ECG
ECG is a recording of the heart's electrical activity, and a watch records a short single-lead trace from the wrist.
On this page 3 sections
ECG stands for electrocardiogram, a recording of the tiny electrical signals the heart makes with each beat. Smartwatches with an ECG feature record a short trace and show it as a graph of the heart rhythm.
How it works
The watch has an electrode on its back and another on the case or crown. When the wearer touches the second electrode with a finger of the other hand, a circuit forms across the chest. The watch measures the voltage and records it, usually for about 30 seconds. Software then examines the pattern for signs of an irregular rhythm.
What it is and is not
- A watch records a single lead, while a hospital test records many leads from electrodes placed on the chest and limbs.
- It is different from a heart-rate sensor, which uses light on the skin to estimate beats per minute.
- The feature may need approval from a health regulator in a country before it is switched on.
What it does not promise
A watch ECG does not diagnose a heart condition or replace a medical test. It can miss problems that a full test would show, and poor contact or movement can spoil a reading. Only a doctor can interpret symptoms.