Cardiac arrest refers to a sudden, profound disturbance in the heart’s rhythm that causes the heart to stop beating completely or slow to the point where the life is unsustainable. Cardiac arrest is not the same as a heart attack. A heart attack, while potentially life threatening, usually offers a short period of time in which treatment can save the person’s life.

Cardiac arrest must be treated immediately to avoid sudden cardiac death (death that results from cardiac arrest). Unfortunately, most people (85 percent) who experience cardiac arrest cannot get help fast enough. Those who survive the event are said to have lived through an “aborted” sudden cardiac death.

Cardiac arrest is most often caused by ventricular fibrillation, a condition in which the heart’s lower chambers quiver rather than pump blood. Ventricular fibrillation is usually accompanied by existing heart disease, especially coronary artery disease and previous heart attack. According to the American Heart Association, 90 percent of adults who succumb to cardiac arrest have two or more narrowed coronary arteries. Moreover, heart attack survivors have up to six times the rate of sudden cardiac death compared to the general population. In some rare cases, cardiac arrest can be provoked by recreational drug use or trauma.

Although there is some confusion in terms of recoding deaths due to cardiac arrest, it is estimated that about 330,000 Americans die every year due to cardiac arrest. The overwhelming majority of these are caused by ventricular fibrillation.

Prevention of cardiac arrest and sudden cardiac death is aimed at controlling underlying heart disease. Experts generally recommend that people make lifestyle changes to prevent the conditions that could trigger cardiac arrest, including atherosclerosis, which is the leading cause of coronary artery disease. Lifestyle changes may include losing weight, reducing LDL cholesterol levels, eating a heart-healthy diet and getting adequate exercise. When warranted, experts also recommend medical treatment of any underlying conditions, which may involve taking medications and/or having surgery (e.g., placing an implantable defibrillator into the patient’s chest).

Cardiac arrest is an event in which the heart abruptly stops or develops a very abnormal heart rhythm that prevents it from pumping blood. Although a heart attack may progress to cardiac arrest -- and cardiac arrest is sometimes referred to as a “massive heart attack” -- the two conditions are not the same. During a heart attack, the heart is still beating, while in cardiac arrest the heart has stopped beating. Once the patient has “gone into arrest,” he or she only has a few minutes to be treated. Otherwise, sudden cardiac death (SCD) will result.

SCD is death that results from cardiac arrest, usually as a result of ventricular fibrillation in the presence of existing heart disease, especially coronary artery disease. Some studies have shown that more than 80 percent of victims of SCD have coronary artery disease, and a majority have suffered from previous heart attacks. SCD can also be caused by severe and persistent bradyarrhythmias (e.g., slow heart rhythms), asystole and the failure of the heart to respond to normal electrical activity (pulseless electrical activity). Sustained ventricular tachycardia accompanied with low blood pressure (hypotension) is a less common cause. In rare cases, the heart muscle may rupture during or after a heart attack leading to sudden death.

Without immediate defibrillation, cardiac arrest will result in sudden cardiac death. SCD claims up to 330,000 American lives every year, accounting for about half of all cardiac deaths. Despite its name, however, people may survive sudden cardiac death. In that case, they are said to have experienced “aborted” sudden cardiac death.

If SCD occurs before six months of age, it is often referred to as sudden infant death syndrome (SIDS). After six months of age, SCD is rare among children and adolescents. After about 45, the incidence begins to climb again, as this population is more likely to suffer from accompanying forms of heart disease. Between the ages of 45 and 64, men are much more likely to suffer from SCD than women. After about 75, however, the rates even out. In general, the incidence rates of SCD closely correlate to the incidence rates of coronary artery disease. Higher rates were also found in the black population as compared to white, American Indian/Alaskan native and Asian/Pacific Islander populations. Hispanic populations appeared to have lower rates of SCD than non-Hispanic populations.

The CDC notes that the proportion of cardiac deaths classified as “sudden” remains high probably because of the unexpected nature of SCD and the failure to recognize early warning symptoms and signs of heart disease.

Although cardiac arrest often strikes without warning, the event rarely takes place in a normal heart unless other factors (e.g., recreational drug use, trauma) are present. Otherwise, there is almost always an underlying heart disease (e.g., coronary artery disease) or heart damage (e.g., from a previous heart attack) that may progress to the point where a critical situation develops.

According to the American Heart Association (AHA), atherosclerosis in two or more coronary arteries is found in up to 90 percent of adults who succumb to cardiac arrest.  Moreover, heart attack survivors have up to six times the rate of sudden cardiac death compared to the general population. For example, people with coronary artery disease are at higher risk of ventricular tachycardiaventricular tachycardia, an abnormally fast heart rate originating from the ventricles. Ventricular tachycardia can worsen and become ventricular fibrillation, in which the ventricles quiver rather than pump, due to abnormal electrical activity. In fact, this is most common cause of cardiac arrest that leads to sudden cardiac death.

Ventricular fibrillation is life-threatening because it results in a heart rate of 350 beats per minute or higher. The heart cannot maintain that rate more than a few minutes without treatment (e.g., with a defibrillator). Unless the condition is treated within six to eight minutes, permanent brain damage and, possibly, death may result.   

However, sudden cardiac death caused by coronary artery disease is much less common among younger people, who generally have less severe coronary artery disease. In this population, a number of other conditions have been observed to contribute to sudden cardiac death, including: 

More rarely, other conditions known to cause cardiac arrest include:

• Certain types of congenital heart disease or heart defects.
  
  
• Embolism. The blockage of a blood vessel by a foreign substance, such as a blood clot.
  
  
• Kawasaki disease. A disease, usually seen in young children, which affects blood vessels and heart muscle.
  
  
• Severe aortic stenosis. Narrowing of the aortic valve of the heart.
  
  
• Coronary artery spasm. An abnormal constriction of the muscle fibers in a coronary artery.
  
  
• Bradycardia. Abnormally slow heart beat.
  
  
• Cardiac tamponade. A condition in which the pericardial space is filled with fluids to a degree that interferes with the filling of the heart and causes the cessation of blood flow from the heart. This may also occur with rupture of the aortic root with rapid accumulation of blood within the pericardial space.

One study linked the presence of “free” fatty acids in the blood to a 70 percent increase in sudden cardiac death among a group of middle-aged healthy men. Although the researchers could not determine why fatty acids in the blood increased the risk so significantly, they noted that high fatty acid levels in the blood have been known to cause abnormal heartbeats (arrhythmias) in people with heart disease.

Cardiac arrest can also be caused by non-disease events, such as choking, electrocution and physical trauma. Recreational drug use has also been known to cause cardiac arrest in otherwise healthy people.

Cardiac arrest is believed to run in families, especially among males. A man whose mother or father went into cardiac arrest has almost double the chance of such an incident as an unrelated person. A family history of sudden cardiac death is an independent predictor of SCD even after other cardiovascular risk factors had been taken into account. In 2003, an international panel of cardiologists recommended that people see a physician if a close relative has died from SCD.

Other causes of cardiac arrest and SCD may involve a genetic mutation. Researchers have identified a calcium-controlling gene that is linked to ventricular tachycardia. This gene produces a protein called RyR2, which in turn controls the release of calcium inside heart cells. When RyR2 malfunctions, there is a “calcium overload” that triggers the arrhythmia. A specific form of ventricular tachycardia - called catacholaminergic polymorphic ventricular tachycardia - that occurs with exercise may be seen due to this mutation. Such research may eventually lead to genetic testing for this and other underlying conditions that might lead to cardiac arrest and sudden cardiac death.

Physicians have long struggled to identify and spot early warning signs that someone is at risk for, or about to go into, cardiac arrest. While there is no specific predictor for cardiac arrest, physicians take any symptoms and/or diagnoses of heart disease seriously and advise appropriate, immediate treatment.

In many cases, patients begin to experience symptoms days, weeks or even months before their arrest. This period is called the prodrome period. It may be marked by increased angina, dyspnea (breathlessness), palpitations, fatigue and other cardiac-related symptoms. However, these symptoms are not specific to cardiac arrest but can also signal an oncoming heart attack. Any heart patient, especially those with multiple risk factors, who experiences a change in their status and symptoms should immediately see a physician.

In the immediate period before a cardiac arrest occurs, the person's heart rate may increase and symptoms may intensify. In many people, however, there are no symptoms and the onset of the cardiac arrest is abrupt. Acute symptoms resemble those of a heart attack, including collapse and a lack of breathing. In a matter of minutes, the combination of a stopped heart and oxygen deprivation to the brain can cause sudden cardiac death. This explains why most sudden cardiac deaths occur before the patient receives emergency medical help or arrives at the hospital.

The risk for sudden cardiac death increases significantly in people with a family history of the condition. Because of this, researchers are developing tests to detect genetic markers that might place a person at higher risk of SCD. In addition, researchers may soon be able to test for a genetic predisposition to develop underlying conditions that might cause cardiac arrest and sudden cardiac death. Patients with a family medical history of sudden cardiac death or the conditions that could lead to cardiac arrest may wish to discuss the possibility of genetic testing with their physicians. However, genetic testing is expensive and may not be covered by traditional healthcare insurance.

When someone goes into cardiac arrest, the first line of treatment is often cardiopulmonary resuscitation (CPR) depending on the access to emergency medical care. CPR does not “cure” cardiac arrest, but it keeps the person alive until a defibrillator can be used to shock the heart back into a normal rhythm. Early CPR intervention does more than keep a person alive until help arrives. It can also prevent or mitigate permanent injury, such as brain damage.

Restarting or “resetting” a heart in cardiac arrest usually requires a defibrillator. Portable defibrillators were once available only on some ambulances and other emergency vehicles, but are now becoming more widely accessible. Police cars, airlines and businesses have been equipped with automatic external defibrillators (AEDs), with more people trained to use them.

AEDs are external devices that can be used in emergency situations by a person with a minimum amount of training. AEDs read the patient’s heart rhythm and administer an electric shock to restart or reset the heart.

The combination of training in both CPR and the use of AEDs has been proven to double survival rates, according to the results of the Public Access Defibrillation trial. This study shows that having a trained team and early access to an AED doubled the chances of survival for victims of cardiac arrest. Additional studies have shown that resuscitation that occurs within four minutes of the onset of sudden cardiac death greatly reduces the chances of long-term organ damage.  Local schools that offer CPR courses may offer courses in using AEDs, and Congress has made money available for the purchase and training of AEDs. 

Once the person has reached the hospital, they will often be put onto advanced life support, which will supply ventilation, stabilize blood pressure, control arrhythmias and restore blood flow to the organs. Depending on their circumstances, the person may require a ventilator to help them breathe, at least temporarily.

For patients in cardiac arrest due to ventricular fibrillation, lidocaine and amiodarone are commonly used drugs when an automatic external defibrillator is not able to shock the heart back into rhythm.

Researchers are also investigating methods to enhance survival and prevent brain damage after the onset of cardiac arrest. Rapid, mild cooling of the body (hypothermia) is one method being currently explored. Hypothermia has been used in some heart operations, sparing the brain from damage by temporarily reducing its oxygen requirements. Researchers have tested this approach in groups of cardiac arrest patients who stayed in a coma after being resuscitated. Compared to those not receiving the treatment, patients undergoing hypothermia had significantly higher rates of survival, with mild or no neurologic (brain) damage. 

Patients who survive cardiac arrest without irreversible damage to their central nervous systems will likely undergo extensive diagnostic and therapeutic testing, including cardiac catheterization and/or an electrophysiology study. If they have underlying heart disease, such as coronary artery disease, this will likely be aggressively managed with medications and lifestyle changes. In addition, many patients may have an implantable cardioverter defibrillator implanted during their hospitalization. This device monitors the heart rhythm and, in the case of a serious arrhythmia, delivers a shock that jolts the heart back into a normal rhythm. These devices can be combined with pacemakers.

Prevention efforts for cardiac arrest are either primary, in which physicians try to identify people who are at specific risk of sudden cardiac death, or secondary, in which the underlying heart disease that usually causes of cardiac arrest is addressed. To reduce their risk of heart disease and cardiac arrest, people are encouraged to take the following steps:

• Learn your family medical history. A patient’s family medical history can greatly increase (or decrease) the risk of the patient developing certain medical conditions that could lead to cardiac arrest or sudden cardiac death. In addition, studies have indicated that a family history of sudden cardiac death increases the risk for an individual.  Some patients prefer to develop their own medical family tree and bring it with them to their doctor appointment. A complete family tree traces the medical history of an individual (and his or her spouse, if applicable), through at least several generations.
  
  
• Eating a heart-healthy diet. Modern research has consistently supported the idea that the health of people’s bodies is largely determined by what they choose to eat. Certain vitamins and minerals have been shown to be helpful to heart health. However, certain fats and oils, such as saturated fat and tropical oils (palm and coconut oil), have been shown to be particularly harmful because they can speed up the development of coronary artery disease, atherosclerosis and obesity.
  
  
• Reducing cholesterol levels. A person’s total cholesterol level (which includes LDL cholesterol, HDL cholesterol and triglycerides) should be no more than 200 milligrams per deciliter and their cholesterol ratio should be no more than 5:1, or total cholesterol more than five times their HDL level. Key strategies for reducing levels of total cholesterol, LDL cholesterol and triglycerides are to eat a heart-healthy diet and exercise regularly. If these strategies do not reduce cholesterol levels, a physician may prescribe cholesterol-reducing drugs.
  
  
• Controlling homocysteine levels. Homocysteine is an amino acid that is produced as a byproduct of internal chemical reactions. High homocysteine levels have been linked to damage of the arteries, which may increase the risk of heart attack, stroke or other cardiovascular problems. Researchers are currently trying to determine whether high homocysteine levels are an actual cause of those conditions, or are simply associated with them for some other reason. The American Heart Association recommends testing homocysteine blood levels in patients with known risk factors for heart disease (e.g., a family history of heart disease). Homocysteine can be kept at moderate, healthy levels if the body has adequate levels of three important B-vitamins: vitamin B-6, vitamin B-12 and folic acid (the synthetic and more easily absorbed version of folate). Therefore people are encouraged to make sure they get enough B-vitamins every day.
  
  
• Exercising regularly. Exercise can be an excellent tool in the both prevention of heart disease and improving quality of life for heart patients. Physically, it can slow or even reverse the process of atherosclerosis, as well as lower blood pressure and reduce cholesterol levels. Emotionally, it can reduce levels of stress and depression.
  
  
• Controlling high blood pressure (hypertension). Individuals with high blood pressure are at greater risk of cardiovascular problems that could lead to cardiac arrest. Hypertension can be controlled through regular blood pressure monitoring and diet/medication therapies, under the care of a physician.
  
  
• Stress management. Stress can lead to high-risk practices such as overeating, smoking, high blood pressure and a lack of exercise. In addition, chronic stress may be a direct contributor to poor health because it produces increases in blood pressure that could become permanent.
  
  
• Quitting smoking (or not starting to smoke). Tobacco smoking is a major contributor to coronary artery disease, cardiac arrest and sudden cardiac death. A 1990 study by the Centers for Disease Control and Prevention (CDC) shows heart disease as the leading smoking-related cause of death in the United States among men and women. The CDC also suggests that the average smoker dies nearly seven years before a nonsmoker.
  
  
• Controlling diabetes. People with diabetes may be more likely to develop heart-related diseases that could lead to cardiac arrest. Preventative care is crucial to the overall health and heart function of diabetic patients.
  
  
• Controlling weight. Obesity and being overweight are major risk factors for a host of serious health conditions that could lead to cardiac arrest or sudden cardiac death. Some weight control methods include limiting fat in a patient’s diet, increasing activity levels, counseling, medication and surgical interventions.
  
  
• Controlling chronic depression. Depression has been linked with a higher risk of developing high blood pressure, heart disease and having a heart attack.

These strategies may help preserve health and prolong life. Even someone who already has heart disease or has had a heart attack can reduce the risk of further problems by making these lifestyle changes. In addition to these preventive techniques, treatments of underlying conditions that could trigger cardiac arrest include taking medications that help to control the heart’s rhythm (antiarrhythmics).

Also, minimally invasive techniques (e.g., cardiac catheterization) or surgery may be used. For example, people may have a surgery in which a device such as an artificial pacemaker or an implantable cardioverter defibrillator (ICD) is implanted in the chest to monitor and, if needed, correct the heart’s rhythm. A recent study showed that ICDs lowered the risk of death by 23 percent in patients with heart failure. An ICD monitors the heart and delivers an electrical charge when a dangerous arrhythmia is detected. Heart failure patients are at increased risk of cardiac arrest and sudden cardiac death. The device may be implanted for secondary prevention (patients who survived  cardiac death) or primary prevention (patients at risk of cardiac arrest such as those with cardiomyopathy, sustained ventricular tachycardia, syncope.)

Pacemakers are indicated to prevent cardiac arrest in patients with bradycardia and severe disease of the heart conductive system.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to cardiac arrest:

1. What caused my cardiac arrest?
   
   
2. How much damage did I suffer after my collapse?
   
   
3. What steps did my medical team take to save me?
   
   
4. Do I need a pacemaker or implantable cardioverter defibrillator?
   
   
5. What medications will I need to take?
   
   
6. What lifestyle changes do I need to make?
   
   
7. Is it possible to estimate my risk for another cardiac arrest?
   
   
8. What symptoms should I be aware of that might indicate another cardiac arrest is imminent?
   
   
9. Are there are dietary supplements I should take? Any I should avoid?
   
   
10. Can I exercise? Have sex?
    
    
11. How long will my recovery period be?
    
    
12. Is my family at increased risk for cardiac arrest? Is there any test we can take to determine who is at increased risk?