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  • 1
    ISSN: 1432-1440
    Keywords: Cerebral blood flow ; Carotid stenosis ; Microspheres ; Ventricular tachycardia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to investigate the effect of hypotensive tachycardias on cerebral blood flow (CBF) in the presence of significant carotid stenosis. The experiments were performed in 57 spontaneously breathing rats during arterial normoxia and normocapnia anesthetized with thiobarbital. CBF was determined with radio-labeled microspheres during control conditions (normofrequent sinus rhythm, normotension; group A; n = 15), during high-rate left ventricular pacing (660–840 ppm) at normotension (group B1; n = 13), borderline hypotension (group B2; n = 15) and severe hypotension (group B3; n = 7). In addition, CBF measurements were performed during borderline hypotension induced by hemorrhage (group C; n = 7). Global CBF was 1.09 ± 0.29 ml g−1 min−1 in group A, 0.93 ± 0.40 in group B1, 0.68 ± 0.31 in group B2 (P 〈 0.05 vs. A), 0.42 ± 0.16 in group B3 (P 〈 0.05 vs. A) and 0.83 ± 0.2 in group C. The highest CBF values were found in the cerebellum (A; 1.43 ± 0.5 ml g−1 min−) and the lowest in the postocclusive tissue of the ipsilateral hemisphere (A; 0.74 ± 0.2 ml g−1 min−1). In all groups a 15% mean CBF reduction in the right hemispherical cerebrum in comparison to the left hemisphere was observed (P 〈 0.01). In contrast, hemispherical CBF of the cerebellum did not differ. The CBF blood pressure relationship shifted to lower CBF values, the threshold of CBF regulation shifted to higher blood pressure values in the tissue regions distal to the occluded vessel during hypotensive tachycardias. One carotid artery occlusion and high rate ventricular pacing seem to be a reliable model for quantifying cerebral hemodynamics during arrhythmias in the presence of carotid stenoses. Using this experimental approach it was demonstrated that hypotensive tachycardias and obstructions within the ectracranial carotid vascular bed such as arterial vessel stenoses and occlusions have an additive effect on CBF reduction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Arrhythmien ; Hypotensive Episoden ; Vaskuläre Demenz ; Inkomplette Infarzierung ; Selektive Vulnerabilität ; Key words Arrhythmias ; Hypotensive episodes ; Vascular dementia ; Incomplete infarction ; Selective vulnerability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary To date clinical and experimental investigations have focused on acute strokes and complete infarctions. Histological and immunological staining in animal experiments and improved imaging techniques in patients suggest that selective or incomplete infarction is a common pathomechanism. Incomplete infarction can manifest as laminar necrosis at autopsy and as leukoaraiosis in imaging studies. An important mechanism in the genesis of leukoaraiosis is vascular pathology of the long penetrating arteries of the deep white matter combined with episodes of decreased perfusion pressure or hypotension. We demonstrate that the cumulative effect of repetitive, moderate hypotensive episodes on cognitive performance or cerebral tissue has not been adequately studied and appreciated.
    Notes: Zusammenfassung Klinische und experimentelle Studien zur Pathophysiologie zerebrovaskulärer Erkrankungen haben sich bisher weitgehend auf akute Ischämien mit kompletter Infarzierung konzentriert. Histologische und immunologische, tierexperimentelle Untersuchungen und moderne, klinische neuroradiologische Verfahren belegen, daß Ischämien nicht immer zu einer kompletten Infarzierung führen und diffuse und selektive Zellschädigungen möglich und vermutlich auch häufig sind. Inkomplette Infarzierungen der weißen Substanz können als Leukoaraiosis imponieren. Pathophysiologisch bedeutsam ist eine Vaskulopathie der langen penetrierenden Marklagerarterien. Für die Entstehung der Gefäßwandveränderung (Hyalinose) wird die Hypertonie wesentlich verantwortlich gemacht. Für die eigentliche ischämische Schädigung sind jedoch eher ein Abfall des Perfusionsdruckes z.B. im Rahmen von hypotonen Episoden verantwortlich. Im folgenden begründen wir, warum wir annehmen, daß chronische, mäßiggradige oder chronische, repetitive Ischämien in Klinik und Forschung bisher unterrepräsentiert sind und ihr kumulativer Effekt in der Pathophysiologie ischämischer Läsionen im Alter vermutlich eine wichtigere Rolle spielen als bisher vermutet.
    Type of Medium: Electronic Resource
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