It featured the first mechanically operated inlet valve. Speed was controlled by means of a throttle valve lever. The mount contained two fluid filled chambers separated by a computer controlled valve. Ports are passages that allow fluid to pass through the valve. They usually have a manual bleed valve or screw. It can directly measure the pressure on both sides of the aortic valve. It involves either the mitral valve or the tricuspid valve. They are equipped with an approved pressure relief valve. The procedure included installation of a mechanical aortic valve. Echocardiography is the most useful method of diagnosing a prolapsed mitral valve. The system was simple, had few controls, a single automatic gas valve, and no blower. This is occasionally due to rupture of the chordae tendineae that support the mitral valve. There are many ways of adding hydraulic functions (also known as adding a valve). Heart tissue receives blood from two arteries which arise just above the aortic valve. This includes bicuspid aortic valve and coarctation (narrowing) of the aorta.