“Is heart artery blockage an emergency?”

Heart artery is serious and the level of threat to life manifested by a heart attack becomes more significant when the lumen of the heart artery becomes more than 70% blocked. Artery blockage which are less that 70% could progress if the risk factors such as uncontrolled diabetes uncontrolled hypertension (high blood pressure) high cholesterol and cigarettes smoking are not controlled

That depends. As all things in medicine where and when or time period. If acute or sudden blockage of a large coronary (heart) artery, yes it’s a medical emergency. That’s what we call a full thickness heart attack or st elevation heart acute myocardial infarction or STEMI. If partially acutely blocked it’s slightly less of an emergency or non-stemi but still a heart attack. If complete or partially blockage happens over years, chronic blockage or chronic coronary stenosis. This is not considered an emergency. But you may have symptoms called a stable “angina” or “angina pectoralis” meaning choking of the chest. Of course the worst ones are not high percentage blockages like 80-90% blockages. They occur over time. The dangerous ones are the 10-30% blockages with atheromas that ruptures and cause sudden thrombosis and complete blockages. This can occur at very young age even in your 30-40s not knowing you had severe coronary artery disease.

Follow up with cardiologist asap. High risk of heart attack with death.

It depends. If blockage occurred suddenly (ie heart attack), yes it is an emergency. If not, especially without any symptoms, then it's not an emergency