Biomedical Engineering Reference
In-Depth Information
140
LV
120
LV
100
80
RV
60
40
RV
20
0
50
100
150
200
Ventricular Volume V
V
[ml]
FIGURE 4.54
Computed work loops for the left and right ventricles under control conditions (solid curves) and
for the case of a weakened left ventricle (dashed curves).
Similar changes are noted when the right ventricle's contractile state is halved. The right
ventricular ejection fraction drops from 55 to 37 percent, root pulmonary artery pulse
pressure decreases from 54/18 to 40/15 mmHg, and right stroke volume decreases from
66 to 56 ml, with an increased end-diastolic volume of 153 ml, from 119 ml. Conversely,
c
can be increased in any heart chamber to depict administration of an inotropic drug.
Although not plotted, pressures, flows, and volumes are available at any circuit site, all
as functions of time.
In summary, the left ventricle may be described as a dynamic pressure generator.
A small number of experimentally derived parameters are sufficient to describe the wide
range of observed cardiovascular dynamics. This approach links experiment and theory,
leading to new ideas and experiments. It also links underlying muscle dynamics to heart
performance. Work is under way to devise a new measure of cardiovascular health using
this model.
TABLE 4.5
Cardiovascular Performance for a Normal Heart and for Weakened Left and Right Ventricles
SV
EDV
EF
p
AO
p
PU
[ml]
[ml]
[%]
[mmHg]
LV
RV
LV
RV
LV
RV
Control
66
66
119
119
55
55
131/58
54/18
Weak LV
53
53
192
109
27
49
102/47
54/24
Weak RV
56
56
106
153
53
37
117/54
40/15
Note: SV denotes stroke volume, EDV denotes end-diastolic volume, EF is ejection fraction, and p
AO
and p
PU
are root aorta and
root pulmonary artery pressures, respectively, for the left (LV) and right (RV) ventricles. Note that SV left and right are equal under
all conditions.
