[Heart position as a determinant of the voltage of the R wave in healthy subjects].

Although many factors have been reported to change the R wave amplitude of the electrocardiogram, the direct measurement without any consideration, has been the method of choice, which leads to controversial findings. We hypothesized that body mass index and heart position are the main modifiers of the R wave amplitude. To test this hypothesis 80 normal subjects were studied with standard electrocardiograms in which correlation with constitutional variables were performed and were also analyzed according to the electrocardiographic heart position. R wave amplitude showed a non-significant inverse relationship to body mass except in severe overweight subjects (p less than 0.05). When analyzed by position, levorotated and S1, S2, S3 hearts showed a significant increase in R wave voltage whereas horizontal and dextrorotated ones showed a diminished amplitude (p less than 0.01) independent of body weight. There was no relation between R wave voltage and body surface. We conclude that: Body mass is not an important modifier of R wave amplitude in thin, normal and light overweight subjects. Heart position may induce significant variation of R wave voltage according to the degree of the projection of the left ventricular electric field to the anterior thoracic surface.