Direction of ECG wave

An ECG lead utilizes a combination of electrodes (attached to the patient) to provide a unique perspective of the electrical activity travelling through the heart. Each lead has a positive pole and a negative pole, and the difference in electrical potential between these poles is graphed over time. As a wave of electrical depolarization moves parallel to the direction of a lead, if it moves towards the positive pole of the lead, a positive deflection occurs on the ECG. If it moves toward the negative pole of the lead, a negative deflection occurs on the ECG.