title: Mechanoenergetics of negative inotropism of ventricular wall vibration in dog heart.
abstract: Mechanical vibration depresses cardiac contractility. We studied the mechanoenergetic effects of this negative inotropism in the left ventricle (LV) of an isolated, cross-circulated dog heart preparation. We took full advantage of the mechanoenergetic relationship among the LV end-systolic elastance (Emax, contractility index), systolic pressure-volume area (PVA), and myocardial oxygen consumption (VO2). PVA is a measure of the total mechanical energy that cardiac contraction generates. PVA correlates closely with VO2. The VO2 intercept of the VO2-PVA relation reflects the VO2 component for excitation-contraction (E-C) coupling plus basal metabolism (PVA-independent VO2). VO2 above the PVA-independent VO2 reflects the VO2 component for mechanical contraction (PVA-dependent VO2). When we applied 70-Hz vibration of 2-mm amplitude to a LV wall region, it instantly decreased Emax and PVA by 20%, followed by a 10% decrease in VO2 at a fixed volume. However, the vibration neither lowered the VO2-PVA relation obtained at different LV volumes, unlike ordinary negative inotropism, nor changed its slope (1.88 +/- 0.23 vs. 1.86 +/- 0.23 x 10(-5) ml O2.mmHg-1.ml-1). The virtually zero delta PVA-independent VO2/delta Emax with vibration indicates a much smaller O2 cost of Emax than that seen with calcium and propranolol inotropism. These mechanoenergetics support the hypothesis that mechanical vibration primarily suppresses cardiac contractility without suppressing E-C coupling.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nishioka
authors.forename: Y
authors.initials: Y
authors.lastname: Goto
authors.forename: K
authors.initials: K
authors.lastname: Hata
authors.forename: T
authors.initials: T
authors.lastname: Takasago
authors.forename: A
authors.initials: A
authors.lastname: Saeki
authors.forename: T W
authors.initials: TW
authors.lastname: Taylor
authors.forename: H
authors.initials: H
authors.lastname: Suga
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001794:Blood Pressure; D001810:Blood Volume; D004285:Dogs; D004548:Elasticity; D004734:Energy Metabolism; D006321:Heart / Q000502:physiology*; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D013599:Systole; D016276:Ventricular Function; D014732:Vibration