks and postmortem examination performed. Esophageal wall thickening and nodular inflammation were noted at the sites where the wire skirts penetrated the mucosa. Injury was limited to the region of the wire skirts and there was no injury due to the radial force of the stent body. There was no free perforation. This preliminary study suggests that endoscopic and fluoroscopic placement of modified silicone-covered Gianturco stents in the esophagus is feasible and safe. More extensive animal studies, followed by clinical investigation for palliation of malignant strictures, are warranted.

Animals↗
PubMed1992

Venous stenoses in patients who undergo hemodialysis: treatment with self-expandable endovascular stents.

During a 32-month period, 25 modified self-expandable endovascular stents were placed in 20 hemodialysis access sites to treat 21 stenoses and four occlusions in 19 patients. All stenoses were initially dilated with a high-pressure balloon. The initial success rate was 90% (18 of 20 access sites). The stents were patent from 0 to 960 days (mean duration of follow-up, 309 days). At 2 years follow-up, the patency rates were as follows: primary, 25%; secondary, 34%; and tertiary, 42%. The morbidity rate associated with this procedure was 15% (three of 20 sites); the mortality rate, 5% (one of 19 patients). All five complications (graft or native-vein thrombosis [n = 2], nerve deficits [n = 2], and death secondary to sepsis [n = 1]) occurred in three patients early in the study, before the use of prophylactic antibiotics and refinements in technique. The best results occurred in patients in whom the stenosis or occlusion affected a large vein that had no acute angle and was away from venous confluences such as the femoral and iliac regions.

Constriction, Pathologic↗
PubMed1992

Ductus arteriosus aneurysm imaging using modern diagnostic methods.

An aneurysm of the ductus arteriosus carries a high risk of rupture. The radiologic findings are described, based on a review of the literature, and on our experience of 5 patients, successfully diagnosed and treated. A left-sided mediastinal mass is always present, obscured only if the aneurysm has already ruptured. Although the lesion seems to be congenital, conventional radiology sometimes demonstrates wall calcifications. Ultrasonography is well suited to demonstrate the vascular nature of the mass, but interpretation may be difficult because of intervening air-containing lung parenchyma. CT, especially using dynamic scanning with contrast enhancement, is an excellent noninvasive diagnostic method. Angiography is frequently necessary to demonstrate patency or occlusion of the aortic and pulmonary ends of the ductus. The differential diagnosis must include a large number of mediastinal tumors. A temporary widening of the ductus in the newborn is common and must be differentiated from a true aneurysm. Surgical treatment today is usually successful.

Aneurysm↗