Apple Watch Series 4 with industry-first features like ECG reading app and irregular rhythm notification will now be available in Europe and Hong Kong. With watch OS 5.2, customers in 19 European countries including Germany can take an ECG reading with Apple Watch Series 4 at any time.

"All recordings, their associated classifications and any noted symptoms are stored securely in the Health app on iPhone," Apple said in a statement late Wednesday.

The ECG app enables customers to take an electrocardiogram right from their wrist. It can capture heart rhythm on demand in a moment when users experience symptoms such as a rapid or skipped heart beat and help provide clinically important data to physicians.

The irregular rhythm notification feature on Apple Watch occasionally checks heart rhythm in the background and sends a notification if an irregular heart rhythm that appears to be atrial fibrillation (AFib) is identified. The ECG app and irregular rhythm notification feature can alert users to signs of AFib.

A recent clinical trial of around 600 participants found that the ECG app on Apple Watch demonstrated 98.3 per cent sensitivity in classifying AFib and 99.6 per cent specificity in classifying sinus rhythm in classifiable recordings, when compared to an ECG administered by a cardiologist.

The irregular rhythm notification feature was recently studied in the Apple Heart Study which found "only 0.5 per cent of participants received irregular pulse notifications, an important finding given concerns about potential over-notification."