The process which is essential and final for the physicist, physiologist, or physician dealing with electrocardiographic wave forms, no matter how obtained or how recorded, is the interpretation of the record. The process of interpretation of electrocardiograms by the physician has for many years been essentially unchanged.
Interpretation of the electrocardiogram has consisted of making a few quantitative measurements, such as the P-R, QRS, and Q-T intervals, and then describing in qualitative or correlative language the size and shape of the deflections. Qualitative descriptive words such as "low," "high," "sagging," "peaked," and "depressed" are frequently used, or correlative words such as "strain," "coronary type," and "digitalis type" are also frequently used. The mental process of the interpreter of the electrocardiogram is remarkable. It involves a visual estimate of the size and shape of the electrocardiographic waves in many leads; an estimate of the size, shape, and direction of the QRS
NEWMAN EV, McGOVERN JF, ARNOLD TG. The Important Recent Advances in Electrocardiography. AMA Arch Intern Med. 1955;96(5):591-599. doi:10.1001/archinte.1955.00250160033003