A layman’s guide to Smartwatch ECGs: written by a doctor, after research

When my patients or Aamra members see me wearing my fitness ring or my fitness tracker on the wrist they often ask me if it is a good way to track the various health parameters, my answer is always the same, it depends on what you are tracking. When a patient with a heart condition asked me this question I decided to dig deeper into the science and tech behind the wearable health tech.

The 2024 Lancet Series on Atrial Fibrillation (AF) and recent reviews in the NEJM suggest that we have moved from the era of "gadgets" to "medical-grade wearables." For an Indian senior, a smartwatch can be a life-saving early warning system, but only if one knows how to use it correctly.

Science & tech of wearable that record ECG

1. The science: how a watch "sees" your heart

Traditional ECGs in a hospital use 12 leads to look at the heart from 12 different angles. A smartwatch with ECG capability is a single-lead ECG.

• How it works: When you touch the crown or the sensor with your opposite hand, you complete an electrical circuit through your chest.

• What it detects: It is primarily designed to detect Atrial Fibrillation (AF) which is the irregular quivering or ineffective beating of the upper two chambers(atria) of the heart.

• What it cannot do: Research in Science magazine reminds us that these watches are not designed to detect heart attacks (clotted arteries). If you have chest pain, the watch saying "Normal" does not mean you are safe.

2.  Available reliable medical grade devices in India

Not all watches are created equal. For medical vigilance, we look for CDSCO (India) or FDA (USA) approved devices.

• The gold standard: Apple Watch (Series 4 and above): This is the most studied wearable in NEJM history. Its atrial fibrillation detection algorithm is highly robust for the Indian population.

• The clinical alternative: KardiaMobile: While not a watch, this is a pocket-sized device used in several Indian clinics. It is a "Lead-I" ECG that is highly recommended for seniors who don't want to wear a smartwatch 24/7. It's available on Amazon and significantly cheaper than an Apple watch.

• The integrated choice: Samsung Galaxy Watch  6: This model has been cleared by CDSCO for ECG use in India and work seamlessly for those in the Android ecosystem.

• The budget-conscious: Fitbit (Sense/Versa/Charge): These offer reliable AF detection, studies showed that up to 98% time the Afib was identified correctly, offering both passive sampling of the heart rhythm and active tracking of the ECG. May have high false positives.

• Garmin Venu 2plus is also approved ECG device in India as of 2025

3. How to take a good ECG

A blurry ECG is as useless as no ECG. To get a reading that a doctor can actually use to make a clinical decision, follow these steps:

1. The "stillness" rule: Sit down. Rest your arms on a table. Movement is the enemy of electrical signals.

2. The moisturization trick: If your skin is very dry which is common in Delhi winter, the sensor might struggle to detect any surface electric current. A tiny bit of water or moisturizer on the finger can improve the "connection."

3. The 30-second rule: Do not stop the reading halfway. The algorithm needs the full 30 seconds to analyze the "R-R intervals" , the spacing between your heartbeats.

4. Proven vs. experimental features

• Proven: Detection of Atrial Fibrillation and Bradycardia (slow heart rate). These are clinical-grade features.

• Proven: High Heart Rate alerts during rest.

• Experimental: Blood Pressure monitoring via the wrist. While some watches in India offer this, The Lancet Digital Health warns that these are not yet accurate enough to replace the traditional arm cuff BP monitoring systems(sphygmomanometer).

• Experimental: Blood Glucose monitoring. Be very careful, there is currently no smartwatch that can accurately measure blood sugar without a needle. Any watch claiming otherwise is a gadget and not a medical device.

5. When should you call your doctor

At Aamra, we tell our members: Treat the patient, not the watch.

• If the watch says "AFib" but you feel fine: Don't panic. Stay still and take one more reading. If it repeats, send the PDF to your doctor.

• If the watch says "Normal" but you feel dizzy or breathless: Ignore the watch. Call for medical help immediately.

Concluding thoughts

Digital health is about empowerment, not anxiety. When used correctly these tools give us a "window" into your heart that we never had before. At Aamra, we help you manage these data points so they become a bridge to better health, not a source of stress.

Dr. Akanksha Saxena is a co-founder of Aamra Seniors Club, a tech enthusiast and a complete geek at heart, she loves to simplify medical jargons for her patients and Aamra members.