|
 | |||
  |
||||
Site FeedbackSudden Cardiac Death
Suggested Links:
Definition
Sudden cardiac death (SCD) is defined by an abrupt change in the heart's rhythm which, if untreated, results in death within minutes. It is the leading cause of death in the United States, claiming more than 400,000 lives each year. SCD occurs without warning, usually in individuals with pre-existing heart disease.
To learn more about whether you or someone you know is at risk from sudden cardiac death, click here to use our Risk Factor Assessment form.
Description
Sudden cardiac death occurs when the heart's electrical system malfunctions. It is not synonymous with heart attack (also known as a myocardial infarction) which occurs when a blockage in a coronary blood vessel interrupts the flow of blood to the heart, causing damage to the heart muscle. Although many cases of SCD are complications of a heart attack, not all heart attacks result in SCD.
The most common cause of cardiac arrest is a heart rhythm disorder or arrhythmia called ventricular fibrillation (VF). In cases of VF, the electrical heart's electrical signals abruptly change, becoming rapid and chaotic. This causes the main pumping chambers of the heart, the ventricles, to quiver (fibrillate) and cease contracting. Blood flow to the brain is interrupted, and loss of consciousness occurs within seconds. Unless an emergency shock is immediately delivered to the heart to restore its regular rhythm, death occurs within minutes. It is estimated that more than 70% of ventricular fibrillation victims die before reaching the hospital.
The 3 most important risk factors for SCD are:
- A previous heart attack:75% of the people who suffer SCD show signs of a previous heart attack.
- Coronary artery disease: 80% of SCD victims have evidence for coronary artery disease, a condition in which the arteries that supply blood to the heart are narrowed or blocked with cholesterol deposits.
- Reduced left ventricular ejection fraction (EF): The ejection fraction is a measurement of how much blood is pumped by the left ventricle, the main pumping chamber of the heart, with each heart beat. A healthy left ventricle pumps 55% or more of its blood with each beat. People at highest risk for SCD have ejection fractions of less than 35%.
There are several tests to determine if you are at risk for sudden cardiac death:
Echocardiogram: Ultrasound (sound wave) imaging of the heart can measure the pumping function of the heart (ejection fraction). People with a measured ejection fraction of less than 35% are at greatest risk for sudden cardiac death.
Electrocardiogram (EKG): A recording of the heart's rate and rhythm. Disturbances in the heart's electrical conduction and evidence for heart muscle damage can often be detected by EKG. Significant abnormalities and other specific electrical patterns are sometimes correlated with increased risk for SCD.
Signal Averaged Electrocardiogram: A modified EKG that analyzes several hundred heart beats to see if there are areas of abnormal conduction which could lead to the development of SCD.
T-Wave Alternans Study: A modified treadmill study performed with highly sensitive skin electrodes that can detect microvoltage oscillations in heart electrical currents that can indicate increased risk for SCD.
Electrophysiology Study (EP Study): An invasive procedure that involves inserting specialized flexible catheters into the heart, and recording the heart's response to electrical stimulation or pacing. If abnormal heart rhythms are observed or inducible, then an increased risk for SCD may exist.
Prevention: Sudden Cardiac Death Can Be Prevented
There are a number of things one can do to decrease the risk of sudden cardiac death. Most importantly, a "heart healthy" lifestyle can help reduce the likelihood of acquiring coronary artery blockages or damaging the heart. This includes regular exercise, smoking avoidance, eating healthful foods, and maintaining a reasonable weight. Aggressive treatment of other diseases and conditions that contribute to heart problems, such as high blood pressure, elevated cholesterol levels, and diabetes mellitus, is also important in preventing heart disease and reducing the likelihood of SCD.
If your heart has been damaged and you have developed a reduced ejection fraction (EF), your doctor may recommend that you visit a heart rhythm specialist or cardiac electrophysiologist. Your heart rhythm specialist may recommend that you undergo surgical placement of an implantable cardioverter defibrillator (ICD).
The ICD is typically placed beneath the skin and soft tissues near the collarbone. The device is attached to the heart via pacing leads that are inserted into the vein beneath the collarbone. ICD devices continuously monitor the heart's rhythm. If a life-threatening arrhythmia occurs, the ICD will automatically and immediately deliver a life-saving internal shock to restore normal heart beating.
In several scientific studies, patients at risk for SCD who receive an implantable cardioverter defibrillator have a reduced risk of death from cardiac arrhythmia.
During your next visit, talk with your doctor about your risk for SCD.