Dr. Paul Underwood:
How good of an idea will you have about a patient's heart after an EKG exam?
Well we can test the heart pretty much as it at rest with the EKG. So looking for abnormalities in the heart muscles they often will show up in different voltages on the EKG. Likewise if a person has extra heartbeats, a lot of extra heartbeats then they will show up on the EKG as well.
If a person has evidence of a scar on the heart, say from a previous heart attack or if the heart is straining from beat to beat, say with the either high blood pressure or if it wants more blood then that would show up on the EKG.
But you are absolutely correct that the EKG can only show us about 10 seconds of activity of the heart and the heart is beating continuously throughout the day.