Now, if your body needs a certain amount of blood flow (oxygen carrying capacity) and your heart rate enters the zone in which cardiac output drops you've just exceeded the supply of oxygen. That is a heart attack. A monitor will keep you in your target zone.
I thought a heart attack was when one of the vessels supplying blood to a portion of the heart became occluded and shut off the oxygen to that part of the heart! This muscle dammage is how an ECG picks up a heart attack, when a certan area of the heart muscle stops firing. Also when the cells of the heart die this is where the enzymes that the lab picks up come from, not just because you exceded the oxygen supply your body was asking for.
I thought when my cardiac output droped below what my skeletal muscle system was begging for is what causes me to get dropped on the hills by fellas in better shape than myself. I was under the impression a heart monitor was so I can train more effectively, not avoid a heart attack.