When the plaque's hard, outer shell cracks, platelets (disc-shaped particles in the blood that aid clotting) come to the area, and blood clots form around the plaque. If a blood clot totally blocks the artery, the heart muscle becomes "starved" for oxygen and nutrients (ischemia) in the region below the blockage. Within a short time, death of heart muscle cells occurs, causing permanent damage. This is called a myocardial infarction (MI) or heart attack.

While it is unusual, a heart attack can also be caused by a spasm of a coronary artery. During coronary spasm, the coronary arteries restrict or spasm on and off, causing lack of blood supply to the heart muscle (ischemia). It may occur at rest and can even occur in people without significant coronary artery disease.

Each coronary artery supplies blood to a region of heart muscle. The amount of damage to the heart muscle depends on the size of the area supplied by the blocked artery and the time between injury and treatment.

Healing of the heart muscle begins soon after a heart attack and takes about eight weeks. Just like a skin wound, the heart's wound heals and a scar will form in the damaged area. The new scar tissue does not contract or pump as well as healthy heart muscle tissue. So, the heart's pumping ability is lessened. The amount of lost pumping ability depends on the size and location of the scar.

What are the symptoms of a heart attack?
Symptoms of a heart attack include:

• discomfort, pressure, heaviness, or pain in the chest (angina), arm or below the breastbone
• discomfort radiating to the back, jaw, throat or arm
• a fullness, indigestion or choking feeling (may feel like heartburn)
• sweating, nausea, vomiting or dizziness
• extreme weakness, anxiety or shortness of breath
• rapid or irregular heartbeats

During a heart attack, symptoms last 30 minutes or longer and are not relieved by rest or oral medications (medications taken by mouth).

Some people have a heart attack without having any symptoms (a "silent" myocardial infarction). A silent MI can occur among all patients, though it is more common among diabetics.

Do not delay getting help
Quick treatment to open the blocked artery is essential to lessen the amount of damage. At the first signs of a heart attack, call for emergency treatment . The best time to treat a heart attack is within one to two hours of the first onset of symptoms. Waiting longer than that increases the damage to your heart and reduces your chance of survival.

Reasons people delay:

• They are young and cannot believe it is happening to them.
• Symptoms are not what they expected.
• They may deny the symptoms are serious and wait until they go away.
• They may ask the advice of others, especially family members.
• They may first try to treat the symptoms themselves, using aspirin or antacids.
• They may think the symptoms are related to other health problems (stomach, arthritis).
• They may put the care of others first (first take care of children or other family members) and not want to worry them.

Chest discomfort can be described many ways. It can occur in the chest or in the arms, back or jaw. If you have symptoms, take notice. These are your heart disease warning symptoms. Treat all chest discomfort as angina or a heart attack unless your doctor has told you otherwise.

Treatments (medications, open heart surgery and interventional procedures) do not cure coronary artery disease. Having had a heart attack or treatment does not mean you will never have another heart attack; it can happen again.

How is a heart attack diagnosed?
Once the emergency care team arrives, they will ask you about your symptoms and begin to evaluate you. The diagnosis of the heart attack is based on your symptoms, ECG and the results of your blood tests. The goal of treatment is to treat you quickly and limit heart muscle damage.

ECG
The ECG (also known as EKG or electrocardiogram) can help to tell how much damage has occurred to your heart muscle and where it has occurred. In addition, your heart rate and rhythm can be watched.

Blood work
Blood may be drawn to measure levels of biochemical markers (sometimes called enzymes). These markers are found inside your body's cells and are needed for their function. When your heart muscle cells are injured, their contents -- including the markers -- are released into your bloodstream. By measuring the levels of these markers, the doctor can determine the size of the heart attack and approximately when the heart attack started. Other blood tests may also be performed.

Echocardiography
Echocardiography can be used during and after a heart attack to learn about how the heart is pumping and what areas are not pumping normally. The echo is also valuable to see if any structures of the heart (valves, septum, etc.) have been injured during the heart attack.

Cardiac catheterization
Cardiac catheterization, also called cardiac cath, may be used during the first hours of a heart attack if medications are not relieving the ischemia or symptoms. The cardiac cath can be used to directly visualize the blocked artery and guide the choice for which procedure (such as angioplasty, stent placement or coronary artery bypass surgery) may follow.

How is a heart attack treated?
Once your heart attack is diagnosed, your treatment begins immediately -- possibly right in the ambulance or emergency room.

Medications
The knowledge gained in past years regarding acute coronary syndromes and what happens in the artery during a heart attack has helped guide medical treatment. The goals of medication therapy are to break up or prevent blood clots, prevent platelets from gathering and sticking to the plaque, stabilize the plaque and prevent further ischemia.

These medications must be given as soon as possible (within one to two hours from the start of your heart attack) to decrease the amount of damage. The longer the delay in starting these drugs, the more damage that occurs and the less benefit they can provide.

Medications for this purpose may include:

• aspirin
• heparin
• thrombolytic therapy ("clot busters")
• other antiplatelet drugs
• any combination of the above

Other drugs, given during or after a heart attack, lessen your heart's work, improve the functioning of the heart, widen or dilate your blood vessels, decrease your pain and guard against any life-threatening heart rhythms.

Interventional procedures
During or shortly after a heart attack, you may go to the cardiac catheterization laboratory to directly evaluate the status of your heart, arteries and the amount of heart damage. In some cases, procedures (such as angioplasty or stents) are used to open up your narrowed or blocked arteries. These procedures may be combined with thrombolytic therapy to open up the narrowed arteries, as well as to break up any clots that are blocking them.

If necessary, bypass surgery may be performed to restore the heart muscle's supply of blood.

How are subsequent heart attacks prevented?
The goal after your heart attack is to keep your heart healthy and reduce your risks, to prevent future damage to your heart. Take your medications, change your lifestyle and see you doctor for regular heart checkups.

Take your medications
Medications are prescribed after a heart attack to:

• prevent future blood clots
• lessen the work of your heart and improve your heart's performance and recovery
• lower cholesterol

Other medications may be prescribed if needed. These include medications to treat irregular heartbeats, lower blood pressure, control angina (chest discomfort) and treat heart failure.

It is important to know the names of your medications, what they are for and how often and at what times to take them. Your doctor or nurse should review your medications with you. Keep a list of your medications and bring them to each of your doctor visits. If you have questions about your medications, ask your doctor or pharmacist.

Change your lifestyle
There is no cure for coronary artery disease. In order to prevent the progression of this disease, you must follow your doctor's advice and make necessary lifestyle changes. You can stop smoking, lower your blood cholesterol, control your diabetes and high blood pressure, follow an exercise plan, lose weight, and control stress and anger.

See you doctor for regular heart check-ups
Make a doctor's appointment four to six weeks after you leave the hospital. Your doctor will want to check the progress of your recovery. Your doctor may ask you to undergo diagnostic tests (such as exercise or pharmacological stress tests or cardiac catheterization) at regular intervals. These tests can help the doctor to diagnose the presence or progression of blockages in your coronary arteries and to plan treatment.

Call your doctor sooner if you have symptoms such as chest pain that becomes more frequent, increases in intensity, lasts longer, or spreads to other areas; shortness of breath, especially at rest; dizziness. or irregular heartbeats.