What Is a Heart Attack?
The electrical instability of the heart causes ventricular fibrillation (chaotic electrical disturbances affecting the ventricles, the lower chambers of the heart). Orderly transmission of electrical signals in the heart is important for the regular beating (and the efficient pumping) of the heart. A heart undergoing ventricular fibrillation simply quivers and can not pump or deliver oxygenated blood to the brain. Permanent brain damage and death can occur unless oxygenated blood flow is restored within five minutes.Many heart attack deaths are due to ventricular fibrillation that occurs before the victim can reach any medical assistance or the emergency room. These electrical disturbances of the heart can often be successfully treated with medications or other means by paramedics in the "field," or upon arrival at the hospital. Approximately 90-95% of heart attack victims who reach the hospital survive. The 5-10% who later die are those who have suffered major heart muscle damage, or who suffer an "extension" or enlargement of their heart attack.
Early heart attack deaths can be avoided if a bystander starts CPR (cardiopulmonary resuscitation) within five minutes of the onset of ventricular fibrillation. CPR involves breathing for the victim and applying external chest compression to make the heart pump. When paramedics arrive, medications and/or electrical shock (cardioversion) to the heart can be administered to convert ventricular fibrillation to a normal heart rhythm. Therefore, prompt CPR and rapid paramedic response can improve the survival chances from a heart attack.The treatment of a heart attack may include the prompt administration of drugs to dissolve and prevent blood clots; an angioplasty or intracoronary stenting to open an obstructed artery; and medications that open (dilate) blood vessels. Early reopening of a blocked coronary artery reduces the amount of heart muscle damage, lessens the size of the heart attack, and improves prognosis. Patients suffering a heart attack are usually hospitalized for several days to detect heart rhythm disturbance, and observe for shortness of breath and chest pain.
A heart attack is also called a myocardial infarction or an MI. Myocardial refers to the myocardium, the heart muscle. Infarction is tissue death due to a local lack of oxygen.
What Are Heart Attack Symptoms and Signs?
The chest pain may be described as tightness, fullness, a pressure, or an ache.Unfortunately, many people do not have these classic signs. Other signs and symptoms of heart attack may include:
- jaw ache,
- the pain only in the shoulders or arms,
- shortness of breath, or
- nausea and vomiting.
This list is not complete, since many times people can experience a heart attack with minimal symptoms. In women and the elderly, heart attack symptoms can be atypical and sometimes so vague they are easily missed. The only complaint may be extreme weakness or fatigue.Pain may also radiate from the chest to the neck, jaw, shoulder, or back and be associated with shortness of breath, nausea, and be sweating.
What Causes Heart Attack?
If the plaque ruptures, a small blood clot can form within the blood vessel, acting like a dam and acutely blocking the blood flow beyond the clot. When that part of the heart loses its blood supply completely, the muscle dies. This is called a heart attack, or an MI - a myocardial infarction (myo=muscle +cardial=heart; infarction=death due to lack of oxygen).
A heart attack is most often caused by narrowing of the arteries by cholesterol plaque and their subsequent rupture. This is known as atherosclerotic heart disease (AHSD) or coronary artery disease (CAD).
While heredity is beyond a person's control, all the other risk factors can be minimized to try to prevent coronary artery disease from developing. If atherosclerosis (atheroma=fatty plaque + sclerosis=hardening) is already present, minimizing these risk factors can decrease further narrowing.
Non-coronary artery disease causes a heart attack may also occur. Examples include:
- Cocaine use. This drug can cause the coronary arteries to go into enough spasm to cause a heart attack. Because of the irritant effect on the heart's electrical system, cocaine can also cause fatal heart rhythms.
- Prinzmetal angina or coronary artery vasospasm. Coronary arteries can go into spasm and cause angina without a specific cause, this is known as Prinzmetal angina. There can be EKG changes associated with this situation, and the diagnosis is made by heart catheterization showing normal coronary arteries that go into spasm when challenged with a medication injected in the cath lab. Approximately 2% to 3% of patients with heart disease have coronary artery vasospasm.
- Anomalous coronary artery. In their normal position, the coronary arteries lie on the surface of the heart. On occasion, in the course of a part the artery can dive into the heart muscle itself. When the heart muscle contracts, it can temporarily kink the artery and cause angina. Again, diagnosis is made by heart catheterization.
- Inadequate oxygenation. Just like any other muscle, heart muscle requires adequate oxygen supply for it to work. If there isn't adequate oxygen delivery, angina and heart attack can occur. There need to be enough red blood cells circulating in the body and enough lung function to deliver oxygen from the air, so that heart cells can be supplied with the nutrients that they need. Profound anemia from bleeding or failure of the body to make enough red blood cells can precipitate angina symptoms. Lack of oxygen in the bloodstream can occur due to a variety of causes including respiratory failure, carbon monoxide poisoning or cyanide poisoning.