About Heart Attacks (Acute Myocardial Infarction)

Heart attacks, or acute myocardial infarctions (AMI), occur in over 1.1 million Americans each year, particularly in seniors. Heart attacks are the leading cause of hospitalizations in patients over 65. Almost two-thirds of patients do not make a complete recovery from a heart attack. Even if a patient lives through a heart attack, 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 a heart attack?
What are the symptoms?
What are the causes?
How is it diagnosed?
What are the effects of a heart attack?

What is a heart attack?

The heart’s job is to pump oxygen-rich blood through the arteries to all parts of the body. A heart attack occurs when a blockage in an artery interrupts the flow of blood to the heart. A lack of blood and oxygen causes heart cells to die.

Two chambers of the heart, called atria, receive blood from the body. The two other chambers, called ventricles, collect blood from the atria and pump it out of the heart. Heart attacks can occur in any of these chambers, but they most often occur in the left ventricle.

What are the symptoms?

The first symptom of heart attack may be a deep pain in the middle of the chest behind the breastbone. Other symptoms may occur either suddenly or develop gradually. Sometimes symptoms occur days to weeks before the event that blocks the flow of blood. Signs of a heart attack include:

• Chest pain, called unstable angina, although not as common in women  
• Pressure in the chest, described as “crushing,” also not as common in women
• A pain that moves to the back, jaw, or left arm
• Shortness of breath
• Fatigue
• Abdominal pain (an “inferior heart attack”)
• Nausea and vomiting
• Very mild discomfort or no symptoms (a “silent heart attack”)

Call your doctor at the earliest sign of symptoms. Early detection and treatment is important to improving your outcome and even your survival.

What are the causes?

A heart attack can be caused by fatty buildup on the wall of an artery, called coronary artery disease. When a patient with coronary artery disease has a heart attack, the blockage in the flow of blood is caused by blood platelets and a tear in the fatty build-up. Blood platelets are parts of the blood that make blood clots to heal wounds. When the platelets find the tear in the fatty build-up, they make a clot around it. The combination of fatty buildup and the blood clot blocks the flow of blood and chokes off oxygen to the heart.

High blood pressure, also known as hypertension, can also lead to a heart attack when blood flow pushes too strongly against artery walls and causes fatty buildup. High cholesterol levels, tobacco use, and physical inactivity are also major factors that contribute to heart attacks.

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

How is it diagnosed?

A doctor usually diagnoses a heart attack based on the medical history of the patient. The diagnosis is confirmed by any of the following tests:

• Electrocardiograms (ECG)—This test measures the rhythm of the heartbeat. It detects the electrical signals that the heart produces. To perform the test, small discs are placed on the patient’s skin. The discs pick up electrical signals from the heart.

• Echocardiograms—This test uses sound waves to record blood flow in the heart. The sound waves are sent through the patient’s skin. If the doctor needs to obtain a clearer image, the sound waves can be sent through the esophagus, a tube that normally carries food to the stomach; this method requires the patient to take medication to relax and numb the body.

• Cardiac catheterization—This test examines coronary arteries by sending a liquid visible to x-rays, called contrast material, through the coronary arteries or chambers of the heart for observation. To perform the test, a doctor passes a small tube, or catheter, through the patient’s blood vessel and into the heart.

• Blood tests—Blood tests may show signs of changes in enzymes in the blood that occur when the heart is damaged. Blood counts, which detect the numbers of blood cells and platelets in the blood, may also be helpful in confirming the diagnosis. To detect injury to the heart muscle, new blood tests that look for the presence of proteins called troponins help to detect injury to the heart muscle.

What are the effects of a heart attack?

Depending on how much of the heart is damaged, it may not function well after a heart attack. This is called heart failure. Heart failure is known to occur in two-thirds of hospitalized patients who have had heart attacks.

Abnormal heart rhythms, also called arrhythmias, are a possible complication of heart attack.

A heart attack often can result in left ventricular systolic dysfunction (LVSD). LVSD means the left side of the heart fails to pump enough blood to the rest of the body. As a result, fluid backs up and accumulates in the lungs, causing breathing difficulties. Hospitals should always check the left side of the heart for weakness when a patient has a heart attack.

More Information

What treatments should you expect after a heart attack? See Quality Care for Heart Attacks to learn more.