title: Ejecting activation differs in energetics from ordinary positive inotropism in the canine left ventricle.
abstract: Ventricular ejection is known to have dual effects on the end-systolic pressure: the ejecting deactivation by a relatively large ejection against a low afterload versus the ejecting activation by a relatively small ejection against a high afterload. We studied how the increase in contractility index (Emax) by the ejecting activation would affect myocardial oxygen consumption (VO2). To this end, left ventricular steady-state ejecting contractions were produced with various stroke volumes from a fixed end-diastolic volume in an excised cross-circulated canine heart. The effect of the ejection-activated Emax on VO2 was assessed by the relation between VO2 and pressure-volume area (PVA). PVA is the total mechanical energy generated by ventricular contraction. In contrast to the elevation of the linear VO2-PVA relation in a parallel manner with an enhanced Emax by ordinary positive inotropic agents such as catecholamines and calcium, the ejection-activated Emax did not elevate the VO2-PVA relation. This result indicates that the ejecting activation enhances Emax in an energetically different manner from ordinary positive inotropism in the canine left ventricle.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yasumura
authors.forename: T
authors.initials: T
authors.lastname: Nozawa
authors.forename: S
authors.initials: S
authors.lastname: Futaki
authors.forename: N
authors.initials: N
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Suga
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D013318:Stroke Volume / Q000187:drug effects* / Q000502:physiology; D016277:Ventricular Function, Left / Q000187:drug effects* / Q000502:physiology
chemical_list: D002316:Cardiotonic Agents; D004280:Dobutamine; D011433:Propranolol