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Biomedical subjects

R G Dreesen

Publications and source records attributed to R G Dreesen.

33 records · Page 2Linked to original sources
PubMed1988

Radiofrequency balloon angioplasty. Rationale and proof of principle.

Post-angioplasty restenosis (PARS) in atherosclerotic lesions of medium and small arteries occurs in about one-third of cases in the first year following percutaneous transluminal angioplasty (PTA) (early PARS). PARS includes acute spasm, dissection with reclosure, elastic recoil, fibrocellular proliferative response, and progressive atheromatous disease. Fibrocellular proliferation (possibly initiated by platelet derived growth factor) is felt to be culpable in many cases of early PARS (months). Pharmacologic regimens, stents, and thermal welding of the intimal-medial cracks of PTA are among the interventions being developed to deal with PARS. Radiofrequency (RF) current as a source of thermal energy may be useful in combination with balloon angioplasty to reduce PARS. Ideally, this combination would (1) weld intimal-medial cracks of PTA; (2) mold plaque and normal vessel to increase lumen diameters without creating intimal-medial cracks; and (3) destroy medial smooth muscle cells and multipotential cells (cellular substrate of PARS). Canine in vivo studies have established the feasibility of RF-mediated vascular tissue welding. Human aortic specimens (N = 28) were manually dissected into intima-media and media-adventitia layers. Bipolar RF energy (650 KHz, total 300 J) and mechanical pressure (1 atm) (experimental group, N = 24) or mechanical pressure alone (control group, N = 4) were applied to the reapposed specimen layers in a special chamber. The chamber was modified with a bipolar electrode designed to reproduce that planned for an RF balloon angioplasty catheter. Welding was demonstrated in normal and atherosclerotic treated specimens (23/24 or 96%) but not controls (0/4).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1987

Detection of acute gastrointestinal bleeding by intra-arterial Tc-99m sulfur colloid scintigraphy in a canine model. Preliminary study.

The diagnostic sensitivities of arteriography, intravenous (IV) Tc-99m sulfur colloid scintigraphy, and intra-arterial (IA) Tc-99m sulfur colloid scintigraphy were evaluated in a canine model of gastrointestinal bleeding. Fifteen dogs were studied at bleeding rates ranging from .4 to 1.0 ml/minute. All three studies were obtained in six of the 15 dogs. Intravenous scintigraphy was superior to angiography in two cases, inferior in three, and equal in one. No significant difference could be shown between these two tests at these bleeding rates. Intra-arterial scintigraphy was superior to angiography in four cases and equal in two (P = .06). It was superior to IV scintigraphy in five cases and inferior in one (P = .10). In this small preliminary study, IA scintigraphy appears to be superior to the other two modalities and may prove useful in the detection of acute bleeding at the time of negative arteriography, and in serial studies in patients receiving Pitressin.

Acute Disease↗
PubMed1986

Intracoronary administration of streptokinase in a canine model. Disturbance in thromboxane A2-prostacyclin balance.

The potential impact of local intracoronary infusion of streptokinase (SK) on vascular prostaglandin synthetic pathways was studied in a canine model. Control animals (n = 10) underwent left coronary artery (LCA) infusion of 50,000 units SK for 90 minutes; experimental animals (n = 10) underwent LCA infusion of normal saline. Plasma samples for radioimmunoassay (RIA) of prostacyclin (PGI-2) and thromboxane (TXA-2) were obtained from the coronary sinus (CS) as follows: one sample preinfusion, six samples during infusion, and three samples postinfusion in each animal. Comparisons between control and experimental plasma levels of PGI-2 and TXA-2 were made for each sampling time. The PGI-2 levels remained at or below the lower limits of detectability by RIA (the most sensitive assay available) in both control and experimental animals. TXA-2 levels were higher in experimental than in control animals at all sampling times, with the most significant differences occurring in samples 3 (after 30 minutes of infusion, .001 less than P less than .01), 4 (after 45 minutes of infusion, .05 less than P less than .10), and 5 (after 60 minutes of infusion, .02 less than P less than .05). We suggest (1) it is unlikely that any of the beneficial effects of coronary streptokinase infusions are PGI-2-mediated, (2) that the TXA-2 increases in our model may represent a pathophysiologic-biochemical correlate of previously identified morphologic evidence of endothelial damage in animals infused with fibrinolytic agents, and (3) that our findings may indicate that fibrinolytic infusions produce competing effects: lysis of thrombi and endothelial injury with TXA-2 production.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Percutaneous creation of arteriovenous hemodialysis grafts: work in progress.

PURPOSE: To develop a technique of percutaneous creation and/or revision of arteriovenous hemodialysis access grafts, and to study the feasibility of the technique in the acute setting. MATERIALS AND METHODS: Arteriovenous shunts, consisting of silicone-covered Wallstents 6 (n = 10) or 8 (n = 1) mm in diameter and 11-17 cm in length, were created in 10 mongrel dogs. All shunts were created percutaneously except one, in which the carotid artery was exposed surgically and the jugular vein accessed percutaneously to create a straight external graft. All other grafts were femoral loops (femoral artery to femoral vein). Eight were tunneled subcutaneously and three were left external. All shunts were delivered through 10-F peel-away sheaths. RESULTS: The 11 shunts were allowed to flow for a mean of 4 hours (range, 1.0-6.5 hours) before the animals were killed. Leakage around the "anastomoses" was not observed. Leaks in the silicone covering were observed, resulting in one early shunt failure. Two attempted survival experiments were aborted due to early shunt dislodgment at 1.5 and 3.5 hours. CONCLUSIONS: Percutaneous arteriovenous shunt creation is feasible through acceptably small sheaths. Peel-away sheath placement of the stent circumvents the technical problem of placing a closed device into both artery and vein. This technique may allow percutaneous revision of existing hemodialysis access grafts and possibly de novo creation of grafts in humans, but modification of the grafts will be needed to prevent dislodgment.

Animals↗
PubMedDate not supplied

Preclinical in vivo testing of a rotational mechanical thrombolytic device.

PURPOSE: To establish the safety and efficacy of the Arrow Trerotola mechanical percutaneous thrombolytic device (PTD) for restoring patency of thrombosed hemodialysis grafts. MATERIALS AND METHODS: The hindlimb model of dialysis grafts was created in six dogs. Animals had either unilateral (n = 4) or bilateral (n = 2) polytetrafluoroethylene grafts, totaling eight grafts. Grafts were deliberately clotted 48 hours before thrombolysis. Thrombolysis was performed with five different versions of the PTD constructed of stainless steel (n = 12) or nitinol (n = 26) and rotated with use of a hand-held motor drive. After thrombolysis, fistulography was performed. RESULTS: Thirty-eight procedures were performed with the PTD, with 100% success. Thirty-day patency, evaluated in a subset of 15 procedures, was 100%. Complications included a single arterial embolus (2.6%) and eight device breakages (21%, all but two with the stainless steel version); none had any clinical consequences. A final modification of the nitinol device yielded 11 consecutive procedures without further breakage. No residual thrombus occurred in any procedure. Pathologic examination showed no significant injury to the vessels or neointima. CONCLUSION: The PTD is highly effective for mechanical thrombolysis in an animal model of clotted dialysis grafts. Based on this animal model, the device appears safe in its final modified form.

Alloys↗
PubMedDate not supplied

Apicoaortic valved conduits in a canine model.

Evaluating new developments in surgical methods and materials of aortic bypass prosthetics requires the use of an appropriate animal model, a well established surgical protocol and post surgical aortography. This article describes the surgical technique, post operative care and the angiographic technique used for an apicoaortic conduit placement in a canine model.

Animals↗
PubMedDate not supplied

Gd-enhanced MR imaging of acute and chronic experimental demyelinating lesions.

Experimental allergic encephalomyelitis, a demyelinating disease with marked similarity to multiple sclerosis, was produced in two of 12 dogs. All dogs were studied with serial MR imaging. T1- and T2-weighted MR images were obtained both before and after IV Gd-DTPA. Multiple, new periventricular white matter demyelinating lesions were observed after each clinical episode of the disease. Like multiple sclerosis, the acute lesions of experimental allergic encephalomyelitis on T2-weighted MR images were indistinguishable from the older, more chronic lesions. However, after Gd-DTPA, there was bright paramagnetic enhancement of the acute lesions and, in one animal, no enhancement of the chronic lesions on T1-weighted MR images. At necropsy, the differences in the MR paramagnetic enhancement correlated well with the relative histologic age of the demyelinating lesions. Our results suggest that MR with Gd-DTPA may be used to differentiate acute, active demyelinating lesions from the more chronic, inactive lesions in this animal model.

Acute Disease↗
PubMedDate not supplied

Creation of atheromatous plaques in experimental animals.

Research of the dissolution of atheromatous plaques requires animal testing before any delivery system can be used on human beings. Using Flemish Giant rabbits, atheromatous plaques are created in our radiology research laboratory by a surgical air drying technique and a high cholesterol diet. Plaque development is monitored by ultrasound scanning and serial angiography.

Animals↗
PubMedDate not supplied

Cerebral angiography of the dog.

Cerebral angiography of the dog performed in the radiology research laboratory is used to demonstrate the results of surgical and imaging research for which the canine model is used. This article describes the catheterization and radiographic techniques of a cerebral angiogram performed in the evaluation of a canine model being developed for use in a study of cerebral aneurysms.

Animals↗
PubMedDate not supplied

Considerations in the humane use of laboratory animals in radiology research.

Our institution has recognized both the scientific and ethical responsibilities for the humane treatment of laboratory animals in the Radiology Research Laboratory. The Laboratory Animal Resource Center is specific in its requirements for the procurement, housing, and general care given to those animals used in our laboratory. In accordance with NIH guidelines, Animal Care Committee rules require investigators to provide detailed descriptions of research protocols so that appropriate care can be assured. The investigator is responsible ultimately for the thoughtful treatment of the animals before, during, and after the investigation. In the forseeable future, the use of laboratory animals will continue to be of paramount importance to the advancement of biomedical and imaging technology.

Animal Care Committees↗
PubMedDate not supplied

A computerized database management system for the radiology research laboratory.

A computerized database management system is being used in our radiology research laboratory. Daily lab activities, inventory records, and experimental data are retrieved easily for editing and reporting purposes. Our database management system is an accurate, efficient system that is easily accessible and requires minimal manpower to maintain.

Database Management Systems↗
PubMedDate not supplied

Effects of streptokinase in thrombolytic therapy: a radiology research project.

A radiology research project investigating the relationship between vascular endothelial injury and thrombolytic therapy using streptokinase has provided valuable data that indicates the need for a re-evaluation of such therapy and warrants further investigation in the animal laboratory. The role of the radiology research technologist in such research is explained as well.

6-Ketoprostaglandin F1 alpha↗