摘要:

BackgroundThe current treatment of many cases of acute myocardial infarction involves the use of thrombolytic agents. Evaluation of this therapy requires determination of the success of reperfusion and assessment of the presence and extent of infarction in the reperfused territory. The present study was designed to simulate in rat models several possible outcomes of reperfusion therapy: (1) successful reperfusion and absence of myocardial infarction, (2) successful reperfu-sion and presence of myocardial infarction, and (3) unsuccess-ful reperfusion. The usefulness of contrast-enhanced fast magnetic resonance (MR) imaging in defining the success of reperfusion was investigated. The dynamic effects were examined of low and high doses of gadolinium-BOPTA/dimeglu-mine (Gd-BOPTA/dimeg) on myocardial signal using MR inversion recovery echo planar imaging (IR-EPI) and gradient recalled echo planar imaging (GR-EPI), respectively.Methods and ResultsRats were subjected to one of the following regimens: reperfused reversible myocardial injury (n=9), reperfused irreversible myocardial injury (n=9), and occlusive infarction (n=9). MR echo planar images were acquired every 1 or 2 seconds before, during, and after administration of Gd-BOPTA/dimeg. In all groups, normal myocardial signal was sharply increased on IR-EPI and decreased on GR-EPI at the peak of the bolus, followed by a gradual decline to baseline. In animals subjected to reperfused reversible myocardial injury, normal and previously ischemic regions were indistinguishable during and after the passage of Gd-BOPTA/dimeg. On the other hand, enhancement of reperfused irreversibly injured myocardium was delayed but increased steadily to a higher level than normal myocardium on IR-EPI. The reperfused irreversibly injured myocardium was identified on IR-EPI as a zone of high signal (hot spot). On GR-EPI, signal loss in reperfused irreversibly injured myocardium was significantly less compared with normally perfused myocardium. In animals with occlusive infarctions, there was no change in signal intensity over the ischemic region on either IR-EPI or GR-EPI. Occlusive infarction was identified as zones of either low (cold spot) or high (hot spot) signal compared with normal myocardium, depending on MR pulse sequence and dose of the contrast medium.ConclusionsThe transit of Gd-BOPTA/dimeg monitored by fast MR imaging techniques can be used to distinguish between reperfused reversibly and reperfused irreversibly injured myocardium and between occlusive and reperfused infarctions.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAlthough dobutamine echocardiography is being increasingly used to determine the presence of viable myocardium in patients who have undergone successful reper-fusion therapy, the physiological basis for such a use has not been clearly defined. Because postischemic myocardium has contractile reserve, we hypothesized that the absolute degree of wall thickening induced by dobutamine during reflow would be directly related to the amount of myocardium that has escaped necrosis.Methods and ResultsThree groups of 12 dogs each were studied at baseline and during 2 to 6 hours of coronary artery occlusion and 15 minutes of reperfusion. In group 1 dogs, which did not receive dobutamine during any of these stages, percent wall thickening at these stages was 32±6%, −2±6%, and 5 ±6%, respectively, and there was no relation between infarct size and percent wall thickening during reflow (r=.20,P=.51). In group 2 dogs, which received 15 μg/kg per minute of dobutamine at all stages, wall thickening at these stages was 40±8%, 0±8%, and 19±10%, respectively, and a good inverse correlation was noted between infarct size and percent wall thickening during reflow (r= −.81,P=.001). In group 3 dogs, in which wall thickening during reflow was measured both before and during infusion of 15 μg/kg per minute of dobutamine, it was 5±8% and 18±14%, respectively, at these stages. Although the correlation between infarct size and percent wall thickening was poor in the absence of dobutamine (r=.36,P=.26), an excellent inverse correlation was noted between the two in the presence of dobutamine (r= −.93,P<.001). A fair inverse correlation was also noted between infarct size and the absolute change in wall thickening induced by dobutamine (r= −.72,P<.01). Maximal wall thickening was noted at a dobutamine dose of 15 μg/kg per minute, and lower doses did not elicit thickening in the presence of larger infarcts despite the presence of viable myocardium.ConclusionsWhen myocardial necrosis coexists with post-ischemic myocardial dysfunction and no residual coronary stenosis, the absolute degree of wall thickening during dobutamine can be used to determine the extent of myocardium that has escaped necrosis. The dose of dobutamine needed to elicit maximal thickening of the postischemic myocardium is related to the amount of myocardial necrosis.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe purpose of this study was to determine whether myocardial perfusion can be quantified with myocardial contrast echocardiography using left atrial (LA) injection of contrast.Methods and ResultsBased on a series of in vitro and in vivo experiments, the optimal dose of sonicated albumin microbubbles injected into the LA for establishing a linear relation between video intensity and blood volume in the anterior myocardium was determined. In 10 open-chest dogs, myocardial blood flow (MBF) was augmented by increasing myocardial blood volume (MBV) with an intravenous infusion of phenylephrine HCl. In the presence of this drug, left anterior descending artery stenosis was produced, followed by release of stenosis, to change MBF within the anterior myocardium. MBV was calculated by dividing radiolabeled microsphere-derived MBF by microbubble transit rate. There was close coupling between MBF and MBV in the anterior myocardium during LA injection of contrast (y=1.0x−0.03, SEE=1.07,r=.92,P<.001). An excellent correlation was also noted between background-subtracted peak video intensity and MBV (y=0.24x+0.73, SEE=0.36,r=.88,P<.001). On multivariate analysis, background-subtracted peak video intensity correlated best with MBV.ConclusionsMyocardial perfusion can be quantified from time-intensity curves derived from the anterior myocardium after LA injection of contrast. Background-subtracted peak video intensity in this situation correlates closely with MBV. When MBV and MBF are closely coupled, such as during inotropic stimulation of the heart, background-subtracted peak video intensity also correlates closely with MBF. Since there are similarities in the models of LA and venous injections, these data indicate that it may be feasible to quantify myocardial perfusion with myocardial contrast echocardiography after venous injection of contrast.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

AbstractCurrently used antithrombotics such as heparin have a number of potential limitations that may be overcome by the new class of agents that directly inhibit thrombin. These agents variously block the active catalytic and/or the anion binding exosites of the thrombin molecule and are potent and specific inhibitors of thrombin's many biological actions, as demonstrated by in vitro and animal models of thrombosis. Preliminary data indicate that the direct antithrombins are safe and efficacious in humans, and their use in acute coronary syndromes and coronary angioplasty in place of heparin has yielded promising early results. Phase III trials in these clinical settings are currently under way. Newer antithrombotics that inhibit thrombin generation and thrombin activity at various strategic points within the coagulation cascade are also in the early stages of development.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundFew data are available on the prevalence of hypertension in Mexico.Methods and ResultsWe compared the prevalence of mild hypertension (systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure ≥90 mm Hg and/or use of antihyper-tensive medications) in 1500 low-income Mexican Americans who participated in the San Antonio Heart Study and 2280 low-income Mexicans who participated in the Mexico City Diabetes Study. The crude prevalence of mild hypertension was 17.1% in Mexican men versus 24.4% in Mexican American men (P=.001) and 17.4% in Mexican women versus 22.0% in Mexican American women (P=.005). After adjustment for age, body mass index (BMI), waist-to-hip ratio (WHR), non-insulin dependent diabetes mellitus (NIDDM), educational attainment, and percent native American genetic admixture (Caucasian and native American), the odds ratio (Mexico City/San Antonio) was 0.55 (95% CI, 0.39, 0.77;P<.001) in men and 0.81 (CI, 0.54, 1.12;P=.201) in women. In a pooled model including both men and women, the odds ratio was 0.67 (95% CI, 0.53, 0.84;P<.001). In the pooled model, city, age, female sex, NIDDM, BMI, WHR, and low educational attainment were significantly related to the prevalence of hypertension.ConclusionsThe causes for these differences in hypertension prevalence are not known but may reflect a less modernized lifestyle in Mexico City, including greater physical activity, less obesity, and the consumption of a high-carbohydrate, low-fat diet.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID