No single smartwatch is the “best” for heart health across the board, but the Apple Watch Series 10 offers the most complete package of heart-monitoring features available right now, combining continuous heart rate tracking, ECG recording, irregular rhythm notifications, blood oxygen sensing, and heart rate variability logging. That said, the right choice depends on which metrics matter most to you and how long you need your device to last between charges.
What Smartwatches Actually Measure
Modern smartwatches track heart health in two fundamentally different ways, and understanding the distinction matters more than any brand comparison. The first is passive optical monitoring: a green LED light on the back of the watch shines into your skin and measures how blood flow changes with each heartbeat. This runs continuously throughout the day and powers your resting heart rate readings, exercise heart rate zones, and irregular rhythm notifications.
The second is active ECG recording. When you place your finger on the watch’s crown or bezel, it creates a circuit that measures the electrical signals driving your heartbeat. This produces a single-lead electrocardiogram, a simplified version of what you’d get in a clinic. The Apple Watch (Series 4 and later), Samsung Galaxy Watch, and Withings ScanWatch all have FDA-cleared ECG capability. The key difference: passive optical scanning flags potential irregularities, while ECG recording gives your doctor something concrete to review.
That distinction has real clinical consequences. In the Apple Heart Study, follow-up monitoring confirmed atrial fibrillation in only 34% of people who received an irregular rhythm notification from the optical sensor. Non-AFib irregular rhythms accounted for 40% of those flagged cases. An ECG tracing, by contrast, gives physicians far more confidence. Clinicians were significantly more likely to act on an ECG reading than on an optical-sensor alert alone.
How Accurate Is AFib Detection?
A systematic review of wearable ECG devices found that sensitivity for atrial fibrillation detection ranged from 83% to 100%, with specificity between 79% and 100%. The Apple Watch specifically showed sensitivity of 93 to 95% and specificity of 96.5 to 100% in one study. When researchers used an enhanced two-step algorithm on Apple Watch data, they pushed sensitivity to 90% and specificity to 92% while eliminating inconclusive readings entirely. Under controlled conditions, the best-performing devices achieved accuracies between 97% and 99% for distinguishing AFib from normal sinus rhythm.
These numbers are impressive for a consumer device, but they come with a caveat. Most validation studies test under controlled conditions with patients sitting still. Real-world accuracy during exercise or movement is lower. The takeaway: a smartwatch ECG is a useful screening tool, not a diagnostic replacement for a 12-lead hospital ECG.
Apple Watch Series 10
The Apple Watch remains the most feature-rich option for heart health monitoring. It tracks continuous heart rate, records single-lead ECGs, monitors blood oxygen levels, measures wrist temperature, and logs heart rate variability. It also sends notifications for unusually high or low heart rates and irregular rhythms. For HRV specifically, the Apple Watch measures SDNN (a standard variability metric) in one-minute windows, taken automatically throughout the day and night.
The tradeoff is battery life. You’ll get roughly 18 hours on a standard charge, or up to 36 hours in low power mode. If you want uninterrupted 24/7 monitoring including sleep tracking, you’ll need to charge it daily, typically during a morning routine or shower. For people who prioritize having every heart metric in one place and don’t mind the charging habit, it’s the strongest all-around choice.
Samsung Galaxy Watch Ultra
Samsung’s top-tier watch matches the Apple Watch on most heart health features: continuous heart rate, ECG, blood oxygen, stress monitoring, skin temperature, and sleep tracking. It runs on Wear OS, making it the natural pick for Android users who want the same caliber of health monitoring that iPhone users get from Apple. Battery life stretches to three or more days with typical use, a meaningful advantage over the Apple Watch for people who want continuous sleep and heart monitoring without daily charging.
Samsung also offers blood pressure monitoring on its Galaxy Watch lineup, though this feature requires calibration with a traditional blood pressure cuff every few weeks. Cuffless blood pressure technology on all smartwatches still relies on estimating pressure from the time delay between your heartbeat’s electrical signal and the pulse wave reaching your wrist. Regular recalibration remains mandatory, and the feature’s availability varies by country due to regulatory differences.
Garmin Venu 3
Garmin doesn’t offer ECG recording, which is its biggest gap for heart health. What it does offer is exceptionally accurate optical heart rate monitoring and strong battery life. In testing against a medical-grade Polar chest strap, the Venu 3 achieved 98.6% heart rate accuracy with no significant lag during real-time exercise tracking. Garmin measures HRV during sleep using RMSSD (a variability metric that reflects your nervous system’s beat-to-beat regulation) in five-minute segments throughout the night, giving you a detailed picture of recovery and stress.
If your primary concern is fitness-oriented heart monitoring, tracking resting heart rate trends, understanding your body’s stress response, and getting accurate exercise data, the Garmin Venu 3 delivers. Battery life runs up to several days in smartwatch mode. But if you specifically want AFib screening or ECG capability, you’ll need to look elsewhere.
Fitbit Sense 2
The Fitbit Sense 2 hits a middle ground: it includes an ECG sensor, continuous heart rate monitoring, blood oxygen tracking, all-day stress detection, and sleep-based HRV measurement. Fitbit calculates HRV as RMSSD across your entire sleep period, giving you a single nightly score rather than periodic snapshots. Battery life lasts six or more days, making it one of the lowest-maintenance options for continuous monitoring.
Fitbit’s health dashboard is particularly approachable for people who aren’t fitness enthusiasts. The stress tracking feature uses skin conductance (a tiny electrical signal on your skin that changes with your stress response) alongside heart rate data, offering a combined readout that’s easy to interpret. The Sense 2 is a solid choice if you want meaningful heart health data without the complexity or price tag of an Apple Watch or Samsung flagship.
Withings ScanWatch
Withings takes a different approach entirely. The ScanWatch looks like a traditional analog watch with a small digital display, and it received FDA clearance for both ECG recording and blood oxygen measurement for atrial fibrillation detection. It’s designed for people who want medical-grade heart screening without wearing something that looks like a computer on their wrist.
The tradeoff is that Withings offers fewer fitness and lifestyle features than Apple, Samsung, or Garmin. There’s no color touchscreen, no app ecosystem, and no voice assistant. But for someone whose primary goal is AFib monitoring, the ScanWatch’s combination of clinical validation and a 30-day battery life makes it uniquely practical, especially for older adults or anyone who simply wants the health data without the smartwatch complexity.
How HRV Tracking Differs by Brand
Heart rate variability is one of the most useful long-term health metrics a smartwatch can track, reflecting how well your nervous system adapts to stress, exercise, and recovery. But each brand measures it differently, which means your HRV number from an Apple Watch won’t match your number from a Garmin or Fitbit, even if your heart is doing the exact same thing.
Apple measures SDNN in one-minute windows taken periodically throughout the day and night. Garmin measures RMSSD in five-minute blocks during sleep. Fitbit measures RMSSD across your entire sleep period as a single value. SDNN and RMSSD capture slightly different aspects of variability, and the recording length alone changes the resulting number significantly. The practical lesson: track your HRV trends over weeks and months on one device rather than comparing raw numbers across brands. A consistent downward trend in your personal baseline is more meaningful than any single reading.
Choosing Based on Your Priority
- Most complete heart health package: Apple Watch Series 10 (ECG, irregular rhythm alerts, SpO2, HRV, continuous heart rate)
- Best for Android users: Samsung Galaxy Watch Ultra (matches Apple’s feature set, longer battery, blood pressure estimation in supported regions)
- Best heart rate accuracy for fitness: Garmin Venu 3 (98.6% accuracy against chest straps, strong battery life, detailed HRV)
- Best battery with ECG: Fitbit Sense 2 (six-plus days, ECG, stress tracking, sleep-based HRV)
- Most discreet medical monitoring: Withings ScanWatch (FDA-cleared ECG and SpO2, analog watch design, 30-day battery)
Your best smartwatch for heart health ultimately depends on whether you need AFib screening specifically, how often you’re willing to charge, and whether you want a fitness-forward device or a quiet health monitor. Any of these watches will track your heart rate accurately enough to spot meaningful trends over time. The ECG-equipped models add a layer of screening that the optical-only devices can’t match, but even a basic continuous heart rate tracker gives you data that didn’t exist outside a hospital 15 years ago.