ECG & Atrial Fibrillation Detection

FDA-cleared Apple Watch ECG and AF burden tracking

What are ECG and Atrial Fibrillation?

  • ECG (Electrocardiogram) - Recording of the heart's electrical activity. Apple Watch provides single-lead ECG recordings.
  • Atrial Fibrillation (AF) - Irregular heart rhythm where the atria quiver instead of contracting normally. Can increase stroke risk.

Why ECG and AF Detection Matter

FDA-cleared Apple Watch ECG can detect atrial fibrillation with high accuracy. The Apple Heart Study (NEJM 2019) showed that smartwatch irregular-pulse alerts can identify AF (NEJM).

  • AF increases stroke risk - 5x higher risk of ischemic stroke
  • Often asymptomatic - Many people with AF have no symptoms
  • High detection accuracy - Meta-analyses report ~95% sensitivity and 95% specificity for Apple Watch ECG AF classification (JACC Advances 2025)
  • Early detection enables treatment - Anticoagulation and rhythm management reduce stroke risk

⚠️ Cardio Analytics does not diagnose AF. It displays Apple Watch ECG classifications and AF episodes for you and your clinician to review. Always consult a qualified clinician for medical diagnosis.

Apple Watch ECG Classifications

Apple Watch ECG provides these classifications (Apple Docs):

Sinus Rhythm

Normal, regular heart rhythm. No action needed.

Atrial Fibrillation

Irregular rhythm detected. Consult clinician for evaluation.

Low/High Heart Rate

Heart rate outside 50-150 bpm range during ECG. May need follow-up.

Inconclusive

Unable to classify. Repeat ECG or consult clinician if symptoms present.

AF Burden Tracking

Apple Watch (watchOS 9+) can estimate AF Burden - the percentage of time you're in atrial fibrillation over a week.

  • Calculated from irregular rhythm notifications and ECG recordings
  • Useful for monitoring AF progression - Is AF becoming more frequent?
  • Helps guide treatment decisions - Higher AF burden may indicate need for rhythm control

📊 Share with your clinician: AF burden data helps cardiologists assess arrhythmia severity and treatment effectiveness.

How Cardio Analytics Uses ECG and AF Data

  • Stores ECG classifications - All Apple Watch ECG recordings with timestamps
  • Tracks AF episodes - Count and timing of AF detections
  • Summarizes AF burden - Percentage of time in AF over days/weeks
  • Surfaces episodes for clinical follow-up - Export AF history in PDF/CSV for your cardiologist
  • Medication correlations - Track relationship between antiarrhythmic drugs and AF episodes

HealthKit Data Types

Cardio Analytics reads ECG and AF data from Apple HealthKit using these identifiers:

  • electrocardiogramType - ECG recordings with HKElectrocardiogram.Classification including .atrialFibrillation (Apple Docs)
  • atrialFibrillationBurden - AF burden percentage (where available, watchOS 9+) (Apple Docs)

Learn More About HealthKit Integration

Scientific References

  1. Perez MV, et al. Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation. NEJM. 2019. https://www.nejm.org/doi/full/10.1056/NEJMoa1901183
  2. Barrera N, et al. Accuracy of Smartwatches in the Detection of Atrial Fibrillation. JACC Advances. 2025. https://www.jacc.org/doi/10.1016/j.jacadv.2025.102133

View All References

Track ECG & AF with Cardio Analytics

Store Apple Watch ECG recordings and monitor AF burden for clinical follow-up.

Download on App Store