Many heart problems change the heart's electrical activity in distinct ways. An electrocardiogram (EKG) can help detect these heart problems.
EKG recordings can help doctors diagnose heart attacks that are in progress or have happened in the past. This is especially true if doctors can compare a current EKG recording to an older one.
An EKG also can show:
Lack of blood flow to the heart muscle (coronary heart disease)
A heartbeat that's too fast, too slow, or irregular (arrhythmia)
A heart that doesn't pump forcefully enough (heart failure)
Heart muscle that's too thick or parts of the heart that are too big (cardiomyopathy)
Birth defects in the heart (congenital heart defects)
Problems with the heart valves (heart valve disease)
Inflammation of the sac that surrounds the heart (pericarditis)
An EKG can reveal whether the heartbeat starts in the correct place in the heart. The test also shows how long it takes for electrical signals to travel through the heart. Delays in signal travel time may suggest heart block or long QT syndrome.