Cardiac cycle diagram

The key point of the cardiac cycle diagram is to be able to use it to explain the flow of blood through the left side of the heart and into the aorta. An appreciation of the timing of the various components is, therefore, essential if you are to draw an accurate diagram with which you hope to explain the principle. 

The cardiac cycle diagram is sometimes plotted with the addition of a curve to show ventricular volume throughout the cycle. Although it is a simple curve, it can reveal a lot of information. 

Mathematical representation of the time-varying elastance is more complicated and is generally based on the characterization of the cardiac work cycle in the pressure-volume plane. In the P-V diagram in Figure 10.5b, the time course of the left ventricular cardiac cycle proceeds as follows. 

Output data from the mock circulatory system, during a cardiac cycle, are the aortic and ventricular pressure diagrams, the flow rate through the valve diagram and the average values of these variables. As an example. Fig. 2 shows the output data obtained while testing a tilting disc Hall Raster (HK) valve of 27 mm tissue anulus diameter (TAD). Nine different tests have been performed at three... 

This trace shows the volume of the left ventricle throughout the cycle. The important point is the atrial kick seen at point a. Loss of this kick in atrial fibrillation and other conditions can adversely affect cardiac function through impaired LV filling. The maximal volume occurs at the end of diastolic filling and is labelled the left ventricular end-diastolic volume (LVEDV). In the same way, the minimum volume is the left ventricular end-systolic volume (LVESV). The difference between these two values must, therefore, be the stroke volume (SV), which is usually 70 ml as demonstrated above. The ejection fraction (EF) is the SV as a percentage of the LVEDV and is around 60% in the diagram above. 

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