ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundAdenosine is a potent vasodilator that has been shown to increase in cardiac tissue in response to hypoxia. However, peripheral vasodilatation also occurs during hypoxia, and the vasoactive substance(s) responsible for skeletal muscle vasodilation have not yet been completely identified. Therefore, the purpose of this study was to measure and quantify skeletal muscle interstitial adenosine during acute systemic hypoxia.Methods and Results-Skeletal muscle interstitial adenosine concentrations were determined by the microdialysis technique, in which 4 semipermeable microdialysis probes were inserted into the vastus lateralis muscle of 6 healthy male subjects and perfused at a rate of 5 [micro sign]L/min with Ringer's solution. Sixty minutes after the insertion of the microdialysis probes, systemic hypoxia was induced for 30 minutes by having the subjects breathe a mixture of 10.5% O2in N2. Arterial oxygen saturation (fingertip oximeter) was lowered (P<0.05) from 96 +/- 0.7% to 74.9 +/- 1.4%, and forearm blood flow was increased 28%. During normoxia, the interstitial adenosine concentration was 0.44 +/- 0.08 [micro sign]mol/L, and it was increased to 1.03 +/- 0.15 (P<0.05) and 0.85 +/- 0.09 (P<0.05) after 15 and 30 minutes of hypoxia, respectively.ConclusionsThese data are consistent with the concept that during acute systemic hypoxia, interstitial adenosine plays a key role in stimulating peripheral vasodilation. (Circulation. 1998;98:1990-1992.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundLipid-lowering secondary-prevention trials of coronary artery disease (CAD) have implicated triglyceride-rich lipoproteins as the main determinants of angiographic progression after elevated LDL cholesterol levels have been lowered with therapy. The present study focuses on the lipoprotein determinants of angiographic CAD progression in men with low HDL cholesterol concentration as their main baseline lipid abnormality who underwent 32 months of randomized therapy with gemfibrozil or placebo.Methods and Results-Men who had undergone coronary bypass surgery (n=372) completed a randomized, placebo-controlled study with gemfibrozil 1200 mg/d. They were selected primarily for HDL cholesterol levels that corresponded to the lowest third for middle-aged men. Average baseline lipid and lipoprotein levels were serum triglyceride, 1.60; serum cholesterol, 5.17; ultracentrifugally separated LDL cholesterol, 3.43; HDL (2) cholesterol, 0.41; and HDL3cholesterol, 0.61 mmol/L. In the gemfibrozil group, these levels were reduced on average by 40%, 9%, and 6% or increased by 5% and 9%, respectively. On-trial IDL and LDL triglyceride and cholesterol levels significantly predicted global angiographic progression, taking into account changes in native segments and in bypass grafts. HDL3but not HDL2cholesterol concentration was associated with protection against progression, especially focal disease in native coronary lesions. VLDL was the lipoprotein most predictive of new lesions in vein grafts; IDL was also significantly related.ConclusionsThis study expands the previous evidence of the triglyceride-rich lipoproteins, especially IDL, as predictors of angiographic progression of CAD but does not negate the significance of mildly elevated LDL levels. Of the HDL subfractions, only HDL3was protective in this group of men selected for their low initial HDL levels. (Circulation. 1998;98:1993-1999.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe distribution of macrophages and smooth muscle cells (SMCs) within atherosclerotic plaques is highly variable. This is clinically relevant because these cell types have opposite effects on the stability of atherosclerotic plaques. The present study was designed to investigate whether local variations in arterial flow over the plaque surface could relate to differences in the distribution of SMCs and macrophages in plaques.Methods and Results-Thirty-three entire carotid plaques were collected at autopsy and marked at their proximal (in relation to the direction of the blood flow) ends, and the cell composition of upstream parts (where high flow and high shear prevail) was compared with that of downstream parts (low flow and low shear stress). Seventy percent of plaques showed more SMCs in their downstream part, and 67% of plaques contained more macrophages in the upstream part. Immunostained macrophage areas were larger in upstream parts (P=0.011). Immunostained SMC areas were larger in downstream parts (P=0.031). Rupture sites of 6 of 9 ruptured plaques, were in the upstream part.ConclusionsSignificant differences in cell composition between upstream and downstream parts of plaques indicate a role for arterial flow in the distribution of different cell types. The low-flow/low-shear downstream areas of plaques contain significantly more SMCs, which could provide the background for slowly progressive growth at distal ends of plaques. The significantly high number of macrophages in the upstream areas suggests a relationship between high flow/high shear and plaque instability. (Circulation. 1998;98:2000-2003.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe diagnostic capability of troponin T (TnT), troponin I (TnI), myoglobin, and creatine kinase (CK)-MB mass for detection of myocardial injury seems evident. Newer studies have found these sensitive markers to carry independent prognostic information in patients with unstable coronary artery disease as well. ST-segment depression in the admission ECG is known to be an important indicator of poor outcome in these patients. The present study investigates the prognostic capacities of the ECG in combination with biochemical admission measurements in 516 patients admitted to hospital with unstable coronary artery disease.or=to5 leads were the only independent predictors of death or myocardial infarction. On the basis of baseline ECG ST-T changes and CK-MB mass/TnT/TnI/myoglobin levels, the patients were divided into 3 subgroups at high (14% event rate), intermediate (6%), and low (3%) risk of early death/myocardial infarction.ConclusionsThe present study found the combination of baseline values of TnT, TnI, CK-MB mass, and ST-T changes in the ECG to be effective for early risk stratification in patients with unstable coronary artery disease. (Circulation. 1998;98:2004-2009.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundAdmission to a hospital with a capability for cardiac procedures is associated with a higher likelihood of referral for a cardiac procedure but not with a better short-term clinical outcome. Whether there are differences in long-term mortality and resource consumption is not clear. We sought to determine whether elderly Medicare patients with acute myocardial infarction admitted to hospitals with on-site cardiac catheterization facilities have lower long-term hospital costs and better outcomes than patients admitted to hospitals without such facilities.Methods and Results-As part of the Cooperative Cardiovascular Project pilot in Connecticut, we conducted a retrospective cohort study using data from medical charts and administrative files. The study sample included 2521 patients with acute myocardial infarction covered by Medicare from 1992 to 1993. The cardiac catheterization rate was higher in the hospitals with facilities (38.6% versus 26.9%; P<0.001), but the revascularization rate was similar (20.5% versus 19.5%) during the initial episode of care and at 3 years (29.7% versus 29.7%). Mortality rates were similar for patients admitted to the 2 types of hospitals at 30 days (OR, 1.08; 95% CI, 0.83 to 1.42) and at 3 years (OR, 1.02; 95% CI, 0.83 to 1.26). The adjusted readmission rates were significantly lower among patients admitted to hospitals with cardiac catheterization facilities (OR, 0.76; 95% CI, 0.61 to 0.94). However, the overall mean days in the hospital for the 3 years after admission was 25.9 for patients admitted to hospitals with facilities and 24.6 for the other patients (P=0.234). Adjusting for baseline patient characteristics, there was no significant difference in the 3-year costs between patients admitted to the 2 types of hospitals.ConclusionsWith higher rates of cardiac catheterization and lower readmission rates, patients admitted to hospitals with on-site cardiac catheterization facilities did not have significantly different hospital costs compared with patients admitted to hospitals without these facilities. There was also no significant difference in short- or long-term mortality rates. (Circulation. 1998;98:2010-2016.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundPatients who have inducible ischemia after acute myocardial infarction (AMI) generally undergo coronary angiography with the intent to revascularize. Whether this approach is superior to intensive treatment with anti-ischemic medications is unknown.Methods and Results-We performed a prospective, randomized pilot study comparing intensive medical therapy with coronary angioplasty (PTCA) for suppression of myocardial ischemia in 44 stable survivors of AMI. Myocardial ischemia was quantified with adenosine (201or=to9%) reduction in PDS (96%) compared with those who did not (65%; P=0.009).ConclusionsIn this small pilot study, intensive medical therapy and PTCA were comparable at suppressing ischemia in stable patients after AMI. Sequential imaging with adenosine SPECT can track changes in PDS after anti-ischemic therapies and thereby predict subsequent outcome. Corroboration of these preliminary findings in a larger cardiac-event trial is warranted. (Circulation. 1998;98:2017-2023.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundIntravascular irradiation with beta-emitters has been proposed for inhibition of restenosis in coronary arteries after balloon angioplasty or stent implantation. Previous studies have shown the effectiveness of gamma-radiation to prevent recurrent restenosis, even in the presence of an implanted stent. The limited range of beta-particles compared with gamma-radiation, however, opens the question of whether absorption and scattering of beta-particles by stent struts will cause significant perturbations in the uniformity and magnitude of the radiation dose, which may in turn compromise treatment.Methods and Results-Nine different stents were deployed with a balloon filled with a beta-emitting radioactive liquid. Dose distributions were measured with Gafchromic film. Stents varied significantly in their absorption of beta-particles. Some stents, constructed of fine meshed wires, produced minimal dose perturbations. Others, with thicker, high-atomic-number struts, induced cold spots in the dose distribution adjacent to the wires of <or=to35%. Average dose reduction varied from 4% to 14% in the presence of various stents.ConclusionsRadiation strategy may have to be tailored to stent design. Stents that minimally perturb the dose distribution may be deployed before irradiation. Those that significantly alter the radiation dose might be better deployed after irradiation. Dose prescriptions may require modification if such perturbations prove clinically significant. Observed dose perturbations, however, decreased rapidly with increasing distance from the stent, which may mitigate the clinical impact of these findings. This, as well as the effects of stents on gamma-dose distributions, requires further investigation. (Circulation. 1998;98:2024-2029.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundNonsustained ventricular tachycardia (NSVT) has significant prognostic implications in the setting of healing and healed myocardial infarction (MI), but only limited information is available on its importance in the setting of acute MI. We evaluated the prognostic significance of NSVT characteristics in the setting of acute MI.Methods and Results-A prospective database was used to identify 112 patients with NSVT within 72 hours of acute MI. A control group was identified matched for age, sex, type of MI, and thrombolytic treatment. Mean age was 64 to 65 years in the 2 groups with 71% to 72% men. Q-wave MI was noted in 52% to 53%, and thrombolytic therapy was administered to 31% to 32% of patients in each group. In-hospital ventricular fibrillation occurred more frequently in the NSVT group (9% versus 0% in the control group; P<0.001), but total in-hospital (10% versus 4%) and follow-up mortality (10% versus 17%) did not differ between the 2 groups. With a Cox regression model, specific NSVT characteristics were predictive of mortality. The strongest predictor was time from presentation to occurrence of NSVT. Shortest RR interval during NSVT was also a univariate predictor of mortality. Multivariate analysis identified time from presentation to occurrence of NSVT as the strongest predictor of mortality (P<0.0001). The increased relative risk of NSVT was first significant when it occurred 13 hours from presentation and continued to increase as the time from presentation to occurrence of NSVT increased, plateauing at [almost equal to]24 hours with a relative risk of 7.5.ConclusionsContrary to prevailing clinical opinion, NSVT that occurs in the setting of acute MI does have important prognostic significance. Specifically, the currently accepted notion that NSVT that occurs within 48 hours of acute MI has no prognostic significance needs to be adjusted. Although NSVT that occurs within the first several hours of presentation does not have an associated adverse prognosis, NSVT that occurs beyond the first several hours after presentation is associated with significant increases in relative risk. (Circulation. 1998;98:2030-2036.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID