Cardilogist Tim Williams with Martha Jefferson Hospital explains that for quite sometime most people usually get symptoms from their heart when their arteries become 50-70% narrow. We used to believe that most people with heart attacks were dying of a step wise plaque build up in arteries that happened over years. Since the prevailing theory was that heart attacks occurred in pre-existing severe lesions, it was thought that most individuals had misinterpreted their symptoms.
Multiple studies however confirmed that for >50% of patients with heart attacks, their first symptoms was the heart attack or death. People started asking more questions and the prevailing theory started to be updated.
The majority of people who have a heart attack suffer from something known as a plaque rupture. That's what's causing most heart attacks. The key step we've learned is that it can happen at any level of narrowing, mild, moderate, or severe. Going back to our diagram, you can see that the cholesterol plaque becomes inflames and ruptures into the blood stream. You can think of it like a cut inside a blood vessel wall that develop clot on it. If the clot reduces the diameter by 50-70%, you may have a warning signs in the few hours leading up to a heart
It usually will be on the order of minutes to hours, but some people may have stuttering symptoms for days leading up to the final closing off of the vessel. We're not 100% sure how frequently plaque ruptures occur in the general population. It may be that a healthy artery takes care of a rupture without the person ever being aware of that it occurred. That's the direction of future research.
You can't 100 percent. In some ways its like asking whose car engine will break. If you take care of your engine, you're more likely to avoid the mechanic, but even someone who does everything right can end up with problems. It's important to stress, however, that most people have identifiable and treatable risk factors.
The most important thing is to know the warning signs and call 911. If and when a vessel closes, the heart becomes in danger of causing an electrical short circuit that can cause sudden death. If you're driving your car, you're not likely to survive such an event and can hurt others if you crash. The rescue squad has portable defibrillators to get you out of the rhythm. Ask any rescue squad EMT, it happens more often than you think.