Normal function of heart valves
The normal heart has 4 one way valves which make sure that blood goes forward not backward with each beat. The main pumping chambers, the right and left ventricles, eject blood at high pressure either across the pulmonary valve into the lungs via the pulmonary artery (from the right ventricle) or into the main circulation across the aortic valve into the aorta (from the left ventricle).
Blood is prevented from going backwards into the right and left atria by the tricuspid and mitral valves respectively.
The shape of these valves means that they do not obstruct blood flow as they open and do not leak significantly when closed. Normal blood flow is remarkably silent but sometimes can be heard as a ‘murmur’ in young or very thin people, or if the heart is overactive such as exercise or normal pregnancy. Noisy blood flow across a normal valve is called an ‘innocent’ murmur.
As the heart grows, heart valves grow with it. These structures are extraordinarily strong, opening and closing at pressure more than 80,000 times a day throughout our lifetime.
Heart valve defects can be a birth defect or occur later due to inherited conditions such as Marfan syndrome which weaken the tissues making them vulnerable to the physical stress these valves are exposed to during daily life. Relatively mild defects such as a bicuspid aortic valve or mitral valve prolapse may take years to cause a problem. There are also inherited metabolic conditions which affect valve function but are rare. Normal valves can be damaged by bacterial or fungal infections directly (endocarditis) or indirectly (rheumatic heart disease).
Age itself leads to calcium deposition in the valve tissues. It mainly affects the aortic valve’s function and less frequently the mitral valve.
The result of damage to a heart valve is it either obstructs blood flow or leaks. The affected chamber has an increased workload consisting of increased pressure or blood volume each beat. Over time this takes a toll on the heart leading to symptoms such as fatigue, breathlessness, light headedness, chest pain on exertion or heart failure.
Traditionally the stethoscope was used to help doctors diagnose heart valve disease but nowadays we use cardiac ultrasound (echocardiography) which is safe, non-invasive and reliable.
The echocardiogram allows us to see the heart valves open and close in 2 dimensions, measure blood flow pressure and volume across valves (Doppler) and, increasingly, see the heart in 3D with the newest technology available.
Newer imaging technology using CT and Magnetic Resonance Imaging is a useful supplement to echocardiography. The CT does involve the small risks of allergic reaction to contrast agents and some radiation exposure. The MRI is less readily available and more expensive than CT of the heart.