Heart Attack

Definition

A heart attack is the common term for a myocardial infarction (MI) a condition that generally occurs when there is a blockage of blood flow to the heart, resulting in the heart not receiving the oxygen and nutrients it needs.

Description

The human heart basically is a muscle that pumps blood. It has its own blood vessels (the coronary arteries) that nourish it with oxygen and nutrients. In most cases when a heart attack occurs, fatty deposits (composed mostly of cholesterol) have lined the coronary arteries. As these deposits build up, they progressively narrow the arteries and decrease or stop the flow of blood to the heart. When there is a decreased flow of blood to the heart, the heart muscle may be damaged - sometimes permanently - if not treated.

A heart attack most often results when a blood clot forms in a narrowed artery and blocks the flow of blood to the part of the heart muscle supplied by that artery. Doctors call this form of heart attack a coronary thrombosis, coronary occlusion or myocardial infarction.

When a heart attack occurs, the dying part of the heart may trigger electrical activity that causes ventricular fibrillation. Ventricular fibrillation is an uncoordinated twitching that replaces the smooth, measured contractions that cause blood to be pumped to the organs of the body. In many cases, if trained medical professionals are immediately available, they can get the heart beating again by using electrical shock and/or drugs.

If the heart can be kept beating and not too much heart muscle is damaged, small blood vessels may gradually reroute blood around the blocked arteries. This is the heart's way of compensating for the clogged artery. It is called collateral circulation.

Causes

Myocardial infarction caused by atherosclerosis or heart disease remains a major cause of morbidity and mortality in the United States.

When one or more of the coronary arteries supplying blood to the heart muscle is blocked, it is usually caused by the buildup of plaque (deposits of fat-like substances) due to atherosclerosis. The plaque may burst or tear, creating an area where a blood clot can form and block the artery.

Why does atherosclerosis occur in the coronary arteries of some people but not others? Many factors, including hypertension (high blood pressure), smoking, diabetes, obesity, a high level of low-density lipoprotein (LDL) cholesterol, family history of heart disease, and a sedentary lifestyle are involved.

Symptoms

The key to surviving a heart attack is promptly recognizing the warning signals and getting immediate medical attention. The major symptoms of a heart attack are intense chest pain, sudden onset of cold, sweating, weakness and/or nausea. If you feel an uncomfortable pressure, fullness, squeezing or pain in the center of your chest (that may spread to your shoulders, neck or arms) and your discomfort lasts for two minutes or longer, you could be having a heart attack. Sweating, dizziness, fainting, nausea, a feeling of severe indigestion or shortness of breath may also occur, although not all these symptoms necessarily do occur.

When a person has these symptoms, it is natural to deny what is happening. No one wants to think that he might be having a heart attack. It is important to know that over 300,000 heart attack victims died before reaching the hospital last year, many of them because they refused to take their symptoms seriously.

What should you do if you think you might be having a heart attack? Call your local emergency medical service (EMS) immediately. If the EMS isn't available, get to the hospital Emergency Room as soon as possible.

While you are waiting for the EMS responders, there is evidence that taking aspirin very early in the course of an MI may help reduce its severity. Thus, taking two aspirin with a small amount of water is advisable.

Know in advance which route from home or work will take you to the hospital the quickest. You might even discuss your possible choices of hospital with your doctor.

Another option is to call your local American Heart Association and ask which recognized emergency medical service and hospitals cover your area. Keep emergency information where you can find it easily and develop a "buddy system" with someone you know.

Diagnosis

A physician will take a complete medical history, including a description of your symptoms, a physical exam, perform an echocardiogram (EKG or ECG) to look for findings suggestive of a heart attack, and order blood tests, including those that check for heart muscle damage.

Other studies may also be performed, including a chest x-ray to check the size and shape of the heart and blood vessels, a nuclear scan to help identify blood flow problems to the heart, an echocardiogram to help identify if an area of the heart has been damaged or is not pumping normally, and a coronary catheterization (angiogram) to see if the coronary arteries are narrow or blocked.

Treatment

Once it's clear you're having a heart attack, initial treatment may include oxygen and medications such as thrombolytics (clot busters), super aspirins and other blood thinning medications, pain relievers, beta blockers and cholesterol lowering medications. The objective of thrombolytic (lysing the thrombus) therapy in acute myocardial infarction is to lyse (dissolve) the coronary thrombus (clot) and allow oxygenated blood to reach the heart muscle as quickly as possible. The goal is that intervention early in the course of infarction will limit infarct size, preserve left ventricular function, prevent pump failure and ultimately, prevent death.

The four thrombolytic agents that have been evaluated extensively in acute infarction are: streptokinase, tissue plasminogen activator (t-PA), reteplase and anistreplase (APSAC). Although there is much debate over which agent to use, the overriding consideration is early adminstration of any one of them.

Super aspirins may help prevent new clots from forming. Blood-thinning medications such as heparin or hirudin also make the blood less likely to form clots. Pain relievers such as morphine help relieve discomfort. Nitroglycerine temporarily improves blood flow by opening narrow blood vessels. Beta blockers help the heart work less hard by relaxing the muscle and slowing the heartbeat. Cholesterol-lowering medications help lower levels of blood cholesterol.

A number of medical centers now manage acute myocardial infarction with primary angioplasty of the affected coronary artery. Your physician may suggest other treatments as well. Coronary bypass surgery may be indicated.

Prevention

Studies in recent years have shown that taking an aspirin every day may reduce the risk of having a heart attack or a stroke caused by a blood clot forming in an artery. However, it is important that you first consult your doctor before beginning aspirin therapy. Other steps which can help you to prevent (and also recover from) a heart attack include:

Get regular checkups
Control your blood pressure
Check your cholesterol and use medication for it if indicated
Don't smoke and avoid second hand smoke
Maintain a healthy weight
Eat a heart healthy diet, including adequate amounts of folic acid (found in greens, leafy vegetables, citrus fruit and whole grains)
Manage stress
Use alcohol in moderation
Engage in physical activityExercise regularly and reduce the amount of time you spend in sedentary activities such as watching TV

Some studies have shown that the risk of a heart attack during or just after heavy physical exertion is two to six times greater than the risk during less strenuous physical activities or no activity, but performing regular physical activity over time diminished the added risk to practically none at all.

Normally sedentary people who try something strenuous like shoveling snow, sprinting to catch a bus, playing tennis or pushing a car out of a snowdrift, may be especially at risk.

Among the cardiovascular benefits of regular of regular physical activity are a diminished tendency of blood to form clots, an improved cholesterol profile, more efficient use of oxygen by the muscles, a larger volume of blood pumped with each heartbeat, and during periods of exertion, greater dilation of the arteries, a lower heart rate and lower blood pressure. Reasonable advice includes the following:

While it is almost always safe to engage in moderate levels of physical activity such as walking, make sure to discuss any intensive, new exercise program with your physician first.
Start slow and easy: For the first week or two, exercise at an easy pace for no more than 10 to 20 minutes at a time.
Build up gradually: As a general rule, do not increase either the intensity, frequency or duration of your exercise sessions by more than 10 percent each week.
Engage in physical activity often: It is safer to get modest amounts of physical activity several times a week than to try making up for days or weeks of inactivity with a single, prolonged workout.
Do not overexert: Beginners should avoid pushing their heart rate higher than 70 percent of its maximum. (Your maximum rate equals roughly 220 minus your age).
Warm up: Begin every workout with a gentle warm-up to boost circulation to the heart muscle. Jog in place, ride a stationary bicycle or do callisthenic exercise for a few minutes. Then stretch to reduce the risk of injury.
Cool down: Rapid muscle movement helps pump blood back to the heart. If you stop exercising abruptly, the heart's blood supply may drop abruptly.
Do not eat and run: During and after a meal, the body sends extra blood to the digestive organs, leaving less blood for the heart and muscles. Try to wait at least two hours after a heavy meal before exercising.
Watch the weather: Blood vessels in the skin and the limbs constrict when it is cold outside, making it more difficult for the heart to pump blood throughout the body. If you exercise outdoors in frigid weather, dress in warm layers and do not push yourself too hard. Working out in hot weather can also threaten the heart, since heavy sweating decreases the total volume of blood, and in turn, the amount flowing to the heart muscle.
Take pollution to heart: Exercising in polluted air increases blood levels of carbon monoxide, which raises the risk of heart attack by replacing oxygen in the blood.