Biomedical Engineering Reference
In-Depth Information
12
3
4
100
50
0
0
0.2
0.4
0.6
0.8
1
Time t [s]
90
80
70
60
50
40
30
0
0.2
0.4
0.6
0.8
1
Time t [s]
500
400
300
200
100
0
-100
0
0.2
0.4
0.6
0.8
1
Time t [s]
FIGURE 4.46
Representative left ventricular and root aortic pressures (top), ventricular volume (middle), and
ventricular outflow (bottom) for an isolated canine heart. The numbers 1-4 at top correspond to distinct phases of
the cardiac cycle, described in the text.
end-diastolic and end-systolic volumes, EDV-ESV, is denoted stroke volume, SV, and is the
amount of blood pumped in one heartbeat. The ratio SV/EDV is the ejection fraction, EF,
and is approximately 50 percent in this example. Clinical blood pressure corresponds to
the maximum and minimum arterial pressures—in this example, around 125/75 mmHg.
Clinicians often study heart performance via pressure-volume work loops, plotting ventric-
ular pressure as a function of ventricular volume, as in Figure 4.47. The four phases of the heart
cycle just described are plotted for the same heart as in Figure 4.46,withisovolumiccontraction
between points 1 and 2, ejection from 2 to 3, isovolumic relaxation between 3 and 4, and
