- Sudden cardiac death introduction
- How is sudden cardiac arrest different from a heart attack?
- What are the symptoms of sudden cardiac arrest?
- What causes sudden cardiac death?
- What are the risk factors of sudden cardiac arrest?
- Can sudden cardiac death be prevented?
- Can sudden cardiac death be treated?
- What do I do if I witness sudden cardiac arrest?
- Sudden cardiac death and athletes
- For more information
Sudden cardiac death introduction
Sudden cardiac death is an unexpected, sudden death caused by sudden cardiac arrest (loss of heart function). Causes and risk factors of sudden cardiac death include (not inclusive): abnormal heart rhythms (arrhythmias), previous heart attack, coronary artery disease, smoking, high cholesterol, Wolff-Parkinson-White Syndrome, ventricular tachycardia or ventricular fibrillation after a heart attack, congenital heart defects, history of fainting, and heart failure, obesity, diabetes, and drug abuse. Treatment of sudden cardiac arrest is an emergency, and action must be taken immediately.
Sudden cardiac death (SCD) is a sudden, unexpected death caused by loss of heart function (sudden cardiac arrest). It is the largest cause of natural death in the U.S., causing about 325,000 adult deaths in the United States each year. SCD is responsible for half of all heart disease deaths.
SCD occurs most frequently in adults in their mid-30s to mid-40s, and affects men twice as often as it does women. SCD is rare in children, affecting only 1 to 2 per 100,000 children each year.
How is Sudden Cardiac Arrest Different from a Heart Attack?
Sudden cardiac arrest is not a heart attack (myocardial infarction) but can occur during a heart attack. Heart attacks occur when there is a blockage in one or more of the arteries to the heart, preventing the heart from receiving enough oxygen-rich blood. If the oxygen in the blood cannot reach the heart muscle, the heart becomes damaged.
In contrast, sudden cardiac arrest occurs when the electrical system to the heart malfunctions and suddenly becomes very irregular. The heart beats dangerously fast. The ventricles may flutter or quiver (ventricular fibrillation), and blood is not delivered to the body. In the first few minutes, the greatest concern is that blood flow to the brain will be reduced so drastically that a person will lose consciousness. Death follows unless emergency treatment is begun immediately.
Emergency treatment includes cardiopulmonary resuscitation (CPR) and defibrillation. CPR is a manual technique using repetitive pressing to the chest and breathing into the person's airways that keeps enough oxygen and blood flowing to the brain until the normal heart rhythm is restored with an electric shock to the chest, a procedure called defibrillation. Emergency squads use portable defibrillators and frequently there are public access defibrillators (AEDs, ambulatory external defibrillators) in public locations that are intended to be available for use by citizens who observe cardiac arrest.
What are the Symptoms of Sudden Cardiac Arrest?
Some people may experience a racing heartbeat or they may feel dizzy, alerting them that a potentially dangerous heart rhythm problem has started. In over half of the cases, however, sudden cardiac arrest occurs without prior symptoms.
What Causes Sudden Cardiac Death?
Most sudden cardiac deaths are caused by abnormal heart rhythms called arrhythmias. The most common life-threatening arrhythmia is ventricular fibrillation, which is an erratic, disorganized firing of impulses from the ventricles (the heart's lower chambers). When this occurs, the heart is unable to pump blood and death will occur within minutes, if left untreated.
What are the Risk Factors of Sudden Cardiac Arrest?
There are many factors that can increase a person's risk of sudden cardiac arrest and sudden cardiac death, including the following:
- Previous heart attack with a large area of the heart damaged (75 percent of SCD cases are linked to a previous heart attack).
- A person's risk of SCD is higher during the first six months after a heart attack.
- Coronary artery disease (80 percent of SCD cases are linked with this disease).
- Risk factors for coronary artery disease include smoking, family history of cardiovascular disease and high cholesterol.
Other risk factors include:
- Ejection fraction of less than 40 percent, combined with ventricular tachycardia.
- Prior episode of sudden cardiac arrest.
- Family history of sudden cardiac arrest or SCD.
- Personal or family history of certain abnormal heart rhythms, including long or short QT syndrome,
Wolff-Parkinson-White syndrome, extremely low heart rates, or heart block.
- Ventricular tachycardia or ventricular fibrillation after a heart attack.
- History of congenital heart defects or blood vessel abnormalities.
- History of syncope (fainting episodes of unknown cause).
- Heart failure: a condition in which the heart's pumping power is weaker than normal. Patients with heart failure are 6 to 9 times more likely than the general population to experience ventricular arrhythmias that can lead to sudden cardiac arrest.
- Dilated cardiomyopathy (cause of SCD in about 10 percent of the cases): a decrease in the heart's ability to pump
- Hypertrophic cardiomyopathy: a thickened heart muscle that especially affects the ventricles.
- Significant changes in blood levels of potassium and magnesium (from using diuretics, for example), even if there is not underlying heart disease.
- Recreational drug abuse.
- Taking drugs that are "pro-arrhythmic" may increase the risk for life-threatening arrhythmias.
Can Sudden Cardiac Death Be Prevented?
If you have any of the above listed risk factors for SCD, it is important that you speak with your doctor about possible steps to reduce your risk.
Keeping regular follow-up appointments with your doctor, making certain lifestyle changes, taking medications as prescribed, and having interventional procedures or surgery (as recommended) are ways you can reduce your risk.
Follow-up Care with Your Doctor: Your doctor will tell you how often you need to have follow-up visits. To prevent future episodes of sudden cardiac arrest, your doctor will want to perform diagnostic tests to determine what caused the cardiac event. Tests may include electrocardiogram (ECG or EKG), ambulatory monitoring, echocardiogram, cardiac catheterization and electrophysiology studies.
Ejection Fraction (EF): EF is a measurement of the percentage of blood pumped out of the heart with each beat. EF can be measured in your doctor's office during an echocardiogram (echo) or during other tests such as a MUGA (multiple gated acquisition) scan, cardiac catheterization, nuclear stress test, or magnetic resonance imaging (MRI) scan of the heart. The EF of a healthy heart ranges from 55 to 65 percent. Your EF can go up and down, based on your heart condition and the effectiveness of the therapies that have been prescribed. If you have heart disease, it is important to have your EF measured initially, and then as needed, based on changes in your condition. Ask your doctor how often you should have your EF checked.
Reducing your risk factors: If you have coronary artery disease -- and even if you do not -- there are certain lifestyle changes you can make to reduce your risk of sudden cardiac arrest.
These lifestyle changes include:
- Quitting smoking
- Losing weight
- Exercising regularly
- Following a low-fat diet
- Managing diabetes
- Managing other health conditions including high blood pressure and cholesterol
If you have questions or are unsure how make these changes, talk to your doctor. Patients and families should know the signs and symptoms of coronary artery disease and the steps to take if symptoms occur.
Medications: To help reduce the risk of sudden cardiac arrest, doctors may prescribe medications to people who have had heart attacks or who have heart failure or arrhythmias such as irregular heart rhythms. These medications may include ACE inhibitors, beta blockers, calcium channel blockers, and other antiarrhythmics. For patients with high cholesterol and coronary artery disease, statin medications may be prescribed.
If medication is prescribed, your doctor will give you more specific instructions. It is important that you know the names of your medications and any directions that you need to follow when taking them. If you have any questions, be sure to ask your doctor or pharmacist.
Implantable cardioverter-defibrillator (ICD): For people whose risk factors put them at great risk for sudden cardiac death, an ICD may be inserted as a preventive treatment. An ICD is a small machine similar to a pacemaker that is designed to correct arrhythmias. It detects and then corrects a fast heart rate. The ICD constantly monitors the heart rhythm. When it detects a very fast or slow heart rhythm, it delivers energy (a small, but powerful shock) to the heart muscle to cause the heart to beat in a normal rhythm again. The ICD also records the data of each abnormal heartbeat, which can be viewed by the doctor through a third part of the system kept at the hospital.
The ICD may be used in patients who have survived sudden cardiac arrest and need their heart rhythms constantly monitored. It may also be combined with a pacemaker to treat other underlying irregular heart rhythms.
Interventional procedures or surgery: For patients with coronary artery disease, an interventional procedure such as angioplasty (blood vessel repair) or bypass surgery may be needed to improve blood flow to the heart muscle and reduce the risk of SCD. For patients with other conditions, such as hypertrophic cardiomyopathy or congenital heart defects, an interventional procedure or surgery may be needed to correct the problem. Other procedures may be used to treat abnormal heart rhythms, including electrical cardioversion and catheter ablation.
When a heart attack occurs in the left ventricle (left lower pumping chamber of the heart), a scar forms. The scarred tissue may increase the risk of ventricular tachycardia. The electrophysiologist (doctor specializing in electrical disorders of the heart) can determine the exact area causing the arrhythmia. The electrophysiologist, working with your surgeon, may combine ablation (the use of high-energy electrical energy to "disconnect" abnormal electrical pathways within the heart) with left ventricular reconstruction surgery (surgical removal of the infarcted or dead area of heart tissue).
Educate your family members: If you are at risk for SCD, talk to your family members so they understand your condition and the importance of seeking immediate care in the event of an emergency. Family members and friends of those at risk for SCD should know how to perform CPR.
Can Sudden Cardiac Death Be Treated?
Yes, sudden cardiac arrest can be treated and reversed, but emergency action must take place immediately. Survival can be as high as 90% if treatment is initiated within the first minutes after sudden cardiac arrest. The rate decreases by about 10% each minute longer it takes to initiate therapy. Those who survive have a good long-term outlook.
What Do I Do if I Witness Sudden Cardiac Arrest?
If you witness someone experiencing sudden cardiac arrest, dial 911 or your local emergency personnel immediately and initiate CPR. If done properly, CPR can save a person's life, as the procedure keeps blood and oxygen circulating through the body until help arrives.
If there is an AED available, the best chance of rescuing the person includes defibrillation with that device. The shorter the time until defibrillation, the greater the chance the person will survive. It is CPR plus defibrillation that saves a person.
After successful defibrillation, most people require hospital care to treat and prevent future cardiac problems.
Sudden cardiac death and athletes
SCD occurs rarely in athletes, but when it does happen, it often affects us with shock and disbelief.
Cause: Most cases of SCD are related to undetected cardiovascular disease. In the younger population, SCD is often due to congenital heart defects, while in older athletes (35 years and older), the cause is more often related to coronary artery disease.
Prevalence: SCD in athletes is rare, but media coverage often makes it seem like it is more prevalent. In the younger population, most SCD occurs while playing team sports. It occurs in about one in 100,000 to one in 300,000 athletes, and more often in males. In older athletes (35 years and older), SCD occurs more often while running or jogging, and in about one in 15,000 joggers and one in 50,000 marathon runners.
Screening: The American Heart Association recommends cardiovascular screening for high school and collegiate athletes and should include a complete and careful evaluation of the athlete's personal and family history and a physical exam. Screening should be repeated every two years, with a history obtained every year. Men aged 40 and older and women aged 50 and older should also have a thorough examination and an exercise stress test and receive education about cardiac risk factors and symptoms. If heart problems are identified or suspected, the individual should be referred to a cardiologist for further evaluation and treatment guidelines before participating in sports.
For More Information
Sudden Arrhythmia Death Syndromes Foundation
A nonprofit organization, established to help prevent sudden and unexpected cardiac death in children and young adults.
508 E South Temple Ste. 20,
Salt Lake City, UT 84102
Heart Rhythm Society
1400 K St., NW, Suite 500,
Washington D.C. 20005
CPR Information: For more information about CPR, please contact your local chapter of the American Red Cross or the American Heart Association. Or ask your doctor for more information.
Reviewed by The Cleveland Clinic Heart Center (2005).
SOURCE: The American Heart Association
Reviewed by David W. Stein, MD on December 01, 2006 and Edited by Tracy C. Shuman, MD on October 01, 2005
WebMD Medical Reference
Top Sudden Cardiac Death Related Articles
Congestive Heart Failure (CHF): Symptoms, Causes, Stages, TreatmentCongestive heart failure (CHF) refers to a condition in which the heart loses the ability to function properly. Heart disease, high blood pressure, diabetes, myocarditis, and cardiomyopathies are just a few potential causes of congestive heart failure. Signs and symptoms of congestive heart failure may include fatigue, breathlessness, palpitations, angina, and edema. Physical examination, patient history, blood tests, and imaging tests are used to diagnose congestive heart failure. Treatment of heart failure consists of lifestyle modification and taking medications to decrease fluid in the body and ease the strain on the heart. The prognosis of a patient with congestive heart failure depends on the stage of the heart failure and the overall condition of the individual.
Does a Dying Person Know They Are Dying?A conscious dying person can know if they are on the verge of dying. Some feel immense pain for hours before dying, while others die in seconds.
Echocardiogram (Echocardiography, Diagnostic Cardiac Ultrasound)Echocardiogram is a test using ultrasound to provide pictures of the heart's valves and chambers. There are several types of echocardiograms, for example, transthoracic echocardiogram, transesophageal echocardiogram (TEE), stress echocardiogram, dobutamine or adenosine/sestamibi stress echocardiogram, and and intravascular ultrasound.
Electrocardiogram (ECG or EKG)An electrocardiogram is known by the acronyms "ECG" or "EKG" more commonly used for this noninvasive procedure to record the electrical activity of the heart. An EKG generally is performed as part of a routine physical exam, part of a cardiac exercise stress test, or part of the evaluation of symptoms. Symptoms evaluated include palpitations, fainting, shortness of breath, dizziness, fainting, or chest pain.
Fainting (Syncope): Guide to Causes, Symptoms, Treatment and PreventionFainting, also referred to as blacking out, syncope, or temporary loss of consciousness has many causes. Often a person will have signs or symptoms prior to the fainting episode. Diagnosis and treatment depends upon the cause of the fainting or syncope episode.
Heart Detail PictureThe heart is composed of specialized cardiac muscle, and it is four-chambered, with a right atrium and ventricle, and an anatomically separate left atrium and ventricle. See a picture of Heart Detail and learn more about the health topic.
Cardiac Arrest: What You Should KnowCardiac arrest is a serious medical emergency that requires immediate medical care. Use this WebMD slideshow to know whether you are at risk for cardiac arrest and what you can do if it happens to a loved one.
CAD SlideshowWhat is heart disease (coronary artery disease)? Learn about the causes of heart disease, arrhythmias and myopathy. Symptoms of heart disease include chest pain and shortness of breath. Explore heart disease diagnosis, treatment, and prevention.
Heart Disease: Causes of a Heart AttackHeart disease prevention includes controlling risk factors like diet, exercise, and stress. Heart disease symptoms in women may differ from men. Use a heart disease risk calculator to determine your heart attack risk.
Arrhythmias (Abnormal Heart Rhythms): Types, Triggers, Warning Signs, and TreatmentHeart rhythm disorders vary from minor palpitations, premature atrial contractions (PACs), premature ventricular contractions (PVCs), sinus tachycardia, and sinus bradycardia, to abnormal heart rhythms such as tachycardia, ventricular fibrillation, ventricular flutter, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), Wolf-Parkinson-White syndrome, brachycardia, or heart blocks. Treatment is dependent upon the type of heart rhythm disorder.
What Is a Heart Transplant?Heart transplant consists of three operations: 1) harvesting the heart from the donor, 2) removing the recipient's damaged heart, and 3) the implantation of the donor heart. The selection and distribution of donor hearts is a careful process so that the hearts are distributed fairly. For the patient requiring a heart transplant, all other important organs in the body must be in good shape. The most common complication of heart transplant is organ rejection.
How the Heart WorksThe heart is a very important organ in the body. It is responsible for continuously pumping oxygen and nutrient-rich blood throughout your body to sustain life. It is a fist-sized muscle that beats (expands and contracts) 100,000 times per day, pumping a total of five or six quarts of blood each minute, or about 2,000 gallons per day.
How Long Can You Live With an Implanted Defibrillator?An implantable cardioverter-defibrillator (ICD) is an electronic device that tracks the heart rate and restores a normal rhythm, if required. It is first-line treatment for patients who are at risk of sudden cardiac death. ICD is useful in reducing the death rate amongst patients suffering from cardiac arrest, heart failure, reduced ejection fraction (reduced amount of blood pumped out of heart’s chambers), specific structural heart diseases. An ICD detects and corrects the abnormal rhythm of the heart.
Implantable Cardiac Defibrillators
An implantable cardiac defibrillator is a device that is inserted into the chest to prevent sudden death from an irregular heartbeat. If the heart develops a life-threatening tachycardia (rapid heart rate), the device administers an electric shock to restore normal rhythm. Cell phones, MRI scanners, metal detectors, and certain heavy-duty electrical powered equipment may interfere with an implantable cardiac defibrillator.
Cardiac Arrest QuizTake the Sudden Cardiac Arrest Quiz. Learning about this potentially deadly condition may save a life.