01 what’s electrocardiogram (ECG)?
People’s lives are gradually accelerating, and cardiovascular disease has become one of the main factors threatening people’s health. This makes ECG monitoring an indispensable part of medical testing. Each time the human body’s heart beats the contraction and relaxation, it will send out corresponding electrical signals. The electrocardiogram records the electrical signals of the heart through the wires placed at various positions of the body.
Because the electrical signal strength of various parts of the body is different, usually the more points are distributed, the more accurate the measurement will be. When we do physical examinations in the hospital, doctors usually use 10 collection points for 12-lead ECG monitoring, that is, stick electrodes at 6 points on the hands, wrists, ankles, and chest.
12-lead ECG and ECG waveform (picture source network)
The various peaks of the ECG waveform in the above figure are the portrayal of the state of the atrium, ventricle and other positions of the heart in a complete heartbeat. When a doctor finds that a certain band deviates from the normal value, he can judge where the heart has a health problem. For example, if the T-band is too low, it means that the patient may be in a state of myocardial ischemia; if the T-band is too high, it may be that the patient is in the hyperacute phase of myocardial infarction.
02 How does smart watch realize ECG
The ECG implementation principle of smart watches such as Apple Watch is to detect the electrical signals of the fingertips and wrists through the titanium electrode on the crown and a layer of silicon chromium nitride on the back of the fuselage. The two collection points at both hands form a loop, so this part of the product can only provide I single-lead ECG monitoring.Smart Watch Single-lead ECG.
When the smart watch is worn on the wrist, it uses lead I by default. Someone abroad has done a study to achieve multiple different leads by changing the contact position between the watch and the body. Studies have shown that, as long as the location is accurate, the results have reference significance.
Test results (Picture Source Network)
In the above figure, the upper, middle, and lower segments are normal people, patients with non-ST-segment elevation myocardial infarction, and ST-segment elevation myocardial infarction. In each group, compare the ECG waveforms of Apple Watch and ECG monitor , With consistency.