Schwartz, Robert S.

Background: Cardiovascular risk factors have an impact on coronary atherosclerosis evolution. However, there is only limited information about the relationship between risk and atherosclerotic plaque as measured invasively by Intravascular Ultrasound Radiofrequency (IVUS-RF) analysis. The Aim of this study was to assess the impact of cardiovascular risk factors not only on overall coronary plaque volume but on coronary plaque composition. Methods: 990 patients from 42 centers were enrolled in the prospective, multicenter, non randomized, global VH-IVUS registry. Coronary lesions were measured by conventional and IVUS-VH parameters using 20MHz Intravascular Ultrasound catheter. The four IVUS-VH plaque components (Dense Calcium-DC, Necrotic Core-NC, Fibrous tissue-F, Fibro Fatty-FF) were analyzed in every recorded frame. The results were expressed as mean cross-sectional areas, and percentage of total plaque volume. Risk factor assessment included correlation with family history of myocardial infarction, past or current smoking, diabetes mellitus, hypertension, and laboratory measurements. Results: Patients with diabetes have an increased relative amount of NC (6.47±0.28% vs. 5.86±0.14%, p=0.037) and DC (4.58±0.27% vs. 3.90±0.14%, p=0.017), Patients with hypertension have an increased relative amount of FF, DC (4.35±0.16% vs. 3.57±0.17%, p=0.02) and NC (6.24±0.17% vs. 5.60±0.19%, p=0.01). Compared with patients with LDL cholesterol 160 mg/dl had higher plaque volume (342.1±26.2mm 3 vs. 318.6±10.7mm 3 ). Linear Regression Analysis showed a correlation between the level of HDL and F (r=−0.149, p<0.01), FF (r=−0 –106, p< 0.01), and NC (r=−0.90, p<0.05). The level of LDL correlated with F (r = 0.110, p < 0.01). Patients with prior MI have an increased percentage of F (30.03±0.59 % vs. 28.20±0.37 %, p<0.009). Smoking had no relevant effect on plaque composition. Conclusion: IVUS-RF analysis detects marked differences in coronary plaque depending on the risk factor profile with particular focus on lipid levels. Patients with greater amounts of necrotic core were associated with hypertension, myocardial infarction, and low HDL. This may have implications for prognosis and systemic treatment of patients with coronary artery disease.

A simple and reliable means for accurate, chronic measurement of pulsatile blood pressure (BP) from conscious, freely moving laboratory mice was developed and validated. The newly developed device consists of a small (1.9 ml, 3.4 g), fully implantable radiotelemetry transmitter. Initial frequency response tests showed an adequate dynamic response; the average −3-dB point found in five transmitters was 145 ± 14 (SD) Hz. BP, heart rate, and locomotor activity were recorded from 16 chronically (30–150 days) implanted mice. Mean arterial and pulse pressure, checked at regular intervals, ranged from 90–140 mmHg and from 30–50 mmHg, respectively, throughout the study. Transmitter BP measurements were validated against a Millar 1.4-Fr. transducer-tipped catheter. The mean error of the transmitters for diastolic pressures was +1.1 ± 6.9 mmHg ( n = 7). The error for systolic pressures was, on average, 2.7 ± 3.9 mmHg larger. This new device accurately monitors BP, heart rate, and locomotor activity in conscious, untethered, freely moving mice living in their home cages for periods of at least 150 days.

AbstractWe tested the effects of overexpression of the endothelial nitric oxide synthase (eNOS) gene in the normal arterial wall by adenoviral-mediated gene transfer. Rabbit carotid arteries were surgically isolated and exposed to adenoviral vectors encoding eNOS (AdeNOS) or β-galactosidase (AdβGal) on the contralateral side. Vector solutions at a concentration of 1×1010plaque forming units/mL were instilled for 20 minutes before restoration of flow. Arteries were harvested 4 days later for immunostaining, measurement of cGMP, and vasomotor studies. Endothelium-specific gene transfer was confirmed by staining for β-galactosidase in the AdβGal arteries. Immunostaining of en face endothelial cell imprints from AdeNOS-transduced arteries with a monoclonal antibody to eNOS showed increased immunoreactivity. Basal cGMP levels were significantly greater in the AdeNOS-transduced arteries (18.4±4.6 versus 4.2±0.5 pmol/mg protein;P<.05). Contractions to phenylephrine were significantly reduced in the AdeNOS-transduced arteries (area under curve, 106±5 versus 119±7;P<.05), but in the presence of the eNOS inhibitor,NG-monomethyl-l-arginine (L-NMMA, 3×10−4mol/L), there was no difference between the two (area under curve, 148±5 versus 153±6;P=NS). Relaxations to acetylcholine obtained during submaximal contractions to phenylephrine were significantly enhanced in the AdeNOS-transduced arteries (EC50, 7.45±0.05 versus 7.23±0.03;P<.05). We conclude that overexpression of eNOS in the endothelium results in diminished contractile responses, as well as enhanced endothelium-dependent relaxations. These findings imply a possible role for vascular eNOS gene transfer in the treatment of vasospasm and endothelial dysfunction.

Abstract —Insulin-like growth factors I and II (IGF-I and -II) and their regulatory proteins are secreted by cells of the cardiovascular system. They are growth promoters for arterial cells and mediators of cardiovascular disease. IGFs are bound to IGF binding proteins (IGFBPs), which modulate IGF ligand-receptor interaction and consequently to IGF action. IGFBPs are in turn posttranslationally modulated by specific proteases. This dynamic balance (IGFs, IGFBPs, and IGFBP proteases) constitutes the IGF axis and ultimately determines the extent of IGF-dependent cellular effects. Dysregulated actions of this axis influence coronary atherosclerosis through effects on vascular smooth muscle cell growth, migration, and extracellular matrix synthesis in the atherosclerotic plaque. IGF-I promotes macrophage chemotaxis, excess LDL cholesterol uptake, and release of proinflammatory cytokines. Endothelial cells also receive the effects of IGFs stimulating their migration and organization forming capillary networks. Neointimal hyperplasia of restenosis after coronary artery injury is also modulated by the IGF axis. IGFs stimulate vascular smooth muscle cell proliferation and migration to form the neointima and upregulate tropoelastin synthesis after disruption of the elastic layer. Understanding IGF axis regulation establishes a scientific basis for strategies directed to limit or reverse plaque growth and vulnerability in atherosclerosis and in the neointimal hyperplasia of restenosis.

Background —Despite the increasing use of stents, few reports have described human coronary artery morphology early and late after stenting. Methods and Results —Histology was performed on 55 stents in 35 coronary vessels (32 native arteries and 3 vein grafts) from 32 patients. The mean duration of stent placement was 39±82 days. Fibrin, platelets, and neutrophils were associated with stent struts ≤11 days after deployment. In stents implanted for ≤3 days, only 3% of struts in contact with fibrous plaque had >20 associated inflammatory cells compared with 44% of struts embedded in a lipid core and 36% of struts in contact with damaged media ( P <0.001). Neointimal growth determined late histological success, and increased neointimal growth correlated with increased stent size relative to the proximal reference lumen area. Neointimal thickness was greater for struts associated with medial damage than struts in contact with plaque ( P <0.0001) or intact media ( P <0.0001). When matched for time since treatment, neointimal cell density in stented arteries was similar to that in unstented arteries that had undergone balloon angioplasty and showed similar proteoglycan deposition. Conclusions —Morphology after coronary stenting demonstrates early thrombus formation and acute inflammation followed by neointimal growth. Medial injury and lipid core penetration by struts result in increased inflammation. Neointima increases as the ratio of stent area to reference lumen area increases. Deployment strategies that reduce medial damage and avoid stent oversizing may lower the frequency of in-stent restenosis.

Background —Electron beam CT (EBCT) is an accurate, noninvasive method to detect and quantify coronary artery calcification, a marker of coronary artery disease (CAD). This investigation examined the accuracy of EBCT to detect obstructive CAD (≥50% stenosis) and determined the optimal strata for quantity of coronary artery calcification to facilitate clinical decision-making. Methods and Results —Clinical research patients (n=213) were examined with coronary angiography and EBCT (angiography group), and 765 research participants were examined with only EBCT (nonangiography group). Of the angiography group, 53% had obstructive CAD. After adjustment for verification bias, the estimated sensitivity and specificity for calcium score ≥1 were 97.0% and 72.4%, respectively. Likelihood ratios for strata of calcium score associated with obstructive CAD were calculated in each sex and 2 age groups. Among those ≥50 years old, the same 4 strata of EBCT calcium scores were identified in each sex; likelihood ratios ranged from 0.03 (calcium score 0) to 12.85 (calcium score ≥200). The same 3 strata of EBCT calcium scores were identified in each sex among those <50 years old; likelihood ratios ranged from 0.13 (calcium score 0) to 190 (calcium score ≥100). Conclusions —A calcium score ≥200 among those ≥50 years old and calcium score ≥100 among those <50 years old provided strong evidence that patients of either sex had obstructive CAD. A calcium score of 0 provided strong evidence that patients ≥50 years old did not have obstructive CAD.

Background —As endothelin binds to ET A receptors, it stimulates vascular smooth muscle cell proliferation and may thus be pivotally involved in the pathogenesis of restenosis. This study assessed the ability of a potent and selective ET A antagonist to reduce neointimal hyperplasia in a porcine coronary artery stented injury model. Methods and Results —Fifty-five pigs were randomized to receive placebo or the oral ET A -selective antagonist ABT147627 twice daily for 28 days in one of three doses: 0.75 mg/kg (low), 3.75 mg/kg (mid), and 10.0 mg/kg (high). Each underwent oversized stent deployment in two randomly assigned major epicardial coronary arteries. Three animals (5.5%) died as a consequence of stent thrombosis within 24 hours of the procedure. The remaining 52 animals (13 pigs per group) survived without complication until predetermined euthanasia at 28 days. In the placebo group, mean injury score was 1.73±0.80, with a mean neointimal response of 0.45±0.24 mm. By comparison, the low-dose group had a similar mean injury score of 1.79±0.75 with reduced neointimal response, 0.36±0.22 mm ( P <0.01). Mean injury score in the mid-dose animals was significantly greater than in the placebo group (1.94±0.92; P <0.05). The neointimal hyperplasia associated with this injury was less than with placebo, although the difference did not reach statistical significance (0.40±0.25 mm; P =0.05). In the high-dose pigs, mean injury score was also significantly greater than in the placebo arm (1.93±0.73; P <0.05). Despite this, neointimal response was also significantly less (0.37±0.37 mm; P <0.01). Conclusions —Oral, selective ET A receptor antagonism significantly reduced neointimal hyperplasia forming over porcine coronary stented injuries in the first 28 days. This strategy may have clinical potential for the limitation and treatment of coronary restenosis after percutaneous revascularization.

Background Adventitial gene transfer may serve as a tool to study vascular biology and may have therapeutic potential. We investigated the hypothesis that adenovirus-mediated transfer of the gene for endothelial nitric oxide synthase (eNOS) to the adventitia would alter vascular reactivity. Methods and Results Rabbit carotid arteries were surgically isolated and adenoviral vectors encoding eNOS (AdeNOS) or β-galactosidase instilled into the periarterial sheath at a concentration of 1×10 10 pfu/mL. Arteries were harvested 4 days later for immunostaining, NOS enzymatic assay, measurement of cGMP, and vasomotor studies. Transgene expression in the adventitia was confirmed by histochemistry for β-galactosidase and immunostaining for eNOS with a monoclonal antibody. Calcium-dependent NOS enzymatic activity and cGMP levels were significantly greater in the AdeNOS-transduced arteries. Maximal contractions to phenylephrine (10 −5 mol/L) were diminished in the AdeNOS-transduced arteries (4.6±0.2 versus 5.6±0.2 g; P <.05), but in the presence of the eNOS inhibitor N G -monomethyl- l -arginine (3×10 −4 mol/L) there was no difference between the two groups (7.1±0.2 versus 7.5±0.3 g; P =NS). Relaxations to calcium ionophore obtained during submaximal contractions to phenylephrine were significantly enhanced in the AdeNOS-transduced arteries (−log EC 50 , 7.77±0.08 versus 7.45±0.07; P <.02). Conclusions We conclude that eNOS gene transfer to the adventitia alters vascular reactivity, as demonstrated by diminished contractile responses to phenylephrine and enhanced relaxations to calcium ionophore. This may represent a therapeutic strategy for vascular diseases characterized by decreased bioavailability of NO.

Background With the thrombogenic tendency and permanent implant nature of metallic stents, synthetic polymers have been proposed as candidate materials for stents and local drug delivery designs. We investigated the biocompatibility of several synthetic polymers after experimental placement in the coronary artery. Methods and Results Five different biodegradable polymers (polyglycolic acid/polylactic acid [PGLA], polycaprolactone [PCL], polyhydroxybutyrate valerate [PHBV], polyorthoester [POE], and polyethyleneoxide/polybutylene terephthalate [PEO/PBTP]) and three nonbiodegradable polymers (polyurethane [PUR], silicone [SIL], and polyethylene terephthalate [PETP]) were tested as strips deployed longitudinally across 90° of the circumferential surface of coil wire stents. Appropriately sized polymer-loaded stents were implanted in porcine coronary arteries of 2.5- to 3.0-mm diameter. Four weeks after implantation, stent patency was assessed by angiography followed by microscopic examination of the coronary arteries. The biodegradable PCL, PHBV, and POE and the nonbiodegradable PUR and SIL evoked extensive inflammatory responses and fibrocellular proliferation (thickness of tissue response: 0.79±0.22, 1.12±0.01, 2.36±0.60, 1.24±0.36, and 1.43±0.15 mm, respectively). Less but still severe responses were observed for the biodegradable PGLA and PEO/PBTP (0.46±0.18 and 0.61±0.23 mm, respectively) and for the nonbiodegradable PETP (0.46±0.11 mm). Conclusions An array of both biodegradable and nonbiodegradable polymers has been demonstrated to induce a marked inflammatory reaction within the coronary artery with subsequent neointimal thickening, which was not expected on the basis of in vitro tests. The observed tissue response may be attributable to a combination of parent polymer compound, biodegradation products, and possibly implant geometry.