Apple Watch ECG vs ECG+: a feature comparison
This isn't an either/or. Your Apple Watch does the hard part: it records the ECG and tells you the overall rhythm. ECG+ reads that same recording and surfaces the detail the built-in app doesn't label. They work together: the watch and Apple's app capture and classify; ECG+ analyzes and explains.
What the built-in Apple ECG app does well
The Apple Watch ECG app is excellent at what it's designed for: taking a 30-second single-lead (Lead I) recording and classifying the overall rhythm as sinus rhythm, atrial fibrillation, high or low heart rate, or inconclusive. It's FDA-cleared for that purpose, it's built in, and it stores every recording in Apple Health. For a quick "is my rhythm normal or AFib?" check, it's all most people need.
What ECG+ adds
ECG+ doesn't re-record anything: it reads the ECGs already in Apple Health and analyzes them beat by beat, all on-device. It marks every PAC and PVC on the strip, measures QT/QTc using five clinical formulas (Bazett, Fridericia, Framingham, Hodges and Rautaharju), calculates HRV as both RMSSD and SDNN, scores AFib irregularity (CV%), and tracks your PAC/PVC burden and QTc trend over time. It builds a heartbeat signature from your median beat, takes on-strip measurements, flags repeat patterns like bigeminy and trigeminy, adds a plain-language AI-assisted interpretation, and turns it all into a clear, annotated report you can hand to your doctor, with a daily streak to keep you checking in.
Side-by-side comparison
| Feature | Built-in Apple ECG app | ECG+ |
|---|---|---|
| Rhythm & detection | ||
| Records the ECGThe Apple Watch hardware does the recording | ✓ | Analyzes existing recordings |
| Overall rhythm resultSinus rhythm, AFib, high/low HR, inconclusive | ✓ | ✓ |
| AFib detection | ✓ | ✓ |
| AFib irregularity score (CV%)Quantifies how irregular the rhythm is | , | ✓ |
| On-device processingAnalysis runs privately on your iPhone | ✓ | ✓ |
| Apple HealthKit sync | ✓ | ✓ |
| Beat-by-beat analysis | ||
| Marks individual PACs & PVCsPremature beats highlighted on the strip | , | ✓ |
| On-strip measurementsIntervals measured directly on the ECG trace | , | ✓ |
| Heartbeat signatureA median-beat template of your heartbeat | , | ✓ |
| PAC / PVC burden (%) | , | ✓ |
| Repeat patternsBigeminy, trigeminy, couplets, triplets | , | ✓ |
| T-wave changesFlattened or inverted T waves | , | ✓ |
| Intervals & metrics | ||
| QT / QTc measurement5 formulas: Bazett, Fridericia, Framingham, Hodges, Rautaharju | , | ✓ |
| Heart rate variability (HRV)Both RMSSD and SDNN, from your ECG | , | ✓ |
| Interpretation & reports | ||
| AI-assisted interpretationPlain-language explanation of your recording | , | ✓ |
| Report to share with your doctor | Basic PDF | Detailed, annotated |
| Tracking over time | ||
| Track findings over time | Stores recordings in Health | ✓ |
| QTc trend | , | ✓ |
| Daily streak | , | ✓ |
| Cost | Built in | Free |
✓ = supported ·, = not provided. Comparison reflects the standard Apple Watch ECG app at the time of writing; Apple's features may change.
Which should you use?
Use both. Keep taking ECGs with your Apple Watch: that's the recording step, and the built-in app's rhythm result is a useful first check. Then open ECG+ when you want to understand the recording: to see exactly where premature beats fall, to get QTc, HRV and burden numbers, and to produce a report your doctor can read at a glance. If you only ever want a yes/no on AFib, the built-in app is enough. If you feel skipped beats, thumps or a racing heart and want evidence a clinician can act on, that's where ECG+ comes in.
New to all this? Start with the Apple Watch ECG FAQ, or see everything ECG+ marks.