KEY POINTS

1. An electrocardiogram is simply a graph, made by a voltmeter that is equipped to plot voltage as a function of time.

2. Atrial depolarization, ventricular depolarization, and ventricular repolarization cause characteristic voltage deflections in the electrocardiogram.

3. The electrocardiogram reveals the timing of electrical events in the heart.

4. Six standardized electrocardiographic leads are used in veterinary medicine.

5. Abnormal voltages in the electrocardiogram are indicative of cardiac structural or electrical abnormalities.

6. Electrical dysfunctions in the heart cause abnormal patterns of electrocardiogram waves.