An electrocardiogram (ECG or EKG) is an excellent test to quickly determine if there is a problem with your heart. An EKG translates your heart's electrical activity onto a piece of paper in the form of lines, spikes, and dips called QRS complexes and T waves.
Some of the questions that an EKG can answer are:
The heart's rate and rhythm
Abnormal electrial activity
Insufficent blood flow to the heart muscle
Abnomal chamber size or wall thickness