New Smartwatch Algorithm for Detecting Sudden Cardiac Arrest

Scientific News

Somani S, Rogers AJ. Just in time: detecting cardiac arrest with smartwatch technology. Lancet Digit Health. 2024 Mar;6(3):e148-e149


Sudden cardiac death is a major cause of cardiovascular mortality, often triggered by sudden cardiac arrest (SCA). Early detection and rapid intervention are critical for survival. A groundbreaking smartwatch algorithm has been developed to detect SCA with high sensitivity and specificity, potentially saving lives by providing early warnings to high-risk individuals.

Understanding Sudden Cardiac Arrest

Sudden cardiac arrest is a condition where the heart suddenly stops beating, leading to a loss of blood flow to the brain and other vital organs. It differs from a heart attack, which is caused by a blockage that stops blood flow to the heart. SCA can be fatal if not treated within minutes. Each minute without defibrillation reduces survival chances by approximately 10-18%.

The Role of Wearable Technology

Recent advancements in wearable technology have enabled the development of algorithms that can monitor vital signs in real time. Smartwatches equipped with photoplethysmography (PPG) and accelerometry sensors can now detect abnormalities in heart rhythms, including those indicative of SCA. This innovation leverages the constant, unobtrusive monitoring capabilities of wearables to provide timely alerts (NIH).

How the Algorithm Works

The new algorithm operates by analyzing data from the smartwatch’s PPG and accelerometry sensors. These sensors measure blood flow and movement, respectively. The algorithm detects signs of circulatory arrest by identifying low-peripheral blood flow states, a hallmark of SCA. It has demonstrated a sensitivity of 98% and a specificity of 99.9% in detecting circulatory arrest in clinical settings.

Advantages of Smartwatch-Based Detection

  1. Early Detection: The algorithm enables early detection of SCA, providing a critical time window for intervention.
  2. Non-Invasive Monitoring: Smartwatches offer a non-invasive method to continuously monitor heart activity.
  3. Accessibility: Wearable technology is widely accessible and can be worn by individuals at high risk of SCA, including those without implanted defibrillators.
  4. Detection of Pulseless Electrical Activity (PEA): The algorithm can detect PEA, a condition where electrical activity is present but no pulse is generated, which is not typically identified by defibrillators.

Challenges and Considerations

While promising, the implementation of this technology faces several challenges:

  • Calibration: Careful calibration is needed to minimize false positives, which can cause unnecessary alarm and psychological stress.
  • Real-World Validation: Further research is required to validate the algorithm’s effectiveness in real-world settings. Controlled environments used in initial studies may not reflect everyday scenarios accurately.
  • Integration with Emergency Response Systems: The integration of smartwatch alerts with existing emergency response systems can enhance the effectiveness of interventions.

Future Research Directions

To optimize the use of this technology, future research should focus on:

  • Broad Clinical Trials: Conducting large-scale clinical trials to test the algorithm across diverse populations and real-world conditions.
  • Improving Specificity: Refining the algorithm to balance sensitivity and specificity, ensuring reliable alerts while minimizing false positives.
  • Exploring Complementary Technologies: Investigating the integration of other detection methods, such as smart speakers for agonal breathing detection or surveillance cameras for fall detection, to create a comprehensive emergency response system.


The development of a smartwatch algorithm for detecting sudden cardiac arrest represents a significant advancement in digital health technology. By enabling early detection and intervention, this innovation has the potential to save lives and improve outcomes for individuals at high risk of SCA. Ongoing research and development will be crucial in addressing current limitations and enhancing the algorithm’s reliability and usability in real-world applications.

For those interested in the latest advancements in wearable technology and cardiac health, keeping abreast of developments in this field will be essential. The promise of wearable technology in healthcare continues to grow, bringing us closer to a future where timely intervention for sudden cardiac arrest is more accessible and effective.

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