Is the left side of heart is high pressure or low pressure?

High pressure.

The left side of the heart is responsible for pumping oxygenated blood throughout the body. In order to do this, it must exert a high pressure to overcome the resistance of the blood vessels. The right side of the heart, on the other hand, is responsible for pumping deoxygenated blood to the lungs. This does not require as much pressure, so the right side of the heart is low pressure.