The influence of constitutional variables on orthogonal electrocardiograms of normal women.

Correlations between 276 orthogonal electrocardiographic measurements and constitutional variables were made in 450 normal women, aged 18 to 90 years. Advancing age led to decreases in amplitudes, left QRS axis shift, rightward and superior displacement of the ST segment, and anterior shift of the T wave. QZ was absent in 1% of normal women over age 40. In the oldest subjects, Ry amplitude was 71% and RZ amplitude was 80% of the respective values in the youngest group. Whereas QRS amplitude decreases with age leveled off at the sixth decade of life, they continued to old age for ST-T measurements. Men revealed steeper age trends than women. Blacks had larger QRS amplitudes and smaller Q/R ratios than whites. Stratification of electrocardiographic criteria according to age, sex, and race appears essential for routine interpretations and for epidemiological studies where new events, such as myocardial infarcts, need to be differentiated from normal age trends.