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Biomedical subjects

R I White

Publications and source records attributed to R I White.

At least 19 recordsLinked to original sources
PubMed1992

In vivo evaluation of iophendylate-cyanoacrylate mixtures.

Cyanoacrylate glue is a rapidly polymerizing agent used for vascular embolization. Polymerization occurs when the glue comes into contact with ions in the blood or on the vascular endothelium. Mixing iophendylate with cyanoacrylate causes slowing of polymerization, allowing flow-directed embolization into the nidus of an arteriovenous malformation (AVM) or the central neovascularity of a tumor or hemangioma. The authors attempted to define the relationship between the iophendylate-glue ratio and polymerization time with an in vivo swine model. In this model, glue setup occurred much more rapidly than predicted on the basis of in vitro studies. This appeared to be due to glue polymerizing on the endothelium at vessel bifurcations and at areas of acute angulation or marked vessel narrowing. On the basis of these data, the authors substantially increased the iophendylate-glue ratio in their most recent AVM embolization procedures and achieved nidus occlusion in each case. With use of the authors' guidelines, it is possible to achieve optimal distal flow-directed embolization with cyanoacrylate.

Angiography↗
PubMed1991

Experimental treatment of thrombotic vascular occlusion.

The role of laser energy in the treatment of thrombotic vascular occlusion was evaluated in two sets of experiments. First, 10 polytetrafluoroethylene grafts were used to replace segments of the superficial femoral arteries in dogs and were thrombosed by distal ligation. Occlusion was maintained for one hour, or for 7, 14, 21, and 28 days in each of two grafts. Patency was restored in all 10 grafts without perforation or anastomotic disruption using a 2 mm hot tip probe powered by an Argon laser. However, increased organization of thrombus related to the duration of occlusion lead to decreased laser channel diameters, and 75% of the 28 day thrombus remained in the graft after recanalization. The second experiments tested the added benefit of thrombolytic infusion following laser recanalization. Bilateral external iliac artery thrombosis was induced in dogs by operative vessel isolation, de-endothelialization, and thrombin injection. At 7 days the efficacy of laser-assisted thrombolysis (LAT) versus enzymatic thrombolysis (ET) alone was compared. Eight vessels underwent ET by urokinase (4000 I.U./min.); 14 vessels were laser recanalized prior to thrombolytic infusion. LAT was performed from a carotid artery approach in 8 vessels (antegrade) and from a femoral artery in 6 vessels (retrograde). In contrast to studies using the hot tip alone, both ET and LAT accomplished complete thrombus removal. However, LAT lead to significant iliac arterial flow in 9 +/- 8 min. (antegrade) and 25 +/- 8 min. (retrograde) while ET required 109 +/- 47 min (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Transcatheter detachable balloon embolotherapy for catheter-induced pulmonary artery pseudoaneurysm.

Pulmonary artery pseudoaneurysm formation may be due to various etiologies, including trauma, pulmonary artery catheterization, infection, and tumor. Transcatheter embolization is a nonsurgical management technique that may be utilized in many of these patients to occlude the affected artery and to prevent further extravasation. Recently, two patients with pulmonary artery pseudoaneurysm formation after balloon-tipped catheter placement were successfully managed with transcatheter embolotherapy with detachable silicone balloons. The article describes their diagnosis and management.

Aged↗
PubMed1991

The natural history of epistaxis in hereditary hemorrhagic telangiectasia.

The purpose of this retrospective study is to document the natural history of epistaxis in patients with hereditary hemorrhagic telangiectasia. A telephone questionnaire was administered to 73 patients who had been previously screened for pulmonary arteriovenous malformations (PAVMs). The incidence of epistaxis in this population was 93%, with a mean onset age of epistaxis of 12 years, a mean frequency of bleeding of 18 episodes per month, and a mean duration of bleeding of 7.5 minutes. More than 90% of patients experienced the onset of epistaxis before the age of 21 and symptoms were progressive with age. There were no differences in the age of onset, frequency of epistaxis, or duration of epistaxis between patients with PAVMs versus those without PAVMs. Although the natural history of epistaxis does not predict the presence or absence of pulmonary arteriovenous malformations, epistaxis is an early marker of the disease, hereditary hemorrhagic telangiectasia, and might guide screening for pulmonary and cerebral arteriovenous malformations in children of affected parents.

Adolescent↗
PubMed1990

Ex-vivo results using a new pullback atherectomy catheter (PAC).

In order to evaluate the feasibility of performing definitive atheromatous plaque removal using a novel retrograde cutting (Pullback) atherectomy catheter, pullback atherectomy was performed in 13 severely diseased cadaveric superficial femoral arteries. All experiments were performed using cadaver tissue either mounted in a perfusion/mounting chamber (n = 10) or left in situ (n = 3). In general, a single cut was made with each of three sequentially larger atherectomy catheters (2.5 mm, 3.0 mm, and then 3.5 mm devices). The results were evaluated by angiography and by light microscopy. Nine of the 13 experiments were performed in totally occluded vessels. The mean pre-atherectomy stenosis (all specimens) was 95 +/- 3%, with a final mean postatherectomy stenosis of 21 +/- 5%. There was one vessel performation. We conclude from these preclinical studies that retrograde atherectomy with the Pullback Atherectomy Catheter is a feasible means of performing definitive atherectomy. Despite the promising potential of retrograde atherectomy, little can be said with certainty about the clinical utility of such a device at this early stage.

Arteriosclerosis↗
PubMed1990

Status of admitting privileges for university-affiliated diagnostic radiology departments.

Members of the Society of Chairmen of Academic Radiology Departments (SCARD) from 135 university hospitals in Canada and the United States were surveyed regarding their experience in admitting patients to diagnostic radiology departments between 1986 and 1989. One hundred departments (74%) replied; of these, 33 departments (33%) admitted patients during 1989. From 1986 to 1989 the percentage of diagnostic radiology departments admitting patients rose from 20% to 33%. Forty-one departments had admitting privileges, and nine departments had applied for admitting privileges. The remaining 50 departments were content to admit patients to medical and/or surgical services or had no interest in obtaining admitting privileges. The rapid growth of noncardiac interventional procedures, the obvious benefit to patients whose disease is manageable with imaging-guided therapy, the increasing interest of nonradiologists in performing interventional radiologic procedures, and the potential financial benefits to the hospital that are associated with short patient stays provide incentive for diagnostic radiologists to admit patients for cardiovascular and interventional procedures.

Hospital Departments↗
PubMed1989

Ocular manifestations in hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease).

Although hereditary hemorrhagic telangiectasia is a cause of blood tears from the conjunctival telangiectasias, visual loss from intraocular vascular malformations is a rare complication. We examined 20 patients with hereditary hemorrhagic telangiectasia to determine the prevalence of ocular abnormalities in this disease. Seven patients (35%) had conjunctival telangiectasias and two (10%) had retinal vascular malformations.

Adolescent↗
PubMed1989

Benign postoperative biliary strictures. Operate or dilate?

At The Johns Hopkins Hospital from 1979 through 1987, 42 patients had 45 procedures for benign postoperative biliary strictures. Three patients were managed with both surgery and balloon dilatation. Twenty-five patients underwent surgical repair with Roux-Y choledocho- or hepaticojejunostomy with postoperative transhepatic stenting for a mean of 13.8 +/- 1.3 months. Twenty patients had balloon dilatation a mean of 3.9 times and were stented transhepatically for a mean of 13.3 +/- 2.0 months. The two groups were similar with respect to multiple parameters that might have influenced outcome. Mean length of follow-up was 57 +/- 7 and 59 +/- 6 months for surgery and balloon dilatation, respectively. No patients died after any of the procedures. The same definition of a successful outcome was applied to both groups and was achieved in 88% of the surgical and in only 55% of the balloon dilatation patients (p less than 0.02). Significant hemobilia occurred more often with balloon dilatation (20% vs. 4%, p less than 0.02). The total hospital stay and cost of balloon dilatation was not significantly different from surgery. We conclude that surgical repair of benign postoperative strictures results in fewer problems that require further therapy. Nevertheless balloon dilatation is an alternative for patients who are at high risk or who are unwilling to undergo another operation.

Catheterization↗
PubMed1989

Porcine model for the development of interventional techniques in the gallbladder.

A technique that permits repeated access to the porcine gallbladder through a surgically placed 18 French latex catheter is described and experience with this system in 22 swine is discussed. This porcine gallbladder model produces a reliable and reproducible means for studying clinically applicable interventional procedures.

Abdominal Muscles↗
PubMed1989

Frequency and determinants of adverse reactions induced by high-osmolality contrast media.

To determine the frequency of and risk factors for adverse reactions to high-osmolality contrast media, the authors prospectively studied hospitalized patients undergoing cardiac catheterization. The authors also studied patients undergoing peripheral angiography and contrast material-enhanced computed tomography (CT) of the head or body who met at least one of the following criteria thought to increase the risk of adverse reactions: age of more than 60 years, diabetes, renal or liver disease, concurrent nephrotoxic drug use, or a history of allergic reactions (n = 795). Criteria were defined and used to group adverse reactions into three classes of clinical severity. Overall, class I (mild), class II (moderate), and class III (severe) reactions occurred in 362 (45%), 44 (5.5%), and three (0.4%) patients, respectively. Class II reactions were relatively common (25%) in patients undergoing cardiac catheterization yet were uncommon (2%) in patients undergoing the other three procedures. Nephrotoxicity occurred in 18 of 651 patients who had follow-up creatinine levels obtained at 48-72 hours. With multivariate regression analysis, the only risk factor (P less than .05) for combined class II and III reactions was diabetes. Diabetes, furosemide use, and a history of atopy (odds ratio = 2.8) were associated with nephrotoxicity (P less than .05). Underlying renal insufficiency was not a risk factor for nephrotoxicity.

Adult↗
PubMed1989

Etiologic factors in renovascular fibromuscular dysplasia. A case-control study.

The role of several factors that have been suggested as being of etiologic importance in renovascular fibromuscular dysplasia was examined in a case-control study of 33 patients with angiographically demonstrated fibromuscular dysplasia and 61 renal transplant donor control subjects with normal renal arteries. The factors studied included use of oral contraceptive agents or markers of sex hormone dysfunction, mechanical stress to the renal artery wall, human lymphocytic antigen (HLA) type, cigarette smoking, history of hypertension for more than 5 years, and family history of cardiovascular disease. The risk of fibromuscular dysplasia was significantly (p = 0.003) increased (odds ratio = 4.1, 95% confidence interval = 1.5-10.9) among cigarette smokers. A significant (p less than 0.001) dose-response relation was noted between cigarette use and the risk of fibromuscular dysplasia developing (odds ratio = 8.6 for those who had smoked more than 10 pack-years). Personal history of hypertension more than 5 years was also associated (odds ratio = 5.0, 95% confidence interval = 1.1-22.8) with a significantly (p = 0.036) increased risk for the development of fibromuscular dysplasia. HLA-DRw6 antigen was more common in the 33 fibromuscular dysplasia patients than in the 61 renal transplant donor control subjects (odds ratio = 3.00, p = 0.067) or a second group of 934 ambulatory control subjects (odds ratio = 2.51, p = 0.031). Adjustment for cigarette smoking increased the odds ratio to 5.0 (95% confidence interval = 1.3-19.6). There was a positive though not statistically significant (odds ratio = 1.7, p = 0.175) association noted between family history of cardiovascular disease and fibromuscular dysplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Percutaneous laser probe femoropopliteal angioplasty: a preliminary experience.

Percutaneous laser probe "hot tip" angioplasty procedures were performed on 47 occluded femoropopliteal artery segments in 27 men and 10 women ranging in age from 31 to 92 (mean, 64.7) years. Indications for the procedure included claudication in 29 (78%) segments, and the occlusion lased was greater than 7 cm in length in 51% of the procedures. Failure to recanalize the occlusion occurred in 14 (30%) segments, and recanalization followed by in-hospital reocclusion occurred in seven (15%) segments, yielding an initial failure rate of 45%. Initial failures were noted in 40% of the less than 3 cm occlusions, 33% of the 4 to 7 cm occlusions, and 54% of the greater than 7 cm occlusions. In nine (43%) instances in these 21 failures there was extension of the occluded segment or decline of the ankle/brachial index or both, precipitating the need for surgery in three (18%) of these 17 patients. Among the successfully treated group, 17 (65%) of these vessels in 15 patients reoccluded from 1 to 14 (mean, 3 1/2) months after the procedure. Cumulative patency among the successfully lased vessels was 69% at 1-month, 38% at 6 months', 29% at 12 months', and 14% at 15 months' follow-up. Fifteen-month patency was 7% of the entire series of 47 vessels treated. Eighteen complications occurred after 15 (32%) of these 47 procedures. Based on these results, the widespread application of laser probe angioplasty cannot be justified without further clinical and laboratory investigation.

Adult↗
PubMed1988

Treatment of a case of thromboembolism resulting from thoracic outlet syndrome with intra-arterial urokinase infusion.

A 36-year-old man with thoracic outlet syndrome, admitted to the hospital with digital ischemia from subclavian artery thrombosis and distal embolization, was given intra-arterial urokinase. Thrombus in the subclavian artery was lysed successfully and peripheral emboli were partially cleared, resulting in relief of digital symptoms. Although surgical decompression and vascular reconstruction at the thoracic outlet may be necessary, this technique provides a means of recanalizing small distal vessels.

Adult↗