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Biomedical subjects

G Kopchok

Publications and source records attributed to G Kopchok.

At least 19 recordsLinked to original sources
PubMed2001

Vena caval filter placement by intravascular ultrasound.

OBJECTIVE: Placement of vena caval filters under fluoroscopic surveillance incurs significant expense and potential risks associated with the transportation of critically ill patients. Intravascular ultrasound (IVUS) allows direct intraluminal visualization of the vena cava and the renal veins. The purpose of this study is to evaluate the accuracy of vena caval filter placement under IVUS in an animal model. METHODS: Fifteen Simon-Nitinol venal cava filters (C.R. Bard, Inc., Covington, GA) were placed under IVUS guidance into four anesthetized sheep. Twelve were placed transfemorally, and three were placed transjugularly. Accuracy of placement was confirmed with fluoroscopy by measurement between the filter tip and the targeted side branch. RESULTS: The vena caval filters placed femorally averaged 0.33+/-0.42 cm distance from the target vein side branch. Jugular approach filter placement was less accurate. Although two out of three filters placed from the jugular vein were correctly positioned, the distance from the target vein side branch was much greater averaging 2.5+/-1.04 cm. CONCLUSION: Femoral placement of vena caval filters under IVUS is extremely accurate. The transjugular route, however, was technically challenging and standard fluoroscopic vena caval filter placement appears to be more appropriate. Our success with the femoral approach merits further clinical investigation in the use of IVUS for critically ill patients that would benefit from bedside vena caval filter placement.

Animals↗
PubMed2001

Abdominal pain and hemoperitoneum: sole presenting symptoms for "leaking AAA" after endovascular repair.

PURPOSE: To describe an unusual presentation of impending aortic endograft rupture and successful endovascular rescue. CASE REPORT: A 77-year-old man with an enlarging aortic aneurysm was treated with a Talent bifurcated endoprosthesis; a moderate endoleak that appeared to be related to either proximal or distal fixation sites was noted in the body of the aneurysm. The patient was observed for 1 month, and repeat imaging demonstrated persistent endoleak without major increase in the aneurysm diameter. Another examination was scheduled for 3 months hence, but, 2 months later, the patient presented with abdominal pain and a hemoperitoneum. A proximal extension cuff resolved the leak and led to resolution of the hemoperitoneum. CONCLUSIONS: A leaking aneurysm can be repaired using endovascular techniques in patients with an existing endograft. The need for frequent imaging surveillance of patients with endoleak is underscored.

Abdominal Pain↗
PubMed1998

Wallgraft endoprosthesis: initial canine evaluation.

This study evaluated the in vivo deployment and the healing characteristics of a self-expanding endoluminal graft [Wallgraft (WG) Endoprosthesis] in a canine (n = 22) aorta. The WG consisted of a 10 or 12 mm x 7.5 cm Wallstents (Schneider, Inc.) covered with polyethylene terephthalate (Dacron) graft material. Twenty-two WGs were deployed using fluoroscopic guidance. Devices were oversized approximately 10 per cent. Intravascular ultrasound (IVUS) was repeated, and balloon expansion along the length of the WG was performed to assure maximum expansion. WGs were evaluated with IVUS, angiography, and histology at 14 (n = 4), 30 (n = 4), 90 (n = 4), 180 (n = 5), and 365 (n = 5) days. Predeployment aortic diameters were 9.9 +/- 1 mm. Mid-WG diameters were 9.0 +/- 0.8 mm before balloon dilation and 9.2 +/- 0.5 mm after dilation with 8- (n = 1), 10- (n = 16), and 12- (n = 5) mm balloons. Twenty-two of 23 devices were deployed accurately with good apposition and aortic flow after deployment. On explant, all of the covered grafts were widely patent on IVUS and angiogram. Four explants demonstrated gaps (due to WG taper) between the proximal or distal ends of the graft on IVUS. The device length (9.1 + 0.5 cm) did not change significantly after deployment. Histologically at 6 months and 1 year the lumens were cell-lined. Scanning electron micrography demonstrated endothelial-like cells. This study demonstrates the ability of a WG to be accurately deployed and maintain excellent patency. Balloon expansion after deployment did not significantly increase the diameter. Clinical evaluation of this device is in progress.

Animals↗
PubMed1997

Intravascular ultrasound: the ultimate tool for abdominal aortic aneurysm assessment and endovascular graft delivery.

Intravascular ultrasound (IVUS) imaging is a relatively new, rapidly evolving technology that enables precise catheter-based assessment of the dimensions and morphology of vascular structures and lesions. In extensive preclinical laboratory developmental studies and in clinical cases of endograft deployment for treatment of abdominal aortic aneurysms, we have found IVUS invaluable for determining key parameters of aortic morphology before and during interventions and for assessing the accuracy of deployment after device placement. By combining the IVUS data with information obtained from angiography, magnetic resonance imaging, and computed tomography (axial and three-dimensional reconstructions), we have been able to size devices and choose optimal fixation sites to prevent endoleaks and maintain luminal patency acutely and in the long term.

Angioplasty↗
PubMed1997

Endoluminal graft exclusion of a proximal para-anastomotic pseudoaneurysm following aortobifemoral bypass.

PURPOSE: To describe a case of endoluminal graft exclusion of a proximal para-anastomotic pseudoaneurysm that occurred 17 years following aortobifemoral bypass for occlusive disease. METHODS AND RESULTS: The lesion was found on abdominal ultrasound examination as part of a work-up for acute abdominal pain and upper gastrointestinal bleeding in a 67-year-old male. A 5-cm saccular pseudoaneurysm was confirmed by preintervention aortography and spiral computed tomography (CT) scanning. Because of the patient's acute symptoms and high-risk medical condition (cardiomyopathy), he was deemed a candidate for endoluminal bypass. At the time of intervention, intravascular ultrasound (IVUS) interrogation identified a 3.5-cm-long separation of the existing aortic graft from the proximal aortic stump with a large pseudoaneurysm. The lesion was isolated and repaired by placement of an aortic-to-right iliac endoluminal bypass, ligation of the left limb of the aortofemoral graft, and femorofemoral bypass to restore blood flow to the lower extremities. Spiral CT scans at 48 hours and 3 months following the procedure confirmed complete isolation of the lesion. CONCLUSIONS: This case illustrates the feasibility of endografting for repair of aortic para-anastomotic pseudoaneurysms, and it also highlights the potential role of IVUS imaging in endoluminal graft deployment.

Aged↗
PubMed1996

Comparison of the deployment and healing of thin-walled expanded PTFE stented grafts and covered stents.

This study evaluated the deployment and short-term healing of thin-walled expanded polytetrafluoroethylene (ePTFE) stented grafts and covered stents as endoluminal prostheses in normal canine aortas and in an abdominal aortic aneurysm (AAA) model. Stented grafts consisted of a 7 cm length of 3 mm internal diameter ePTFE graft (Impra, Inc., Tempe, Ariz.) with two P-188 Palmaz stents (Johnson & Johnson Interventional Systems, Warren, N.J.) deployed along the inner surface of the ends of the graft to secure the prosthesis to the arterial wall. Covered stents were fabricated by placing a 3.7 cm length of 3 mm internal diameter thin-walled ePTFE graft over a P-394 Palmaz stent. Four covered stents and four stented graft prostheses (two of each prototype in the normal canine aorta and AAA model) were implanted in eight animals. One prosthesis of each type in each model was removed at 30 days and one at 60 days. Prior to removal, prostheses were evaluated by CT scan, arteriography, and intravascular ultrasound imaging with values compared to those obtained when the prostheses were deployed. Gross inspection and microscopic evaluation were performed at scheduled explantation. In general, the stented grafts were more difficult to accurately deploy. Healing and maintenance of long-term patency without significant luminal obstruction or occlusion occurred in only one 30-day sample in a normal canine aorta. The 30-day stented graft specimen that had been implanted in an AAA and required the addition of a covered stent to seal a maldeployment of the distal segment was also patent. The 60-day stented graft in the normal canine aorta was occluded with narrowing of the graft between the stents. The 60-day stented graft in the AAA was patent with one central fold and thrombus occupying approximately 20% to 30% of the lumen at this site. In contrast, the covered stent devices were less difficult to accurately deploy. All of the covered stent devices were patent with well-incorporated surfaces. Deployment of covered stents was more accurate and less complicated compared to stented grafts. All patent endoluminal prostheses and stent surfaces were well incorporated into aortic tissues. Problems with graft narrowing, folding, and subsequent thrombosis occurred in the unstented segments of the stented grafts. These preliminary findings support the further development and use of completely supported (stented) devices as endoluminal prostheses.

Angioplasty, Balloon↗
PubMed1996

Deployment technique and histopathological evaluation of an endoluminal vascular prosthesis used to repair an iliac artery aneurysm.

PURPOSE: To describe the deployment technique, function, and gross healing of an endoluminal vascular prosthesis deployed in a high-risk patient for treatment of a common iliac artery (CIA) aneurysm. METHODS: An 82-year-old, high-risk male with a 4-cm-diameter CIA aneurysm approximately 4.5 to 5 cm long was treated with endoluminal exclusion of the lesion using a 6-cm-long, 14-mm-internal diameter Dacron vascular prosthesis with Palmaz 308 stents sutured to either end of the graft. Intravascular ultrasound (IVUS) imaging facilitated sizing of the endograft and its accurate positioning so as to occlude both the aneurysm and the hypogastric artery, which was a potential source of retrograde flow to the aneurysm. Exclusion of the lesion and occlusion of the hypogastric artery were demonstrated on delayed angiographic images and contrast computed tomography scans obtained at 16 days postprocedure. Unfortunately, the patient died 67 days following implantation from a nonprocedure-related gastrointestinal complication. RESULTS: At autopsy, the aortoiliac segment was excised and examined grossly and histologically; the evaluation confirmed complete isolation of the aneurysm by the fully expanded endoluminal prosthesis. The surface of the vascular graft was covered by a glistening, thin, fibrinous membrane. The graft material was filled with hypocellular compact fibrinous material with no evidence of endothelialization. These observations confirm preliminary sealing and isolation of the iliac artery aneurysm as healing of the endograft progressed. CONCLUSIONS: The data acquired from the analysis of this specimen provide information regarding the utility and early healing of an endograft used for iliac artery aneurysm exclusion. This case also exemplifies the utility of IVUS in endograft deployment.

Aged↗
PubMed1995

Comparison of the utility of CT scans and intravascular ultrasound in endovascular aortic grafting.

Using CT scans and intravascular ultrasound (IVUS), aortic, aneurysm neck, and endoluminal graft cross-sectional dimensions were compared in a canine model before and after placement of endoluminal grafts in normal aortas (n = 10) and in artificially constructed abdominal aortic aneurysms (n = 15). Measurement of diameters (n = 83) revealed an average difference or bias between imaging modalities of 0.17 +/- 0.92 mm. Measurements obtained using IVUS were slightly larger than CT values (8.84 +/- 1.0 vs. 8.65 +/- 1.1, p < 0.03) but correlated very well by linear regression analysis (r = 0.948, p < 0.02). Analysis of cross-sectional area (n = 44) revealed an average difference or bias of 7.21 +/- 7.76 mm2 between the two modalities. Again IVUS measurements were larger than CT measurements (65.0 +/- 16.5 vs. 57.9 +/- 11.9, p < 0.001) and linear regression analysis showed less correlation (r = 0.897, p < 0.001). Qualitative assessment of the graft and stent characteristics was more precise using IVUS. Graft folding, stent-aorta interfaces, and thrombus formation were easily identified by IVUS, whereas these more subtle characteristics were missed by CT scanning and arteriography. These studies demonstrate that IVUS measurements were slightly larger than CT values; however, both modalities demonstrate small bias and good correlation. Qualitative analysis of the aneurysmal aorta and endoluminal graft using IVUS is comparable to and in some respects more detailed than measurements from CT scanning and arteriography.

Animals↗
PubMed1995

The role of cinefluoroscopy and intravascular ultrasonography in evaluating the deployment of experimental endovascular prostheses.

PURPOSE: This study compares the utility of cineangiography and real-time intravascular ultrasonography (IVUS) in achieving successful deployment of endovascular prostheses. METHODS: Five types of 5 cm long, 8 mm internal diameter polyester vascular grafts were secured in the infrarenal aorta of mongrel dogs by 18 mm long Palmaz balloon expandable vascular stents sutured to each end of the prostheses. The endovascular prostheses were delivered by crimping the stents at the ends of the grafts onto a 10 mm outside diameter, 8 cm long polyethylene balloon-dilation catheter. Real-time IVUS of the procedure was provided by a 0.035-inch, 20 MHz imaging element passed through the guide wire lumen in the balloon catheter. Two prostheses of each type were implanted, with one removed at 30 days and the other at 60 days for analysis. RESULTS: At implantation, both angiography and IVUS provided information regarding the choice of site for placement of the device and sizing of the aortic lumen. Real-time IVUS enhanced the information obtained by cineangiography by displaying tomographic views of the vessel anatomy, enabling determination of cross-sectional areas, assessing full stent expansion, and providing information regarding surface topography along the length of the prostheses. Several critical observations were apparent only on IVUS, including incomplete initial stent expansion during two procedures evidenced by pulsation of the aortic wall independent of the stent and movement of unstented segments of thin-walled grafts. Some of these observations led to further interventions at the time of deployment. At death, a comparison of cineangiography, IVUS, and ultrafast computed tomography outlined lumenal continuity and areas of irregularity, thrombus, or narrowing, with IVUS being more sensitive than cineangiography or computed tomography for determining most parameters. CONCLUSIONS: We conclude that IVUS is a promising alternative method for precise placement of intravascular grafts.

Animals↗
PubMed1994

Innovations in vascular imaging: arteriography, three-dimensional CT scans, and two- and three-dimensional intravascular ultrasound evaluation of an abdominal aortic aneurysm.

This report compares the information obtained from arteriography, CT scans, and intravascular ultrasound evaluation of an abdominal aortic aneurysm. The two- and three-dimensional imaging techniques described in this report add information that is redefining the pre- and intraoperative analysis of arterial lesions. The new data may have an influence on the evolution of diagnostic methods and future interventional therapy for vascular disease. This case highlights the developing potential of the methods.

Aged↗
PubMed1994

Changes in arterial wall compliance after endovascular stenting.

PURPOSE: The response of arterial wall to endovascular stenting after angioplasty is not well understood. Additionally, changes in the elastic properties of stented vessels are unknown in situ. Vascular compliance was measured in normal canine iliac arteries (n = 11) before and after intravascular ultrasound-guided deployment of self-expandable metallic stents. METHODS: Nine animals were restudied and killed 1, 2, and 4 weeks after initial deployment, and two dogs were studied at deployment only. An absolute induction angiometer was used to make in situ measurements of vessel compliance via catheter-based delivery. The angiometer consists of a wire loop probe, which conforms to the diameter of the vessel in which it is placed. Systolic/diastolic changes in loop diameter are translated into measureable changes of induced voltage. RESULTS: Mean compliance of the artery before and immediately after stenting was 4.4 +/- 2.1 and 1.9 +/- 2.0 (x 10(-2) diameter %/mm Hg), respectively. As early as 1 week after deployment, stented arteries began to lose expansile properties, and some were noncompliant. At explantation diminished compliance was accompanied by a periadventitial fibrous reaction around stented vessels. A thin, unobstructing layer of neointimal hyperplasia covered the iliac stents at all intervals, and all vessels remained patent and free of thrombus. CONCLUSIONS: The potential advantages provided by a flexible, radially compliant stent are lost within a relatively short time after implantation in nonatherosclerotic canine arteries.

Animals↗
PubMed1991

In vivo human comparison of intravascular ultrasonography and angiography.

This study evaluates the in vivo correlation of intravascular ultrasonography and uniplanar angiography in determining the luminal dimensions of normal and moderately atherosclerotic human arteries. Five French and 8F rotating A scan intravascular ultrasound catheters were used to obtain 48 images in four superficial femoral arteries, five iliac arteries, and one aorta in eight patients undergoing vascular surgery. Cross-sectional areas measured by intravascular ultrasonography were compared to cross-sectional areas calculated by uniplanar angiography of the same location in the vessel. Maximum and minimum luminal diameters were also measured from intravascular ultrasound images. An ellipticity index was defined as the maximum/minimum diameter ratio (max/min) and ranged from 1.0 to 1.8 (mean, 1.2). Comparison of the cross-sectional areas measured from intravascular ultrasound images and those calculated from uniplanar angiography showed no significant difference at any level of ellipticity studied. However, when the values of cross-sectional areas were analyzed in groups corresponding to the diameter of the vessel, that is, aortic, iliac, and femoral, the values for the iliac arteries calculated from uniplanar angiography were significantly greater by 9.8% +/- 0.7% (n = 29, p = 0.03) when compared to those measured by intravascular ultrasonography. In addition to providing accurate luminal determinations, intravascular ultrasound images displayed transmural morphology, the location and character of the atherosclerotic lesions, and the thickness of the vessel wall. We conclude that intravascular ultrasound imaging provides accurate, novel information regarding human vessels and that this technology may play a significant role in future diagnostic and interventional therapies.

Angiography↗
PubMed1990

In vitro and in vivo evaluation of intraluminal ultrasound in normal and atherosclerotic arteries.

This study evaluated the dimensional and morphologic precision of arterial images obtained using intraluminal rotating A-scan ultrasound catheters [5.0F (30 mHz) and 8.0F (20 mHz)]. Dimensions of in vitro ultrasound images from human arteries (eight normal and nine arteriosclerotic) were compared with those from histologic sections of the vessels. In addition, in vivo ultrasound studies (23 normal and 22 arteriosclerotic) of canine femoral arteries were compared with luminal dimensions obtained from angiograms of the vessels. The correlation of in vitro ultrasound images to luminal diameters (n = 22, r = 0.96), adventitial diameters (n = 19, r = 0.83), and wall thickness (n = 19, r = 0.68) in normal human vessels was significant (p less than 0.05). In vitro measurements of images and histologic specimens from human atherosclerotic arteries also correlated significantly (p less than 0.05) with luminal diameters (n = 27, r = 0.91), adventitial diameters (n = 24, r = 0.60), and wall thickness (n = 24, r = 0.62). Morphologically, in vitro images of the wall of normal human arteries had a concentric laminated appearance and atherosclerotic vessels had patchy echodense and echolucent areas. In vivo studies showed significant correlation of diameters for both normal (n = 16, r = 0.91, p less than 0.05) and arteriosclerotic (n = 16, r = 0.57, p less than 0.05) canine arteries compared with luminal dimensions measured from uniplanar angiograms. We conclude that rotating A-scan intraluminal ultrasound accurately defines both normal and atherosclerotic arterial wall morphology and dimensions. This technology may be valuable for intravascular guidance of angioplasty devices by identifying the location and consistency of lesions.

Animals↗
PubMed1989

Enterotomy fusion with laser energy: preliminary results in rabbit ileum.

The utility of enterotomy closure with the argon and CO2 lasers was examined in New Zealand white rabbit ileum. Thermal properties of 10 argon (0.5 W power for 30 s, energy fluence 230 J/cm2) and 10 CO2 (1.0 W power for 30 s, energy fluence 2700 J/cm2) laser-fused enterotomies were determined during acute fusion experiments using an AGA 782 digital thermographic camera. Healing of the fusions created by the two lasers was subsequently assessed in an additional group of 28 rabbits by comparing three 1.0-cm longitudinal ileal enterotomies, with each rabbit having both types of laser-welded closures and a sutured control. Thermal measurements made from the 10 closures with each laser revealed that the CO2 fusions generated significantly higher temperatures (max. 198 degrees C, mean 106 +/- 37 degrees C, n = 100) than argon (max. 85.2 degrees C, mean 60.5 + 8.1 degrees C, n = 100) p less than 0.001. In the healing studies, four rabbits died from weld failures (one argon and one CO2 disruption, two rabbits with both welds disrupted). Two additional rabbits died at 1 day and one at 10 days for undetermined reasons. The remainder of the animals were sacrificed at 1 (n = 11), 2 (n = 2) and 4 (n = 9) weeks postoperatively. Sutured closures exhibited more granulation tissue and adhesions surrounding the wounds than did welded closures and seven microabscesses were noted adjacent to sutured repairs. One of the CO2 repairs had an abscess at 4 weeks and none of the argon laser fusions had evidence of disruption or abscess.(ABSTRACT TRUNCATED AT 250 WORDS)

Abscess↗
PubMed1988

Thermal studies of in-vivo vascular tissue fusion by argon laser.

There are conflicting opinions regarding the mechanism of welding or fusion of vascular tissue by lasers. In this study, we measured the effects of saline irrigation on tissue temperature and fusion produced by argon laser welding of eight femoral and four carotid arteriovenous fistulas. Temperatures were continuously recorded using a digital thermographic camera. Forty 1-cm. welds were performed using powers of 0.50 (n = 24), 0.75 (n = 8), and 1.00 (n = 8) watt (W), with an energy fluence of 1100 J/cm2 per 1 cm segment, and cooling of the anastomotic site by saline irrigation (3 ml/minute). The "success" of fusions was determined by testing integrity of the repairs by exposure to blood flow. At 0.50 and 0.75 W, successful welds were formed when the temperatures were 44.2 +/- 1.6 (n = 28) and 55.0 +/- 3.6 degrees C (n = 20), with maximum temperatures of 47.9 and 59.9 degrees C respectively. At 1 W, the tissue was desiccated and the welds disrupted when exposed to blood flow with temperatures measured at 63.7 +/- 10.0 degrees C (n = 22) and maximum of 88.0 degrees C. Eight welds were also attempted without saline irrigation at 0.25 (n = 4) and 0.50 W (n = 4). At 0.25 W, tissue fusion was achieved but disrupted when exposed to intraluminal pressures with temperatures 50.3 +/- 2.0 degrees C (n = 10) and maximum of 52.6 degrees C. At 0.50 W, the fusion failed after only minimal exposure to the laser energy because of tissue drying and retraction with temperatures measured at greater than 125 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Large vessel sealing with the argon laser.

This study compared the histology, biochemistry, and tensile strength of laser-welded and sutured canine venotomies, arteriotomies, and arteriovenous fistulas. Twelve animals had bilateral femoral vessels studied, with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks (four animals for each type of repair), and were evaluated histologically by hematoxylin and eosin, elastin, and trichrome stains; biochemically by the formation of [3H]hydroxyproline as an index of collagen synthesis; and mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms, or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welding may be an alternative to sutures for repair of large-diameter venotomies, arteriotomies, and arteriovenous fistulas, as healing is comparable to that seen with suture repairs up to 4 weeks postoperatively.

Animals↗
PubMed1987

Preliminary report: a new technique of enterotomy closure using Nd:YAG laser welding compared to suture repair.

This study compared the histology and tensile strength of Nd:YAG laser welded and sutured small bowel enterotomies in Sprague-Dawley rats. Enterotomies (0.5 cm long) were either welded with the Nd:YAG laser (1 W and 10.6 sec pulses) or repaired with interrupted, simple 6-O silk sutures. Group I consisted of seven animals; five with enterotomies repaired by laser welding and two repaired by suturing. Group II consisted of eight animals with each having both laser and suture repairs. Animals were killed and specimens were removed and examined at 1 day, and at 1, 2, and 3 weeks postoperatively to compare the progression of healing. On macroscopic examination the laser welded enterotomies were closed 84% of the time and only 23% had adhesion formation while 90% of sutured repairs were closed and 100% had adhesion formation. Histologic examination of both suture and laser welded enterotomies demonstrated active healing at 1 week with minimal collagen bridging the enterotomies. At 2 and 3 weeks the sutured enterotomies had granulomatous reaction around the sutures while the laser welded enterotomies had minimal inflammatory response and near normal small bowel histology. The tensile strength of the 3-week specimens from both the suture and laser welded enterotomies were 50% of normal bowel. These findings suggest that the laser welding of small bowel enterotomies is comparable in closure and tensile strength to suture repair. The time required to repair the enterotomy is significantly decreased, the procedure is easily performed, and there is a marked decrease in adhesion formation following laser repair.

Animals↗