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Site FeedbackSudden Cardiac Death
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Sudden Cardiac Arrest (SCA) is the leading cause of death in the United States, followed by heart attack and cancer. According to the American Heart Association, it strikes without warning and kills more than 325,000 people each year.
Implant Device Helps Prevent Sudden Cardiac Death
Often confused with a heart attack, SCA occurs when the heart's electrical system malfunctions, causing the heart to beat in a fast, dangerous rhythm and then stop beating altogether. This is also known as cardiac arrest. To differentiate, a heart attack occurs when a blockage in a blood vessel interrupts the flow of blood to the heart, causing the heart muscle to die.
"We hear a lot about cancer, HIV, and other diseases, but there is no other disease responsible for so many deaths each year as SCA," says Steven Kang, M.D., cardiac electrophysiologist with John Muir Medical Center's Walnut Creek and Concord campuses.
Know Your "EF"
People considered at risk for sudden cardiac arrest are those with a weakened heart muscle, and are also referred to as having a low "ejection fraction," or EF. An ejection fraction is a measurement of how much blood is pumped by the ventricles with each heartbeat. A healthy heart pumps 55 percent or more of its blood with each beat, but those people with an ejection fraction lower than 40 percent are at particular risk. Most cases of low ejection fraction result from a major heart attack that is associated with coronary artery disease (a condition in which the arteries that supply blood to the heart are narrowed or blocked). Other cases of low ejection fraction can be caused by a viral infection or through genetic predisposition.
When the severely abnormal heart rhythm, or arrhythmia, occurs, it can cause the heart to stop beating and a loss of blood flow to the brain. In cardiac arrest, this arrhythmia is known as ventricular fibrillation (VF). Without blood flow to the brain, a person can lose consciousness in seconds. Emergency response has only four to six minutes to check breathing, pulse, and perform CPR before damage or death occurs. At this point, the heart's electrical system must be "restarted" through the use of a defibrillator in order to save the person's life. Portable defibrillators are carried by most emergency medical services, and can even be found on airplanes.
However, despite the increase in availability of portable defibrillators, nine out of 10 victims die before reaching the hospital.
Implant Allows Faster Response For SCA Prevention
There is a better way to respond in time after VF occurs. Instead of chancing the small window of time to react to VF, doctors are taking a more proactive approach for those at risk for SCA through the use of an implantable cardioverter defibrillator (ICD). Similar in size to a pacemaker, this small defibrillator is placed beneath the skin near the collarbone and monitors every heartbeat for dangerous heart rhythms. If one is detected, the defibrillator delivers the same life-saving shock as a portable defibrillator found in an Emergency Department. Studies have shown that ICDs reduced mortality rates for those in the high risk group.
"An ICD provides an assurance of protection for our patients that in the event of VF, the implant will respond and save their lives," says Dr. Kang. "We believe as the population continues getting older, the number of patients who can benefit from an ICD will increase."
"A defibrillator is the only tool available to restore a regular rhythm to the heart once VF occurs," says Carleton T. Nibley, M.D., cardiac electrophysiologist on staff at John Muir Medical Center's Walnut Creek and Concord campuses. "Education at every level is still a challenge," Dr. Nibley says. "Ongoing effort to raise awareness to local doctors and the public, and getting those potentially at risk for SCA to ask their doctors about further evaluation is essential to reducing SCA mortality rates," he adds. Drs. Nibley and Kang say that John Muir Medical Center's Walnut Creek and Concord campuses perform about 250 ICD operations each year.
People who are determined to be at risk for SCA may be sent by their doctor to a cardiac electrophysiologist for further testing to see if an ICD is appropriate for them.
Sudden Cardiac Arrest Can Be Prevented
Making significant lifestyle changes are imperative to reducing the risk of sudden cardiac arrest or other heart conditions, according to Dr. Nibley. This includes exercising regularly, eating foods that are healthy, maintaining a reasonable weight and not smoking. Treating and monitoring other diseases and conditions that can lead to heart problems, such as high blood pressure, high cholesterol and diabetes, is also important. "People must increase their awareness and be educated on the details of their own situation," says Dr. Nibley, adding that people who are concerned that they may be in one of the high risk categories should ask their doctor or cardiologist about getting further testing.
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