AFib irregularity over time on Apple Watch ECG
A single recording tells you about one moment. The ECG+ trend chart shows how your beat-to-beat irregularity, your AFib irregularity (CV%), has changed across all your AFib recordings, with each point representing one recording. That bigger picture is far more informative than any single result.
The two reference lines
The chart includes two dashed reference lines to help you interpret your results:
- Green line (15%): the lower boundary of the typical AFib range. Scores below it suggest a calmer, more controlled rhythm.
- Red line (30%): the upper boundary of the typical AFib range. Scores above it indicate more pronounced beat-to-beat variation.
Most people with AFib have scores between the two lines, the expected zone for AFib irregularity, based on clinical research (Tateno & Glass, 2001).
What to look for
- Consistently below 15%: your rhythm has been relatively calm, often reflecting good rate control.
- Fluctuating between the lines: normal variation for AFib. Activity, stress and medication timing all affect the score.
- Repeatedly above 30%: worth mentioning to your doctor, especially if it doesn't improve over time.
What affects the score
CV% can shift from recording to recording based on your heart rate at the time, physical activity, stress, medications (especially rate-control drugs), and the natural progression of an AFib episode. A higher score doesn't necessarily mean your AFib is worsening, which is exactly why the trend matters more than any one point.
Share it with your doctor
Bring your ECG+ recordings, including this trend, to your next appointment. Long-term patterns give your doctor much more context than any individual result. Our guide on what to ask your doctor can help you make the most of the conversation.
This information is for general education only and isn't a substitute for professional medical advice, diagnosis or treatment. Always consult your healthcare provider with any concerns about your heart rhythm.
Frequently asked questions
What do the green and red lines on the AFib trend chart mean?
The green line (15%) marks the lower edge of the typical AFib range, and the red line (30%) marks the upper edge. Most people with AFib sit between them, the expected zone based on clinical research.
Does a higher CV% mean my AFib is getting worse?
Not necessarily. CV% shifts from recording to recording with heart rate, activity, stress, medication timing and the natural progression of an episode. The long-term trend is more informative than any single point.