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Biomedical subjects

C J White

Publications and source records attributed to C J White.

At least 19 recordsLinked to original sources
PubMed1992

A new balloon-expandable tantalum coil stent: angiographic patency and histologic findings in an atherogenic swine model.

The angiographic patency and histologic characteristics of a new balloon-expandable tantalum stent were studied after implantation intervals ranging from 1 to 32 weeks in atherogenic miniature swine peripheral and coronary arteries. Stents were placed in 34 arteries (10 coronary and 24 iliac arteries) in a total of 13 swine. Two swine died within 24 h of stent implantation. Follow-up angiography was performed before death was induced in 11 swine (8 coronary and 19 iliac arteries) and revealed 100% patency without evidence of lumen stenosis, thrombosis or migration of the stents. The neointimal thickening was maximal at 4 weeks after stent implantation and was at its minimum at 32 weeks after implantation with reendothelialization of the stents generally complete at that time. An advantage of this balloon-expandable device is its inherent longitudinal flexibility. The coil configuration allowed the nondeployed stent to negotiate acute bends in coronary arteries to reach the site of implantation and also allowed the deployed stent to conform to the natural contour of tortuous coronary arteries. The tantalum device was remarkable for its radiographic visibility, which greatly aided its placement under fluoroscopic guidance. This study demonstrates this stent's ease of implantation, excellent patency rate and absence of restenosis due to neointimal proliferation for up to 8 months in this atherogenic swine model.

Angioplasty, Balloon, Coronary↗
PubMed1992

Ambiguous coronary angiography: clinical utility of intravascular ultrasound.

We report the use of intravascular ultrasound (IVUS) in situations where angiography was ambiguous or uncertain in assessing the significance of coronary stenoses. The indications for performing intravascular ultrasound were 1) angiographic findings did not correlate with the clinical presentation (n = 5) and 2) the lesion was not seen well by angiography because of overlapping vessels at the site of suspected stenosis (n = 3). We studied eight lesions in seven patients. Six nonobstructive stenoses on angiography were shown by IVUS to be significant. In two patients, stenoses were thought to be significant on angiography, but, due to overlapping of the vessels, there was doubt regarding the severity of the narrowing. In these two patients, IVUS clearly showed that the lesions were nonobstructive. As seen from the above results, angiography underestimated 6/8 stenoses and overestimated in 2/8 stenoses when compared to IVUS. We conclude that IVUS can be used to clarify ambiguous angiographic findings which can have a major impact on the clinical decision making.

Aged↗
PubMed1992

Intracoronary thrombus: chronic urokinase infusion and evaluation with intravascular ultrasound.

Percutaneous revascularization of coronary arteries with intraluminal thrombi is a clinical problem. We report a patient in whom we administered prolonged infusion of intracoronary urokinase and then assessed the stenosis with intravascular ultrasound before and after atherectomy. We found both angiography and intravascular ultrasound to be misleading in determining the presence of residual thrombus after thrombolysis.

Adult↗
PubMed1992

Options for percutaneous coronary and peripheral revascularization.

Angioplasty has become an established treatment for both coronary and peripheral atherosclerosis, and a number of new techniques and devices promise to improve the results of percutaneous intervention during the coming decades. It is likely that balloon angioplasty will remain the percutaneous treatment of choice for both coronary and peripheral intervention; however, we look with hope toward the development of new devices that will expand the role of percutaneous angioplasty and improve the long-term success of these procedures. As technical expertise grows with the new procedures, prospective randomized trials comparing them with standard PTCA will be required to enable physicians to judge their clinical utility.

Angioplasty, Balloon, Coronary↗
PubMed1992

Immune response of elderly individuals to a live attenuated varicella vaccine.

The Oka strain live attenuated varicella-zoster virus (VZV) vaccine was administered subcutaneously to 202 VZV-immune individuals who were 55 to greater than 87 years old. The dose administered varied from 1100 to 12,000 pfu. One cohort received 3000 pfu with a 3000 pfu booster 3 months later. The vaccine was well tolerated. VZV-specific immunologic responses were evaluated over a 24-month period. The mean anti-VZV antibody level was significantly increased for 12 months after vaccination. Interferon-gamma production in vitro by peripheral blood mononuclear cells (PBMC) of vaccinees was also increased for 6 months after vaccination. Most significantly, VZV-specific proliferating T cells in PBMC of vaccinees were increased in frequency from 1 in 68,000 to 1 in 40,000. This vaccine-enhanced frequency of VZV-responding T cells is similar to the frequency observed in 35- to 40-year-old adults. Dose and age of the vaccinees did not significantly influence the magnitude of the mean cell-mediated immune response. The data indicate that VZV immunity in the elderly can be boosted by active immunization. If the increased incidence of herpes zoster that accompanies aging results from the natural waning of immunity, active immunization may prevent or attenuate zoster in the elderly.

Aged↗
PubMed1992

Modified cases of chickenpox after varicella vaccination: correlation of protection with antibody response.

Four thousand forty-two healthy children and adolescents, ages 12 months to 17 years, were vaccinated with a single dose of live attenuated varicella vaccine (VARIVAX; Merck Sharp and Dohme Research Laboratories) containing approximately 1000 to 1625 plaque-forming units/dose during clinical trials conducted from 1987 to 1989. Clinical follow-up of vaccinees revealed that 2.1 and 2.4% of vaccinees developed modified cases of varicella in the first and second years, respectively, after vaccination. Most of those who developed varicella postvaccination had an attenuated illness, characterized by fewer lesions and a lower incidence of fever (greater than or equal to 100 degrees F, oral) than after natural infection. The likelihood of developing varicella postvaccination decreased (P less than 0.0001) as the 6-week postvaccination glycoprotein-based enzyme-linked immunosorbent assay titer increased. In addition the number of lesions in these cases tended to decrease (P = 0.07 for Year 1 and P = 0.02 for Year 2) as the 6-week glycoprotein-based enzyme-linked immunosorbent assay titer increased. Thus the 6-week postvaccination glycoprotein-based enzyme-linked immunosorbent assay titer can be used as a surrogate marker for protection from natural disease.

Adolescent↗
PubMed1992

Morphological effects of coronary balloon angioplasty in vivo assessed by intravascular ultrasound imaging.

BACKGROUND: Histological examination of the effects of balloon angioplasty have been described from in vitro experiments and a limited number of pathologic specimens. Intravascular ultrasound imaging permits real time cross-sectional observation of the effect of balloon dilation on the atherosclerotic plaque in vivo. METHODS AND RESULTS: The morphological effects of coronary angioplasty were visualized at 66 lesions in 47 patients immediately after balloon dilatation with an intravascular ultrasound imaging catheter. Cross-sectional images were obtained at 30 frames per second as the catheter passed along the length of the artery. Quantitative and qualitative assessments of the dilated atherosclerotic plaque were made from the angiograms and the ultrasound images. Six morphological patterns after angioplasty were appreciated by ultrasound imaging. Type A consists of a linear, partial tear of the plaque from the lumen toward the media (seven lesions); Type B is defined by a split in the plaque that extends to the media (12 lesions); Type C demonstrates a dissection behind the plaque that subtends an arc of up to 180 degrees around the circumference (18 lesions); Type D was a more extensive dissection that encompasses an arc of more than 180 degrees (four lesions); and Type E may be present in either concentric (Type E1, 14 lesions) or eccentric (Type E2, 11 lesions) plaque and is defined as an ultrasound study without any evidence of a fracture or a dissection in the plaque. There was a large amount of residual atheroma in each type of morphology (7.8 +/- 2.9 mm2, 61.6 +/- 15.4% of cross-sectional area); there was no difference, however, in lumen or atheroma cross-sectional area among these six patterns. There was a good correlation between ultrasound and angiography for the recognition of a dissection. Calcification was seen in only 14% of lesions on angiography, whereas most lesions (83%) revealed calcification on ultrasound imaging. As determined by intravascular ultrasound, calcified plaque was more likely to fracture in response to balloon dilatation than noncalcified plaque (p less than 0.01). Thirteen of 66 lesions (20%) developed clinical and angiographic restenosis. Restenosis was more likely to occur when the original dilatation left a concentric plaque without a fracture or dissection (Type E1, 50% incidence) compared with a mean restenosis rate of 12% in the remaining morphological patterns (p = 0.053). CONCLUSIONS: Intravascular ultrasound provides a more complete quantitative and qualitative description of plaque geometry and composition than angiography after balloon angioplasty. In addition, intravascular ultrasound identified a subset of atherosclerotic plaque that has a higher incidence of restenosis. This information could be used prospectively to consider other therapeutic options in this subset. Intravascular ultrasound provides a method to describe the effects of angioplasty that will be useful in comparing future coronary intervention studies.

Adult↗
PubMed1992

In vivo assessment of vascular pathology resulting from laser irradiation. Analysis of 23 patients studied by directional atherectomy immediately after laser angioplasty.

BACKGROUND: The pathological consequences of cardiovascular laser irradiation have been studied extensively in vitro. Previous in vivo studies of laser-induced injury have included analyses of acute and/or chronic findings in experimental animals. Little information, however, is available regarding the acute effects of laser irradiation of human vascular tissues in vivo. METHODS AND RESULTS: To determine the acute pathology resulting from laser irradiation of human vascular tissue in vivo, specimens retrieved from 23 patients by directional atherectomy immediately after laser angioplasty (19 peripheral and four coronary) were examined by light microscopy. Of the 23 patients, three (13.0%) were treated with a metal-capped ("hot-tip") fiber coupled to a continuous-wave neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using up to 18 W power and 18-305 seconds of cumulative exposure time; in all three patients (100%), thermal injury, including frank charring several cell layers thick, was seen along the luminal borders of the atherectomy specimen. In eight of the 23 patients (34.5%), laser angioplasty was performed using a 250-microseconds holmium:YAG laser at fluences up to 2,300 mJ/mm2, a repetition rate of 5 Hz, and 25-200 seconds of cumulative exposure; in seven of eight patients (85.5%), the atherectomy specimen showed signs of vacuolar injury consisting of central and satellite Alcian-blue-negative vacuoles. In two patients (25.0%), there was a "smudged" or "shredded" edge, whereas in one patient, frank signs of thermal injury were observed. Finally, in 12 of the 23 patients (52.2%), laser angioplasty was performed using a 120-nsec excimer laser at fluences up to 60 mJ/mm2, a repetition rate of 25 Hz, and a cumulative exposure time of 21-315 seconds. Pathological findings among these 12 patients were limited to nine patients (75%) in whom a weakly basophilic, smudged, and/or shredded appearance approximately one cell layer thick was observed along the luminal border of the atherectomy specimen and two patients (16.7%) with small foci of vacuolar injury. None of the atherectomy specimens retrieved after excimer laser angioplasty disclosed signs of thermal injury. CONCLUSIONS: These findings document that acute pathological alterations resulting from in vivo laser angioplasty are variable, depending on the laser source used, and are similar to that predicted by experimental studies performed previously in vitro. The prognostic implications of these varying pathological features remain to be clarified.

Aged↗
PubMed1991

Guiding catheter-assisted renal artery angioplasty.

A guiding catheter was used in seven patients who underwent balloon dilation of nine renal arteries. The advantages of using a guiding catheter for renal angioplasty are analogous to the benefits obtained with a coronary angioplasty guiding catheter used in coronary angioplasty. The guiding catheter provides back-up support to cross lesions and allows selective contrast visualization of the lesion before, during, and after dilation. It is also possible, when using a guiding catheter, to measure pressure gradients across lesions without having to recross the lesion which may help to ensure that adequate dilation of the stenosis has been accomplished.

Aged↗
PubMed1991

Recanalization of arterial occlusions with a lensed fiber and a holmium:YAG laser.

Laser recanalization of totally occluded swine iliac arteries was performed to assess the safety and efficacy of a lensed fiber laser angioplasty system with a holmium:YAG (2.1 microns) laser. Silica lenses of 1.0 mm, 1.3 mm, and 1.5 mm in diameter attached to the distal end of a 300-microns diameter silica fiber delivered fluences of 79.5 J/cm2, 31.4 J/cm2, and 25.5 J/cm2, respectively. The pulse duration of the laser was 250 microseconds and the repetition rate was 4 Hz. The mean length of the total occlusions was 5.3 +/- 2.0 cm (range 0.5 cm to 8.0 cm). Successful recanalization was obtained in 16/16 lesions without angiographic vessel perforation. Angiographically significant residual stenoses (greater than 50%) remained in every case following successful laser recanalization. Histologically there was minimal evidence of thermal or acoustic tissue injury; however, in 4 of 16 arteries there was evidence of deep arterial dissection following laser recanalization. We conclude that this lensed fiber coupled with a holmium:YAG laser is a safe and effective method for crossing total occlusions in the relatively straight iliac arteries of this animal model.

Angioplasty, Laser↗
PubMed1991

Antibody assays suitable for assessing immune responses to live varicella vaccine.

An enzyme-linked immunosorbent assay for antibodies to varicella-zoster virus (VZV), using purified viral glycoproteins as antigen (gpELISA), was compared with other assays for measuring vaccine-induced antibody responses. The gpELISA was more sensitive than conventional assays, proved highly specific for VZV and agreed well with an assay for neutralizing antibody activity. It was successfully applied to large-scale testing of live varicella vaccine in humans.

Antibodies, Viral↗
PubMed1991

Percutaneous angioscopy during coronary angioplasty using a steerable microangioscope.

The feasibility of using a flexible, steerable angioscope to perform coronary angioscopy before and after percutaneous coronary angioplasty was tested. The microangioscope fits through an 8F coronary angioplasty guiding catheter and contains a multifiber viewing bundle incorporated into the body of a 4.3F balloon catheter with a central lumen for distal flushing and guide-wire passage. Angioscopy was performed without complications 45 times in 24 patients, including 6 patients with stable and 18 with unstable angina. Circumferential visualization of the target lesion was successful in 20 (83%) of the 24 patients and improved with operator experience. Excellent visualization of the target lesion was achieved in 16 (94%) of the last 17 patients. Plaque, thrombus and dissection were among the abnormal findings in the 20 patients (4 with stable, 16 with unstable angina) in whom circumferential viewing of the target lesion was achieved. In four patients with restenosis after angioplasty, the lesion morphology was distinctly different from that of lesions in arteries without prior angioplasty. In patients with stable angina, no thrombus or dissection was seen by angiography or angioscopy before angioplasty. In patients with unstable angina, thrombus was detected more frequently by angioscopy than by angiography before angioplasty (8 versus 2 of 16) and after (15 versus 2 of 16) angioplasty. Intimal dissection was also seen much more frequently by angioscopy than by angiography before angioplasty (7 versus 0 of 16) and after angioplasty (16 versus 7 of 16). It is concluded that high resolution percutaneous coronary angioscopy can be performed safely in conjunction with balloon angioplasty. Further investigation is needed before this diagnostic tool can be applied clinically.

Angina Pectoris↗
PubMed1991

Percutaneous coronary angioscopy in patients with restenosis after coronary angioplasty.

Percutaneous transluminal coronary angioscopy with a flexible steerable microangioscope was performed in five patients undergoing repeat angioplasty. Recurrent lesions were assessed by angioscopy before and after the angioplasty procedure. The most common surface morphology observed in these restenosis lesions was that of white unpigmented lesions consistent with the proliferation of fibrous tissue. Also noted during angioscopy was the presence or absence of thrombus or dissection in association with the lesions either before or after angioplasty. Filmy wisps of tissue, presumably intimal flaps, were commonly visualized after angioplasty. There were no complications related to angioscopy or angioplasty in these patients. The surface morphology of restenosis lesions appears to be different from that of primary atherosclerotic lesions. The lesions in these five patients with restenosis were generally white and fibrotic in appearance, as opposed to the pigmented yellow to yellow-brown lesions commonly seen in undilated atherosclerotic lesions. It was also noted that the presence of intracoronary thrombus was strongly associated with the clinical syndrome of unstable angina. These findings support the hypothesis that restenosis lesions are the result of a reparative process consisting of smooth muscle cell proliferation and fibrosis.

Adult↗
PubMed1991

Varicella vaccine (VARIVAX) in healthy children and adolescents: results from clinical trials, 1987 to 1989.

A total of 3303 healthy children and adolescents, aged 12 months to 17 years, were vaccinated with one of five production lots of a live attenuated varicella vaccine (VARIVAX) containing 1000 to 1625 plaque-forming units per dose. The vaccine was generally well tolerated. Ninety-six percent (2381/2475) of vaccinees responded to vaccination by producing antibody as measured by a glycoprotein-based enzyme-linked immunosorbent assay; 99% (569/576) of those tested maintained antibody at 1 year following vaccination. The incidence of varicella following household exposure in vaccinees was approximately 12%; household contact historically results in 87% infection. Nearly all of the vaccinees who had varicella after vaccination had a clinically modified disease.

Adolescent↗