Aortic pressure curve

2021-06-02 03:13 PM

After the aortic valve closes, the aortic pressure decreases slowly during diastole because the blood contained in the elastic arteries continues to flow through the peripheral vessels to return to the veins.

When the left ventricle contracts, ventricular pressure rises rapidly until the aortic valve opens. The pressure in the ventricles then increases at a much slower rate, as blood flows directly out of the ventricles into the arteries and into the distribution system.

Blood flow into the internal arteries during systole causes the walls of the arteries to stretch and the pressure to rise to about 120 mmHg.

Then, at the end of systole, after the left ventricle has stopped ejecting and the aortic valve is closed, the elastic coat of the artery maintains a high pressure in the artery, even during diastole.

A defect appears in the pressure curve when the aortic valve is closed. That's because a brief period of blood flow returns just before the valve closes, then stops abruptly.

After the aortic valve closes, the aortic pressure decreases slowly during diastole because the blood contained in the elastic arteries continues to flow through the peripheral vessels to return to the veins. Before the next systole, the aortic pressure usually drops to about 80 mmHG (diastolic pressure) which is two-thirds of the maximum pressure of 120 mm Hg (systolic pressure) in the aorta when the ventricles co.

The pressure curves in the right ventricle and pulmonary artery are the same as those in the aorta, except that the pressure is only 1/6.

Relationship between heart sound and heart pumping

When listening to the heart with a stethoscope, we cannot hear the opening of the valves because it is a rather slow process that normally produces no sound. However, when the valve is closed, the leaflets and surrounding fluid vibrate due to the sudden change in pressure, creating sound that travels in all directions through the ribcage.

When the ventricles contract, the first sound heard is the closing of the AV valve. The low and relatively long vibration is called the first heart sound. When the aortic and pulmonary valves close at the end of the systole, a short crackling sound is heard due to the rapid closing of the valve and the brief surrounding vibrations. It's the second heart sound.

Work of the heart

The heart's contractile work is the energy the heart successfully transfers with each beat as it pumps blood into the arteries. Contraction work per minute is the total energy successfully transferred in 1 minute; is equal to contractile work times heart rate per minute.

The work of the heart has two forms. First, most of the energy used to push blood from a low-pressure vein into a high-pressure artery is called volume-pressure or external work. Second, a small fraction of the energy is used to push the blood to its velocity when it is ejected through the aortic and pulmonary arteries, which is the kinetic energy of the blood flow.

The normal external work of the right ventricle is about 1/6 of the left ventricle due to a 6-fold difference in the systolic pressures of the two ventricles. The amount of work required by each ventricle to produce kinetic energy of blood flow is proportional to the volume of blood pumped multiplied by the square of the ejection rate.

Normally, the work of the left ventricle that is lost to generate the kinetic energy of the blood flow accounts for only about 1% of the total contractile work of the ventricles, thus not affecting the result of the total contractile work. However, in some unusual conditions, such as aortic stenosis, where blood flows at a high rate through the narrowed valve, it may take more than 50% of the total contractile work to generate kinetic energy.