Research Article

Simulation of Exercise-Induced Syncope in a Heart Model with Severe Aortic Valve Stenosis

Figure 4

Data are arranged in four columns according to the type of homeostasis failure, after the steady state is established. The upper two sections of columns (a–d) present the time course of AoP, MAoP, LVP, LAtP, ventricular volume, and CO during systole and part of diastole (543.7 s–544.3 s). Note that the pressure gradient and its magnitude are dependent on the Sy and on the heart rate. In the bottom of each column there are the corresponding P-V loop diagrams. In these, for the sake of comparison, also the P-V loop diagram in exercise is shown (cf. Figure 3(d)). If the heart rate is 120/min and the Sy is 1 FGU 4(a), the P-V loop diagram is depressed, shifted to the right, and narrowed. If in this condition Sy is decreased (0.5 FGU; 4(b)), these changes are even more pronounced. They agree excellently with the corresponding time course of various variables, showing the decreased LVP and SVLV and the increased EDVLV. If the heart rate is 45/min and the Sy is 0.5 FGU, the P-V loop diagram is shifted to extreme right, but maintains its width. EDVLV is strongly increased, increasing also SVLV. If in this condition the Sy is increased to 1.5 FGU, the P-V loop diagram is shifted to the left, increasing its width: the EDVLV is decreased, but the SVLV is increased, as is also shown in the time course of ventricular volume and pressure.
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