This set of related words pertains to disorders or malfunctions of the circulatory system. Serious confusion can result from treating any one of them as a synonym for any other. Heart attack refers to a sudden interference with or stoppage of the heart’s pumping action for any reason; such a seizure may cause pain and death, but one may also recover from it, with or without functional impairment. In common usage, heart failure may suggest a permanent stoppage of a weak or overtaxed heart, as in exertion or old age. Medically speaking, heart failure refers instead to a condition in which the heart cannot beat strongly enough or pump a sufficient supply of blood round the body; this condition need not occur as a sudden seizure but can manifest itself by a gradual worsening. When it is not fatal, impairment or loss of physical activity may result. A coronary is a sudden episode of heart failure in which the coronary arteries cannot supply enough blood to nourish the heart muscle, whether because of blockage or narrowing of arterial passages. Congestive heart failure occurs when the blood returned to the heart by the veins cannot be pumped out into the arteries at the same rate.

Arteriosclerosis is a general term for any hardening or thickening of the artery walls which results in a narrowing of arterial passages. This can be one cause of a coronary . Atherosclerosis is a specific form of arteriosclerosis in which he narrowing and hardening is caused by fatty deposits on the inside walls of the arteries; this also can be the cause of a coronary . Hypertension and hypotension are simply technical terms for high and low blood pressure. Both these conditions can ultimately lead to a heart attack or to heart failure .

Because damage to the brain is a frequent result of any non-fatal heart attack or heart failure , a stroke is often confused with these two conditions. A stroke results when an artery supplying blood to the brain is ruptured or blocked in such a way as to cause brain damage. An abrupt loss of consciousness occurs, followed by some degree of temporary or permanent mental impairment or physical paralysis should the person survive. Thus, while the heart itself is not involved, circulatory malfunction is present and there is a resemblance to heart attack or failure in onset and outcome. A stroke can result either from an arterial haemorrhage in the brain, such as might be caused by hypertension , or from an arterial obstruction. Thrombosis and embolism both refer to such obstructions in any blood vessel anywhere in the body. Thrombosis pertains to the growth of a blood clot (thrombus) in a blood vessel when it remains attached to its original site; the resulting obstruction can cause a coronary , a heart attack or a stroke . An embolism is an obstruction that can cause similar damage, but it results from the lodging of an abnormal body (embolus) circulating in the blood, such as a clot or an air bubble. Thus, a clot formed by a thrombosis elsewhere in the body can detach itself and, as an embolus, circulate to the heart or brain, where it may lodge, cause an embolism , and possibly result in a heart attack or stroke .