heart attack (myocardial infarction)
A heart attack, also known as myocardial infarction or coronary thrombosis, occurs when the supply of blood and oxygen to an area of heart muscle is blocked, usually by a clot in a coronary artery. Often, this blockage leads to arrhythmias (irregular heartbeat or rhythm) that cause a severe decrease in the pumping function of the heart and may bring about sudden death. If the blockage is not treated within a few hours, the affected heart muscle will die and be replaced by scar tissue.
A heart attack is a life-threatening event. Everyone should know the warning signs of a heart attack and how to get emergency help. Many people suffer permanent damage to their hearts or die because they do not get help immediately.
Each year, more than a million persons in the US have a heart attack and about half (515,000) of them die. About one-half of those who die do so within 1 hour of the start of symptoms and before reaching the hospital.
Emergency personnel can often stop arrhythmias with emergency CPR (cardiopulmonary resuscitation), defibrillation (electrical shock), and prompt advanced cardiac life support procedures. If care is sought soon enough, blood flow in the blocked artery can be restored in time to prevent permanent damage to the heart. Yet, most people do not seek medical care for 2 hr or more after symptoms begin. Many people wait 12 hr or longer.
A heart attack is an emergency. Prompt treatment of a heart attack can help prevent or limit lasting damage to the heart and can prevent sudden death.
Most heart attacks are caused by a blood clot that blocks one of the coronary arteries (the blood vessels that bring blood and oxygen to the heart muscle). When blood cannot reach part of your heart, that area starves for oxygen. If the blockage continues long enough, cells in the affected area die.
Coronary artery disease (CAD) is the most common underlying cause of a heart attack. CAD is the hardening and narrowing of the coronary arteries by the buildup of plaque in the inside walls (atherosclerosis). Over time, plaque buildup in the coronary arteries can:
A less common cause of heart attacks is a severe spasm (tightening) of the coronary artery that cuts off blood flow to the heart. These spasms can occur in persons with or without CAD. Artery spasm can sometimes be caused by:
What makes a heart attack more likely
Certain factors make it more likely that you will develop CAD and have a heart attack. These are called risk factors. Risk factors you cannot change include:
- Women: over age 55
- Heart disease diagnosed in mother or sister before age 65
- A previous heart attack
- A surgical procedure (angioplasty, heart bypass) to increase blood flow to your heart.
Risk factors that you can change include:
Signs and symptoms
The warning signs and symptoms of a heart attack can include:
Signs and symptoms vary from person to person. In fact, if you have a second heart attack, your symptoms may not be the same as for the first heart attack. Some people have no symptoms. This is called a "silent" heart attack.
The symptoms of angina can be similar to those of a heart attack. If you have angina and notice a change or a worsening of your symptoms, talk with your doctor right away.
Diagnosis (and treatment) of a heart attack can begin when emergency medical personnel arrive.
At the hospital emergency room, doctors will work fast to find out if you are having or have had a heart attack. They will consider your symptoms, medical and family history, and test results. Initial tests will be quickly followed by treatment if you are having a heart attack.
Tests used include:
- Troponin test. This test checks the troponin levels in the blood. It is considered the most accurate blood test to see if a heart attack has occurred and how much damage was done to the heart.
- CK or CK-MB test. These tests check for the amount of the different forms of creatine kinase in the blood.
- Myoglobin test. This test checks for the presence of myoglobin in the blood. Myoglobin is released when the heart or other muscle is injured.
A heart attack is a medical emergency. Delaying treatment can mean lasting damage to your heart or even death. The sooner treatment begins, the better your chances of recovering. Your treatment may begin in the ambulance or in the emergency room and continue in a special area called a coronary care unit or CCU.
In the hospital
If you are having a heart attack, doctors will:
Restoring blood flow to the heart is vital to prevent or limit damage to the heart muscle and to prevent another heart attack. The main treatments are the use of thrombolytic ("clot-busting") drugs and procedures such as angioplasty.
The CCU is specially equipped with monitors that continuously measure your vital signs. Those that can show signs of complications include:
Medications used in treating heart attacks include:
The length of your hospital stay after a heart attack depends on your condition and response to treatment. Most people spend several days in the hospital after a heart attack. While in the hospital, your heart will be monitored, and you will receive needed medications. You will probably have further testing, and you will be treated for any complications that arise.
While you are still in the hospital or after you go home after your heart attack, your doctor may order other tests, such as:
Your doctor may prescribe cardiac rehabilitation (rehab) to help you recover from a heart attack and help prevent another heart attack. Almost everyone who has survived a heart attack can benefit from rehab.
The cardiac rehab team may include:
Rehab has two parts:
After leaving hospital
After a heart attack, your treatment may include cardiac rehab in the first weeks or months, checkups and tests, lifestyle changes, and medications. You will need to see your doctor for checkups and tests to see how your heart is doing. Your doctor will most likely recommend lifestyle changes, such as quitting smoking, losing weight, changing your diet, or increasing your physical activity.
After a heart attack, most people take daily medications. These may include: