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Biomedical subjects

Briain D MacNeill

Publications and source records attributed to Briain D MacNeill.

9 recordsLinked to original sources
PubMed2006

Diagnostic accuracy of optical coherence tomography and integrated backscatter intravascular ultrasound images for tissue characterization of human coronary plaques.

OBJECTIVES: The purpose of the present study was to validate the diagnostic accuracy of optical coherence tomography (OCT), integrated backscatter intravascular ultrasound (IB-IVUS), and conventional intravascular ultrasound (C-IVUS) for tissue characterization of coronary plaques and to evaluate the advantages and limitations of each of these modalities. BACKGROUND: The diagnostic accuracy of OCT for characterizing tissue types is well established. However, comparisons among OCT, C-IVUS, and IB-IVUS have not been done. METHODS: We examined 128 coronary arterial sites (42 coronary arteries) from 17 cadavers; IVUS and OCT images were acquired on the same slice as histology. Ultrasound signals were obtained using an IVUS system with a 40-MHz catheter and digitized at 1 GHz with 8-bit resolution. The IB values of the ultrasound signals were calculated with a fast Fourier transform. RESULTS: Using histological images as a gold standard, the sensitivity of OCT for characterizing calcification, fibrosis, and lipid pool was 100%, 98%, and 95%, respectively. The specificity of OCT was 100%, 94%, and 98%, respectively (Cohen's kappa = 0.92). The sensitivity of IB-IVUS was 100%, 94%, and 84%, respectively. The specificity of IB-IVUS was 99%, 84%, and 97%, respectively (Cohen's kappa = 0.80). The sensitivity of C-IVUS was 100%, 93%, and 67%, respectively. The specificity of C-IVUS was 99%, 61%, and 95%, respectively (Cohen's kappa = 0.59). CONCLUSIONS: Within the penetration depth of OCT, OCT has a best potential for tissue characterization of coronary plaques. Integrated backscatter IVUS has a better potential for characterizing fibrous lesions and lipid pools than C-IVUS.

Calcinosis↗
PubMed2005

Catheter-based ventricle-coronary vein bypass.

The goal of this study was to investigate the feasibility of a catheter-based ventricle-to-coronary vein bypass (VPASS) in order to achieve retrograde myocardial perfusion by a conduit (VSTENT) from the left ventricle (LV) to the anterior interventricular vein (AIV). Percutaneous coronary venous arterialization has been proposed as a potential treatment strategy for otherwise untreatable coronary artery disease. In an acute setting, the VSTENT implant was deployed percutaneously using the VPASS procedure in five swine. Coronary venous flow and pressure patterns were measured before and after VSTENT implant deployment with and without AIV and left anterior descending artery (LAD) occlusion. In a separate chronic pilot study, the VPASS procedure was completed on two animals that had a mid-LAD occlusion or LAD stenosis. At day 30 post-VPASS procedure, left ventriculography and magnetic resonance imaging (MRI) were performed to assess the patency and myocardial viability of the VSTENT implants. Pre-VSTENT implantation, the mid-AIV systolic wedge pressure was significantly lower than LV systolic pressure during AIV blockage (46 +/- 19 vs. 90 +/- 16 mm Hg; P < 0.01). The VSTENT implant deployment was performed without complication and achieved equalization of the AIV and LV systolic pressures and creation of retrograde flow in the distal AIV (maximal flow velocity: 37 +/- 7 cm/sec). At day 30 post-VPASS procedure, left ventriculography showed VSTENT implant patency. MRI perfusion images demonstrated myocardial viability even with an LAD occlusion. Coronary retrograde perfusion using the VPASS procedure is feasible and may represent a potential technique for end-stage myocardial ischemia.

Animals↗
PubMed2004

Focal and multi-focal plaque macrophage distributions in patients with acute and stable presentations of coronary artery disease.

OBJECTIVES: This study was designed to utilize optical coherence tomography (OCT) images of coronary atherosclerotic plaque macrophages to investigate the relationship between macrophage distributions and clinical syndrome. BACKGROUND: The relative significance of focal macrophage infiltration and generalized coronary inflammation for predicting acute coronary events is a currently a source of considerable controversy in cardiology. Lack of a high-resolution cross-sectional imaging modality has limited macrophage evaluation in vivo. METHODS: Intracoronary OCT imaging was performed at culprit and non-culprit plaques in patients presenting with stable angina pectoris, unstable angina pectoris,and ST-segment elevation myocardial infarction. Macrophage densities were quantified from these images and analyzed with respect to the clinical presentations of the patients under investigation. RESULTS: A significantly greater macrophage density was found in unstable patients, both for fibrous and lipid-rich plaques (p = 0.025 and p = 0.002, respectively). Within each patient, the macrophage densities at culprit and non-culprit lesions correlated significantly (r = 0.66, y = 0.88x + 0.43, p = 0.01). Sites of plaque rupture demonstrated a greater macrophage density than non-ruptured sites (6.95 +/- 1.60%, 5.29 +/- 1.17%; p = 0.002). Surface macrophage infiltration was a stronger predictor of unstable clinical presentation than subsurface infiltration for culprit lesions (p = 0.035) but not for remote lesions (p = 0.80). CONCLUSIONS: Our results demonstrate that increases in both multi-focal and focal macrophage densities are highly correlated with symptom severity. By providing a means of detecting increases in plaque macrophage content before an acute event, this technique may aid in determining prognosis and guiding preventive therapy.

Aged↗
PubMed2003

Intravascular modalities for detection of vulnerable plaque: current status.

Progress in the diagnosis, treatment, and prevention of atherosclerotic coronary artery disease is dependent on a greater understanding of the mechanisms of coronary plaque progression. Autopsy studies have characterized a subgroup of high-risk, or vulnerable, plaques that result in acute coronary syndromes or sudden cardiac death. These angiographically modest plaques share certain pathologic characteristics: a thin, fibrous cap, lipid-rich core, and macrophage activity. Diagnostic techniques for vulnerable-plaque detection, including serologic markers and noninvasive and invasive techniques, are needed. Recent advances in intravascular imaging have significantly improved the ability to detect high-risk, or vulnerable, plaque in vivo by using various features of plaque vulnerability as methods of identification. The characteristic anatomy of a thin, fibrous cap overlying a lipid pool has promoted high-resolution imaging, such as intravascular ultrasound, optical coherence tomography, and intracoronary magnetic resonance. The lipid-rich core is identifiable by angioscopically detected color changes on the plaque surface or by its unique absorption of energy, or "Raman shift," of its cholesterol core, driving coronary spectroscopy. Finally, temperature heterogeneity arising at foci of plaque inflammation has prompted the development of intracoronary thermography. In this review, we will discuss these techniques, their relative advantages and limitations, and their potential clinical application.

Angioscopy↗
PubMed2003

Prophylaxis of contrast-induced nephropathy in patients undergoing coronary angiography.

Contrast-induced nephropathy (CIN) is a common complication of cardiac catheterization, reported to result in a 15% incidence of acute renal failure. Convincing evidence supports the prophylactic use of prehydration and low volumes of contrast medium. Recently, the antioxidant acetylcysteine has been shown to have a potential preventive role. The aim of this study was to examine the hypothesis that acetylcysteine prevents CIN. Patients undergoing cardiac catheterization with a serum creatinine >/= 1.5 mg/dl were prospectively randomized to receive acetylcysteine or placebo. A total of five doses of acetylcysteine 600 mg b.i.d. or placebo was administered, commencing on the day of the procedure. All patients were prehydrated with 0.45% saline and during the catheterization a nonionic low-osmolality contrast medium was used. Serum creatinine and urea were measured at 24, 48, and 72 hr postprocedure. A total of 43 patients were studied. There was no significant difference between the groups in terms of baseline characteristics, including baseline renal function. No adverse events were experienced with acetylcysteine treatment. Serum creatinine levels at 48 and 72 hr remained largely unchanged in the acetylcysteine group but continued to rise at 48 and 72 hr in the placebo group. By 72 hr, the incidence of CIN, defined as a 25% increase in baseline creatinine, was significantly lower in the acetylcysteine arm compared to placebo (5% for acetylcysteine vs. 32% for placebo; P = 0.046). In patients with mild to moderate renal impairment undergoing cardiac catheterization, prophylactic treatment with oral acetylcysteine reduces the incidence of contrast-induced nephropathy.

Acetylcysteine↗
PubMed2003

Targeting signaling pathways in heart failure by gene transfer.

Congestive heart failure represents an enormous clinical problem demanding effective therapeutic approaches. The varied etiologies of heart failure include abnormalities of ion handling, cellular signaling, neurohormonal control, and apoptosis, all of which are potentially amenable to genetic manipulation. Gene therapy holds the promise of retarding the progression, preventing, and perhaps reversing heart failure. Advances in our knowledge of possible targets, vectors, and delivery techniques have revolutionized this field in recent years, bringing us close to clinical application.

Gene Targeting↗
PubMed2002

Toward a new blood vessel.

Strategies to treat atherosclerotic coronary artery disease include coronary artery bypass grafting (CABG), in which grafts are used to bypass atherosclerotic vessels and restore blood flow to the ischemic myocardium. The grafts used include healthy arteries or veins harvested from a separate site. Results with arterial grafts have been superior to venous grafts; promoting the practice of total arterial revascularization using only arterial grafts. Suitable arterial grafts, however, are scarce and harvest procedures add to morbidity and cost. Tissue engineering combines the principles of engineering with life sciences for the development of biological substitutes and restore, maintain or improve tissue function. Advances in this field have included the development of tissue-engineered blood vessels, with the potential to serve as arterial grafts, conduits or fistulae. This review describes the history of tissue engineering arteries, the techniques used, and progress to date. The source of cells and the future direction of this field are explored.

Blood Vessel Prosthesis↗
PubMedDate not supplied

Intravascular optical coherence tomography: cellular imaging.

The vast majority of acute coronary events are attributed to rupture or erosion of high-risk or vulnerable plaques. Novel imaging techniques are being actively sought that can detect quiescent vulnerable features within coronary plaque and thereby identify populations at risk, monitor plaque progression, and target therapy appropriately. Optical coherence tomography is an intravascular imaging modality capable of detecting and characterizing coronary plaque in vivo. Recently, optical coherence tomography quantification of macrophage infiltration within atherosclerotic plaque ex vivo was demonstrated. Application of this technique to clinical practice yields a hybrid image incorporating plaque morphology with a measure of biologic activity. In a recently conducted clinical study assessing macrophage distributions in patients, evidence supporting both the vulnerable plaque model and the hypothesis of multifocal inflammatory risk, linked by the common thread of increased macrophage infiltration, has been found. These results suggest that elevated multifocal coronary macrophage content, present both in culprit lesions and at remote sites, serves as a background for heightened risk. Superimposed on this inflammatory background, local increases in macrophage content, particularly at the cap surface and at areas at high risk for rupture, further promote the instability of individual lesions.

Blood Vessels↗