ECG Availability

ECG is

viewed as a medical device which mean it require official approval from the

government of a country before it's legal for apple to offer

these are

the countries which has provided with said approval so far

watchOS - Feature Availability - Apple

ECG

implies that citizens' medical data be stored by a foreign third-party company

without individual approval by the government of said country, and that is not

something all countries feel comfortable with.

If it isn't available now in your location you will find out only when Apple announces it. Nobody in this user community has any special knowledge about future services.