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Arresting Sudden Cardiac Death

Reasons, Risks and Response to a Common Killer

heart time bombSometimes nightmares aren't just the stuff of dreams. Sudden cardiac death (SCD) is a frightening reality, often occurring without prior history of cardiovascular disease.

In Southeast Asian countries, such as the Philippines and Thailand, SCD is so common that it carries the name bangungot, a Filipino word meaning "nightmare," as this condition is notorious for claiming lives during periods of sleep. Frequently striking middle-aged Southeast Asian males, these deaths are caused by Brugada syndrome, an inherited heart rhythm disorder emanating from the lower right chamber of the heart.

A non-Asian ethnic heritage will not keep you safe from nightmares, however. While Brugada syndrome is prevalent and well-studied in the Southeast Asian population, it also affects people worldwide. And Brugada syndrome is just one of many heart conditions that can lead to sudden death, according to Alfred E. Buxton, MD, a cardiac electrophysiologist at the CardioVascular Institute (CVI) at Beth Israel Deaconess Medical Center.

Common Killer

Alfred E. Buxton, MD

"Sudden cardiac death is the single most common killer of Americans and has been for years," says Buxton. "In fact, 50 percent of all deaths in people with heart disease occur suddenly and unexpectedly. And, when we consider that heart disease causes more deaths than all other medical conditions combined, that adds up to a significant public health problem."

You may be surprised to know that SCD claims 1,000 U.S. lives every day. Sudden cardiac death occurs most frequently in adults in their early 60s and affects men twice as often as it does women.

"For half of SCD victims, sudden death is actually the first manifestation of heart disease and occurs in people who have had no prior symptoms," Buxton explains.

What Causes the Heart to Halt?

Sudden cardiac death occurs when the electrical pulse that drives the heart to beat at a steady rate suddenly malfunctions, disrupting the heart's normal rhythm, causing it to beat at a dangerously rapid pace.

The heart's ventricles may quiver uselessly, and the heart is no longer able to pump blood. Within a few minutes, the person loses consciousness because blood can't flow to the brain. Without immediate medical intervention, death can occur within minutes.

Sudden cardiac death is usually caused by cardiovascular disease, including the following conditions:

  • Coronary artery disease - build-up of plaque inside the coronary arteries
  • Ventricular fibrillation or tachycardia - severely abnormal heart rhythms that prevent the heart from pumping effectively
  • Congestive heart failure - inability of a weakened heart to pump enough blood
  • Cardiomyopathy - a heart muscle that is too thick or rigid to pump properly
The Cardiac Conduction System

Researchers also know that a history of previous heart attack increases the likelihood of SCD. A heart attack (in which blood flow is partially blocked, but not enough to stop the heart) puts an individual at risk for SCD, especially within the first six months after having experienced one.

In addition, genetic defects cause about 25 to 30 percent of sudden cardiac death cases.

Symptoms of Sudden Cardiac Death

Most events occur without any warning, while a minority of patients experience crushing chest pain or other symptoms such as general discomfort, shortness of breath, or lightheadedness.

Unfortunately, in most cases there are few symptoms preceding cardiac arrest, and very little time to take life-saving actions.

Preventive Measures

Buxton recommends that anyone over age 40 undergo an EKG, but it's especially important to have one if there's a history of heart disease or heart rhythm disorders in the family, or if a family member died suddenly at a young age.

In patients with coronary artery disease, preventive measures to reduce the risk of SCD focus on addressing risk factors through lifestyle changes or the use of medication.

Other risk factors include:

  • Smoking
  • High blood pressure
  • High cholesterol
  • Obesity
  • Diabetes
  • Sedentary lifestyle
  • Age - the risk of sudden cardiac arrest increases with age; after age 45 for men and age 55 for women
  • Gender - men are more likely to suffer sudden cardiac arrest
  • Using illegal drugs, including cocaine or amphetamines
  • Lightning strike or another electrical shock
  • Immersion in cold water

Treating an (Almost) Untreatable Condition

Because sudden cardiac death is sudden, it can be difficult to treat. In most cases, SCD cannot be predicted, and while preventive measures can be taken, there is no way to know if SCD will strike until it may be too late.

Researchers are making progress treating sudden cardiac arrest and reducing the probability of death in those first few moments after it strikes.

Cooling the body down after the heartbeat is restored can help reduce the risk of brain damage incurred by deprivation of oxygen. One study showed that 56 percent of the 140 patients who experienced sudden cardiac arrest lived to be discharged from the hospital after receiving induced hypothermia at the hospital. This is marked improvement from the 10 percent national average of patients who survive sudden cardiac arrest.

Hiding in the shadows and striking without warning, sudden cardiac death is truly the thing of nightmares. Researchers at BIDMC and beyond are hard at work to keep sudden cardiac death at bay, studying the genome sequence to pinpoint mutations that can lead to more accurate treatment recommendations and developing treatments that reduce the damage caused by sudden cardiac arrest.

Above content provided by the CardioVascular Institute at Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Posted April 2012