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    Progression of myocardial remodeling and mechanical and dysfunction in the spontaneously hypertensive rat

    Sands, Gregory B.; Pope, Adèle J.; LeGrice, Ian J; Whalley, Gillian; Doughty, Robert N.; Smaill, Bruce H.

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    Date
    2012-09-21
    Citation:
    LeGrice, I.J., Pope, A.J., Sands, G. B., Whalley, G., Doughty. R.N. and Smaill, B.H. (2012). Progression of myocardial remodeling and mechanical and dysfunction in the spontaneously hypertensive rat. American Journal of Physiology. Heart and Circulatory Physiology (Online). 303, H1353-H1365.
    Permanent link to Research Bank record:
    https://hdl.handle.net/10652/2502
    Abstract
    The progression of hypertensive heart disease (HHD) to heart failure (HF) is associated with myocardial remodeling. Corresponding changes in three-dimensional organization of cardiac extracellular matrix have not been quantified or related fully to the development of HF. Spontaneously hypertensive rats (SHRs) and Wistar-Kyoto controls were studied at 3, 12, 18, and 24 mo. Hemodynamic and morphological data, brain natriuretic peptide levels, and echocardiography demonstrate four distinct disease stages: systemic hypertension, diastolic dysfunction, early systolic failure, and decompensated HF. Passive left ventricular (LV) pressure-volume relationships were determined in vitro. Transmural specimens from the anterior LV free wall were imaged using extendedvolume confocal microscopy, and three-dimensional myocardial architecture was quantified. In SHRs, LV compliance was reduced at 12 mo and increased progressively thereafter. However, it was less than in controls for filling pressures 10 mmHg and not significantly different at 10 mmHg. Myocyte cross section was enlarged, with increased variability from 12 mo, while collagen fraction increased progressively. Perimysial collagen fraction remained unchanged with age, although endomysial collagen increased from 12 mo. Perimysial collagen between adjacent muscle layers fused at 12 mo and continued to thicken subsequently, while muscle layers became more dispersed and disordered. We conclude that LV dilatation, which accompanies decompensated HF in this model of HHD, is not due to LV “softening.” While perimysial (and endomysial) collagen networks are substantially remodeled, they are not dissolved, as has been proposed. We argue that progressive disruption of the laminar organization of LV myocardium may contribute to impaired systolic function in HHD.
    Keywords:
    hypertension, cardiomyopathy, connective tissue, perimysium, endomysium, myocardium, laminar architecture
    ANZSRC Field of Research:
    110201 Cardiology (incl. Cardiovascular Diseases)
    Copyright Holder:
    American Physiological Society
    Available Online at:
    http://www.ncbi.nlm.nih.gov/pubmed/23001837
    Rights:
    This digital work is protected by copyright. It may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use: Any use you make of these documents or images must be for research or private study purposes only, and you may not make them available to any other person. You will recognise the author's and publishers rights and give due acknowledgement where appropriate.
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