Sudden Cardiac Death

Each day in the United States, more than 930 lives are lost to sudden cardiac death (SCD). Every 90 seconds, this insidious killer claims another victim. Sudden cardiac death is the leading cause of natural deaths in the United States, taking more than 335,000 lives each year, more than are lost to lung cancer, breast cancer and AIDS combined. Yet, because there are few warning signs or symptoms to identify people at risk, and since SCD is by definition fatal, there are few survivors to spread the word about this devastating killer. Until SCD hits close to home, most people usually are unaware of its prevalence and the danger that it poses, even to young, seemingly healthy people. It often strikes adults in their mid-30s to mid-40s, though it can strike teenagers as well as senior citizens.

What is sudden cardiac death?
What causes sudden cardiac death?
Can sudden cardiac arrest be reversed?
What are the tests that predict risk?
Can anything be done to prevent SCD?
Are athletes at risk for SCD?

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What is sudden cardiac death?

Sudden cardiac death, also called sudden cardiac arrest (SCA), is a term used to describe a situation in which the heart stops working, abruptly and without warning, so no blood can be pumped to the rest of the body. It is responsible for more than half of all heart disease deaths in this country. And, while overall death rates for heart disease are decreasing, those from sudden cardiac death continue to increase. Sudden cardiac death is not a heart attack, which occurs when a blockage in a blood vessel interrupts the flow of oxygen-rich blood to the heart, causing heart muscle to die.

Sudden cardiac death occurs when the heart's electrical system malfunctions. The most common cause of SCD is a heart rhythm disorder, or arrhythmia, called ventricular fibrillation (VF) (a quivering of the heart's lower chambers) or ventricular tachycardia (extremely rapid but ineffective beating of the heart's lower chambers).

This irregular heart rhythm causes the heart suddenly to stop pumping blood to the rest of the body. If blood does not flow to the brain, it becomes starved of oxygen, and the person loses consciousness in a matter of seconds.

Death can occur within ten minutes unless CPR is administered and an emergency shock is delivered to the heart with a defibrillator to restore its normal rhythm. Survival is directly linked to the amount of time between the onset of sudden cardiac arrest and defibrillation. A victim's chances of survival are reduced by seven to ten percent with every minute of delay until defibrillation. The VF sudden cardiac arrest survival rate is only two to five per cent if defibrillation is provided more than twelve minutes after collapse. It is estimated that about 95% of sudden cardiac arrest victims die before reaching the hospital.

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What causes sudden cardiac death?

SCD often occurs in active, seemingly fit and healthy people with no known heart disease or other health problems. But in reality sudden cardiac death is not an arbitrary incident.

Most victims have heart disease or other health problems, although they may not know it and may have had no symptoms until their heart suddenly stops pumping blood to the rest of their body. There can be numerous contributors to sudden cardiac arrest, but some of the more prevalent ones are:

A previous heart attack; 75% of the people who die of SCD show signs of a previous heart attack.
Coronary artery disease (CAD); 80% of SCD's victims have signs of coronary artery disease. This is a condition in which the arteries that supply blood to the heart are narrowed or blocked.
When SCD occurs in young adults, other heart abnormalities, including congenital ones, can be the cause. Adrenaline released during intense physical or athletic activity often acts as a trigger when these abnormalities are present.
Under certain conditions, various heart medications and other drugs - as well as the use of some illegal drugs - can lead to abnormal heart rhythms that can cause SCD.

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Can sudden cardiac arrest be reversed?

Cardiac arrest is reversible if it is treated within a few minutes with an electric shock to the heart to restore a normal heartbeat. This process is called defibrillation. A victim's chances of survival are reduced by seven to ten percent with every minute that passes without defibrillation. The American Heart Association supports the "chain of survival" to rescue people who suffer a sudden cardiac arrest. The chain of survival consists of:

Early access to medical care. If someone becomes unconscious, call 9-1-1 immediately.
Begin chest compressions IMMEDIATELY/ Early CPR. Learn CPR in your community.
Early defibrillation. Many communities have defibrillators in public places. Contact University of Arizona Sarver Heart Center or your local chapter of the American Heart Association to find out more.
Early advanced care. Prompt medical attention saves lives. Remember: When sudden cardiac arrest strikes, EVERY SECOND COUNTS.

What are the signs and symptoms of sudden cardiac death? As its name implies, sudden cardiac death strikes suddenly and without warning. In many cases, the victim had no previous indication that there was a problem. However, if you or a loved one experiences any of the following symptoms, consult a doctor without delay to evaluate the risk for SCD:

An abnormal heart rate or rhythm (arrhythmia) of unknown cause.
An unusually rapid heart rate (tachycardia) that comes and goes, even when the person is at rest.
Episodes of fainting (syncope) of unknown cause.
A low ejection fraction (EF). The ejection fraction is a measurement of how much blood is pumped by the ventricles with each heartbeat. A simple test can determine the ejection fraction.

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What are the tests that predict risk?

There are many tests your doctor may perform to evaluate your risk for SCD. Among these are:

Electrocardiogram (EKG)
Echocardiogram
Holter monitor
Event recorder
Electrophysiology study (EPS)

What are the treatments for survivors?

If an episode of sudden cardiac arrest was due to ventricular tachycardia or ventricular fibrillation, survivors are at risk for another arrest, especially if they have underlying heart disease. Survivors of sudden cardiac arrest must have all causes corrected to prevent future episodes.

Depending on the underlying cause of sudden cardiac arrest, possible tests and treatments include:

Cardiac catheterization
Coronary artery bypass surgery
Balloon angioplasty or PTCA antiarrhythmic
Medication
Implantable cardioverter defibrillator (ICD)
Implantable pacemaker
Heart Transplant

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Can anything be done to prevent SCD?

Living a heart-healthy life can help reduce the chances of dying from sudden cardiac arrest or other heart conditions. This includes eating a healthy diet, exercising regularly, maintaining a reasonable weight and avoiding smoking. It also is important to monitor and treat diseases and conditions that can contribute to heart problems, including high blood pressure, high cholesterol and diabetes. For some people, preventing sudden cardiac death means controlling the abnormal heart rhythms that may trigger ventricular fibrillation.

Treatment can include medication, an implantable cardioverter defibrillator or other medical interventions. Consult with your doctor to determine the treatment plan that is best for you.

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Are athletes at risk for SCD?

Generally, athletes are in peak physical form. Yet, even well conditioned athletes may be at risk for SCD. The earliest documented case of sudden cardiac death occurred in 490 B.C., when Pheidippides, a Greek soldier and conditioned runner, ran from Marathon to Athens to announce the military victory over Persia, only to deliver his message then collapse and die. More recently, SCD has claimed the lives of some high-profile athletes. In 1993, professional basketball player Reggie Lewis collapsed and died during an off-season practice. He was only 27. Olympic gold-medal ice skater Sergei Grinkov died from SCD at the age of 28. Steve Gootter, a fit and healthy, accomplished amateur athlete, was stricken by sudden cardiac death at the age of 42, with no previous warning signs of any health problem.

Sudden cardiac death in professional athletes is still relatively rare. Yet, health experts worry that "weekend warriors" may unknowingly be at risk. Researchers estimate that sudden cardiac death strikes one out of every 15,000 to 18,000 joggers or vigorous exercisers age 35 and older. Most of these people are unaware that they are at risk for the condition. Doctors urge health screenings for all marathon runners and those who regularly participate in vigorous exercise. Younger runners may have congenital heart problems that put them at risk for sudden cardiac death. Runners over 35 may have early signs of coronary artery disease. Often, they are unaware of their risk because they have no symptoms. Before launching any exercise or training program, always consult your doctor and get an evaluation of your risk for SCD and other heart disease.

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