Availability still very limited:

https://support.garmin.com/en-US/?faq=QssFZHtIOfAYNSSmzXNwY9

Garmin’s ECG app is currently available in the following regions:

United States
   American Samoa
    Commonwealth of the Northern Mariana Islands
    Guam
    Puerto Rico
    US Virgin Islands
Hong Kong
Philippines
Singapore
Taiwan
Vietnam