Apple Watch Series 4's much-touted electrocardiogram (ECG) is now available in Singapore via a software update.

An ECG is a medical test that detects abnormalities such as atrial fibrillation (AFib), which is a form of irregular rhythm in a person's heart, by measuring the electrical activity generated by the heart as it contracts.

This test is usually done by a technician attaching 12 small electrode patches to the skin of a patient's chest, arms and legs.

But with the Apple Watch Series 4 smartwatches, the wearer needs only to stay still and hold the smartwatch's digital crown for 30 seconds to get an ECG reading.

Singapore is the second market in Asia after Hong Kong, and the first in South-east Asia, to get the ECG feature, now available in 31 markets around the world. The Apple Watch Series 4 was launched in September last year.

The ECG feature needs the approval of a local health authority before it can become available. In Singapore, the Health Sciences Authority (HSA) is the approving authority.

Dr Sumbul Desai, Apple's vice-president of health, told The Straits Times in a telephone interview: "HSA took time to review the ECG feature and understand it… they were positive about us bringing the feature to Singapore."

The biggest benefit of the Apple Watch Series 4's ECG feature is "democratising health information so individuals can engage and empower themselves", said Dr Desai, who is also a practising physician.

She added: "You now have the ability to take snapshots of what is going on with your heart as you are living your everyday life, so that when you go to your doctor, you have more information."

She emphasised that the ECG feature of Apple Watch Series 4 will not replace physicians, but rather, provide another avenue of data for them to better understand their patients.

"We look at it as a way of augmenting the physician-patient relationship," she said.

Apple emphasised that the ECG cannot detect a heart attack, blood clots, stroke or other heart-related conditions.

If left untreated, AFib can cause blood to clot in the heart. This can lead to a stroke, heart failure or other medical conditions.

Dr Julian Tan, an interventional cardiologist at The Cardiology Practice, said: "For cardiologists, the key is the validation (and accuracy) of such portable ECG systems. Based on Apple's white paper, I am quite confident of the usability and feasibility of such devices."

Along with the ECG feature, the watchOS 5.3 update launched yesterday will also add an irregular heart rhythm detection feature to all Apple Watch smartwatches from Series 1 to 4.

Taking an ECG reading using the Apple Watch Series 4 smartwatch

You can take an ECG at any time, when you are feeling symptoms such as a rapid or skipped heartbeat or when you have other general concerns about your heart health. However, you have to be at least 22 years old to take an ECG reading using the Apple Watch Series 4.

• Make sure your Apple Watch is strapped on snugly and that you have selected the correct watch-wearing wrist - either left or right wrist - in the Apple Watch app.

• Launch the ECG app.

• Rest your watch-wearing arm on a table or on your lap and keep it steady.

• Rest your index finger - of the hand not wearing the watch - on the digital crown and hold it there (but do not press).

• The ECG recording takes 30 seconds. You will not get a reading if you remove your finger from the digital crown before the stipulated time. At the end of the recording, you will receive a classification. Tap Add Symptoms and choose your symptoms, which can include fatigue, shortness of breath and chest tightness.

• Tap Save, followed by Done.