Clinical studies indicate ejection fraction is the number one predictor of the risk of sudden cardiac death. An online quiz conducted by the Society showed that fewer than half of people self-identified as survivors of myocardial infarction could estimate their ejection fraction or level of sudden death risk.

"Sudden cardiac death is devastating because it strikes like a bolt out of the blue, even in apparently healthy people who have no known heart disease," said Eric Prystowsky, M.D., president of the Society. "We now know, however, that most victims of cardiac arrest do have underlying disease or other risk factors, although they may not be aware of it. We also have the tools to identify patients at risk for sudden cardiac death and can take steps to prevent it."

A total of 160 people completed the online quiz, although not every person answered each question. Nearly 55 percent of respondents (80 of 146) did not know their ejection fraction. Of those who did, almost half reported their ejection fraction as 35 percent or lower against the norm of 55 percent or higher. Patients with an ejection fraction of 40 percent or lower should have additional testing of their cardiac rhythm.

In addition, more than one third of respondents (52 of 146) did not know if their myocardial infarction had affected cardiac pumping ability. In addition, 23 percent (33 of 146) had never been monitored for cardiac rhythm or did not know if they had such testing. Nearly half (44 percent, or 65 of 148 respondents) had not been tested or did not know if they had been tested to determine risk for sudden cardiac death.

"These results highlight the importance of informing the public about the heart's electrical system and its relationship to heart rhythm disorders and sudden cardiac death. Most people know their blood pressure and their cholesterol level. If heart attack survivors knew one more number, their ejection fraction, thousands of lives could be saved. If people are tested and found to be at high risk, we can treat them to prevent sudden cardiac death," said Dr. Prystowsky.

Those who are at high risk of sudden cardiac death may be candidates for an implantable cardioverter defibrillator, which would automatically monitor rhythm to detect and correct dysrhythmias. Recent clinical studies conducted with infarction survivors who had an ejection fraction of 35 percent or lower showed that survival rates were significantly greater for those with implantable cardioverter defibrillators than for those without the devices.