摘要:

BackgroundBrief episodes of ischemia induced by proximal coronary artery occlusion can precondition the myocardium. Whether other stressful stimuli have the potential to protect the myocardium from subsequent ischemia remains controversial.Methods and ResultsTo study the hypothesis that transient α-adrenoceptor stimulation mimics preconditioning, for 5 minutes we administered 0.25 μg · kg−1spkg min−1norepinephrine or saline 10 minutes before a 30-minute coronary occlusion and 4 hours of reperfusion in an in vivo rabbit model. The area of necrosis (AN) and area of risk (AR) were measured. We found that norepinephrine pretreatment caused a reduction in infarct size when compared with controls (AN/AR, 0.17±0.04 versus 0.31±0.04;P<.02). Ischemic preconditioning also reduced infarct size (AN/AR, 0.22±0.03). The protection observed with norepinephrine treatment was entirely eliminated by pretreatment with α-adrenergic blockade using prazosin (AN/AR, 0.42±0.06). Tyramine, an agent that causes release of endogenous catecholamines, was administered (1.5 mg/kg IV) 10 minutes before coronary occlusion in another group of rabbits. Tyramine pretreatment resulted in a smaller infarct size than in untreated controls (AN/AR, 0.16±0.04 versus 0.41±0.07;P<.01). Both norepinephrine and tyramine caused an increase in systemic arterial pressure during infusion; tyramine also increased heart rate. In rabbits pretreated with prazosin, heart rate and systemic pressure during the norepinephrine infusion were similar to baseline values. During coronary occlusion, the degree of ischemia was similar in all groups.ConclusionsExposure of the heart to either transient exogenous norepinephrine or endogenous release of norepinephrine and/or other catecholamines by tyramine can mimic the effects of ischemic preconditioning in rabbits.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

AbstractThis article discusses escalating health care costs in terms of their principal component, cardiovascular diseases. The role of cigarette smoking is highlighted throughout. A Smoker's Accountability Trust is proposed for the prevention of nonfatal myocardial infarction. It is demonstrated that this approach can contain costs by controlling the root causes of their acceleration.

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:

AbstractAlthough intracoronary ultrasonography allows detailed tomographic imaging of the arterial wall, it fails to provide data on the structural architecture and longitudinal extent of arterial disease. This information is essential for decision making during therapeutic interventions. Three-di-mensional reconstruction techniques offer visualization of the complex longitudinal architecture of atherosclerotic plaques in composite display. Progress in computer hardware and software technology have shortened the reconstruction process and reduced operator interaction considerably, generating three-dimensional images with delineation of mural anatomy and pathology. The indications for intravascular ultrasonography will grow as the technique offers the unique capability of providing ultrasonic histology of the arterial wall, and the need for a three-dimensional display format for comprehensive analysis is increasingly recognized. Consequently, three-dimensional imaging is being rapidly implemented in the catheterization laboratories for guidance of intracoronary interventions and detailed assessment of their results. However exciting the prospects may be, three-dimensional reconstructions at present remain partially artificial because the true spatial position of the imaging catheter tip is not recorded, and shifts in its location and curves of the arterial lumen result in pseudoreconstructions rather than true reconstructions. In this report, we address the principles of three-dimensional reconstruction with a critical review of its limitations. Potential solutions for refinement of this exciting imaging modality are presented.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundNumerous reports suggest that coronary artery disease can regress with lipoprotein manipulation. Many of these reports lack control groups and contain relatively small numbers.Methods and ResultsTen randomized controlled clinical trials using coronary arteriography to assess the effect of lipoprotein manipulation on the rate of progression and regression of atherosclerosis have been either published or reported as an abstract at a national meeting. These studies were critically reviewed for individual differences and combined clinically applicable lessons. These trials involved a total of 2095 subjects and have consistently reported reduction in the percentage of patients arteriographically defined as progressing (mean, 23.6%) and an increase in the percentage regressing (mean, 20.0%) compared with control groups. Com-pared with large clinical trials using clinical end points, lipoprotein change was greater, achieving on average a 28% reduction in low-density lipoprotein cholesterol, 11% reduction in triglycerides, and 1% increase in high-density lipoprotein cholesterol compared with control groups. Four investigations used a nonpharmacological approach, and seven used single and multiple drug therapy combined with diet. Despite the relatively brief treatment time of often 2 to 4 years, clinical events were fewer in the treatment groups; within some studies, this reached statistical significance. Side effects from the different therapies were tolerated by most patients, and severe adverse clinical events were few.ConclusionsThese trials present convincing evidence that aggressive lipoprotein manipulation can result in improved arteriographic measurements and fewer cardiovascular events in a relatively short period of time of 2 to 4 years. Extrapolation of this information to the larger population with known coronary artery disease suggests that directed lipoprotein manipulation can reduce clinical events in a cost-effective manner.

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

摘要:

BackgroundRecent clinical studies have proposed standard deviation of heart rate as a diagnostic tool for the outcome of cardiac infarction. Mathematical analysis of heart rate variability shows that heart rate is influenced by different frequency components derived from different parts of the autonomous nervous system. In the experimental part of this study, we investigated the possibility of calculating a variable describing the parasympathetic branch of the autonomous nervous system exclusively.Methods and ResultsIn 60 healthy volunteers, heart rate was measured to 1 millisecond during two different conditions: 5 minutes of rest, and 5 minutes of intermittent handgrip dynamometry; the latter is known to increase sympathetic arousal selectively. Heart rate was found to be lower at rest (65.9±9.7 beats per minute) than during dynamometry (72.8±10.4 beats per minute,P<.001). Respiratory sinus arrhythmia (RSA) calculated from the mean absolute differences between successive heart beats showed no significant change (3.01± 1.62 beats per minute at rest versus 2.97±1.30 beats per minute during dynamometry). In contrast, standard deviation increased from 5.19±1.98 to 9.22±3.56 beats per minute (P<.001).ConclusionsIt can be concluded from these data as well as from other plots presented in this article that RSA is a measure of the parasympathetic vagal tone, whereas standard deviation is increased by both sympathetic and parasympathetic arousal. Clinical evidence and data from physiological experiments are presented to show that a selective measure of vagal tone like RSA may offer advantages over standard deviation as a prognostic tool in cardiology.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

AbstractSudden cardiac death usually occurs secondary to a ventricular tachyarrhythmia. Even under ideal circumstances only 20% of patients who have an out-of-hospital cardiac arrest survive to hospital discharge. Therefore, aggressive treatment and screening of high-risk patients are mandatory to improve survival rates. Risk stratification of high-risk patients, such as the post – myocardial infarction (M1) population, has been of limited value. Between 70% and 85% of “high-risk” post-MI patients, as defined by these screening tests, will not have a sustained ventricular tachyarrhythmia over several years of follow-up. The use of β-blockers and possibly amiod-arone may have some benefit in reducing mortality in high-risk patients after an MI. Several ongoing trials are studying the use of serial drug testing, amiodarone, and implantable cardioverter-defibrillators in reducing the incidence of sudden cardiac death in patients with potentially lethal ventricular arrhythmias. Although implantable cardioverter-defibrillators appear to be superior to antiarrhythmic drugs in reducing sudden cardiac death, total mortality may not be altered. In sustained ventricular tachyarrhythmias, sotalol and amiodarone appear to be superior to other drugs in preventing arrhythmia recurrence. Ongoing trials, such as the Antiar-rhythmic Drug versus Implantable Device (AVID) trial may define the best strategy in these high-risk patients.

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