Swollen feet can be the first sign of heart dysfunction (heart failure), a result of heart weakness or abnormal flow of blood through the cardiac valves. Very often, it develops alongside breathlessness, but can also be the only sign present. The feet swell up because the heart cannot do its job, which is to pump the blood through the circulation. The gravity causes fluid to come out of the arteries and veins and into the tissues of the feet. Therefore, a good way of improving the leg swelling is to keep the legs high when sitting on a chair. This will not cure the problem that caused the swelling in the first place but can improve the severity of it. Swollen feet can sometimes be a result of other non-cardiac problems, such as vein insufficiency, lymphoedema, infection, vein clots.
Common things to look for when the peripheral oedema is a result of a heart problem are:
The swelling affects both legs/feet
It is usually symmetrical (both feet are swollen at the same degree)
It is usually not painful when you press it
It usually leaves a skin dent when you apply pressure on it, that goes away few seconds later
It is not chronic (this is usually related to vein insufficiency)