A structure-function analysis of the left ventricle

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dc.contributor.authorSnelling, E.
dc.contributor.authorSeymour, R.
dc.contributor.authorGreen, J.
dc.contributor.authorMeyer, L.
dc.contributor.authorFuller, A.
dc.contributor.authorHaw, A.
dc.contributor.authorMitchell, D.
dc.contributor.authorFarrell, A.
dc.contributor.authorCostello, M.
dc.contributor.authorIzwan, A.
dc.contributor.authorBadenhorst, M.
dc.contributor.authorMaloney, S.
dc.date.issued2016
dc.description.abstractLeft ventricular external mechanical work rate was calculated from cardiac output and systemic mean arterial blood pressure in resting sheep (Ovis aries; N = 4) and goats (Capra hircus; N = 4) under mild sedation, followed by perfusion-fixation of the left ventricle, and quantification of the cardiac capillary-tissue geometry and cardiomyocyte ultrastructure. The investigation was extended to heavy exercise by increasing cardiac work according to published hemodynamics during sustained treadmill exercise. Left ventricular work rate averaged 0.017 W cm(-3) of tissue at rest, and was estimated to increase to ~0.060 W cm(-3) during heavy exercise. We predicted that oxygen consumption increases from 195 nmol O2 s(-1) cm(-3) at rest, to ~600 nmol O2 s(-1) cm(-3) during heavy exercise, which is within 90% of the demand rate and consistent with work remaining predominantly aerobic. Mitochondria represent 21 - 22% of cardiomyocyte volume and consume oxygen at a rate of 1150 nmol O2 s(-1) cm(-3) of mitochondria at rest, and ~3600 nmol O2 s(-1) cm(-3) during heavy exercise, which is within 80% of maximum in vitro rates and consistent with mitochondria operating near their functional limits. Myofibrils represent 65 - 66% of cardiomyocyte volume, and according to a Laplacian model of the left ventricular chamber, generate peak fiber tensions between ~54 and 62 kPa at rest and during heavy exercise, which is less than maximum tension of isolated cardiac tissue (120 - 140 kPa), and is explained by an apparent reserve capacity for tension development built into the left ventricle.
dc.description.statementofresponsibilityEdward P. Snelling, Roger S. Seymour, J. E. F. Green, Leith C. R. Meyer, Andrea Fuller, Anna Haw, Duncan Mitchell, Anthony P. Farrell, Mary-Ann Costello, Adian Izwan, Margaret Badenhorst, Shane K. Maloney
dc.identifier.citationJournal of Applied Physiology, 2016; 121(4):900-909
dc.identifier.doi10.1152/japplphysiol.00435.2016
dc.identifier.issn8750-7587
dc.identifier.issn1522-1601
dc.identifier.orcidSeymour, R. [0000-0002-3395-0059]
dc.identifier.orcidGreen, J. [0000-0001-5061-9563]
dc.identifier.urihttp://hdl.handle.net/2440/103864
dc.language.isoen
dc.publisherAmerican Physiological Society
dc.relation.granthttp://purl.org/au-research/grants/arc/DP120102081
dc.relation.granthttp://purl.org/au-research/grants/arc/DE130100031
dc.rightsCopyright © 2016 the American Physiological Society
dc.source.urihttps://doi.org/10.1152/japplphysiol.00435.2016
dc.subjectCapillary
dc.titleA structure-function analysis of the left ventricle
dc.typeJournal article
pubs.publication-statusPublished

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