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Biomedical subjects

T J Collins

Publications and source records attributed to T J Collins.

At least 55 records · Page 3Linked to original sources
PubMed1996

Myocardial contrast echocardiography in human beings: correlation of resting perfusion defects to sestamibi single photon emission computed tomography.

The presence of myocardial perfusion abnormalities is generally accepted to suggest underlying coronary artery disease. In previous animal studies, myocardial contrast echocardiography (MCE) has been shown to be useful in delineating areas at risk after coronary occlusions. We sought to compare the presence or absence, size, and location of perfusion defects detected in human beings by MCE and sestamibi single photon emission computed tomography (SPECT). Regional wall motion was qualitatively assessed in the parasternal and apical views of a resting two-dimensional echocardiogram. Coronary angiography was performed in all patients and myocardial contrast echocardiography performed with 2 ml of intracoronary sonicated meglumine (Nycomed). A cine loop of the digitized contrast echocardiograms was used to analyze perfusion defects. Gated SPECT resting images in standard views were obtained after technetium 99m sestamibi (20 mCi) was administered. Visually perceived perfusion defects were established at 30% of maximal counts at end diastole. Perfusion defects by both techniques were planimetered, assigned to one of three perfusion artery territories, and expressed as a percentage of the perfusion territory studied. Comparison was made by linear regression analysis. Forty-one patients were studied. Perfusion defects were observed in 12 (29%) patients by MCE, 19 (46%) patients by SPECT, and 11 (27%) patients by both techniques. No perfusion defects were detected by MCE in 29 (70%) patients, by SPECT in 22 (53%) patients, or by either technique in 21 (51%) patients. The two techniques agreed in 78% of the patients. In 67 matching orthogonal views suitable for comparison between the two techniques, an 82% concordance for the presence or absence of defects was observed. The location of the defects matched in 86% of the cases. A significant correlation (p < 0.001; r = 0.62) between these techniques was observed in assessing the size of perfusion defects. In conclusion, our results suggest that MCE and sestamibi SPECT are comparable techniques for detecting severely underperfused myocardium in human beings.

Adult↗
PubMed1995

Predictive model to assess risk for cardiac allograft vasculopathy: an intravascular ultrasound study.

OBJECTIVES: This study was performed to assess the influence and interdependence of immunologic and nonimmunologic risk factors in the development of cardiac allograft vasculopathy. Another primary objective was to establish a clinically useful model for risk assessment of cardiac allograft vasculopathy that would facilitate identifying those heart transplant recipients likely to have severe intimal proliferation and thereby at greater risk for adverse clinical events. BACKGROUND: To our knowledge, no comprehensive intravascular ultrasound study has assessed the relative influences of both nonimmunologic and immunologic factors in the development of cardiac allograft vasculopathy, currently the major limitation to long-term cardiac allograft survival. METHODS: Using a computer-assisted model of stepwise logistic regression, immunologic and nonimmunologic risk factors were evaluated to help identify the development of severe intimal thickening in 101 subjects who underwent intravascular ultrasound. Prospective validation of the findings was performed in a separate consecutive cohort of 37 heart transplant recipients, and the accuracy of this model to predict a relative risk > 1 for the development of severe intimal hyperplasia was assessed. RESULTS: Significant independent predictors of severe intimal hyperplasia in this model included a donor age > 35 years, a first-year mean biopsy score > 1 (a measure not only of severity of rejection, but also of frequency of insidious rejection) and hypertriglyceridemia at two incremental levels of risk (150 to 250 mg/dl [1.70 to 2.83 mmol/liter] and > 250 mg/dl [2.83 mmol/liter]). Based on the absence (0) or presence (1) of these factors, 12 individual categories of risk were ascertained with increasing relative risks and predicted probabilities for severe intimal hyperplasia. Prospective validation of this model revealed a sensitivity and specificity of 70% and 90%, respectively, and the positive and negative predictive values were 85% and 80%, respectively. Additionally, subjects with severe intimal thickening had a four-fold higher cardiac event rate than those without severe intimal proliferation on intravascular ultrasound. CONCLUSIONS: This study establishes a clinically useful predictive model that can be applied to individual heart transplant recipients to assess their risk for developing significant cardiac allograft vasculopathy and, thus, aids in the identification of patients at risk for cardiac events in whom closer surveillance and risk factor modification may be warranted.

Adult↗
PubMed1995

Unstable angina. A comparison of angioscopic findings between diabetic and nondiabetic patients.

BACKGROUND: Patients with diabetes mellitus have a higher prevalence of atherosclerotic heart disease and a higher incidence of myocardial infarction than the general population. Diabetic patients also have several hematologic, rheologic, and metabolic abnormalities not present in their nondiabetic counterparts that may predispose them to atherosclerotic plaque rupture and intraluminal thrombosis and consequently may lead to the formation of morphologically complex plaques and the development of acute coronary syndromes. METHODS AND RESULTS: Percutaneous coronary angioscopy was performed in 55 consecutive patients with unstable angina. We observed plaque color, texture, and the incidence of intracoronary thrombus associated with the culprit lesions of these patients. The population consisted of 17 (31%) diabetic and 38 (69%) nondiabetic patients. The presence of coronary risk factors was not significantly different between the two populations. Ulcerated plaque was found in 16 of 17 (94%) diabetic patients versus 23 of 38 (60%) nondiabetic patients (P = .01). Intracoronary thrombi were seen in 16 of 17 (94%) diabetic patients versus 21 of 38 (55%) nondiabetic patients (P = .004). CONCLUSIONS: The results of the angioscopic examination show that diabetic patients with unstable angina have a higher incidence of plaque ulceration and intracoronary thrombus formation than nondiabetic patients. This increased frequency of complex lesion morphology is consistent with the disproportionately higher risk for development of acute coronary syndromes in these patients.

Aged↗
PubMed1995

Coronary angioscopy of abrupt occlusion after angioplasty.

OBJECTIVES: This study used angioscopy to determine the specific cause of vessel occlusion after percutaneous transluminal coronary angioplasty and compared the angiographic and angioscopic lesion morphologies in this setting. BACKGROUND: Occlusion of a dilated coronary artery is the major cause of morbidity and mortality after coronary angioplasty. Attempts to reopen occluded vessels are either empirically guided or directed by angiography, which has inherent limitations. Angioscopy, the in vivo direct visualization of the endovascular surface, is potentially a more accurate means of identifying the cause of vessel occlusion after angioplasty. METHODS: Percutaneous coronary angioscopy was performed in 17 patients (17 vessels) after angiographic confirmation of postangioplasty vessel occlusion. RESULTS: Angioscopy demonstrated the primary cause of the postangioplasty occlusion to be dissection in 14 patients (82%) and intracoronary thrombi in 3 (18%). Compared with angioscopy, angiography was significantly less accurate in identifying the specific cause of the occlusion and correctly identified the cause of vessel occlusion in only 5 (29%) of 17 patients (p < 0.001), including 4 (29%) of 14 deep dissections and 1 (33%) of 3 occlusive thrombi. CONCLUSIONS: Angioscopy specifically identified the cause of occlusion in every patient, with coronary dissection the predominant cause of abrupt occlusion after coronary angioplasty. However, angiography was unable to identify a specific cause for vessel occlusion in the majority of our patients. Angioscopy may therefore prove useful in selecting specific treatment strategies for patients with abrupt occlusion after angioplasty, such as stent placement, atherectomy, repeat dilation or thrombolysis.

Aortic Dissection↗
PubMed1995

Differential regulation of epidermal growth factor and transforming growth factor-alpha messenger ribonucleic acid in the rat anterior pituitary and hypothalamus induced by stresses.

Evidence has shown that epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) are present in the anterior pituitary as well as the hypothalamus, and that EGF can influence the function of pituitary cells, particularly corticotropes in vivo and in vitro. However, little is known about their exact functional roles and how they are regulated in these two areas. The present study was designed to determine if EGF and TGF alpha messenger RNA (mRNA) are expressed in the rat anterior pituitary and hypothalamus and how stress conditions such as cold, ether, or restraint affect their local expression. A sensitive mRNA detection method, the ribonuclease protection assay, detected both EGF and TGF alpha mRNA in the rat anterior pituitary and hypothalamus. Reverse transcription-polymerase chain reaction (RT-PCR) further showed the presence of EGF and TGF alpha mRNA in these two areas and several other rat tissues (submandibular gland, liver, kidney, lung cerebral cortex, and testis). No TGF alpha mRNA was found in the kidney, however. EGF mRNA was up-regulated in the anterior pituitary after 30 min acute cold stress (CS) and restrainer-restraint stress (RS) but not 30 min after ether stress (2 min, ES), novelty stress (NS), or tape-restraint stress (TS). Further analysis showed that EGF mRNA expression decreased after 1 h CS (1C) and then increased after 3 h CS (3C). In contrast, TGF alpha mRNA in the anterior pituitary and hypothalamus and hypothalamic EGF mRNA did not show significant changes in response to either acute stresses (CS, ES, RS, TS, NS) or longer CS (1C, 3C). Our results suggest that 1) EGF, is up-regulated after some stresses; 2) increased pituitary EGF mRNA in response to stresses varies with the type of stress; and 3) pituitary TGF alpha and hypothalamic EGF and TGF alpha may be not involved in the stress response.

Adrenocorticotropic Hormone↗
PubMed1995

In vitro folliculogenesis of rat preantral follicles.

The impact of various gonadotropic hormones on the growth and development of secondary follicles from primordial and primary follicles obtained by enzymatic dissociation of the ovaries of immature 14-day-old rats was studied in vitro. The substratum-adherent culture technique developed for studying folliculogenesis in the current study permitted direct visualization of follicular growth on a day to day basis by avoiding the cumbersome process of fixing and sectioning follicles in culture. The cultures were maintained in a serum-free modified McCoy's medium in a humidified atmosphere containing 5% CO2 at 37 C. Daily observation of the culture dishes under the phase contrast microscope revealed that the follicles grew and developed from primordial to primary and secondary follicular stages in the presence of FSH. Large antral follicles were able to secrete estradiol and progesterone into the medium, indicating that the follicles are not merely formed by cellular reorganization, but are physiologically functional competent units. The organized release of the oocyte with accompanying corona radiata was made possible in some secondary follicles with large antral structures by introducing LH into the culture medium. However, introduction of hCG (which has the biological properties of LH) into the cultures on day 1 resulted in follicular degeneration within 3-4 days of culture. Follicular organization was also disrupted when LH was introduced together with FSH into the medium on day 1 of culture. Primordial or primary follicles obtained from the ovaries could survive, but could not transform to secondary follicles in the absence of FSH. The results of our in vitro studies indicate, and therefore are in agreement with earlier in vivo studies, that FSH alone is essential for the progression of folliculogenesis to the preovulatory condition, and that LH is essential for the organized expulsion of the oocyte from a mature follicle. Our technique, described in the current study, for producing physiologically functional secondary follicles in culture not only allows progress in folliculogenesis to be monitored very closely, but also serves as a model for studying the various intrinsic factors that may be involved in the successful development of dominant mature Graafian follicles that can finally ovulate. It also facilitates access to the growing follicle along with its oocyte, which can, therefore, be used as a powerful model to study the effects of various test substances on follicular development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

New developments in the diagnosis and management of cardiac allograft vasculopathy.

The major cause of late death in cardiac transplant recipients is cardiac allograft vasculopathy, also referred to as cardiac transplant atherosclerosis, which occurs in as many as 45% of transplant recipients who survive longer than 1 year. It differs from typical atherosclerosis in that intimal hyperplasia is concentric and diffuse, the internal elastic lamina remains intact, calcification is rare, and the disease tends to develop rapidly. Intravascular ultrasound and coronary angioscopy are more sensitive diagnostic measures of cardiac allograft vasculopathy than is coronary angiography. Although retransplantation at present seems to be the only definitive therapy for cardiac allograft vasculopathy, it has shown only fair results. Recent studies have suggested that calcium entry blockers and angiotensin-converting enzyme inhibitors may play a beneficial role in delaying the progression of cardiac allograft vasculopathy.

Angioplasty, Balloon, Coronary↗
PubMed1995

Coronary angioscopy.

Coronary angioscopy will not replace angiography as the gold standard for imaging atherosclerotic coronary arteries. However, there may well be a clinical niche for a technology that gives accurate information regarding a specific lesion, if that information can be used to improve the acute or chronic outcome of an interventional procedure. Our experience demonstrates that angioscopy indeed provides this information. Using angioscopy, we now have access to information regarding arterial wall disease that heretofore has been available only at necropsy. In addition, whereas angiography has provided only a 2-dimensional, gray-scale image of the coronary vessels, angioscopy offers a full-color, 3-dimensional perspective of the intracoronary surface morphology. These important lesion-specific details, not reliably available from angiography alone, may ultimately be used to improve patient outcome and to assess risk.

Angioplasty, Balloon, Coronary↗
PubMed1994

Cardiac allograft vasculopathy assessed by intravascular ultrasonography and nonimmunologic risk factors.

The genesis of cardiac allograft vasculopathy has been linked to nonimmunologic endothelial injury. Studies evaluating the role of nonimmunologic risk factors have thus far been limited to angiographic assessment. Intravascular ultrasound can detect cardiac allograft vasculopathy before it becomes angiographically evident. To assess the influence of nonimmunologic risk factors in the development of cardiac allograft vasculopathy, we studied 101 consecutive cardiac transplant recipients who underwent intracoronary ultrasound imaging during routine, annual coronary angiography. Based on the severity of intimal thickening, patients were divided into 2 groups: group 1 = minimal, mild, or moderate intimal thickness; and group 2 = severe intimal thickness. Cardiac transplant recipients with severe intimal thickness had higher levels of total cholesterol (267 +/- 70 vs 227 +/- 41 mg/dl, p = 0.0008), low-density lipoprotein cholesterol (187 +/- 47 vs 139 +/- 31 mg/dl, p = 0.0001), and triglycerides (237 +/- 75 vs 182 +/- 88 mg/dl, p = 0.0004), a higher percentage of weight gain (12 +/- 4% vs 8 +/- 5%, p = 0.0001), a larger body mass index (30 +/- 4 vs 25 +/- 3, p = 0.0001), and older donor age (27 +/- 5 vs 23 +/- 7 years, p = 0.005) than recipients with mild or moderate intimal thickness. Multiple regression analysis established that total cholesterol, low-density lipoprotein cholesterol, triglyceride levels, obesity indexes, donor age, and years following cardiac transplantation (p < 0.01) were independent predictors of the severity of intimal thickening, and thus the severity of cardiac allograft vasculopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Determination of a monoclonal antibody binding activity using immunodetection.

A method for measuring the binding of chimeric IgG BR-96 to the Lewis Y antigen using the ImmunoDetection technology has been developed. The procedure is rapid (2 min), highly reproducible (< 5% CV), and has excellent correlation with the Lewis Y and anti-idiotypic enzyme immunoassays. Samples that were degraded by heat or by repeated freeze-thaw cycles showed reduced binding activity. There was minimal cross-reactivity with other proteins typically found in hybridoma media or with another chimeric IgG directed against a different antigen (L6). The fact that this assay can be performed using conventional HPLC equipment makes it especially attractive because it can be completely automated using equipment readily available.

Antibodies, Monoclonal↗
PubMed1994

Predictors of restenosis: a morphometric and quantitative evaluation by intravascular ultrasound.

Despite advances in catheter-based interventional techniques, restenosis remains a major complication of angioplasty. Recently, intravascular ultrasound imaging (IVUS) has provided new insight into plaque composition and geometric distribution inside the vessel. To investigate if IVUS-defined parameters can predict restenosis in patients after coronary angioplasty, we performed IVUS in 33 patients (33 lesions) after balloon angioplasty (n = 25) or directional atherectomy (n = 8). Qualitative analysis included assessment of plaque composition, plaque eccentricity, plaque fracture, and presence of dissection. In addition, minimal luminal diameter, percent diameter stenosis, percent area stenosis, plaque burden, and elastic recoil were quantitatively analyzed. Follow-up data were obtained 1, 2, and 6 months after angioplasty and were available for 30 patients. Angiographic restenosis occurred in 11 patients (group 1), and no restenosis occurred in 19 patients (group 2) by clinical (n = 10) or angiographic (n = 9) assessment. Plaque fracture was noted in 30% of group 1 patients and 74% of group 2 patients (p = 0.04). Major dissections were more frequent in group I than in group II (78% vs 10%, p = 0.009). Of the quantitative parameters analyzed, plaque burden was significantly higher in group 1 than in group 2 (0.50 +/- 0.05 vs 0.34 +/- 0.05, p = 0.0001). In 78% of the patients with plaque burden of > 0.40, restenosis developed. Thus, of the various parameters analyzed, the absence of plaque fracture, the existence of a major dissection, and greater plaque burden were associated with increased incidence of restenosis. Our results indicate that IVUS can identify a subset of patients in whom restenosis is likely to develop. Information about the morphologic features of the atheroma and its composition may be used to modify the interventional strategy and thus optimize lumen size and possibly reduce the chance of restenosis.

Aged↗
PubMed1994

Influence of donor and recipient gender on cardiac allograft vasculopathy. An intravascular ultrasound study.

BACKGROUND: Cardiac allograft vasculopathy remains the leading limitation to long-term survival after cardiac transplantation. While the influence of donor and recipient gender in the pathogenesis of cardiac vasculopathy is still poorly understood, studies have indicated that female allografts may be at higher risk for the development of cardiac allograft vasculopathy. The purpose of this study was to characterize the influence of donor and recipient gender on the early genesis of cardiac allograft vasculopathy by using intravascular ultrasound. METHODS AND RESULTS: Thirty-six consecutive cardiac transplant recipients were divided into three groups on the basis of donor and recipient gender as follows: group 1, female donor and male recipient (n = 8); group 2, male donor and female recipient (n = 7); and group 3, male donor and male recipient (n = 21). The three groups were similar with regard to donor and recipient age, weight, body surface area, serum lipids, left ventricular function, histocompatibility, cellular and vascular rejection, and cytomegalovirus infection. To precisely quantitate the extent of cardiac allograft vasculopathy, intravascular ultrasound was performed in all patients at the time of first annual angiography. Intimal thickening and intimal index were accurately quantitated by intravascular ultrasound. Intimal thickening was significantly greater in group 1 (0.55 +/- 0.15 mm) than in group 2 (0.18 +/- 0.04 mm) or group 3 (0.29 +/- 0.05 mm) (P < .05). In addition, the intimal index was greater in group 1 (0.20 +/- 0.04) than in group 2 (0.07 +/- 0.02) or group 3 (0.15 +/- 0.02) (P < .01, group 1 versus group 2). CONCLUSIONS: Male recipients of female allografts have a higher degree of vascular intimal hyperplasia detected by intravascular ultrasound at 1 year after heart transplantation. These findings indicate that donor and recipient gender influences the early genesis of cardiac allograft vasculopathy.

Age Factors↗
PubMed1993

Assessment of intracoronary morphology in cardiac transplant recipients by angioscopy and intravascular ultrasound.

Percutaneous coronary angioscopy and intravascular ultrasound are sensitive intravascular imaging methods for detecting early changes in coronary morphology in cardiac transplant recipients. To compare the 2 imaging modalities, 29 consecutive cardiac transplant recipients underwent percutaneous coronary angioscopy and intravascular ultrasound during annual coronary angiography. Surface morphology, presence of plaque, and percent area stenosis were determined with each procedure. Percutaneous coronary angioscopy was more sensitive in detecting the presence of plaque and stenosis than was coronary angiography (plaque: 79 vs 10% [p < 0.001]; and stenosis: 24 vs 3% [p < 0.01]). Intravascular ultrasound was also more sensitive in detecting plaque (76 vs 10%; p < 0.001) and stenosis (45 vs 3%; p < 0.001) than was coronary angiography. Although both angioscopy and ultrasound identified atherosclerotic plaque, only percutaneous coronary angioscopy could show luminal surface morphology and pigmentation of the plaque. Conversely, ultrasound could detect calcification and presence of intimal thickening, and was more accurate in assessing the severity of stenosis (45 vs 24%; p < 0.01). In conclusion, percutaneous coronary angioscopy and intravascular ultrasound, in conjunction, provide information not only regarding the appearance of the luminal surface, but also quantitative information regarding the structure and extent of the disease in the coronary artery wall.

Adult↗
PubMed1993

Placement of "biliary" stents in saphenous vein coronary bypass grafts.

Angioplasty of coronary saphenous vein grafts has been associated with less favorable results than in native coronary arteries owing to a higher acute complication rate and an increased incidence of restenosis. We placed 16 nonarticulated balloon expandable stainless steel "biliary" stents at the sites of 13 stenotic or occluded aortocoronary saphenous vein graft lesions in 11 patients. All of the lesions were stented successfully. There were no instances of stent thrombosis or stent embolism. The percent diameter stenosis was reduced from 85.5 +/- 14.1% to 3.5 +/- 4.4% (p < .001), and the minimal lumen diameter of the lesion increased from 0.7 +/- 0.7 mm at baseline to 3.7 +/- 0.2 mm (p < .001) after stent placement. We conclude that this noncoronary stent appears to be safe and effective for treating saphenous vein coronary bypass grafts. The high procedural success rate and excellent angiographic results are very encouraging, while the restenosis rates remain to be determined.

Angioplasty, Balloon, Coronary↗
PubMed1993

High-speed rotational ablation (Rotablator) for unfavorable lesions in peripheral arteries.

A strategy of using a single, conservatively sized percutaneous transluminal rotational ablation device with or without adjunctive balloon angioplasty was employed in 18 vessels in 17 patients selected because of unfavorable lesion morphology for balloon angioplasty alone. Fifteen patients had lower extremity occlusions and/or heavily calcified lesions and two patients had ostial renal artery stenoses. We were able to achieve a 94% (17/18 lesions) technical success rate, and a 94% (16/17 patients) clinical success rate. In the patients with lower extremity lesions, the baseline ankle-brachial blood pressure index increased from 0.55 +/- 0.15 to 0.90 +/- 0.19 (p < .001) 1 day after the procedure. Follow-up at 6.8 +/- 2.8 months revealed clinical evidence of restenosis in only one patient. We conclude that a cost-effective strategy of treating unfavorable lesions with a single Rotablator burr and adjunctive balloon angioplasty is safe and effective.

Adult↗
PubMed1993

Holmium: YAG laser-assisted coronary angioplasty with multifiber delivery catheters.

Mid-infrared lasers are attractive for coronary angioplasty based upon their excellent fiberoptic transmission and enhanced tissue absorption. Using a solid-state, mid-infrared holmium:YAG laser with prototype multifiber laser delivery catheters, we performed coronary laser angioplasty with or without adjunctive balloon angioplasty or directional atherectomy in 14 patients with 17 stenoses. Procedural laser success was obtained in 13/14 (93%) patients and 16/17 (94%) lesions; however clinical success was achieved in 9/14 (64%) patients and 12/17 (71%) stenoses. Angiographic restenosis at 4.6 +/- 1.6 months was found in 5/8 (63%) patients. We achieved an excellent procedural laser success rate in patients with generally unfavorable angioplasty anatomy. However, our clinical success rate was not different from that expected with conventional angioplasty alone. The holmium laser remains an attractive energy source for laser angioplasty; but as is the case for all coronary laser systems, its utility as a stand-alone therapy is limited by catheters which create small channels. In this small group, we could demonstrate no clinical benefit for laser-assisted angioplasty in complex coronary lesions. Our results suggest that a randomized trial comparing laser-assisted angioplasty and conventional angioplasty be performed to determine the clinical benefits of this more expensive therapy.

Adult↗