increased, indicating changing cardiac contractility (Fig. 4.1.6).
Thus, the coupling ratio
can be altered by either change in cardiac
contractility or arterial load.
Pressure-volume diagrams of the ventricleillustrating the steady state coupling
the ventricle and the arterial system using the ratio of
With methoxamine and
nitroprusside infusions, the slope
Ees is unchanged, while E,
dobutmine infusion, Ees is increased, while
is unchanged. From Starling
The effects of alterations of windkessel model parameters on the
ventricular pressure-volume relation under steady state conditions have
been investigated (Maughan
The changes in arterial
compliance and peripheral resistance have little effects on the slope
the end-systolic pressure-volume relation,
However, the shape and the
left ventricular elastance are significantly altered.
It should be noted here that there are other indices to cardiac
performance, such as the pump function curve proposed by Van den
Horn et al.
984), the maximum velocity of cardiac muscle shortening
concept suggested by Brutsaert (1
based on force-velocity-length
Dynamic Heart-Arterial System Interactions
pressure varies during the cardiac
cycle. Thus, vascular
also expected to vary continuously. This dynamic time-
varying, pressure-dependent compliance property is incorporated in a