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

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundA novel 3-dimensional left ventricular (LV) mapping system uses low-intensity magnetic field energy to determine the location of sensor-tipped electrode catheters within the LV. Using this system, we sought to distinguish between infarcted, ischemic, and normal myocardium by comparing LV electromechanical mapping data with myocardial perfusion imaging studies.Methods and Results-Unipolar voltage potentials and local endocardial shortening (LS) were measured in 18 patients (mean age, 58 +/- 12 years) with symptomatic chronic angina having reversible and/or fixed myocardial perfusion defects on single photon emission computed tomography imaging studies using201T1 at rest and99mTc-sestamibi after adenosine stress. Overall, a significant difference in voltage potentials and LS values was found between groups (P<0.001 for each comparison by ANOVA). The average voltage potentials (14.0 +/- 2.0 mV) and LS values (12.5 +/- 2.8%) were highest when measured in myocardial segments (n=56) with normal perfusion and lowest (7.5 +/- 3.4 mV and 3.4 +/- 3.4%) when measured in myocardial segments with fixed perfusion defects (n=20) (P<0.0001). Myocardial segments with reversible perfusion defects (n=66) had intermediate voltage amplitudes (12.0 +/- 2.8 mV, P=0.048 versus normal and P=0.005 versus fixed segments) and LS values (10.3 +/- 3.7%, P=0.067 versus normal and P=0.001 versus fixed segments).ConclusionsIn patients with myocardial ischemia, LV mapping, compared with myocardial perfusion imaging, shows (1) mild reduction of endocardial voltage potentials and LS in segments with reversible perfusion defects and (2) profound electromechanical impairment in segments with fixed perfusion defects. Thus, such an LV mapping procedure may allow the detection on-line of myocardial viability in the catheterization laboratory. (Circulation. 1998;98:1837-1841.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundAsymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase. Because endothelial NO elaboration is impaired in hypercholesterolemia, we investigated whether plasma concentrations of ADMA are elevated in young, clinically asymptomatic hypercholesterolemic adults. We further studied whether such elevation of ADMA levels was correlated with impaired endothelium-dependent, NO-mediated vasodilation and urinary nitrate excretion. In a randomized, double-blind, placebo-controlled study, we investigated whether these changes could be reversed with exogenous L-arginine.100% (2.17 +/- 0.15 versus 1.03 +/- 0.09 [micro sign]mol/L; P<0.05) in HC subjects compared with NC adults. L-Arginine levels were similar, resulting in a significantly decreased L-arginine/ADMA ratio in HC subjects (27.7 +/- 2.4 versus 55.7 +/- 5.4; P<0.05). In 8 HC subjects, intravenous infusion of L-arginine significantly increased the L-arginine/ADMA ratio and normalized endothelium-dependent vasodilation and urinary nitrate excretion. ADMA levels were inversely correlated with endothelium-mediated vasodilation (R=0.762, P<0.01) and urinary nitrate excretion rates (R=0.534, P<0.01).ConclusionsWe find that ADMA is elevated in young HC individuals. Elevation of ADMA is associated with impaired endothelium-dependent vasodilation and reduced urinary nitrate excretion. This abnormality is reversed by administration of L-arginine. ADMA may be a novel risk factor for endothelial dysfunction in humans. (Circulation. 1998;98:1842-1847.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundElevated plasma homocysteine is a risk factor for arteriosclerosis, but a cause-and-effect relationship remains to be fully established. Endothelial dysfunction, an early event in the atherogenic process, has been shown to be associated with hyperhomocysteinemia in experimental and human studies. To further establish a direct relationship between changes in plasma homocysteine and endothelial dysfunction, we investigated whether moderate hyperhomocysteinemia induced by an oral methionine load would acutely impair flow-mediated endothelium-dependent vasodilatation in healthy adults.Methods and Results-Twenty-four healthy volunteers completed a randomized crossover study in which an oral methionine load (0.1 g/kg) was administered on 1 of 2 study days, 7 days apart. At each visit, plasma homocysteine and brachial artery endothelium-dependent and -independent dilatation were measured at baseline and at 4 hours. To further elucidate the temporal relationship between methionine, homocysteine, and endothelial function, an oral methionine load was administered in 10 subjects on a separate visit, and the time courses of plasma methionine, homocysteine, and flow-mediated brachial artery dilatation were measured at baseline and after 1, 2, 3, 4, and 8 hours. After oral methionine, plasma homocysteine increased from 7.9 +/- 2.0 [micro sign]mol/L at baseline to 23.1 +/- 5.4 [micro sign]mol/L at 4 hours (P<0.0001, n=24) and was associated with a decrease in flow-mediated brachial artery dilatation from 0.12 +/- 0.09 to 0.06 +/- 0.09 mm (P<0.05). The time course of the impairment of flow-mediated vasodilatation mirrored the time course of the increase in homocysteine concentration.ConclusionsOral methionine loading raises plasma homocysteine and impairs flow-mediated endothelium-dependent vasodilatation. This supports the view that homocysteine may promote vascular disease by inducing endothelial dysfunction. (Circulation. 1998;98:1848-1852.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe baseline cardiac troponin T (cTnT) level strongly predicts short-term mortality in acute coronary syndromes, but the added value of later measures to predict short- and long-term outcome and in the context of baseline clinical characteristics is unclear.0.1 ng/mL), 323 became positive later, and 151 remained negative (<or=to0.1 ng/mL). Mortality at 30 days was 10% in the baseline-positive group, 5% in late-positive patients, and 0% in negative patients. After adjustment for baseline characteristics, any positive cTnT result predicted 30-day mortality (baseline, chi squared=8.96, P=0.0113; 8-hour, chi squared=6.51, P=0.0107; 16-hour, chi squared=8.40, P=0.0038). Both the 8- and the 16-hour results added to the strength of the baseline result (baseline+8-hour, chi squared=12.04, P=0.0072; baseline+16-hour, chi squared=13.52, P=0.0036). Only age and ST-segment elevation were stronger predictors of 30-day mortality than baseline cTnT; results were similar for prediction of 1-year mortality. Most of the mortality difference between cTnT-positive and -negative patients occurred within the first 30 days.ConclusionsThe cTnT level is a strong, independent predictor of short-term outcome in acute coronary syndromes. The addition of later samples to a baseline level is useful to evaluate the risk of serious cardiac events. (Circulation. 1998;98:1853-1859.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundRecurrent ischemia after an acute coronary syndrome portends an unfavorable outcome and has major resource-use implications. This issue has not been studied systematically among the spectrum of patients with acute coronary presentations, encompassing those with and without ST-segment elevation.Methods and Results-We assessed the 1-year prognosis of the 12 142 patients enrolled in the GUSTO-IIb trial by the presence (n=4125) or absence (n=8001) of ST-segment elevation. This latter group was further categorized into those with baseline myocardial infarction (n=3513) or unstable angina (n=4488). We also assessed the incidence of recurrent ischemia and its impact on outcomes. Recurrent ischemia was significantly rarer in those with ST-segment elevation (23%) than in those without (35%; P<0.001). Mortality at 30 days was greater among patients with ST-segment elevation (6.1% versus 3.8%; P<0.001) but less so at 6 months; by 1 year, mortality did not differ significantly (9.6% versus 8.8%). Patients with non-ST-segment-elevation infarction had higher rates of reinfarction at 6 months (9.8% versus 6.2%) and higher 6-month (8.8% versus 5.0%) and 1-year mortality rates (11.1% versus 7.0%) than such patients who had unstable angina.ConclusionsRefractory ischemia was associated with an approximate doubling of mortality among patients with ST-segment elevation and a near tripling of risk among those without ST elevation. This study highlights not only the substantial increase in late mortality and reinfarction with non-ST-segment-elevation infarction but also the opportunities for better triage and application of therapeutic strategies for patients with recurrent ischemia. (Circulation. 1998;98:1860-1868.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundBoth radionuclide perfusion tracers and contractile response to dobutamine have been used to identify hibernating myocardium. The aim was to compare (201) Tl (thallium) single photon emission CT (SPECT),99mTc-tetrofosmin (tetrofosmin) SPECT, and dobutamine cine MRI for identifying regions of reversible myocardial dysfunction.Methods and Results-Thirty patients with 3-vessel coronary artery disease and impaired left ventricular function (mean LVEF, 24.0%; SD, 8.3%) scheduled for coronary bypass grafting were recruited. All underwent rest/dobutamine stress (5 to 10 [micro sign]g [middle dot] kg-1[middle dot] min-1) cine MRI, stress/rest tetrofosmin SPECT, and stress/redistribution and separate-day rest/redistribution thallium SPECT before surgery. Stress/redistribution thallium SPECT and resting MRI were repeated after surgery. In a 9-segment model, SPECT images were scored visually for tracer uptake, which was also measured from a polar plot of myocardial counts. MRI was scored visually for endocardial motion, myocardial thickening, and thickness. Five patients died before follow-up, and 2 declined postoperative investigation. In the remaining 23 patients, mean LVEF increased from 24.0% (SD, 8.3%) to 29.7% (SD, 11.1%) (P<0.05). Of 207 segments analyzed, 145 had significantly abnormal wall motion before surgery, and 82 of these improved function after revascularization. The criteria for predicting recovery of severely hypokinetic segments on preoperative imaging were tracer uptake graded "moderately reduced" or better, or positive inotropic response on dobutamine MRI. Late-rest thallium images showed the highest sensitivity (76%), compared with stress-redistribution thallium (68%) and rest tetrofosmin (66%) (P<0.05). All 3 tracer techniques were nonspecific (44%, 51%, and 49%, respectively). Redistribution of thallium after the resting injection was insensitive (18%) but highly specific (83%). Inotropic response to dobutamine was also insensitive (50%) but specific (81%).ConclusionsRadionuclide uptake is a sensitive but nonspecific predictor of myocardial functional recovery, whereas dobutamine MRI is specific but insensitive. (Circulation. 1998;98:1869-1874.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe role of coronary stenting in the treatment of patients with small vessels is not well defined. The purpose of this study was to investigate the influence of vessel size on long-term clinical and angiographic outcome after coronary stent placement.3.2 mm. Event-free survival at 1 year was 69.5% in the group with smaller vessels, 77.5% in the second group, and 81% in the group with larger vessels (P<0.001). Late lumen loss was similar between the 3 groups (1.12 +/- 0.73, 1.12 +/- 0.79, and 1.09 +/- 0.88 mm, respectively). Angiographic restenosis rate was significantly higher in the small-vessel group (38.6%, 28.4%, and 20.4% in groups 1, 2, and 3, respectively; P<0.001). The analysis identified subgroups with different risk for restenosis even among patients with small vessels. Within this group, the restenosis rate may be as low as 29.6% in patients without additional risk factors and as high as 53.5% in patients with diabetes and complex lesions.ConclusionsPatients with small vessels present a higher risk for an adverse outcome after coronary stent placement because of a higher incidence of restenosis. However, the unusually high risk for restenosis is confined to those patients with small vessels who have concomitant risk factors such as diabetes and complex lesions. (Circulation. 1998;98:1875-1880.)

ISSN:0009-7322    

出版商:OVID    

年代:1998

数据来源: OVID