Cardiac Sympathetic Stimulation Increases Cardiac Contractility But Decreases Contractile Efficiency in Canine Hearts In Vivo

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The effect of cardiac sympathetic stimulation on cardiac contractile efficiency was studied in dogs. In 19 anesthetized and open-chest dogs, left ventricular(LV)pressure, LV volume, coronary blood flow and coronary venous oxygen saturation were measured simultaneously. The LV end-systolic pressure volume relations(ESPVR)and the relation between myocardial oxygen consumption(VO_2)-pressure volume area(PVA)were obtained during a transient occlusion of the inferior vena cava before and after sympathetic stimulation(9V, 6Hz, 40sec)both with and without 50mg/kg of 2, 3-butanedione monoxime(BDM). Without BDM, sympathetic stimulation increased the slope of ESPVR by 62%(p<0.05), the slope of the VO_2-PVA line by 19%(p<0.05)and the y-axis intercept of the VO_2-PVA by 65%(p<0.05). With BDM, the increase in the slope of the VO_2-PVA line became insignificant although other responses were similarly preserved. These data imply that cardiac sympathetic stimulation decreases cardiac contractile efficiency through mechanisms by which norepinephrine-induced β-adrenergic activation enhances myosin ATPase-operating ATP hydrolysis in crossbridge formation.
社団法人日本循環器学会の論文
1998-11-20