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Biomedical subjects

D Pavcnik

Publications and source records attributed to D Pavcnik.

At least 19 recordsLinked to original sources
PubMed2005

Small intestinal submucosa sandwich Zilver stent-grafts for TIPS: experimental pilot study in swine.

The aim of this study was the evaluation of preliminary suitability of the piglet small intestinal submucosa (SIS) sandwich Zilver endograft for experimental transjugular intrahepatic portosystemic shunt (TIPS) creation. TIPS was created in six swine. The five surviving animals underwent the follow-up portogram and were sacrificed at four weeks after TIPS creation. Gross and histologic examination was performed in all animals. TIPS creation was successful in all animals. One animal died four days after TIPS creation. In the five surviving animals, one shunt was occluded and four shunts were stenosed on the follow-up portogram. The mean percentage narrowing of the most advanced stenoses was 72% (range, 60%-100%). The most advanced stenosis was located in the parenchymal tract in three shunts and in the hepatic vein portion in one shunt. Gross and histologic examination showed abundant neointimal formation composed mainly of fibroblasts leading to the significant shunt stenoses. The piglet SIS sandwich Zilver stent-graft was found to offer only limited TIPS patency and should not be used for the definitive long-term TIPS study.

Journal Article↗
PubMed2002

Late complications and shape changes of the endografts after gigantic thoracic aortic aneurysm repair over a 7-year follow-up.

This report details a 7 years follow up observations in a 71-year-old patient treated with custom made endograft for gigantic thoracic aortic aneurysm (TAA). Progressive changes of the thoracic aorta and aneurysm after endograft placement led to two late complications including proximal stent graft prolapse into the aneurysm and extreme kinking of the endograft and aorta 28 and 51 months after treatment, respectively. Both complications were successfully treated with new endografts placement. Percutaneous endovascular repair is a promising, minimally invasive alternative to exclude TAA. This technique allows long-term treatment of patients who are unsuitable for conventional surgical procedures.

Aged↗
PubMed2001

Effects of intraarterial thrombin in the swine model.

PURPOSE: To evaluate the effects of catheter-directed thrombin in the peripheral arterial circulation of swine. MATERIALS AND METHODS: Thrombin was injected into a single femoral artery in 20 domestic swine. Each of five animals from four dose groups received 50, 150, 250, or 1,000 U as a single dose. Bilateral femoral arterial flow was monitored for as long as 4 hours and evaluated relative to baseline and contralateral limb flow. Interval arteriographic results were evaluated by segmental patency and a numeric angiographic score. RESULTS: Mean baseline flow was 136 mL/min +/- 44, with an internal arterial diameter of 3.4 mm +/- 0.5. A transient increase in blood flow after thrombin administration was followed by diminished flow and thrombosis. These findings varied directly with dose and inversely with baseline flow. Angiographic and flow abnormalities generally improved with time and recovery was generally better in swine that received 50 or 1,000 U than in other groups. However, one animal that received 1,000 U (13.2 U/mL/min) developed stable, complete limb thrombosis. The degree of recovery varied with thrombin dose and thrombus location. At doses greater than 50 U (0.33 U/mL/min +/- 0.05), abnormalities were commonly persistent. Animals receiving the 150-U dose (1.33 U/mL/min +/- 0.41) had a higher incidence of persistent distal occlusion. Distal occlusions were less likely to resolve than proximal occlusions. CONCLUSIONS: The effect of intraarterial thrombin is directly related to dose and inversely related to baseline blood flow. In swine, a threshold for significant flow disruption and thrombosis exists above a dose of 50 U (0.33 U/mL/min +/- 0.05). A threshold dose for irreversible occlusion may also exist. Although small amounts of thrombin in a high-flow vessel may not cause significant complication, administration into the arterial circulation should be avoided.

Angiography↗
PubMed2001

Bifurcated drum occluder endograft for treatment of abdominal aortic aneurysm: an experimental study in dogs.

PURPOSE: To evaluate a new, low profile, home-made, bifurcated drum occluder endograft (BDOEG), designed for percutaneous, transcatheter treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAA was created in 10 dogs with over-dilated Palmaz stents. To prevent back filling, the lumbar arteries, inferior mesenteric artery, and common internal iliac arteries were embolized. The BDOEG was constructed of a drum occluder device and two PTFE endografts. The drum device consisted of a modified Z stent with Dacron stretched across and held within the ends of the stent, each with two 8 x 6-mm slits through which PTFE endografts were delivered. The PTFE endografts were 8 mm in diameter and 9.5 cm in length. Preloaded, the BDOEG was delivered through a 10-F sheath from both femoral arteries in a three-step procedure. All 10 animals were treated with BDOEG. Aortography was performed immediately, 6 weeks, and 12 weeks after stent-graft placement. Five animals were killed at 6 weeks and five were killed at 3 months. Gross and histologic evaluation was performed. RESULTS: The infrarenal aortic diameters and both external iliac arteries ranged from 8.0 mm to 10.3 mm (mean, 9.4 mm +/- 0.6) and from 5.2 mm to 6.8 mm (mean, 5.8 mm +/- 0.5), respectively. Creation of the AAA was successful in all 10 dogs. AAA diameters ranged from 13.7 mm to 15.9 mm (mean, 14.9 mm +/- 0.7). Complete exclusion of the AAA was achieved immediately after BDOEG placement and aneurysms remained excluded without perigraft leak to the time of killing in all 10 animals. There was a high incidence of aortoiliac limb occlusion. Occlusion of 12 aortoiliac limbs (60%) caused by intimal hyperplasia at the distal end of the endografts in iliac arteries developed in nine animals (90%). In six animals (60%), one limb occluded and, in three animals (30%), there was occlusion of both limbs. CONCLUSION: This study suggests a new approach for treatment of AAA. BDOEG use reduces sheath size for endograft delivery and may eliminate the need for a surgical cut down on femoral arteries. Tapering of the iliac ends of endografts to the size of the artery will be needed to prevent distal intimal hyperplasia.

Animals↗
PubMed2001

Progesterone regulation of vascular thromboxane A(2) receptors in rhesus monkeys.

We hypothesized that progesterone regulates thromboxane A(2) receptor (TxA(2)R) density in primate vascular muscle and that TxA(2)R density correlates with coronary reactivity in vivo and in vitro. Reactivity to serotonin + U-46619 was determined by angiography in surgically postmenopausal [ovariectomized (Ovx)] rhesus monkeys without progesterone replacement and after 2-wk progesterone treatment (1-2 ng/ml). In untreated Ovx animals, 100 micromol/l serotonin + 1 micromol/l U-46619 (syringe concentrations) provoked vasospasm-like constrictions in six of six monkeys; zero of six progesterone-treated monkeys developed vasospasms. Sustained Ca(2+) responses in vascular muscle cells isolated from Ovx coronaries (208 +/- 63% of basal 20 min after stimulation) treated with serotonin + U-46619 contrasted with transient Ca(2+) responses (143 +/- 18% of basal and decreasing 5 min after stimulation) in progesterone-treated monkeys. The maximum density of [1S-(1I,2J(5Z),3I(1E,3R*),4I)]-7-[3-(3-hydroxy-4-(4'-[(125)I]iodophenoxy)- 1-butenyl)-7-oxabicyclo[2.2.1]heptan-2-yl]-5-heptenoic acid ([(125)I]-BOP) binding was greater (P < 0.01) in carotid arteries and aortic membranes from Ovx (109 +/- 11 fmol/mg) compared with progesterone-treated (43 +/- 15 fmol/mg) monkeys. TxA(2)R immunolabeling revealed greater coronary TxA(2)R labeling in Ovx compared with progesterone-treated monkeys. The results suggest that progesterone can decrease arterial TxA(2)R in Ovx monkeys.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2000

Autologous vein stent-graft: feasibility study.

PURPOSE: To evaluate expandable stents healed into vein wall as autologous vein stent-grafts for endoluminal grafting. MATERIALS AND METHODS: Balloon expandable stents were placed into external jugular veins of eight dogs. Stent and vein patency was followed by ultrasonography. Five weeks after stent placement, jugular veins with endothelialized stent were harvested. The autologous vein stent-grafts were divided into two groups. In group A, autologous vein stent-grafts (n = 3) were placed immediately into Baker solution for microscopic examination. In group B, autologous vein stent-grafts (n = 3) underwent mechanical manipulation; they were compressed, mounted on angioplasty balloon, pushed through a 9-F sheath and dilated. The autologous vein stent-graft endothelialization and changes after mechanical manipulation were evaluated by light and electron microscopy. RESULTS: Stent placement was successful in seven dogs. One stent migrated into the pulmonary artery. One well placed stent was damaged by compression dressing and thrombosed. At 5 weeks, gross and microscopic examinations revealed the autologous vein stent-grafts were fully covered by a 0.115- +/- 0.036-mm-thick neointimal layer. Small wall thrombus was observed in one autologous vein stent-graft. Repeated manipulations did not result in any intimal damage or stent loosening in the autologous vein stent-grafts. CONCLUSION: Expandable stents healed into a vein have potential to be used as autologous vein stent-grafts for endoluminal grafting without risk of disruption during percutaneous transcatheter introduction.

Animals↗
PubMed2000

The square stent-based large vessel occluder: an experimental pilot study.

PURPOSE: The purpose of this study is in vitro and in vivo experimental evaluation of a square stent-based vascular occlusion device for large vessels. MATERIALS AND METHODS: Square stent-based large vessel occluders (LVO) 5 mm-50 mm in size were constructed from stainless-steel square stents covered by porcine small intestine submucosa (SIS). The LVOs with two back-side barbs were delivered through a guiding catheter. The LVOs with two back-side barbs and two frontal barbs were front-loaded and delivered coaxially. A pusher with a retention mechanism at its end was used for deployment. In vitro testing for competency was performed with use of a flow model with pressure increases. In an experimental pilot study in seven pigs and five dogs, 16 LVOs were placed into the aorta (n = 4), common iliac artery (n = 2), pulmonary artery (n = 4), and medial sacral artery (n = 6). Four animals received two LVOs in different locations. Angiography was performed before and after placement of each LVO. Animals were followed for as long as 3 months with use of angiography and were then killed for gross and histologic evaluation. RESULTS: In vitro LVOs with two and four barbs were easily collapsed and pushed through or front-loaded into guiding catheters (6-F for a 5-mm occluder, 10-F for a 50-mm occluder). A 20-mm LVO adapted to tubular structures 10-15 mm in diameter, forming polygons 17-18.5 mm in length. In the flow model, LVOs endured pressure increases to 300 mm Hg. In vivo, the LVOs self-expanded and adapted to the vessel without migration in all cases. The locking pusher allowed precise LVO placement and engagement of its barbs into the vessel wall before complete deployment, preventing dislodgment by blood flow. Complete arterial occlusion occurred within 10-20 minutes and arteries remained occluded until the animal was killed in all cases. After 2 months, histologic evaluation revealed replacement of SIS by host tissue and its remodeling with variable fibrocytes, fibroblasts, and some inflammatory cells. Complete endothelialization was seen on both sides of the LVO. CONCLUSION: The SIS LVO is effective and reliable for acute and chronic occlusion in a high flow model in an experimental animal.

Angiography↗
PubMed1999

Twin-tube endografts for aortic aneurysms: an experimental feasibility study.

PURPOSE: To explore feasibility of twin-tube endografts (TTEGs) for treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAAs were created in six dogs by overdilation of Palmaz stents. TTEGs made of seven 9.5-mm-diameter Gianturco Rösch Z (GRZ) stents and covered with PTFE were deployed simultaneously from both femoral arteries through 10-F sheaths to exclude the AAA. Follow-up aortography was performed immediately and at 2, 4, and 8 weeks. Two dogs were killed at 4 weeks and four were killed at 8 weeks. Gross and histologic examinations were performed. RESULTS: AAA creation and TTEG placement were successful in all six dogs. TTEGs completely excluded AAAs in five dogs. Minor temporary perigraft leak was seen in one dog immediately after stent placement. Four dogs had TTEGs patent to termination at 8 weeks. In two dogs with oversized TTEGs, one of the twin endografts occluded at 2 weeks. At autopsy, TTEGs were formed in semicircular shape and histology did not show any significant inflammatory reaction. CONCLUSION: TTEGs show promise for treatment of AAA, with the potential of reducing the introductory sheath size. Further experimental studies, particularly with TTEGs extended into iliac arteries, are warranted.

Angiography↗
PubMed1999

Percutaneous transjugular kidney biopsy in swine with use of a side-cutting needle with a blunt-tipped stylet.

PURPOSE: To evaluate a new 19-gauge blunt-tipped, side-cutting, single throw transjugular biopsy needle for transvenous kidney biopsies. MATERIALS AND METHODS: Transjugular transvenous kidney biopsies were performed with a modified 70-cm biopsy needle utilizing fluoroscopic guidance in nine swine. Three tissue specimens were obtained with four biopsy device passes in five animals and three biopsy device passes in four animals. Renal arteriography and venography were performed immediately before and after renal biopsy. Five animals were killed immediately after biopsy. Four animals were allowed to recover and underwent arteriography and venography prior to being killed, which varied from 1 to 6 weeks. Gross and histologic examinations of the biopsied kidney were performed after euthanasia. A pathologist reviewed all biopsy specimens for quality based on the number of glomeruli present. RESULTS: Results of immediate and delayed arteriography and venography were normal in all cases. Histologic evaluation of all biopsy specimens demonstrated a range of two to 13 glomeruli per sample (mean, 6.5), with successful acquisition of the cortex. In one animal killed immediately after biopsy, a small subcapsular hematoma was present. CONCLUSION: The 19-gauge, side-cut biopsy needle with a blunt-tip stylet proved to be efficacious for obtaining renal cortical samples in right swine kidneys via a transjugular approach.

Animals↗
PubMed1998

Percutaneous retroperitoneal splenorenal shunt: an experimental study in swine.

PURPOSE: To evaluate the technical possibility of creating a percutaneous retroperitoneal splenorenal shunt (PRESS) in swine as a minimally invasive treatment of portal hypertension. MATERIALS AND METHODS: Five normal domestic swine underwent creation of a PRESS. A modified transjugular intrahepatic portosystemic shunt puncture set was introduced from the right femoral vein into the left renal vein. The proximal splenic vein was punctured transvenously through the retroperitoneal cavity. Noncovered metallic stents were then placed to connect both veins. The animals were sacrificed 1 hour after the procedure, after follow-up splenic venography and necropsy were performed. RESULTS: Puncture of the splenic vein and stent placement were successfully completed in all cases. In four of five cases, the splenic venogram revealed good flow from the splenic vein to the left renal vein through the shunt track 1 hour after creation of the PRESS, and there was no evidence of leakage. No changes in vital signs were noticed. At necropsy, a small retroperitoneal hematoma along the stent and minimal intraperitoneal bleeding were observed. The stents were found in the retroperitoneal cavity connecting both veins in all animals. CONCLUSION: Creation of a PRESS is technically possible, and further experimental studies of its efficacy are warranted.

Animals↗
PubMed1997

Transballoon intravascular ultrasound imaging during balloon angioplasty in animal models with coarctation and branch pulmonary stenosis.

BACKGROUND: Intravascular ultrasound (IVUS) studies performed after balloon dilation provide a method for evaluating the adequacy of angioplasty and the nature of associated changes in vessel walls. Previously, IVUS studies required the use of separate scanning catheters inserted independently before and after balloon angioplasty. We tested a 0.035-in, 30-MHz IVUS transducer wire that images from within commercially available 5F balloon dilation catheters. METHODS AND RESULTS: Seven stenoses were created in the left pulmonary artery (n = 3) and in the aortic isthmus (n = 4) in six lambs (weight, 3.4 to 12.5 kg). The balloon catheter selected was advanced across the stenotic area and the IVUS wire advanced in the guide lumen to the center of the balloon. Continuous IVUS images were obtained through balloons before, during, and after dilation. Transballoon imaging confirmed balloon location within the stenotic segment. Luminal diameters of stenotic and adjacent vessel segments before and after angioplasty by IVUS showed good correlation with angiographic measurements (r = .93, P < or = .001). After successful dilation, imaging during deflation allowed the assessment of vascular elastic recoil, mural dissection, and luminal size without requiring changes in balloon position. Repeat dilation could be undertaken and the inflation pressure and technique modified on the basis of the observed results. CONCLUSIONS: This transballoon IVUS system provides important on-line information about lumen diameter and wall structure for evaluation of angioplasty without the need for catheter changes, providing a method to possibly reduce the likelihood of excessive wall damage and to potentially reduce the number of angiograms required to accomplish and confirm results.

Angiography↗
PubMed1997

Transjugular intrahepatic portosystemic shunt with silicone-covered Wallstents: results in a swine model.

PURPOSE: To evaluate the use of impermeable silicone-covered Wallstents for transjugular intrahepatic portosystemic shunt creation. MATERIALS AND METHODS: A transjugular intrahepatic portosystemic shunt was created in 14 young swine (weight, 20-32 kg) by using impermeable silicone-covered Wallstents. In eight animals, the silicone covering extended from the portal vein to the inferior vena cava. In two swine, the silicone covering ended short of the inferior vena cava, in two it ended short of the portal vein wall, and in two it ended short at each end. Follow-up transhepatic portal venography was performed weekly for 6 weeks or until the shunt was occluded. Animals were then sacrificed for gross and histologic evaluation. RESULTS: Only two of 14 shunts were patent after 3 weeks; both were stenosed with luminal narrowing of more than 50% in the middle of the shunt. By 6 weeks, all shunts were occluded. At histologic evaluation, a marked foreign-body reaction with superimposed thrombosis was demonstrated. CONCLUSION: In comparison with uncovered Wallstents, impermeable silicone-covered Wallstents are associated with decreased patency at transjugular intrahepatic portosystemic shunt creation. This is likely due to increased thrombogenicity and a foreign-body reaction.

Animals↗
PubMed1996

Asymmetric hypertrophic cardiomyopathy diagnosed by echocardiography and magnetic resonance imaging. Case reports.

The authors present 3 patients with asymmetric hypertrophic cardiomyopathy, which was diagnosed by echocardiography. Magnetic resonance imaging, however, proved superior in visualizing the cardiac anatomy of the left ventricle and enabled myocardial evaluation with determination of the location, severity, and extent of the abnormality. Magnetic resonance imaging can also differentiate unusual asymmetric hypertrophy from other pathologic states.

Adult↗
PubMed1995

Transfemoral intraluminal stent graft implanted for thoracic aortic aneurysm.

We describe two patients with inoperable descending thoracic aortic aneurysm. The first patient had complained of severe back pain for at least thirteen years. Radiological examination revealed a large posterior mediastinal mass that was misdiagnosed in 1981. Follow-up studies in 1992 revealed this mass to be a large descending thoracic aortic aneurysm, eroding the vertebral bodies of T3 through T6 and entering the spinal canal. Because of the high risk, thoracic aortic surgery was not performed. The second patient had an acute descending thoracic aortic aneurysm. There was contraindication to a second surgical approach due to previous thoracotomy. Both patients underwent an intraluminal bypass of the descending thoracic aorta with a stent graft. Postplacement aortogram and follow-up studies showed that aneurysm was effectively excluded. We believe that this type of therapy should be offered to selected individuals who are considered by cardiovascular surgeons to be a high risk for thoracic aneurysm surgery.

Acute Disease↗
PubMed1995

Lipomatous hypertrophy of the interatrial septum: diagnosis by echocardiography and magnetic resonance imaging. A case report.

Lipomatous hypertrophy of the interatrial septum is generally a benign abnormality characterized by deposition of adipose tissue in the interatrial septum, usually extending to the atrial wall and interventricular septum. It is most often detected as an incidental echocardiographic finding. Transesophageal echocardiography can provide additional details, but in this case magnetic resonance imaging proved superior to it in assessing the involvement of other cardiac structures.

Cardiomegaly↗