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

Abstract

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.

Modulators of normal electrocardiographic intervals identified in a large electronic medical record

“…Limitations of the study include lack of standardized recording of parameters such as height and weight and the absence of research parameters such as chest diameter, which was found to be a significant variable in earlier studies. 2,39 Also, designation as "normal" by clinical cardiologists may include a selection bias, such as patients with low HR automatically designated as abnormal when they may represent physiologic bradycardia. Thus, groups such as young athletes may be underrepresented.…”