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  • 1
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Background: While aortic valve prostheses are known to perform well at rest, few studies have examined them under stress. We compared stress hemodynamics of mechanical valves and nonstented porcine valves in the aortic position to that of normal native aortic valves. Methods: Dobutamine echocardiography was used to assess mean and peak gradients and effective orifice area index (EOAI) at rest and exercise in patients with the Toronto Stentless Porcine Valve (SPV) (n = 13, mean implant size 25.7 mm), Sorin Bicarbon mechanical valve (SOR) (n = 11, mean implant size 24.5 mm), and patients with normal native aortic valves (NOR) (n = 10). Dobutamine infusion was started at 5 µ/kg per minute, and increased by increments of 5 µ/kg per minute until the target heart rate was achieved or until a maximal dose of 40 µ/kg per minute. Results: At rest and exercise, respectively, cardiac output (L/min) was 5.2 and 10.4 for Toronto SPV; 7.4 and 13.5 for SOR; and 4.6 and 11.2 for NOR. Measured EOAI (cm2) was 1.1 ± 0.2 and 1.15 ± 0.2 for TORONTO SPV; 1.60 ± 0.3 and 1.58 ± 0.3 for SOR; and 1.45 ± 0.2 and 1.46 ± 0.2 for NOR. Mean gradients (mmHg) were 5.48 1±.1 and 5.83 ± 0.9 for TORONTO SPV; 5.26 ± 0.8 and 11.3 ± 1.8 for SOR; and 1.54 ± 0.4 and 2.18 ± 0.7 for NOR. Peak gradients (mmHg) were 11.9 ± 2.0 and 21.0 ± 3.7 for TORONTO SPV; 10.79 ± 1.7 and 25.9 ± 3.4 for SOR; and 2.38 ± 0.9 and 6.1 ± 2.3 for NOR. Conclusions: Although the mechanical group (SOR) had larger measured EOAI, the greater increase in gradients with exercise in this group suggests that the TORONTO SPV is less obstructive to flow.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 163 (1968), S. 429-438 
    ISSN: 0005-2736
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 73 (1978), S. 200-207 
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zasammenfassung An Schnitten von isolierten Herzen, die mit einer modifiziertenKrebs-Henseleit-Lösung mit oder ohne Zusatz von Isoproterenol perfundiert worden waren, wurde eine Röntgenmikroanalyse durchgeführt. Nach Isoproterenolperfusion konnten Veränderungen der P-, Ca- und Zn-Konzentrationen und eine Beziehung dieser Änderungen zu hämodynamischen und morphologischen Parametern festgestellt werden. Das P/Ca-Verhältnis in den Kernen der Muskelfasern und die Calcium-Relation zwischen den Kernen der interstitiellen Zellen einerseits und der Myokardfasern andererseits zeigten eine direkte Beziehung zum Zustand des Herzens.
    Notes: Summary X-ray microanalysis was carried out on sections from isolated hearts perfused with a modifiedKrebs-Henseleit solution with or without isoproterenol. Changes in P, Ca and Zn concentrations could be detected after isoproterenol and some correlation with hemodynamic and morphological parameters was observed. Ratios between P/Ca in myonuclei and the ratios of interstitial cell to myofiber nucleus calcium were related directly to the state of the heart.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 72 (1977), S. 1-10 
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Infusion von 25%igem Mannitol in den Ramus circumflexus oder interventricularis anterior der linken Kranzarterie verursachte bei 10 anästhetisierten Hunden eine signifikante Steigerung der mittels Dehnungsmeßstreifen gemessenen myokardialen Kraftentwicklung (F). Die Änderungen waren auf den jeweils perfundierten Bezirk des herzens beschränkt. Der Anstieg der systolischen Kraft war dosisabhängig. Er betrug 20% bei einer Infusionsrate von 0,55 ml/min, 28% bei 1,4 ml/min, 32% bei 2,8 ml/min und 57% bei 5,5 ml/min. Ein ähnliches Vorhaben zeigte die Geschwindigkeit des systolischen Kraftanstiegs (dF/dt). Auch der Anstieg der systolischen Kraft in der ersten Minute war dosisabhängig. Er betrug 9% bei 0,55 ml/min und 40% bei 5,5 ml/min. Bei Infusion von Kochsalz wurden keine Veränderungen der Kontraktilität gesechen. Das gleiche gilt unter Mannitol für den (nicht perfundierten) Kontrollbezirk. Eine Abnahme der systolischen Kraft von 10,5% wurde nach der initialen Steigerung beobachtet, wenn Mannitol bei einer Infusionsrate von 5,5 ml/min infundiert wurde. Dieser Effekt beseitigte jedoch den initialen Anstieg nicht völlig. Änderungen im Blutdruck, der Herzfrequenz, dem linksventrikulären systolischen und diastolischen Blutdruck sowie von dP/dt wurden während der Experimente nicht beobachtet. Aus den Ergebnissen wird geschlossen, daß klinisch gebräuchliche Dosen von Mannitol einen direkt inotropen Effekt auf das intakte Hundeherz haben.
    Notes: Summary Infusion of 25% mannitol into either the circumflex or left anterior descending coronary artery caused a significant increase in myocardial force development, measured by means of strain gauge in 10 anesthetized dogs. The changes were confined to the area perfused. The increase in developed force was dosedependent, 20% at an infusion rate of 0.55 ml/min, 28% at 1.4 ml/min, 32% at 2.8 ml/min and 57% at 5.5 ml/min. There was a similar increase in dF/dt. The increase in developed force in the first minute was also dose-dependent, being 9% at 0.55 ml/min and 40% at 5.5 ml/min. No change in developed force occurred in the control (non-perfused) area or during saline infusion to the same artery at similar rates. A decrease in developed force of 10.5% was observed after the initial rise when mannitol was infused at 5.5 ml/min. This effect did not completely abolish the initial increase. No change in blood pressure, heart rate, LV systolic and diastolic pressure of LV dp/dt occurred during the experiment. It is concluded that doses of mannitol which are in clinical use have a direct positive inotropic effect on the intact canine heart.
    Type of Medium: Electronic Resource
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