Ejecting activation differs in energetics from ordinary positive inotropism in the canine left ventricle.
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.
Yasumura
Y
Y
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
Nozawa
T
T
Futaki
S
S
Tanaka
N
N
Suga
H
H
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
D002316:Cardiotonic Agents; D004280:Dobutamine; D011433:Propranolol