Abstract
The effects of intravenous norepinephrine and phenylephrine on myocardial V̇ O 2 of 20 intact anesthetized dogs were studied. Ventricular pressure, flow, volume, and V̇ O 2 were measured, and mean systolic force, pressure-time and force-time, fiber velocity, work and power of cardiac contraction were calculated. The best correlation of V̇ O 2 was with power in the control state but there was also a significant correlation of V̇ O 2 with work and force parameters. This correlation remained highly significant during catecholamine infusion only for work and power, whereas the correlation with pressure-time or force-time disappeared. Stroke work correlated closely (r = 0.96) with contractile element work. Myocardial anaerobiosis did not conribute significantly to energy requirement. The mean efficiency of contraction was slightly increased by these agents. Correlation of V̇ O 2 with stroke power or contractile element power was not significantly better than the correlation with stroke work, suggesting that the net effect, if any, of fiber velocity on myocardial oxygen consumption in the intact heart is small.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call