Complete diagrams as instructed in the tasks.

Question

Include proper values on the x & y-axis as well as labeling those. Make sure to label ESV, EDV, aortic and mitral valve opening and closing, and Isovolumetric relaxation and contraction where possible on the diagrams regarding blood volumes and pressure.

Case Studies Tasks:

1. Jose recently visited the Doctor and was informed he has a blood pressure of 165/110 mmHG. Diagram a graph/loop for pressure vs volume. The graph should contain a normal pressure to volume graph in a healthy heart and also a pressure vs. volume graph for Jose's hypertension. And what factors contribute to Jose's blood pressure being high? The average EDV for an averaged size man is 120ml and the ESV 50ml. Make sure to label the diagram as described above.

Answer 1

A pressure/volume curve displays left ventricular pressure on the Y axis and left ventricular volume on the X axis. As the cardiac cycle continues, there are dynamic changes in each. Note, the pressure/volume curve is a measurement of the LEFT VENTRICLE. It does not include the descriptions of any other chamber in the heart.

For a crude diagram, imagine a loop in the shape of a box, with the bottom-most left point of the box representing the opening of the mitral valve after the left atrium contract with enough force to force blood through it, into the left ventricle. Just before the mitral valve opens, the volume in the left ventricle is the end systolic volume (ESV), which is 50ml as stated in the prompt. As blood fills the left ventricle, the volume increases, eventually reaching the end of the left atrial systole, meaning the left atrium has no more blood to force into the left ventricle. This section represents the rapid filling stage of the cardiac cycle. At the end of ventricular filling, the mitral valve closes. The blood volume in the left ventricle now is the end diastolic volume (EDV), which is 125ml as stated in the prompt. This is the bottom right point of our box/loop.

At the end of ventricular diastole, the left ventricle begins to contract. The aortic valve maintains the blood inside the left ventricle. As the ventricle contracts, the pressure builds inside, representing the isovolumetric contraction stage, as none of the blood volume has been ejected from the left ventricle just yet. After the force of contraction overcomes the aortic valve force, then the aortic valve opens. This represents the top right part of our crude box/loop. After the aortic valve opens, the systolic ejection stage of the cardiac cycle takes place, meaning that the left ventricle ejects its blood content.

Once the blood volume is ejected from the left ventricle, the aortic valve closes. This represents the top left point of our box/loop. At this stage, the ventricle relaxes, and no blood enters the chamber just yet, as the mitral valve is still closed at this stage. Therefore, the left ventricle undergoes isovolumetric relaxation, meaning that there is no entering blood volume as the ventricle relaxes. After the ventricle relaxes completely, we arrive back at the bottom-most left point, at which point the left atrium contracts and the mitral valve opens to begin the cardiac cycle again.

Hypertension is equivalent to having increased afterload, meaning that there is more resistance for the left ventricle to eject its blood volume. This causes more blood to remain in the ventricle at the end of systole, meaning that the ESV is higher in someone with hypertension and the left side of our box/loop is shifted over to the right on the X axis. The left atrium forces a similar amount of blood into the left ventricle, causing relative increased blood volume at the end of diastole, causing EDV to be increased as well.

The left ventricle also has to squeeze a lot harder to eject the blood out. It takes more force to open the aortic valve, therefore the isovolumetric contraction stage is increased to a higher point on the Y axis.

In simple terms, the "box" of the the normal cardiac cycle turns into a long rectangle in the setting of hypertension. Many factors can contribute to increased blood pressure, including lifestyle factors such as diet and exercise in combination with some genetic predispositions.