The heart works 24 hours a day, pumping oxygen and nutrient rich blood to the body. Blood is supplied to the heart through its coronary arteries. In coronary heart disease (CHD), plaques or fatty substances build up the walls of the arteries. The plaques also attract blood components, which stick to the artery wall lining. Called atherosclerosis, the process develops gradually, over many years. It often begins early in life, even in childhood.
The fatty buildup or plaque can break open and lead to the formation of a blood clot that seals the break. The clot usually stops blood flow. The cycle of fatty buildup, plaque rupture, and blood clot formation causes the coronary arteries to narrow, reducing blood flow.
When too little blood reaches the heart, the condition is called ischaemia. Chest pain, or angina, may occur.
The pain can vary in occurrence and be mild and intermittent, or more pronounced and steady. It can be severe enough to make normal everyday activities difficult. The same inadequate blood supply also may cause no symptoms, a condition called silent ischaemia.
If a blood clot suddenly cuts off most or all blood supply to the heart, a heart attack results. Cells in the heart
muscle that do not receive enough oxygen carrying blood begin to die. The more time that passes without treatment to restore blood flow, the greater the damage to the heart.
A heart attack is often sudden and intense, but may follow episodes of chest pain (angina) which may be
unrecognized. A person may clutch his or her chest and fall over. If you feel such a symptom, you may not be sure what’s wrong. Your symptoms may even come and go. Even those who have had a heart attack may not recognize their symptoms, because the next attack can have entirely different ones.
Source: http://www.heartfoundation.org.jm/heart_attacks.html
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