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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Visual comparison of rest/stress cardiac positron emission tomography indicates coronary flow reserve for diagnosing and assessing severity of coronary artery disease. An accurate, rapid, automated method for comparison and quantitation of paired cardiac PET studies has been developed to analyze size, intensity, statistical significance of and changes in perfusion or metabolism. The method utilizes polar coordinate maps derived from circumferential profiles of true short axis slices; from the short axis data algorithms determine mean and minimum activity levels in the anterior, septal, lateral, inferior and apical regions of the myocardium, percent of the cardiac image in specific ranges of activity levels or their changes and the percent of myocardium beyond 1.5, 2.0, and 2.5 standard deviations from the normal range with blackout display of the areas beyond these statistical limits for rest, stress, and stress/rest ratio polar maps. Additional applications include comparing stress-stress images to evaluate progression/regression of stenoses, early and late resting rubidium images for determining myocardial viability based on rubidium washout kinetics, and perfusion-metabolic comparisons for quantifying ischemia, viability and necrosis after acute myocardial infarction.
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PMID:Automated quantitation of three-dimensional cardiac positron emission tomography for routine clinical use. 280 43

Pilots of high-performance aircraft are subject to transient loss of consciousness due to cerebral ischemia resulting from sudden high gravitational stress. To assess the effects of gravitational stress-induced blackout on cerebral metabolism and electrical function, we developed an animal model in which global cerebral ischemia is produced repeatedly at short intervals. Rats were prepared by ligation of subclavian and external carotid arteries and the right carotid artery was cannulated bidirectionally to measure circle of Willis and systemic pressures. Ischemia was induced by inflation of an occluder about the left carotid artery. Interleaved 31P and 1H NMR spectra were acquired on a 4.7-T Biospec system simultaneously with EEG recordings. We report results from 20 experiments of 30-min duration in which rats were subject to 30 1-min ischemia:reflow cycles of 10I:50R, 20I:40R, 30I:30R, and 40I:20R [numbers are seconds of ischemia (I) and reflow (R) during each 1-min cycle]. During ischemia the graded delivery of the ischemic insult permitted direct correlations between 2- to 5- and 7- to 20-Hz EEG activity and progressive changes in pH, lactate, ATP, phosphocreatine (PCr) and Pi. The best correlations were found between EEG activity and pH and PCr; correlation coefficients ranged from 0.93 to 0.95. A loss of EEG activity was observed without significant sustained energy loss in all but the most severe cycle.
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PMID:Concomitant EEG, lactate, and phosphorus changes by 1H and 31P NMR spectroscopy during repeated brief cerebral ischemia. 779 37

Visual alterations, peripheral light loss (PLL) and blackout (BO), are components of acceleration (+Gz) induced loss of consciousness (LOC) and recovery of consciousness (ROC). The kinetics of loss of vision (LOV) and recovery of vision (ROV) were determined utilizing ocular pressure induced retinal ischemia and compared to the kinetics of LOC and ROC resulting from +Gz-induced cephalic nervous system (CPNS) ischemia. The time from self-induced retinal ischemia in completely healthy subjects (N = 104) to the onset of PLL and complete BO was measured. The time from release of ocular pressure, with return of normal retinal circulation, to the time for complete recovery of visual fields was also measured. The kinetics of pressure induced LOV and ROV was compared with previously developed kinetics of +Gz-induced LOC and ROC focusing on the rapid onset, vertical arm, of the +Gz-induced LOC and ROC curves. The time from onset of increased ocular pressure, immediately inducing retinal ischemia, to PLL was 5.04 s with the time to BO being 8.73 s. Complete recovery of the visual field from BO following release of ocular pressure, immediately abolishing retinal ischemia, was 2.74 s. These results confirm experimental findings that visual loss is frequently not experienced prior to LOC during exposure to rapid onset, high levels of +Gz-stress above tolerance. Offset of pressure induced retinal ischemia to ROV was 2.74 s, while the time from offset of +Gz-induced CPNS ischemia to ROC was 5.29 s. Recovery of retinal function would be predicted to be complete before consciousness is regained following +Gz-induced LOC. Ischemia onset time normalization in neurologic tissues permits comparison between different stress-induced times to altered function. The +Gz-time tolerance curves for LOV and LOC provide comparison and integration of neurologic state transition kinetics in the retina and CPNS.
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PMID:Neurologic state transitions in the eye and brain: kinetics of loss and recovery of vision and consciousness. 2624 24