What Are Abnormal Marks on an ECG Called?

The marks on an electrocardiogram are called waves, and abnormal waves may indicate an abnormal heart rhythm, also known as arrhythmia, explains WebMD and MedlinePlus. Other causes of abnormal waves on an ECG include damage to the heart muscle, enlargement of the heart and congenital heart defect.

Abnormal waves on an ECG test may also indicate a change in the amount of electrolytes in the blood, inflammation of the heart and poor blood supply to the heart. Conditions that can cause changes in an ECG test include heart failure, sick sinus syndrome, atrial fibrillation, and Wolff-Parkinson-White syndrome, according to MedlinePlus.