A new risk score brings doctors closer to predicting the previously unpredictable: Who is most likely to suffer sudden cardiac arrest.

Sudden cardiac arrest, an electrical disturbance in the heart rhythm that causes the heart to stop beating, can potentially be prevented—if there is a way to determine who is likely to have one and get them the appropriate medical interventions in time. Today more than 90% of people who experience a cardiac arrest die.

"For most people who have a sudden cardiac arrest, it is too late for them by the time 911 is called," said the study's senior author, Dr. Sumeet Chugh, director of the Heart Rhythm Center at the Cedars-Sinai Heart Institute. "Because so few survive, it's crucial for us to predict which patients are most vulnerable. This new risk score gives us a better idea of who is most likely to have cardiac arrest. Best of all, it is broadly accessible. It uses widely available and very inexpensive technology."

The new risk score from Dr. Chugh and his team is based on readings from a 12-lead electrocardiogram (EKG) test—the oldest and least expensive cardiac test available. The score is calculated using multiple pieces of data from EKG readings, such as heart rate, the thickening of the heart walls in the left ventricle, and four specific measures of how the heart muscle undergoes electrical stimulation and relaxation.

Patients are scored on a scale of 0 to 6. Patients scored at 4 or above have as much as 20 times the increased risk for sudden cardiac arrest as patients with lower scores.

Patients determined to be at high risk for sudden cardiac arrest can be preemptively treated to help prevent it.

More than 350,000 out-of-hospital cardiac arrests occur annually in the US. In conversation, people often use "sudden cardiac arrest" and "heart attack" interchangeably—but the conditions are different. A sudden cardiac arrest is an electrical disturbance in the heart rhythm that causes the heart to stop beating, and usually causes death immediately. A heart attack is caused when one of the major arteries leading to the heart becomes clogged, usually with plaque, disrupting the flow of blood to the heart muscle.

Because sudden cardiac death is a major public health problem, finding a better way to identify who is at high risk has long been a priority for the medical community.

"This new risk score has the potential to provide clinicians with a user-friendly, inexpensive, data-driven tool for determining which of their patients could benefit from interventions to prevent sudden cardiac arrest," Dr. Chugh says.

The findings, published today in European Heart Journal, came out of a larger research enterprise called the Oregon Sudden Unexpected Death Study, an ongoing, comprehensive assessment of all sudden cardiac arrests in the Portland, Oregon metropolitan area, home to 1 million people. The study, founded and led by Dr. Chugh, has been underway for more than 15 years. Data collected from it provides Dr. Chugh and his team with unique, community-based information to mine for answers to what causes sudden cardiac arrest.

The study is a good step forward for creating a better means of predicting who is likely to have a cardiac arrest, and is ready for more clinical study, says Dr. Chugh.

The National Heart, Lung, and Blood Institute funded the study (grant numbers R01HL122492 and R01HL126938 to Sumeet Chugh, MD).