Heart Disease: Heart Attacks

More than 1 million Americans have heart attacks each year. A heart attack, or myocardial infarction (MI), is permanent damage to the heart muscle. "Myo" means muscle, "cardial" refers to the heart and "infarction" means death of tissue due to lack of blood supply.

What Happens During a Heart Attack?

The heart muscle requires a constant supply of oxygen-rich blood to nourish it. The coronary arteries provide the heart with this critical blood supply. If you have coronary artery disease , those arteries become narrow and blood cannot flow as well as it should. Fatty matter, calcium, proteins and inflammatory cells build up within the arteries to form plaques of different sizes. The plaque deposits are hard on the outside and soft and mushy on the inside.

Heart Attack

When the plaque's hard, outer shell cracks (plaque rupture), 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. 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, reducing 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. But, the new scar tissue does not contract or pump as well as healthy heart muscle tissue. So, the heart's pumping ability is lessened after a heart attack. 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, arm or below the breastbone
  • Discomfort radiating to the back, jaw, throat or arm
  • Fullness, indigestion or choking feeling (may feel like heartburn)
  • Sweating, nausea, vomiting or

What Do I Do if I Have a Heart Attack?

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 (usually 911). 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.

Keep in mind that 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 signs. Seek medical care immediately.

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.

Tests You Take

  • ECG. The ECG (also known as EKG or electrocardiogram) can tell how much damage has occurred to your heart muscle and where it has occurred. In addition, your heart rate and rhythm can be monitored.
  • Blood tests. Blood may be drawn to measure levels of cardiac enzymes in the blood that indicate heart muscle damage. These enzymes are normally found inside the cells of your heart and are needed for their function. When your heart muscle cells are injured, their contents -- including the enzymes -- are released into your bloodstream. By measuring the levels of these enzymes, the doctor can determine the size of the heart attack and approximately when the heart attack started. Troponin levels will also be measured. Troponins are proteins found inside of heart cells that are released when they are damaged by ischemia. Troponins can detect very small heart attacks as well as those that occurred more than a day after symptoms ensued.
  • Echocardiography. Echocardiography is an imaging test that can be used during and after a heart attack to learn how the heart is pumping and what areas are not pumping normally. The "echo" can also tell 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 help your doctor determine which procedure is needed to treat the blockage.