About Acute Myocardial Infarction

Acute myocardial infarctions (AMI) occur in over 1.1 million Americans each year, particularly in seniors. AMI is the leading cause of hospitalizations in patients over 65. Almost two-thirds of patients do not make a complete recovery from AMI. Even if a patient lives through an AMI, the risk of a related illness or death is two to nine times greater. According to the Maryland vital statistics report, more than 12,000 people in Maryland died from diseases of the heart in 2003.

Read on for more information, or click on a topic in the list:

What is AMI?
What are the symptoms?
What are the causes?
How is it diagnosed?
What are the effects of a heart attack?
How is it treated?

Acute myocardial infarction occurs when a part of the heart muscle is injured, and this part may die because of sudden total interruption of blood flow to the area. It is often a life-threatening medical emergency which demands both immediate attention and activation of the emergency medical services. AMI can occur in any chamber of the heart, but it most often occurs in the left ventricle.

The first symptom of AMI may be a deep pain in the middle of the chest behind the breastbone, although this symptom is not as common in women. Other symptoms that may occur suddenly or develop gradually include: varying degrees of chest pain or discomfort, weakness, sweating, nausea, vomiting, and arrhythmias, and sometimes loss of consciousness. Symptoms can occur days to weeks before the event that blocks the flow of blood.

Chest pain is the most common symptom of AMI. Pain may radiate to the jaw, neck, arms, back, and epigastrium, most often to the left arm or neck. Chest pain is more likely caused by myocardial infarction when it lasts for more than 30 minutes. The patient may complain of shortness of breath (dyspnoea), especially if the AMI leads to left ventricular systolic dysfunction (LVSD) with pulmonary congestion or even pulmonary edema.
Approximately one quarter of all AMIs are silent, without chest pain or other symptoms. This happens more often in elderly patients and patients with diabetes mellitus. They may complain of atypical symptoms like fatigue, syncope, or weakness. Approximately half of all AMI patients have experienced warning symptoms like angina pectoris prior to the AMI.

AMI can occur when an atherosclerotic plaque slowly builds up in the inner lining of a coronary artery and then suddenly ruptures, totally occluding the artery and preventing blood flow downstream.

Hypertension can also lead to AMI. High cholesterol levels, tobacco use, and physical inactivity are also major factors that contribute to AMI.

Other less common causes of AMI include cocaine use and a spasm of the coronary arteries. A blockage occurs during these events because the artery suddenly contracts and stops blood flow.

Classic cases of AMI are often identified quickly by ambulance staff, emergency room doctors, and cardiac specialist nurse practitioners. Yet many smaller AMIs are not recognized by victims, never receive medical attention, and result in either sudden death or progressive heart weakness.

For a more complete diagnosis, three factors should be assessed:

• Medical history to screen patients for further enzyme and electrocardiogram testing.
• Electrocardiogram to determine where in the heart the damage has occurred.
• Blood tests to measure the extent of cardiac injury. A positive troponin test, accompanied by chest pain, may predict a high likelihood of AMI in the near future.

Myocardial perfusion tests (stress tests) and echocardiograms can also be helpful.

Damage from AMI leads to heart failure in two-thirds of patients hospitalized for AMI. Arrhythmias are another possible complication of AMI.

AMI often results in LVSD, in which the left side of the heart fails to pump enough blood to the rest of the body and fluid backs up and accumulates in the lungs, causing breathing difficulties. Hospitals should always check the left side of the heart for weakness in an AMI patient.

The Centers for Medicare & Medicaid Services and Joint Commission for the Accreditation of Healthcare Organizations have determined that the following treatments are indicators of quality care for AMI:

• Aspirin within 24 hours
• ACE inhibitor
• Beta blocker
• Advice for smokers on how to stop smoking
• Aspirin at discharge

Practitioners can find more information about treating AMI in Best Practices for AMI.

Information in this document is taken from Wikipedia.com, 2005.