INFLUENCE OF AGE, SEX, AND BODY HABITUS ON THE MEAN QRS ELECTRICAL AXIS IN CHILDHOOD AND ADOLESCENCE

The "mean QRS electrical axis " has been defined by Ziegler (1951) as the average direction in which the excitatory process spreads throughout the ventricular myocardium. This mean axis or vector in the frontal plane may be calculated from the standard limb leads and used as an index of cardiac abnormality. In biometrics the term "deviation " is usually used to indicate the departure of a measurement from an established normal value. Thus in electrocardiography right or left axis deviation denotes departure of the electrical forces from the normal toward one or other side of the body. Accurate interpretation of such deviation is dependent upon well-established normal standards, and several authorities (Johnston, 1961; Ezra, 1961; Milnor, 1962) have indicated that those values currently available for older children and adolescents are inadequate. Most previous studies have contained insufficient numbers to permit statistical analysis (Lincoln and Nicolson