In ST segment elevation myocardial infarction (STEMI), the coronary artery is completely blocked by a blood clot. It is the most serious type of heart attack. The best treatment for STEMI patients is to have the blocked artery opened by balloon inflation within 90 minutes of arriving at a hospital. The 90-minute window is called âdoor-to-balloon time.â The shorter the door-to-balloon time, the greater the chance of survival. Treatment of this life-threatening illness is reviewed in this issue.