Heart attack

A heart attack is the result of the muscles of the heart not receiving enough oxygen, usually due to infarction in one of the major arteries inside of the heart (a myocardial infarction). However, it can also be due to a heart arrhythmia.
=== Stages of a heart attack ===
The heart attack usually proceeds through three stages:
* Angina: When heart muscles are deprived of oxygen, they can still produce energy anaerobically by converting sugar to lactic acid like other muscles. However, the lactic acid buildup has the same effect as it does in any other muscle - it causes pain in the muscle and signals the body to pump blood faster to provide oxygen to the muscle and to increase the respiration rate. Depending on the severity of the blockage, this can last several minutes or even up to an hour.
* Fibrillation: As the heart muscles start to fail, the co-ordinated rhythm of the heart also starts to fail. The heart muscles start firing randomly and the heart stops pumping blood to the rest of the body. The brain starts to feel the loss of blood and the patient loses consciousness. At this point, CPR or defibrillation becomes an option.
* Cardiac arrest: The heart stops beating entirely. CPR is still an option, but the heart must be restarted by defibrillation or the patient will die. If blood flow is not re-established either through heart bypass or restarting the heart, the brain will begin to suffer irreversible damage within three minutes.
=== Treatment ===
Oxygen is administered immediately to allow the lungs to take in more useful oxygen without strain. Blood thinners are usually administered in an attempt to break up clots. A balloon angioplasty will force the narrowed vein open. Stents are placed in weak arteries to keep them open. An external pacemaker can be used to maintain the heartbeat. In many cases, the underlying problem will resolve itself and the patient will recover. Recovery time is also dependent on the severity of the muscle damage.