title: Reduced mechanical efficiency in left-ventricular trabeculae of the spontaneously hypertensive rat.
abstract: Long-term systemic arterial hypertension, and its associated compensatory response of left-ventricular hypertrophy, is fatal. This disease leads to cardiac failure and culminates in death. The spontaneously hypertensive rat (SHR) is an excellent animal model for studying this pathology, suffering from ventricular failure beginning at about 18 months of age. In this study, we isolated left-ventricular trabeculae from SHR-F hearts and contrasted their mechanoenergetic performance with those from nonfailing SHR (SHR-NF) and normotensive Wistar rats. Our results show that, whereas the performance of the SHR-F differed little from that of the SHR-NF, both SHR groups performed less stress-length work than that of Wistar trabeculae. Their lower work output arose from reduced ability to produce sufficient force and shortening. Neither their heat production nor their enthalpy output (the sum of work and heat), particularly the energy cost of Ca(2+) cycling, differed from that of the Wistar controls. Consequently, mechanical efficiency (the ratio of work to change of enthalpy) of both SHR groups was lower than that of the Wistar trabeculae. Our data suggest that in hypertension-induced left-ventricular hypertrophy, the mechanical performance of the tissue is compromised such that myocardial efficiency is reduced.
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
authors.forename: June-Chiew
authors.initials: JC
authors.lastname: Han
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Tran
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
authors.forename: Callum M
authors.initials: CM
authors.lastname: Johnston
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Engineering Science, The University of Auckland, Auckland, New Zealand.
authors.forename: Poul M F
authors.initials: PM
authors.lastname: Nielsen
authors.affiliation: Department of Physiology, The University of Auckland, Auckland, New Zealand.
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Barrett
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Engineering Science, The University of Auckland, Auckland, New Zealand.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Taberner
authors.affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Physiology, The University of Auckland, Auckland, New Zealand.
authors.forename: Denis S
authors.initials: DS
authors.lastname: Loiselle
keywords: Cardiac efficiency; cardiac hypertrophy; heart failure; hypertension