Biomedical subjects

D Pavcnik

Publications and source records attributed to D Pavcnik.

30 records · Page 2Linked to original sources

PubMed1992

Development and initial experimental evaluation of a prosthetic aortic valve for transcatheter placement. Work in progress.

A prosthetic caged-ball aortic valve that can be placed with transcatheter techniques was designed, constructed, and initially evaluated in 12 adult mongrel dogs. The prosthesis consisted of a ring, cage, and ball. The ring was made of stainless steel wire coiled in a springlike configuration and covered with an expandable nylon mesh. The cage consisted of a self-expanding Gianturco stent with flat stainless steel wires attached across the cranial end. The ball was a detachable latex balloon filled with a radiopaque silicone prepolymer system. The self-expanding valve was easily passed through an 11- or 12-F Teflon sheath and was placed in the ascending aorta by means of the carotid approach. The stability and efficacy of the prosthesis were evaluated radiographically for as long as the valve remained functional (1-3 hours). The competency of the valve and the patency of the coronary arteries were determined angiographically over the same period. The results of these studies indicate that development and transcatheter placement of a prosthetic aortic valve are feasible.

Animals↗

PubMed1990

Perforation of the heart in a newborn with critical valvar pulmonary stenosis during balloon valvoplasty.

We describe the perforation of the right ventricular outflow tract with a 0.021 inch wire in a newborn infant with critical pulmonary valvar stenosis in an attempt to balloon dilatation of the pulmonary valve. The complication was diagnosed by contrast injection into the pericardium. The infant was followed with sector scan echocardiography and recovered completely from that injury. The dilatation was successfully repeated a few days later with the use of a soft tipped wire to cross the pulmonary valve.

Cardiomyopathy, Hypertrophic↗

PubMedDate not supplied

Monodisk: device for percutaneous transcatheter closure of cardiac septal defects.

The Monodisk, a device to facilitate percutaneous closure of cardiac septal defects, was developed and tested in vitro and in vivo. Atrial septal defects (8-10 mm) were created in five dogs using transcatheter techniques. The defects were then closed with the Monodisk. The device was easily and successfully fixed in place in all dogs. The efficacy of the device was determined radiographically. No shunting of contrast medium was observed in any case. Animals were followed for 6 months. Results showed good biocompatibility and several advantages of the device: it requires only a simple one-step placement procedure; it utilizes a small delivery system; it is easy to place and detach; it is self-centering and stable; and it can be repositioned or retrieved prior to detachment. Its possible clinical applications include correction of atrial septal defects, ventricular septal defects, patent ductus arteriosus, as well as creating an aortopulmonary window.

Animals↗

PubMedDate not supplied

Idiopathic enlargement of the right atrium.

A case of aneurysmal enlargement of the right atrium was found accidentally during a routine examination. The patient was asymptomatic and free of palpitations or proven rhythm disturbances. The results of echocardiography, magnetic resonance imaging, and cardiac catheterization excluded cardiac malformation, which could have caused secondary enlargement of the right atrium. A partial pericardial defect as a likely cause of herniation of the right atrium was ruled out by magnetic resonance imaging. In keeping with these results, isolated aneurysmal enlargement of the right atrium was diagnosed.

Adolescent↗

PubMedDate not supplied

Square stent: a new self-expandable endoluminal device and its applications.

The square stent is a new, simply constructed, self-expanding device that has recently been described. Compared with other stents, the square stent has a minimal amount of metal and thus requires a smaller-diameter catheter for introduction. Despite the small amount of metal present, the square stent has adequate expansile force. We have been evaluating the square stent for various interventional applications. In addition to the basic square stent, combinations of square stents and coverings for square stents were developed and evaluated to expand its uses and indications. One of the coverings tested is a new biomaterial: small intestinal submucosa (SIS). This paper will discuss the various applications of the square stent, which include a retrievable inferior vena cava filter, vascular occluder, graft adapter, and venous and aortic valves. In addition, we will review the important properties of SIS as a covering for the square stent.

Animals↗

PubMedDate not supplied

Endoluminal treatment of ruptured abdominal aortic aneurysm with small intestinal submucosa sandwich endografts: a pilot study in sheep.

PURPOSE: To evaluate efficacy of small intestinal submucosa (SIS) Sandwich endografts for the treatment of acute rupture of abdominal aortic aneurysms (AAA) and to explore the short-term reaction of the aorta to this material. METHODS: In eight adult sheep, an infrarenal AAA was created transluminally by dilation of a short Palmaz stent. In six sheep, the aneurysm was then ruptured by overdilation of the stent with a large angioplasty balloon. Two sheep with AAAs that were not ruptured served as controls. A SIS Sandwich endograft, consisting of a Z stent frame with 5 bodies and covered inside and out with SIS, was used to exclude the ruptured and non-ruptured AAAs. Follow-up aortography was done immediately after the procedure and before sacrifice at 4, 8, or 12 weeks. Autopsy and histologic studies followed. RESULTS: Endograft placement was successful in all eight sheep. Both ruptured and non-ruptured AAAs were successfully excluded. Three animals with AAA rupture developed hind leg paralysis due to compromise of the arterial supply to the lower spinal cord and were sacrificed 1 day after the procedure. In five animals, three with rupture and two controls, follow-up aortograms revealed no aortic stenoses and no perigraft leaks. Gross and histologic studies revealed incorporation of the endografts into the aortic wall with replacement of SIS by dense neointima that was completely endothelialized in areas where the endograft was in direct contact with the aortic wall. In central portions of the endograft, in contact with the thrombosed aneurysm, endothelialization was incomplete even at 12 weeks. CONCLUSION: The SIS Sandwich endografts effectively excluded simple AAAs and ruptured AAAs. They were rapidly incorporated into the aortic wall. A detailed long-term study is warranted.

Angioplasty↗

PubMedDate not supplied

Percutaneous transcatheter aortic disc valve prosthesis implantation: a feasibility study.

PURPOSE: Over the past 30 years there have been experimental efforts at catheter-based management of aortic valve regurgitation with the idea of extending treatment to nonsurgical candidates. A new catheter-based aortic valve design is described. METHODS: The new catheter-delivered valve consists of a stent-based valve cage with locking mechanism and a prosthetic flexible tilting valve disc. The valve cage is delivered first followed by deployment and locking of the disc. In acute experiments, valve implantation was done in four dogs. RESULTS: Valve implantation was successful in all four animals. The implanted valve functioned well for the duration of the experiments (up to 3 hr). CONCLUSION: The study showed the implantation feasibility and short-term function of the tested catheter-based aortic disc valve. Further experimental studies are warranted.

Animals↗

PubMedDate not supplied

Polyurethane-coated Dacron-covered stent-grafts for TIPS: results in swine.

PURPOSE: To evaluate shunt patency after placing a new polyurethane-coated Dacron-covered spiral Z stent-graft to create a transjugular intrahepatic portosystemic shunt (TIPS). METHODS: TIPS stent-grafts were placed in six young swine, using polyurethane-coated, Dacron-covered spiral Z stent-grafts. Animals were followed weekly by transhepatic portal venography until shunt occlusion or up to 6 weeks, then were sacrificed for gross and histologic evaluation. RESULTS: Five of six TIPS stent-grafts were found to be occluded by 3 weeks and none were patent at 6 weeks. Histologic evaluation demonstrated a marked foreign body reaction with superimposed thrombosis occluding the graft lumen. CONCLUSION: Polyurethane-coated Dacron-covered stent-grafts do not improve TIPS patency.

Animals↗

PubMedDate not supplied

Retrievable IVC square stent filter: experimental study.

PURPOSE: In vitro and in vivo evaluation of a new retrievable, home-made, inferior vena cava (IVC) Square stent filter (SSF) with two trapping levels. METHODS: In vitro, the SSF was compared in a flow model with the stainless steel Greenfield filter (SGF) for emboli-trapping efficiency by serially passing 300 emboli of 3 and 6 mm in diameter and 15-30 mm in length in each type of filter. Nine swine were used for the in vivo testing of the SSF for deployment and retrievability, emboli-trapping efficiency, stability, and self-centering ability and two were used (total of 11 swine) for testing repositioning and retrievability of the SSF at 2 weeks and for gross and histologic IVC changes at 2 months. RESULTS: In vitro, the SSF and SGF had similar efficiency in trapping large emboli but the SSF had significantly better efficiency than the SGF for trapping all sizes of emboli (91.7% vs 81%), medium size emboli (93% vs 80%), and small emboli (86% vs 69%). Efficiency decreased in both filters from the first to the fifth embolus in each series but was still significantly better for the SSF. With the SSF, 89% of emboli were caught at the primary and 11% at the secondary filtration level. In the nine animals used for acute studies, the SSF was easily placed in all 27 attempts, assumed a central position 26 times, and was easily retrieved in 21 of 22 attempts. One tilted filter needed additional manipulation for retrieval. During emboli injection in five swine, the SSF had 97.2% emboli-trapping efficiency and demonstrated good stability. In the two animals used for longer-term evaluation, the filters were easily retrieved 2 weeks after implantation. Histologic evaluation at 2 months showed neointimal proliferation around the SSF wires in contact with the IVC wall, which was otherwise normal. CONCLUSION: The SSF is a promising filter. It is easy to place and retrieve, is stable after placement, and has high efficiency for trapping emboli. Promising results justify further experimental and eventual clinical studies with a commercially manufactured SSF.

Animals↗

PubMedDate not supplied

Small intestinal submucosa covered expandable Z stents for treatment of tracheal injury: an experimental pilot study in swine.

PURPOSE: To evaluate efficacy of small intestinal submucosa (SIS) as a stent covering in healing experimentally created tracheal defects and to explore the trachea's reaction to placement of SIS-covered stents. MATERIAL AND METHODS: A tracheal defect with a diameter of approximately 10 mm was created in six swine with use of a blade or electrocauterization. A double-body, self-expandable SIS-covered Gianturco Rösch Z stent was placed into the trachea to cover the defect. The animals were observed, and were killed when they developed respiratory problems. Autopsy and histologic studies were performed. RESULTS: The SIS-covered stents were accurately placed without immediate complications related to placement. All animals developed respiratory problems on follow-up. One animal died 9 days after procedure because of pneumonia, the others five were killed at 12, 17, 18, 28, and 56 days because of stridor, wheezing, and cough. At autopsy and histology, the tracheal defects were found to be completely healed, with epithelial lining and regeneration of submucosal glands. Animals whose defects were created with a blade demonstrated cartilage remodeling between 9 and 18 days, and apparent deposition of new cartilage at 28 days after SIS placement. The defects made by electrocauterization showed only fibrous tissue with no cartilage regeneration. The tracheal lumen was narrowed by overgrowth of granulation tissue, particularly at the end wires of the stents. In three animals, polypoid masses caused 60%, 70%, and 80% tracheal obstruction, respectively. CONCLUSION: Placement of SIS-covered stents contributed to rapid and effective healing of large tracheal defects. Rigidity and oversizing of Gianturco Rösch Z stents led to secondary changes of the tracheal wall, causing significant airway obstructions. Smaller size and flexible stents should be selected for future work.

Animals↗

PubMedDate not supplied

Attempted induction of chronic portal venous hypertension with polyvinyl alcohol particles in swine.

PURPOSE: Creation of presinusoidal chronic portal venous hypertension by means of repeated portal vein (PV) embolization was explored in an attempt to improve a porcine model of transjugular intrahepatic portosystemic shunt (TIPS) patency. MATERIALS AND METHODS: Six microswine underwent weekly PV embolization for 5 weeks with a total of 10.4-12.6 g of polyvinyl alcohol (PVA) particles (0.149-0.250 mm in size). Portography, liver function tests, pressure measurement in the PV and inferior vena cava (IVC) before and after PV embolization, and histopathologic evaluation of the livers were performed. RESULTS: Transhepatic portal venography performed after each embolization demonstrated diffuse PV branch occlusion in all cases. At weekly follow-up, reconstitution of flow was demonstrated in these branches; permanent occlusion of PV branches was not achieved. The mean PV pressure elevated acutely from 17.3 mm Hg +/- 0.9 to 24.5 mm Hg +/- 4.2 (P < .01) after each embolization. However, the pressure always returned to baseline on the follow-up studies 1 week later. Liver function tests were normal. Histopathologic evaluation of the liver showed, in multiple PV branches, central plugs of PVA with peripheral recanalization. The liver parenchyma was otherwise normal. CONCLUSION: Massive embolizations of PV with PVA at weekly intervals failed to create permanent portal hypertension or induce hepatic fibrosis.

Animals↗

PubMedDate not supplied

Percutaneous transthoracic duct catheterization to the neck and esophagus: a feasibility study.

PURPOSE: To assess the feasibility of inserting a drain catheter percutaneously from the cisterna chyli (CC) through the thoracic duct (TD) wall to the neck or esophagus for potential long-term T-cell sampling or drainage in acute or short-term experiments. MATERIALS AND METHODS: Percutaneous transabdominal catheterization of the TD from the CC was performed in four animals to insert a 65-cm, 21-gauge needle over a microguidewire. In two dogs, the distal TD was perforated into the neck to connect the TD drain to an access port. In acute experiments on two swine, the esophagus was accessed by puncturing an intraluminal Foley-catheter balloon through the mid TD wall. In one animal, the TD catheter tip was left to drain in the distal esophagus; in the other animal, the catheter distal tip was pulled back through a gastrostomy until the proximal end had retracted into the proximal TD. RESULTS: TD-to-neck port connection was well tolerated short-term. One dog developed dehiscence over the port at 10 days necessitating its removal; in the other dog, the whole drain retracted into the neck from the proximal TD. The technique for TD-to-esophagus catheterization in swine was feasible with no acute complications or mediastinal leakage of contrast medium. CONCLUSIONS: Transabdominal percutaneous inside-out TD puncture for drainage to a neck port or to the esophagus is feasible in dogs and swine, respectively.

Animals↗