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  • 1
    Online Resource
    Online Resource
    American Physiological Society ; 2010
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 298, No. 1 ( 2010-01), p. H158-H162
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 298, No. 1 ( 2010-01), p. H158-H162
    Abstract: In the failing myocardium a subendocardial plexus can develop. Detection of the presence or function, however, of such a plexus does not form part of the present diagnostic spectrum for heart failure. This may now change as new methods for high-resolution imaging of myocardial perfusion distribution are being developed. A severely hypertrophic heart was harvested during transplantation and analyzed for morphology of the intramural coronary arterial vasculature. The heart only had one coronary ostium, and the main branches of the coronary artery were cannulated. A fluorescent casting material was infused that was allowed to harden under physiological pressure. The entire heart was frozen and placed in a novel imaging cryomicrotome and sequentially cut in 25-μm slices. High-resolution images of each cutting plane were acquired, allowing a detailed three-dimensional reconstruction of the arterial vasculature. The epicardial layer of the free wall demonstrated a normal vasculature with penetrating branching arteries. The endocardial layer and the septum revealed a highly interconnected vascular plexus with large vessels oriented parallel to the apicobasal axis. An extensive endocardial network with collaterals was detected, forming connections between the main epicardial branches. We conclude that an outward remodeling of transmural vessels did not prevent the generation and growth of subendocardial conduit arteries. The orientation and vascular volume in the plexus provides an opportunity for detection by novel techniques of MRI contrast imaging currently developed. Knowledge of the effect on perfusion studies is required to prevent a misinterpretation of subendocardial perfusion images in heart failure.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2010
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Wiley ; 2019
    In:  Pacing and Clinical Electrophysiology Vol. 42, No. 12 ( 2019-12), p. 1503-1516
    In: Pacing and Clinical Electrophysiology, Wiley, Vol. 42, No. 12 ( 2019-12), p. 1503-1516
    Abstract: The extracellular electrogram is caused by transmembrane currents that flow into extracellular space during propagation of the electrical impulse. Electrograms are usually recorded in unipolar or bipolar mode that have different characteristics, but provide complementary information. Both recording modes have specific advantages, but also suffer from disadvantages. Techniques to circumvent some of the weaknesses are reviewed. The origin of remote and fractionated deflections and their relation with electrode characteristics are discussed. Epicardial and endocardial sites of origin and breakthrough sites as well as the effect of fatty tissue on extracellular electrograms are presented. Induction of tachycardia to assess the arrhythmogenic area is not always possible because of hemodynamic instability of the patient. Techniques to assess sites with high reentry vulnerability without induction of arrhythmias are outlined such as activation‐repolarization mapping and decremental stimulation. Pitfalls of substrate mapping and techniques to avoid them as omnipolar mapping and characterization of complex electrograms by entropy are presented. Technical aspects that influence electrogram morphology as electrode size, filtering, contact force, and catheter position are delineated. Data from the various publications suggest that a combination of unipolar and bipolar electrogram analysis techniques is helpful to optimize determination of target sites for ablation.
    Type of Medium: Online Resource
    ISSN: 0147-8389 , 1540-8159
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2037547-5
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