Affiliation:
1. Department of Biomedical Engineering, The Johns Hopkins University Medical School, Baltimore, Maryland 21205
Abstract
We have previously shown in the normally ejecting canine left ventricle that
E
(
t
), the time-varying ratio of instantaneous pressure,
P
(
t
), to instantaneous volume,
V
(
t
), is little affected by end-diastolic volume or aortic pressure. The present study on an excised, supported canine heart preparation indicates that the thesis on
E
(
t
) is also valid for either totally isovolumic or auxobaric beats. Intraventricular volume was measured more accurately than it was in the previous study by a new volumetric system. Regression analysis of the data showed that the instantaneous pressure-volume relationship could be approximated by the equation
P
(
t
) =
E
(
t
).[
V
(
t
) -
V
d
], where
V
d
is an empirical constant, over a wide range of intraventricular volume. Similar
E
(
t
) curves were obtained from both isovolumic and auxobaric beats for a given contractile state. When the contractile state of the preparation was enhanced by a constant-rate infusion (0.2 µg/min) of norepinephrine or isoproterenol into the coronary artery, the peak magnitude of
E
(
t
) increased 63% from 3.6 mm Hg/ml and the time to peak
E
(
t
) shortened 10% from 175 msec. We conclude that the present investigation substantiates our earlier study which established a link between
E
(
t
) and the contractile state of the heart.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
1271 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献