title: On the normal scalar ECG. A new classification system considering age, sex and heart position.
abstract: 472 randomly selected men and women from the city of Lund were examined for disease in the heart, lungs and for hypertension. 163 men and 194 women who had no symptom or sign of disease were accepted for the further study. The prevalence of various exclusion criterias, such as symptoms and signs of heart disease, lung disease and other diseases which may possibly affect the ECG are reported as well as the distribution of blood pressures in the sample. A computer-averaged standard 12-lead ECG (leads aVL, I, -aVR, II, aVF, III, V1-V6) was recorded. All measurements of ECG-deflections have been made visually using a magnifying glass (6 times). ST-segments were classified according to the Punsar code by independent visual observers as well as by the computer. The mean frontal QRS-axis shifted to the left with advancing age, but the shift was statistically significant only in men. In both men and women there was a leftward shift of the mean frontal QRS-axis with increased weight, increased chest circumference and increased obesity index. The normal range of axis was found to be 0 degrees to 90 degrees in men and +15 degrees to 90 degrees in women. The problems concerning the definition of the electrical heart position is discussed. The concept of a Q-axis is introduced as an alternative way to indicate electrical heart position. There is a statistical significant relationship between the Q-axis and the QRS-axis in the frontal plane, although this relationship is not always apparent in the individual ECG. The presence or absence of a Q-wave in an individual lead was used to denote a lead as being a left ventricular lead or not. Using the Q-wave as a marker of heart position in the individual lead is more practical than to use the QRS-axis or the transitional zone. Duration and amplitude of the Q-wave have been measured. The upper limit of normal duration exceeded 0.03 s in leads aVL and aVF in men but not in women. The R-wave amplitudes proved to vary with age and heart position in men. In women variation of the R-wave amplitude was found with heart position but not with age.(ABSTRACT TRUNCATED AT 400 WORDS)
mesh_terms: D000328:Adult; D000367:Age Factors; D000886:Anthropometry; D001794:Blood Pressure; D006332:Cardiomegaly / Q000503:physiopathology; D003201:Computers; D003327:Coronary Disease / Q000175:diagnosis / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006321:Heart / Q000033:anatomy & histology* / Q000502:physiology; D006331:Heart Diseases / Q000175:diagnosis / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D012737:Sex Factors