A widow maker is when you get a big blockage at the beginning of the left main artery or the left anterior descending artery (LAD). They're a major pipeline for blood. If blood gets 100% blocked at that critical location, it's almost always fatal without emergency care.
I remember a 25 year old Russian skater died from one and this trainer Bob Harper. He got lucky a Dr was working out at his NYC gym. Many ignore symptoms like feeling dizzy (Bob fainted one time), shortness of breath at times, chest pain, light headedness, jaw pain, unexplained arm/shoulder pain with migraine.
Better to be safe than sorry if feeling symptomatic and get things checked.
Also worth noting is gear thickens blood and
over time can lead to build up in these arteries.
