Biomedical Engineering Reference
In-Depth Information
FIGURE 4.40
Isolated canine left ventricle used to develop a new biomechanical model of the heart.
Photo cour-
tesy of Dr. Jan Mulier, Leuven, Belgium.
left ventricle [17, 24, 23]. This model should be simple and versatile and should have direct
physiological significance, in contrast with simulations, which merely mimic physiological
behavior. The model was developed using isolated canine heart experiments, as depicted in
Figure 4.40. The left ventricle was filled with an initial volume of blood, subjected to different
loading conditions, stimulated, and allowed to beat. Ventricular pressure, and in some experi-
ments ventricular outflow, was then measured and recorded.
Experiments began with measurement of isovolumic ventricular pressure. For each experi-
ment the isolated left ventricle was filled with an initial end-diastolic volume and the aorta was
clamped to prevent outflow of blood. The ventricle was stimulated, and generated ventricular
pressure was measured and recorded. The ventricle was then filled to a new end-diastolic vol-
ume and the experiment was repeated. As in the famous experiments of Otto Frank (c. 1895),
isovolumic pressure is directly related to filling. Figure 4.41 shows a set of isovolumic pressure
curves measured on a normal canine left ventricle.
These isovolumic pressure curves were then described by the following equation. Ventric-
ular pressure
p
v
is a function of time
t
and ventricular volume
V
v
according to
"
#
Þ
e
ð
t
t
b
a
a
e
ð
t
c
Þ
r
Þ
ð
1
t
2
p
v
¼
a
ð
V
v
b
Þ
þð
cV
v
d
Þ
ð
4
:
75
Þ
e
ð
t
t
c
Þ
Þ
e
ð
t
p
t
b
a
a
r
Þ
ð
1
t
or written more compactly,
2
p
v
ð
t
,
V
v
Þ¼
a
ð
V
v
b
Þ
þð
cV
v
d
Þ
f
ð
t
Þ
ð
4
:
76
Þ
