HEART ATTACKS ARE DANGEROUS

Almost all heart attacks occur when a blood clot suddenly and completely blocks a coronary artery. The condition is called a coronary thrombosis, or simply a coronary. The heart muscle supplied by the blocked artery becomes damaged because it receives too little oxygen. Unless blood flow returns within minutes, muscle damage increases. The heart cells begin to die after four to six hours without blood. The damage can affect the heart's ability to pump and cause the death of the victim. The body reacts to a heart attack with its own defenses. Substances in the blood can dissolve clots and permit blood to flow freely again. If the clot is dissolved within four to six hours of the attack, the heart suffers less damage.The machine removes carbon dioxide from the blood and delivers oxygenated blood to the body tissues. A coronary bypass can ease symptoms of angina and prolong the lives of patients with more severe CAD. But it does not stop atherosclerosis.

Symptoms. Before having a heart attack, many people suffer from angina, feel dizzy, have indigestion, or experience other symptoms. Some people have no warning signs. Most heart attacks cause severe pain. Victims describe the pain as a dull, crushing ache in the chest, but it may extend into the neck, jaw, arms, or back. The pain may last from a few minutes to several hours. A person who has chest pain and suspects it may mean a heart attack should seek medical help immediately. Some victims may stop breathing, and their heart may stop beating. A first-aid technique called cardiopulmonary resuscitation (CPR) can maintain a person's breathing and circulation until medical help arrives and the victim is taken to a hospital. But cardiopulmonary resuscitation should be performed only by someone trained in the technique. A mild heart attack may force a person to lead a less active life. A severe attack may make the heart unable to supply the body with enough blood even at rest and so cause a person's death. Disease may also strike other parts of the heart with equally destructive effects.

Diagnosis and treatment. Soon after a heart attack victim reaches the hospital, doctors use an ECG to make sure the patient actually had a heart attack and not chest pain resulting from some other disorder. Injured heart muscle causes abnormal ECG waves. Doctors also use certain blood tests to detect a heart attack. But the tests are not useful until six hours after the attack. If a victim still has pain, doctors may administer a painkilling drug, such as morphine. They also use drugs to dissolve clots in the blocked artery. If the drugs fail to dissolve the clots, doctors may perform emergency angioplasty or bypass surgery. After being hospitalized, heart attack patients are monitored for complications in the intensive care unit. Two major complications are heart failure and arrhythmia. Heart failure occurs if the heart does not pump enough blood because of extensive damage to the heart muscle. In most cases, heart failure can be successfully treated. In arrhythmia, the heart's electrical system produces an abnormal rhythm. One kind of arrhythmia, ventricular fibrillation, occurs when electrical signals in the ventricles fire randomly.

Ineffective heart rhythm and sudden death may result from ventricular fibrillation. Arrhythmias can be readily treated under medical care. The death rate among heart attack victims who do not get medical care is more than 20 percent. Some of them die before reaching a doctor. Other victims ignore their symptoms. The death rate among hospitalized patients ranges from 5 to 10 percent. Heart attack patients with repeated chest pain, arrhythmias, or heart failure have a greater risk of another attack than do patients without those problems. Plaques can completely block an artery and stop the blood flow. In addition, they can narrow an artery and so reduce blood flow enough to form a thrombus (blood clot). Plaques often crack, releasing substances that also can lead to blood clots. If a blood clot blocks a coronary artery, it causes a heart attack. A blood clot that occurs in an artery in the brain causes a stroke.