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  • 1
    ISSN: 1432-2013
    Keywords: Inert gas dilution method ; Deconvolution ; Circulatory transport function ; Indicator transit time ; Heterogeneity of myocardial blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following single breath inhalations of helium 49 simultaneous inlet-outlet pairs of helium dilution curves were recorded in seven dog experiments from the aortic and coronary sinus blood by use of mass spectrometric technique. After numeric deconvolution of the dilution curves the weighting function of tracer transit times was used for calculation of the mean myocardial blood flow per unit of tissue, which closely correlated with directly measured flow. Secondly, the degree of blood flow heterogeneity was estimated from the first moments of the weighting function of transit times and by compartmental analysis based on an inverse Laplace transform. In the intact heart the results suggest a rather constant dispersion of flows relative to the mean flowFF in the order of σ/FF=0.3. The apparent dispersion of flows is increased by α-adrenergic stimulation with pressure and volume load, particularly in a state of β-blockade, a finding, which may be attributed to variations of intercapillary distances and to a heterogeneity of blood flow per unit of tissue.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Cardiac metabolism ; Ischemia ; Isosorbide dinitrate ; Nicorandil ; Oxygen-debt ; Oxygen-repayment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study was designed to investigate the effects of nicorandil in comparison to isosorbide dinitrate (ISDN) on hemodynamics, on myocardial metabolism and on effectiveness in the preservation of ischemically stressed myocardium. Repeated ischemia (3 min) was produced in anaesthetized open-chest mongrel dogs by proximal, intermittent left anterior descending artery occlusion with subsequent reperfusion. In each experiment 2–3 control occlusions were compared to 2–3 occlusions under nicorandil or ISDN. Application of both nicorandil (0.64 μmol·kg−1 body weight, i.v.) and ISDN (1.27 μmol·kg−1 body weight, i.v.) led to a significant afterload reduction and to a decrease of the coronary vascular resistance. The efficiency of the compounds in the protection of ischemic myocardium was examined by quantification of oxygen-debt and oxygen-repayment in the occlusion and reperfusion periods. Compared to control, premedication with nicorandil led to a significant increase of oxygen-debt, whereas ISDN reduced it significantly. Oxygen-repayment remained unchanged. The influence of the drugs on the metabolism of glucose, lactate and free fatty acids (FFA) was examined under basic conditions, in ischemia and during reperfusion. For all substrates, extraction, extraction ratio and oxygen extraction ratio were calculated. Under basic conditions, glucose metabolism was significantly enhanced in both groups but FFA metabolism was inhibited only by ISDN. In ischemia, FFA metabolism was enhanced by nicorandil and depressed by ISDN. Data obtained in this study suggest that nicorandil may even aggravate the metabolic and energetic situation of ischemic myocardium and, on the other hand, clearly support the well documented protective effects of ISDN.
    Type of Medium: Electronic Resource
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