<Li> repolarization of the heart toward the positive electrode produces a negative deflection </Li> <Li> repolarization of the heart away from the positive electrode produces a positive deflection </Li> <P> Thus, the overall direction of depolarization and repolarization produces a vector that produces positive or negative deflection on the ECG depending on which lead it points to . For example, depolarizing from right to left would produce a positive deflection in lead I because the two vectors point in the same direction . In contrast, that same depolarization would produce minimal deflection in V and V because the vectors are perpendicular and this phenomenon is called isoelectric . </P> <P> Normal rhythm produces four entities--a P wave, a QRS complex, a T wave, and a U wave--that each have a fairly unique pattern . </P>

What are the two types of leads used to record an ecg waveform