What constitutes a "positive" deflection in an EKG lead?

A "positive" deflection in an EKG lead is characterized by an upward movement from the isoelectric line. This upward deflection indicates electrical activity moving toward the positive electrode of the lead being measured. In clinical practice, positive deflections are often associated with depolarization waves passing through the heart, which can signify various phases of the cardiac cycle depending on the timing and context of the recording.

For example, in lead II of an EKG, positive deflections typically reflect the depolarization of the atria and ventricles when the electrical impulse moves in the direction of that lead's positive pole. Understanding the significance of deflections plays a crucial role in interpreting EKGs, as different patterns can indicate normal heart activity or various arrhythmias and other cardiac conditions. Recognizing an upward deflection as positive is fundamental to reading and diagnosing EKGs accurately.