Heart Attack

What Is Heart Attack?

Heart Attack
A heart attack is most often caused by narrowing of the arteries by cholesterol plaque and their subsequent rupture. This is known as atherosclerotic heart disease (AHSD) or coronary artery disease (CAD).

If you believe that you are having the symptoms of a heart attack, please call 911 immediately and seek medical attention.

The heart is a muscle like any other in the body. Arteries supply it with oxygen-rich blood so that it can contract and push blood to the rest of the body. When there isn't enough oxygen flow to a muscle, its function begins to suffer. Block the oxygen supply completely, and the muscle starts to die.

  • The heart muscle gets its blood supply from arteries that originate in the aorta just as it leaves the heart.
  • The coronary arteries run along the surface of the heart and supply oxygen-rich blood to the heart muscle.
  • The right coronary artery supplies the right ventricle of the heart and the inferior (lower) portion of the left ventricle.
  • The left anterior descending coronary artery supplies the majority of the left ventricle, while the circumflex artery supplies the back of the left ventricle.
  • The ventricles are the lower chambers of the heart; the right ventricle pumps blood to the lungs and the left pumps it to the rest of the body.

What Causes a Heart Attack?

Picture of Heart Attack (Myocardial Infarction)
Picture of Heart Attack (Myocardial Infarction)

Over time, plaque can build up along the course of an artery and narrow the channel through which blood flows. Plaque is made up of cholesterol buildup and eventually may calcify or harden, with calcium deposits. If the artery becomes too narrow, it cannot supply enough blood to the heart muscle when it becomes stressed. Just like arm muscles that begin to ache or hurt when heavy things are lifted, or legs that ache when you run too fast; the heart muscle will ache if it doesn't get adequate blood supply. This ache or pain is called angina. It is important to know that angina can manifest in many different ways and does not always need to be experienced as chest pain.

If the plaque ruptures, a small blood clot can form within the blood vessel, acting like a dam and acutely blocking the blood flow beyond the clot. When that part of the heart loses its blood supply completely, the muscle dies. This is called a heart attack, or an MI - a myocardial infarction (myo=muscle +cardial=heart; infarction=death due to lack of oxygen).

Heart Attack Symptoms and Signs of a Heart Attack

Classic symptoms of a heart attack may include:

  • chest pain associated with shortness of breath,
  • profuse sweating, and
  • nausea.

The chest pain may be described as tightness, fullness, a pressure, or an ache.

Unfortunately, many people do not have these classic signs. Other signs and symptoms of heart attack may include:

  • indigestion,
  • jaw ache,
  • pain only in the shoulders or arms,
  • shortness of breath, or
  • nausea and vomiting.

This list is not complete, since many times people can experience a heart attack with minimal symptoms. In women and the elderly, heart attack symptoms can be atypical and sometimes so vague they are easily missed. The only complaint may be extreme weakness or fatigue.

Pain may also radiate from the chest to the neck, jaw, shoulder, or back and be associated with shortness of breath, nausea, and sweating.

Heart Attack Risk Factors

A heart attack is most often caused by narrowing of the arteries by cholesterol plaque and their subsequent rupture. This is known as atherosclerotic heart disease (AHSD) or coronary artery disease (CAD).

The risk factors for AHSD are the same as those for stroke (cerebrovascular disease) or peripheral vascular disease. These risk factors include:

While heredity is beyond a person's control, all the other risk factors can be minimized to try to prevent coronary artery disease from developing. If atherosclerosis (atheroma=fatty plaque + sclerosis=hardening) is already present, minimizing these risk factors can decrease further narrowing.

Non-coronary artery disease causes a heart attack may also occur. Examples include:

  • Cocaine use. This drug can cause the coronary arteries to go into enough spasms to cause a heart attack. Because of the irritant effect on the heart's electrical system, cocaine can also cause fatal heart rhythms.
  • Prinzmetal angina or coronary artery vasospasm. Coronary arteries can go into spasms and cause angina without a specific cause, this is known as Prinzmetal angina. There can be EKG changes associated with this situation, and the diagnosis is made by heart catheterization showing normal coronary arteries that go into spasm when challenged with a medication injected in the cath lab. Approximately 2% to 3% of patients with heart disease have coronary artery vasospasm.
  • Anomalous coronary artery. In their normal position, the coronary arteries lie on the surface of the heart. On occasion, in the course of a part, the artery can dive into the heart muscle itself. When the heart muscle contracts, it can temporarily kink the artery and cause angina. Again, diagnosis is made by heart catheterization.
  • Inadequate oxygenation. Just like any other muscle, the heart muscle requires an adequate oxygen supply for it to work. If there isn't adequate oxygen delivery, angina and heart attack can occur. There need to be enough red blood cells circulating in the body and enough lung function to deliver oxygen from the air, so that heart cells can be supplied with the nutrients that they need. Profound anemia from bleeding or failure of the body to make enough red blood cells can precipitate angina symptoms. Lack of oxygen in the bloodstream can occur due to a variety of causes including respiratory failure, carbon monoxide poisoning, or cyanide poisoning.

When to Seek Medical Care for a Heart Attack

Chest pain is almost always considered an emergency. Aside from heart attacks, pulmonary embolus (blood clot in the lung) and aortic dissection or tear can be fatal causes of chest pain.

Classic pain from a heart attack is described as chest pressure or tightness with radiation of the pain to the jaw and down the arm, accompanied by shortness of breath or sweating. But it is important to remember that heart problems may not always present as pain or with the classic symptoms. Indigestion, nausea, profound weakness, profuse sweating, or shortness of breath may be the main symptom of a heart attack.

Should any symptoms occur that you believe are related to your heart, activate the emergency medical system by calling 911. First responders, emergency medical technicians, and paramedics can begin testing and treatment even before you arrive at the hospital.

Remember to take an aspirin immediately if you are concerned that you are having a heart attack.

Doctors and nurses in Emergency Departments take an individual experiencing chest pain very seriously. You are not wasting anybody's time, and you are not bothering anybody when you seek care for chest pain.

Many people die before they seek medical care because they ignore their symptoms out of fear that something bad is happening, or by diagnosing themselves in error with indigestion, fatigue, or other illnesses. It is much better to seek medical care if you are unsure whether your symptoms are related to heart disease and find that all is well, than to die at home.

Heart Attack Diagnosis: Medical History and Physical Exam

Diagnosis and treatment tend to occur at the same time in patients who are experiencing chest pain. If there is concern that heart muscle is at risk, delays need to be minimized so that blood supply to that muscle can be restored.

Medical History

The diagnosis of angina is made by the history of the patient. If the story that the patient tells is suggestive of cardiac ischemia (cardiac= heart + ischemia= decreased blood supply), then the health care practitioner will continue on the path to determine whether a heart attack has occurred.

Important questions include:

  1. When did the pain start?
  2. What were you doing?
  3. Did you have to stop?
  4. Did the pain get better with rest?
  5. Did the pain come back with activity?
  6. Did the pain stay in your chest or did it move somewhere else, like the jaw, teeth, arm, or back?
  7. Did you get short of breath?
  8. Did you become nauseous?
  9. Were you sweating profusely?

The medical history also includes assessing risk factors for heart disease, including:

Questions may be asked about changes in exercise tolerance that might provide clues as to whether heart disease is present:

  1. Have there been episodes of previous chest pain?
  2. Is there shortness of breath on exertion?
  3. Can you walk to get the mail?
  4. Can you climb a flight of stairs?

The questions may try to distinguish between stable angina and unstable angina. Stable angina tends to be predictable. For example, it may occur after climbing a flight of stairs or walking a couple of blocks and then resolves quickly with rest. Unstable angina may occur without warning when the body is at rest and the heart is not stressed, for example, while sitting or sleeping.

Anginal symptoms that change and occur with less activity or sound unstable are worrisome and may be due to increased narrowing of a coronary artery.

Since other diagnoses will be considered, some questions may be asked to identify potential symptoms of conditions such as reflux esophagitis (GERD), gastritis, trauma, pulmonary embolus (blood clot in the lung), or pneumonia.

Physical examination

While the diagnosis is based on history, the physical exam can give some clues.

  • Are the blood pressure and pulse rate normal?
  • Do the lungs sound clear?
  • Are there findings suggestive of an infection (pneumonia) or fluid (edema)?
  • Are there unusual heart sounds? New murmurs can be associated with a heart attack.
  • Are bruits (noises produced by narrowed blood vessels that are heard with a stethoscope) present when listening to the neck, abdomen, or groin?
  • Is there tenderness in the abdomen that would suggest the chest pain is due to gallbladder, pancreas, or ulcer disease?

Heart Attack Diagnosis: Other Tests

EKGs, blood tests, and chest X-rays are other tests that are likely to be performed to assist with the diagnosis.


The electrocardiogram (ECG or EKG) will help direct what happens acutely in the ER. The EKG measures electrical activity and conduction in the heart muscle. In a heart attack in which the full thickness of the heart muscle is involved, the EKG shows characteristic changes that establish the diagnosis of myocardial infarction. Some heart attacks only involve small parts of the heart muscle; in these cases, the EKG can look relatively normal.

Blood tests

If the EKG does not diagnose a heart attack (an EKG can be normal even in the presence of a heart attack) blood testing may be required to further look for heart damage. When the heart muscle becomes irritated it may leak chemicals that can be measured in the blood. Levels of the cardiac enzymes myoglobin, CPK, and troponin are often measured, alone or in combination, to assess whether heart muscle damage has occurred. Unfortunately, it takes time for these chemicals to accumulate in the bloodstream after the heart muscle has been insulted. Blood samples need to be drawn at the appropriate time so that the results can be usefully interpreted. For example, the recommendation for the troponin blood test is to draw the first sample at the time the patient arrives in the ER, and then a second sample 6-12 hours later. Usually, it requires two negative samples to confirm that no heart muscle damage has occurred. (Please note that under special circumstances, one sample may be sufficient.)

Chest X-ray

A chest X-ray may be taken to look for a variety of findings including the shape of the heart, the width of the aorta, and the clarity of the lung fields.

If a heart attack has been proven not to have occurred, that is a heart attack has been "ruled out," further evaluation of the heart may be undertaken using stress tests, echocardiography, CT scans, or heart catheterization. The decision as to which test(s) to use, needs to be individualized to the patient and his or her specific situation.

Heart Attack Treatment

If the EKG shows that there is an acute heart attack (myocardial infarction), the goal is to open the blocked artery as soon as possible and restore blood supply to the heart muscle.

When a heart attack strikes, the key thing to remember is that time equals muscle. The longer the delay in seeking medical care, the more heart muscle will be damaged. There is a window of opportunity to restore blood supply to the heart muscle by unblocking the affected heart artery. Treatments must be done in a hospital and include administration of clot-busting drugs to dissolve the clot at the site of the ruptured plaque and heart catheterization and angioplasty (in which the blood vessel is opened by balloon, often with the adjunctive placement of a stent), or both.

Not all hospitals have the equipment or cardiologists available to perform emergency heart catheterizations, and thrombolytic therapy (the use of clot-busting drugs) may be the first step to open the blood vessel and return blood supply to the heart muscle.

Heart Attack Self-Care at Home

  • The first step to take when chest pain occurs is to call 911 and activate the Emergency Medical System. First responders, EMTs, and paramedics can begin treating a heart attack en-route to the hospital, alert the Emergency Department that the patient is on the way, and treat some of the complications of a heart attack should they occur.
  • Step two is to take an aspirin. Aspirin makes platelets less sticky and can minimize blood clot formation and prevent further blockage of the artery.
  • Step three is to rest. When the body does work, the heart has to pump blood to supply oxygen to the muscles and clear the waste products of metabolism. When heart function is limited because it doesn't have an adequate blood supply itself, asking it to do more work may cause more damage and risk further complications.

Heart Attack Emergency Medical Treatment

Hospitals have established treatment plans to minimize the time to diagnose and treat people with a heart attacks. National guidelines suggest that an electrocardiogram (EKG) be done within 10 minutes of the patient's arrival in the ER.

Many things will occur at the same time as the EKG being completed. The doctor will take a history and complete a physical exam while the nurses start an intravenous line (IV), place heart monitor lines on the chest, and administer oxygen.

Medications are used to try to restore blood supply to the heart muscle. If it wasn't taken before arrival in the ER, aspirin will be used for its antiplatelet action. Nitroglycerin will be used to dilate blood vessels. Heparin or enoxaparin (Lovenox) will be used to thin the blood. Morphine can also be used for pain control. Antiplatelet medications such as clopidogrel (Plavix) or prasugrel (Effient) are also recommended.

There are two options (depending on the resources at the hospital) 1) if the EKG shows an acute heart attack (myocardial infarction), and 2) if there are no contraindications.

Heart catheterization

The favored treatment is heart catheterization. Tubes are threaded through the femoral artery in the groin or through the brachial artery in the elbow, into the coronary arteries, and the area of blockage is identified.


Angioplasty (angio= artery + plasty=repair) is then considered if possible. A balloon is placed at the blockage site and as it opens, it compresses the plaque into the blood vessel wall. Afterward, a stent or a mesh cage is placed across the angioplasty site to keep it from closing down. Guidelines recommend that from the time the patient arrives at the hospital to have the blood vessel open be less than 90 minutes.

Picture of Coronary Angioplasty Procedure
Picture of Coronary Angioplasty Procedure

Not all hospitals have the capability of doing heart catheterizations 24 hours a day and may transfer the patient with an acute heart attack to a hospital that has the technology available. If the transfer time will delay angioplasty treatment beyond the 90-minute window recommendation, clot-busting drugs may be considered to dissolve the blood clot that has obstructed the coronary artery. Tissue plasminogen activator (TPA or TNK) can be used intravenously. After TPA infusion, the patient may still be transferred for heart catheterization and further care.

If the EKG is normal but the history is suggestive of a heart attack or angina, the evaluation will continue with the blood tests described above. However, the patient will likely be treated as if the heart attack was occurring. Patient treatment would include aspirin, oxygen, nitroglycerin, and blood-thinning medications until the presence of heart damage is has been ruled out. In other words, the treatment presumes heart disease until proven otherwise.

Heart Attack Complications

When a heart attack occurs, part of the heart muscle dies and is ultimately replaced with scar tissue. This leaves the heart weaker and less able to meet the needs of the body. This will lead to exercise intolerance including early fatigue or shortness of breath on exertion. The amount of disability is dependent on the amount of heart muscle pumping function lost.

The muscle that loses its blood supply becomes electrically irritable. This may cause a short circuit of the electrical conduction system of the heart. This may cause ventricular fibrillation, a situation in which the ventricles do not beat in a coordinated function. Instead, they jiggle like a bowl of Jello and cannot pump blood to the body. Sudden death occurs. Patients are kept in the ER or admitted to the hospital while assessing chest pain to monitor their heart rhythm and hopefully prevent sudden death from an acute heart attack or unstable angina which may result in ventricular fibrillation.

If this rhythm occurs while monitored in the hospital, it can be rapidly treated with defibrillation, an electric shock to try to restore a normal electric rhythm and heartbeat.

Heart Attack Follow-up

Medications that may be recommended on discharge from the hospital include:

  • aspirin for its anti-platelet effect,
  • a beta blocker to blunt the effect of adrenaline on the heart and make it beat more efficiently,
  • a statin drug to control cholesterol and
  • clopidogrel (Plavix) or prasugrel (Effient), other anti-platelet drugs.

Since the heart may have been damaged, further testing may be needed to assess its pumping capabilities. Echocardiography can measure ejection fraction, the amount of blood that heart pumps out to the body compared to how much it receives. A normal ejection fraction should be greater than 50% to 60%.

A monitored exercise program may be arranged.

Attempts will be made to minimize cardiac risk factors including:

Some patients will require coronary artery bypass surgery if their angiogram shows multiple areas of blockage.

Special Situations

Prinzmetal Angina

In some people, the coronary arteries can go into spasm and cause decreased blood flow to heart muscle. This can lead to chest pain known as Prinzmetal angina, even if there is no buildup of plaque in the blood vessels. In severe episodes the EKG can suggest a heart attack, and muscle damage can be confirmed by measuring cardiac enzymes.


There is a strong correlation between cocaine usage and heart attack. Aside from the artery spasm that cocaine induces, the drug turns on the adrenaline system of the body, increasing pulse rate and blood pressure, requiring the heart to do more work.

How to Prevent a Heart Attack

While people cannot control their family history and genetics, they can minimize risk factors for heart disease by:

These are all lifelong challenges to prevent heart disease, stroke, and peripheral vascular disease.

Even with the best of preventive care, heart attacks happen. Develop an emergency plan so that if chest pain occurs make certain you, your family, and friends know how to activate the Emergency Medical Services in your area or call 911.

Heart Attack in Women

Know the Symptoms

  1. Chest pain or discomfort
  2. Unusual upper body discomfort
  3. Shortness of breath
  4. Breaking out in a cold sweat
  5. Unusual or unexplained fatigue (tiredness)
  6. Light-headedness or sudden dizziness
  7. Nausea (feeling sick to the stomach)

A woman suffers a heart attack every 90 seconds in the United States. Yet according to a 2009 American Heart Association survey only half of women indicated they would call 9-1-1 if they thought they were having a heart attack and few were aware of the most common heart attack symptoms.


Medically reviewed by Robert J. Bryg, MD; Board Certified Internal Medicine with subspecialty in Cardiovascular Disease


eMedicine.com. Myocardial Infarction.