Search PubMed⌕ Search

Biomedical subjects

S R Bailey

Publications and source records attributed to S R Bailey.

At least 55 records · Page 3Linked to original sources
PubMed1998

Plasma 5-hydroxytryptamine constricts equine digital blood vessels in vitro: implications for pathogenesis of acute laminitis.

Cumulative concentration response curves to 5-hydroxytryptamine (5-HT; 10(-10)-10(-4) mol/l) were constructed using isolated rings of equine digital, facial, tail and coronary arteries (endothelium intact). 5-HT was 17.7 and 41 times more potent as a vasoconstrictor of digital arteries than facial and tail arteries respectively. Removal of the endothelium increased the vasoconstrictor potency of 5-HT in the facial artery by 3.7-fold (P<0.05) but did not alter the sensitivity of digital arteries to 5-HT. Coronary arteries failed to contract to 5-HT. Coronary arteries pre-contracted with U44069 showed concentration dependent relaxation to 5-HT, a response which was partially dependent on the presence of the endothelium. No vasorelaxant effects were found in the digital or facial arteries. The concentration of 5-HT in platelet poor and platelet rich equine plasma was found to be 6.70+/-1.1 x 10(-8) mol/l and 1.77+/-0.36 x 10(-6) mol/l (mean +/-s.e.) respectively by high performance liquid chromatography (HPLC). Plasma which contained no detectable platelets had a 5-HT concentration of 1.12+/-0.48 x 10(-8) mol/l. Isolated digital arteries constricted when exposed to dilutions of platelet poor and platelet depleted equine plasma. These plasma induced contractions were almost completely inhibited by 5-HT receptor antagonists, ketanserin and methiothepin. The change in isometric tension in rings of equine digital artery in vitro was therefore used as a bioassay for plasma 5-HT and the results obtained by this method showed an excellent correlation (r2 = 97.2%, P<0.001) with the concentration estimated by HPLC. Circulating free concentrations of 5-HT in normal horses may be sufficient to constrict digital blood vessels partially in vivo but are well below the threshold for contraction of other peripheral blood vessels examined.

Animals↗
PubMed1997

Stent placement compared with balloon angioplasty for obstructed coronary bypass grafts. Saphenous Vein De Novo Trial Investigators.

BACKGROUND: Treatment of stenosis in saphenous-vein grafts after coronary-artery bypass surgery is a difficult challenge. The purpose of this study was to compare the effects of stent placement with those of balloon angioplasty on clinical and angiographic outcomes in patients with obstructive disease of saphenous-vein grafts. METHODS: A total of 220 patients with new lesions in aortocoronary-venous bypass grafts were randomly assigned to placement of Palmaz-Schatz stents or standard balloon angioplasty. Coronary angiography was performed during the index procedure and six months later. RESULTS: As compared with the patients assigned to angioplasty, those assigned to stenting had a higher rate of procedural efficacy, defined as a reduction in stenosis to less than 50 percent of the vessel diameter without a major cardiac complication (92 percent vs. 69 percent, P<0.001), but they had more frequent hemorrhagic complications (17 percent vs. 5 percent, P<0.01). Patients in the stent group had a larger mean (+/-SD) increase in luminal diameter immediately after the procedure (1.92+/-0.30 mm, as compared with 1.21+/-0.37 mm in the angioplasty group; P<0.001) and a greater mean net gain in luminal diameter at six months (0.85+/-0.96 vs. 0.54+/-0.91 mm, P=0.002). Restenosis occurred in 37 percent of the patients in the stent group and in 46 percent of the patients in the angioplasty group (P=0.24). The outcome in terms of freedom from death, myocardial infarction, repeated bypass surgery, or revascularization of the target lesion was significantly better in the stent group (73 percent vs. 58 percent, P = 0.03). CONCLUSIONS: As compared with balloon angioplasty, stenting of selected venous bypass-graft lesions resulted in superior procedural outcomes, a larger gain in luminal diameter, and a reduction in major cardiac events. However, there was no significant benefit in the rate of angiographic restenosis, which was the primary end point of the study.

Aged↗
PubMed1997

Applications of a novel balloon catheter during coronary angioplasty.

A new balloon catheter design utilizing multiple polymeric materials to produce noncompliant balloon ends and a compliant central portion has recently been released. We describe two cases, a discrete fibrotic lesion and final dilation of an intracoronary stent, in which this novel balloon catheter has potential advantages during coronary angioplasty. We conclude that this device may be useful in avoiding proximal or distal vessel dissection during high-pressure balloon inflations.

Adult↗
PubMed1997

Angioscopic evaluation of site-specific administration of ReoPro.

Systemic administration of newer antiplatelet agents such as the GP IIb/IIIa agent ReoPro (Centocor BV Leiden, The Netherlands) has been shown to decrease the early incidence of recurrent ischemia and recurrent myocardial infarction. The currently approved protocol for administration of ReoPro involves an initial weight adjusted bolus followed by a systemic infusion over the next 12 hr. The systemic administration is proposed as the only route of administration because it is stated that the drug must be exposed to circulating platelets. An alternative approach would be to deliver ReoPro locally and allow the platelets to disaggregate only when in contact with the local arterial wall. The optimal method of monitoring the efficacy of such a strategy is to visually assess the presence of platelet rich or red blood cell rich thrombus using angioscopy. We report our initial experience in 12 patients who received local administration of ReoPro using currently approved catheters for local administration of agents into coronary arteries who were evaluated before and after intervention using intracoronary angioscopy. None of the patients received a subsequent 12-hr infusion. There was successful resolution of thrombus in 11 of 12 patients. Recurrent ischemia occurred in one patient without myocardial infarction.

Abciximab↗
PubMed1997

Novel technique for coil embolization of intercostal branch of internal mammary artery graft.

Coronary artery steal resulting from a large unligated intercostal or pericardial side branch of the internal mammary artery graft causing postoperative angina has been previously described. Transcatheter coil occlusion of internal mammary artery side branch has successfully been performed to treat coronary steal syndrome. Unsuccessful deployment of the microcoils can be due to inadequate guiding support in the LIMA or prolapse of the delivery catheter in the side branch. We report a new approach for the precise deployment of coils in the side branch of a LIMA graft, when inadequate guiding support is present.

Angina Pectoris↗
PubMed1997

Evaluation of the AVOXimeter: precision, long-term stability, linearity, and use without heparin.

OBJECTIVES: Because the AVOXimeter uses disposable cuvettes and makes its measurements directly in whole blood without first hemolyzing the sample, it does not need the care and maintenance that conventional co-oximeters require, it operates faster than conventional co-oximeters, and it is less expensive. Therefore, the objectives of the study were (1) to evaluate the precision and linearity of the AVOXimeter's measurements of total hemoglobin concentration and oxyhemoglobin saturation; (2) to assess its long-term stability and thus the required interval for recalibration; (3) to determine whether measurements can be made without anticoagulants; and (4) to assess the feasibility of storing blood samples in the disposable cuvettes. METHODS: Measurements made by the test instrument were compared with those of conventional co-oximeters or with standardized hemoglobin solutions. Blood samples were also collected with and without heparin to determine whether anticoagulation is necessary. RESULTS: Our tests confirmed the specified precision of 0.3 g/dl for total hemoglobin and 0.5% for oxyhemoglobin. The results also showed that these measurements were linear when compared with a conventional co-oximeter, and they were consistent with the specified accuracy of 0.45 g/dl for total hemoglobin and 1% for oxyhemoglobin. Weekly checks with control solutions showed that the instrument holds its calibration for a year or more. Although treating syringes with heparin caused dilution errors, heparin did not affect the measurements when dilution was avoided. When blood samples were placed in disposable cuvettes and read repeatedly at 1-min intervals for 20 min, the readings drifted appreciably away from the original value. This drift occurred so slowly that readings taken at the first and second minute after the cuvette was filled were within 1 or 2% of the original reading. CONCLUSIONS: In our experience the test instrument was simple and easy to operate. It met the specification for precision and accuracy, its measurements were highly linear, and it maintained a stable calibration for one year. If the cuvettes are filled as soon as blood is drawn, anticoagulation is unnecessary. However, the cuvettes should be read with 1 min of filling the cuvette.

Blood Specimen Collection↗
PubMed1996

Interleukin-2 receptor-specific fusion toxin inhibits barotrauma-induced arterial atherosclerosis.

Immunocytochemical analyses of human plaques and experimental arterial lesions have implicated activated lymphocytes and monocytes in the pathogenesis of atherosclerosis, as demonstrated by the expression of interleukin-2 (IL-2) membrane receptors and major histocompatibility complex class II epitopes. The objective is to determine if targeting these cells with an IL-2 receptor-specific chimeric toxin, DAB486-IL-2, can inhibit experimental post-angioplasty vascular neointimal thickening. Twenty-two atherogenically modeled rabbits were treated in vivo with DAB486-IL-2 (0.1 mg/kg per day i.v.; n = 11) or placebo (n = 11) for 10 days following aortic balloon angioplasty (4 atm x 30 s each x 2 dilatations). In vitro 3H-leucine incorporation studies of mononuclear leukocyte and vascular smooth muscle cell protein synthesis inhibition by DAB486-IL-2 were also performed. Angioplasty sites were examined for evidence of hyperproliferative atherosclerotic narrowing by quantitative angiography and histomorphometry of neointimal cross-sectional area at baseline and 6 weeks after injury. In vitro Concanavalin-A stimulated rabbit mononuclear leukocyte protein synthesis was 50% inhibited by DAB486-IL-2 at a concentration (IC50) of 6 x 10(-11) M. Rabbit vascular smooth muscle cells were approximately 150-fold less sensitive to DAB486-IL-2 (IC50 = 10(-8) M). In vivo studies showed no change in angioplasty site angiographic minimum luminal diameter at 6 weeks in DAB486-IL-2 treated animals (from 2.96 +/- 0.52 to 2.96 +/- 0.48 mm; percent cross-sectional area reduction = 1 +/- 10%; P = N.S.). In control animals, luminal diameter decreased from 2.79 +/- 0.4 to 2.32 +/- 0.52 mm at 6 weeks, and percent cross-sectional area was reduced by 34 +/- 14% (P < 0.01 vs. placebo). Quantitative histomorphometric angioplasty segmental intimal cross-sectional area reduction of treated and placebo vessels also differed significantly (19 +/- 16% vs. 31 +/- 21%; P < 0.05). DAB486-IL-2 caused no adverse effects on animal survival, weight or hepatic transaminase levels. We conclude that post-angioplasty administration of the chimeric toxin DAB486-IL-2 inhibits angiographic narrowing and neointimal thickening in the atherogenic rabbit model. Although this IL-2 receptor-specific molecule was cytotoxic in vitro for activated mononuclear leukocytes and vascular smooth muscle cells, systemic toxicity did not occur in vivo at a dose comparable to that evaluated in clinical trials of this agent. Potential anti-proliferative effects of this chimeric toxin may be mediated by direct local inhibition of leukocyte-mediated inflammation, or through the indirect modification of vascular cell mitogenesis and cytokine release.

Angioplasty, Balloon↗
PubMed1996

Insulin resistance and coronary artery disease.

The purpose of the present study was to quantitate insulin-mediated glucose disposal in normal glucose tolerant patients with angiographically documented coronary artery disease (CAD) and to define the pathways responsible for the insulin resistance. We studied 13 healthy, normal weight, normotensive subjects with angiographically documented CAD and 10 age-, weight-matched control subjects with an oral glucose tolerance test and a 2-h euglycaemic insulin (40 mU.m-2.min-1) clamp with tritiated glucose and indirect calorimetry. Lean body mass was measured with tritiated water. All CAD and control subjects had a normal oral glucose tolerance test. Fasting plasma insulin concentration (66 +/- 6 vs 42 +/- 6 pmol/l, p < 0.05) and area under the plasma insulin curve following glucose ingestion (498 +/- 54 vs 348 +/- 42 pmol.l-1.min-1, p < 0.001) were increased in CAD vs control subjects. Insulin-mediated whole body glucose disposal (27.8 +/- 3.9 vs 38.3 +/- 4.4 mumol.kg fat free mass (FFM)-1.min-1, p < 0.01) was significantly decreased in CAD subjects and this was entirely due to diminished non-oxidative glucose disposal (8.9 +/- 2.8 vs 20.0 +/- 3.3 mumol.kg FFM-1.min-1, p < 0.001). The magnitude of insulin resistance was positively correlated with the severity of CAD (r = 0.480, p < 0.05). In the CAD subjects basal and insulin-mediated rates of glucose and lipid oxidation were normal and insulin caused a normal suppression of hepatic glucose production. In conclusion, subjects with angiographically documented CAD are characterized by moderate-severe insulin resistance and hyperinsulinaemia and should be included in the metabolic and cardiovascular cluster of disorders that comprise the insulin resistance syndrome or "syndrome X'.

Blood Glucose↗
PubMed1996

Care of the elective intracoronary stent patient.

Recently, the Palmaz-Schatz coronary stent was approved by the FDA as an alternative to coronary angioplasty in the treatment of de novo native coronary stenosis. Developed by Dr. Julio Palmaz and Dr. Richard Schatz, the Palmaz-Schatz intracoronary stent design was implanted in 1987 at Brooke Army Medical Center. During the past 7 years, The University of Texas Health Science Center-San Antonio (clinical sites include University Hospital, Brooke Army Medical Center, and Audie Murphy Veterans Administration Hospital) has used this intracoronary stent to treat more than 300 patients. Nursing care for this patient population is both distinct and challenging. Successful patient outcomes require a knowledgeable staff and a team approach. This article will emphasize the nursing care and patient education required both before and after the stent procedure, as well as considerations for long-term follow-up.

Aftercare↗
PubMed1996

Mechanisms of delivery and local drug delivery technologies.

Therapy of atherosclerotic vascular disease and neointimal hyperplasia after percutaneous interventions remain enigmatic. Despite new interventional devices, we have not altered the underlying pathological process. New devices are under development that offer the opportunity to deliver high concentrations of therapeutic agents directly to the diseased segment. The devices fall into three major mechanisms of delivery (1) diffusion, (2) infusion under pressure and (3) mechanical delivery. Diffusion catheters are atraumatic but require prolonged exposures in excess of 20 min while the pressurized infusion and mechanical catheters are more traumatic. Additionally, each system will need to be characterized with respect to efficiency of delivery with each agent used. The clinical opportunity for site-specific treatment of vascular disease is rapidly approaching. In the near future we will be able to open a narrowed vessel and also apply some agent into the lesion to facilitate healing.

Animals↗
PubMed1995

Effects of chronic beta-blockade on rest and exercise hemodynamics in mitral stenosis.

beta-blocker therapy for mitral stenosis is controversial. This study compares right and left heart hemodynamics at rest and supine submaximal exercise in patients (n = 7) receiving chronic beta-antagonists with untreated patients (n = 17) matched for age (mean +/- SD = 51 +/- 12 years) and valve area (0.7 +/- 0.2 cm2/m2). Little benefit was observed with treatment at rest. Although pulmonary capillary wedge pressures (PCWP) were lower during exercise in the beta-blocker group (22 +/- 4 vs. 31 +/- 9 mmHg; P < 0.05), exercise performance was not enhanced and cardiac output response during exercise was reduced (control = 41% increase vs. 12% for beta-blockade). PCWP rose rapidly when diastolic filling periods were < 300 msec in both groups. Pulmonary capillary wedge pressure was found to be a nonlinear functions (P < 0.001) of diastolic filling period (PCWP = 15.9 + 5.84 x 10(5)/dfp2). These data suggest that there is a critical heart rate in patients with mitral stenosis above which hemodynamic compromise rapidly occurs.

Adrenergic beta-Antagonists↗
PubMed1995

Coronary artery stenting in active duty soldiers.

The treatment of coronary artery disease in young patients must take into account the long-term success of the treatment modality and the possibility of repeat interventions. Elective placement of Palmaz-Schatz coronary stents have been shown to reduce six month restenosis rates in discrete, de novo lesions in native coronary arteries albeit at a significant risk of bleeding and vascular complications. The present study was undertaken to evaluate the role of intracoronary stenting in young active duty soldiers. Between March 1988 and December 1994, fifteen active duty soldiers (age 37 to 53 years) underwent elective placement of one or more Palmaz-Schatz coronary stents at our institution. Angiographic success was 100% with no complications (acute/subacute closure, bleeding requiring transfusion, vascular repair, myocardial infarction, death, or in-hospital coronary artery bypass grafting). Six month angiographic follow-up is available in 13 patients (87%) with angiographic restenosis in one patient (8%) and no target vessel revascularization at six months. Clinical follow-up is available on all patients at a mean of 33 months (range 6-65) after the procedure. There was one death (7%) attributed to progression of coronary disease in another vessel and one patient (7%) who underwent target vessel revascularization for silent ischemia at 24 months after the procedure. These preliminary encouraging results suggest there may be a significant role for intracoronary stenting in active duty soldiers with coronary artery disease.

Adult↗
PubMed1994

Echocardiographic assessment of right and left ventricular function after single-lung transplantation.

To evaluate the impact of single-lung transplantation on right and left ventricular performance and to identify potential preoperative characteristics that could predict postoperative outcome, a large group of patients were retrospectively evaluated by means of serial Doppler echocardiography. Twenty-six of 57 consecutive single-lung transplant patients had satisfactory Doppler echocardiographic studies before and after surgery. A significant reduction in right ventricular diastolic and systolic areas and an increase in right ventricular fractional area were noted after transplantation. The left ventricular contractility remained unchanged. In addition, significant reduction in right atrial area, right ventricular free wall thickness, and tricuspid regurgitation were also seen. Paradoxical septal motion present in eight patients before the procedure resolved in all of them after single-lung transplantation. Transthoracic echocardiography is a useful technique to document improvement in right ventricular function in 63% of patients following single-lung transplantation. Preoperative paradoxical septal motion identifies single-lung transplant recipients who have the largest postoperative right ventricular area reduction and fractional area increase. Alternative imaging modalities should be sought for single-lung transplant candidates in whom conventional transthoracic echocardiography is suboptimal.

Adult↗
PubMed1993

Comparison of results of percutaneous balloon valvuloplasty in patients with mild and moderate mitral stenosis to those with severe mitral stenosis. The North American Inoue Balloon Investigators.

Most reported studies of percutaneous balloon valvuloplasty in adults with acquired mitral stenosis have used patients with severely stenosed valves. The risks and benefits of valvuloplasty were examined in a multicenter registry of patients to determine whether balloon valvuloplasty can effectively dilate less severely obstructed valves, and to clarify the role of this procedure in symptomatic patients with mild and moderate mitral stenosis. The study groups were derived from the North American Inoue Balloon Valvuloplasty Registry. Full hemodynamic data were available in 264 patients; 45 (17%) with mild or moderate mitral stenosis (mitral valve area > or = 1.3 cm2) were compared with the remaining 219 with severe mitral stenosis (valve area < 1.3 cm2). Percutaneous balloon valvuloplasty was performed using the anterograde transseptal technique with an Inoue balloon. The mean age of patients with mild and moderate mitral stenosis was 53 +/- 13 years, and all were symptomatic with a mean New York Heart Association functional class of 2.9 +/- 0.7. Balloon valvuloplasty resulted in an increase in calculated mitral valve area from 1.4 +/- 0.1 to 2.3 +/- 0.7 cm2 (p < 0.05), and a final valve area > or = 1.9 cm2 was achieved in 37 patients (82%). There were no procedural deaths, but complications included right atrial perforation, transient ischemic attack and emergency surgery for severe mitral regurgitation. One-year follow-up evaluation revealed symptomatic improvement in most patients (mean New York Heart Association class 1.4 +/- 0.6; p < 0.0001). However, 2 patients needed repeat valvuloplasty for restenosis, and 5 had mitral valve replacements.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗