heart attack

Heart Attack

Almost all heart attacks occur when a blood clot suddenly and completely blocks a coronary artery.

This condition is called a coronary thrombosis, or simply a coronary. The part of the heart muscle nourished by the blocked artery becomes damaged by lack of oxygen.

Unless blood flow returns within minutes, muscle damage increases. Heart cells begin to die after four to six hours without blood. The damage can affect the heart's ability to pump and may cause the patient's death. If the clot can be dissolved within four to six hours, damage to the heart can be reduced. Symptoms. Some people have no warning signs at the beginning of a heart attack. But many people experience angina, dizziness, indigestion, or other symptoms. Most heart attacks cause severe pain. Patients describe the pain as a dull, crushing ache in the chest, but discomfort may extend into the neck, jaw, arms, or back.

The pain may last from a few minutes to several hours. Anyone with chest pain who suspects the pain may be due to a heart attack should seek medical help immediately.

Some patients may stop breathing, and their hearts may stop beating. A first-aid technique called cardiopulmonary resuscitation (CPR) can maintain breathing and circulation until a patient can be taken to a hospital. But CPR should be performed only by someone trained in the technique.

Diagnosis and treatment.

Injured heart muscle causes abnormal ECG waves. Soon after a patient reaches the hospital, doctors administer an ECG to determine that symptoms result from a heart attack and not some other disorder. Doctors also use certain blood tests to detect a heart attack. But these tests are not useful until a few hours after an attack. Doctors may administer a strong painkilling drug, such as morphine, to relieve the pain of a heart attack. They also use drugs to dissolve clots in the blocked artery or may perform emergency angioplasty or bypass surgery.

After doctors stabilize the condition of a heart attack patient, they admit the person to the hospital and monitor him or her for complications in the intensive care unit. Some hospitals have a specialized intensive care unit called a coronary care unit for heart patients. Two major complications are heart failure and arrhythmia. Heart failure occurs if the heart cannot 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 pattern of beats. Most arrhythmias can be readily treated, but a type called ventricular fibrillation can cause sudden death. Ventricular fibrillation occurs when electrical signals in the ventricles fire randomly.

More than 20 percent of heart attack patients who do not get medical care die. Some people die before they can reach a doctor, but other patients ignore their symptoms and delay treatment. The death rate among hospitalized patients ranges from 5 to 10 percent. Heart attack patients with ongoing chest pain, arrhythmias, or heart failure have a greater risk of another attack than do patients without these problems.

Source : World Book 2005




What is the problem and what is known about it so far?

Severe blockage of the arteries that supply blood to heart muscle is known as a heart attack (the medical term is “myocardial infarction”). Heart muscle is weakened immediately after a heart attack but gradually regains its strength. Occasionally, the heart muscle progressively weakens, leading to chronic failure of the heart to work as an efficient pump. Although several techniques and drugs are used to improve blood flow to heart muscle rapidly after a heart attack (known as reperfusion therapy), the factors that influence development or improvement of heart muscle weakness are not known.

Why did the researchers do this particular study?

To see whether clinical or laboratory test characteristics can predict recovery of heart muscle strength after a heart attack.

Who was studied?

249 patients with heart attacks who had undergone reperfusion therapy. These patients had taken part in a separate study of treatment with several different doses of a drug that reduces the workload on the heart (the Healing and Early Afterload Reduction Therapy [HEART] study).

How was the study done?

The researchers reanalyzed data from the HEART study, including clinical characteristics; blood tests for creatine kinase (CK); and the results of echocardiography done 1, 14, and 90 days after patients’ heart attacks. Creatine kinase is a chemical that spills into the bloodstream when heart muscle cells are damaged. Echocardiography uses sound waves to analyze heart size and muscle function.

What did the researchers find?

Patients with the highest levels of CK in their blood were least likely to have complete recovery of heart muscle strength. In addition, patients with enlargement of the left ventricle (the main pumping chamber of the heart) during the 90-day observation period were less likely to show improvement in overall pumping ability, although a few patients with such enlargement did have improvement. Only 26% of patients with any degree of left ventricular enlargement recovered complete strength of the heart muscle.

What were the limitations of the study?

The groups that received different doses of the drug that reduces workload of the heart all recovered heart muscle function about equally. The study therefore does not tell us whether drugs of this kind can improve recovery of heart muscle function. Moreover, the researchers could not tell which patients actually achieved reperfusion and which did not. Thus, they could not tell whether successful reperfusion improved recovery of heart muscle strength. Finally, only one type of heart attack was studied; the results of this study may not apply to other types.

What are the implications of the study?

Measuring CK levels in the blood and testing for enlargement of the heart by using echocardiography can help predict which patients will recover heart muscle strength after a heart attack.

Source :
Annals of Internal Medicine. American College of Physicians–American Society of Internal Medicine


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