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Unless it's treated quickly, sudden cardiac arrest—when the heart stops functioning properly—is often fatal. But hands-only cardiopulmonary resuscitation (CPR), if begun immediately, can double or triple the chances of survival. That's why it is so important to know these red flags.

Learn more about your heart and how to keep it healthy. Start by taking our heart rhythm quiz.

Reviewed 8/21/2025

Sources

• American Heart Association. "CPR is Key to Survival of Sudden Cardiac Arrest." https://www.heart.org/en/news/2018/07/12/cpr-is-key-to-survival-of-sudden-cardiac-arrest.
• American Heart Association. "Emergency Treatment of Sudden Cardiac Arrest." https://www.heart.org/en/health-topics/cardiac-arrest/emergency-treatment-of-cardiac-arrest.
• American Heart Association. "Hands-Only CPR Fact Sheet." https://cpr.heart.org/-/media/CPR-Files/Courses-and-Kits/Hands-Only-CPR/2024-HOCPR-Resources/DS19398_ECC_CPRWeek_Fact_Flyer_2024_PDF.pdf.
• American Red Cross. "Hands-only CPR." https://www.redcross.org/take-a-class/cpr/performing-cpr/hands-only-cpr.