That the position of the heart in the chest has an influence on the shape of the electrocardiogram as taken by the usual three leads was pointed out in the early work from Einthoven's laboratory.1 The modifications appearing on rotation of the body from side to side, on changes from the recumbent to the erect position, and in the phases of respiration have all been attributed to this factor. Dextrocardia offers one of the greatest possible variations in cardiac position and here, as is well known, the electrocardiogram is reversed. Stout subjects with transversely placed hearts usually give electrocardiograms with R3 of least amplitude while slender subjects with pendulous hearts usually show the least amplitude in R1. Lateral displacements of the heart due to pleural effusions, air or adhesions also are known to modify the electrocardiogram. According to Pardee,2 such displacements to the right reduce the height of R and
MEEK WJ, WILSON A. THE EFFECT OF CHANGES IN POSITION OF THE HEART ON THE Q-R-S COMPLEX OF THE ELECTROCARDIOGRAM. Arch Intern Med (Chic). 1925;36(5):614–627. doi:10.1001/archinte.1925.00120170023002
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