Clinical electrocardiography / by Sir Thomas Lewis.

  • Thomas Lewis
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Clinical electrocardiography / by Sir Thomas Lewis. Source: Wellcome Collection.

    29/136 (page 17)
    The physiological auricular complex. P, the auricular representative, is found as a summit* in all normal and young adult subjects and in all leads ; it is small and rarely exceeds 1*7 scale divisions in amplitude ; it is followed by a short line which is horizontal or dipping. Amongst the variations of form, which P presents in the normal subject, is occasional bifurcation (Fig. 10). Auricular complexes of these forms are known from experiment to express the origin of the heart heat at the normal site of impulse formation and the passage of the contraction wave through the whole of the auricidar tissue in definite directions. Fig. 10. A normal electrocardiogram, showing a divided P summit; a prominent U summit occurs at the beginning of diastole. The physiological ventricular complex. The variations which are found in the type of the physiological ventricular complex are many. R and T are always present, Q and S are often absent. All the deflections vary much in amplitude and shape, and T may vary in its direction. The$i?A group of deflections is of short duration and in normal subjects does not exceed a total duration of one-tenth second. The presence of a QRS group of rapid deflections, followed by a slow blunt T deflection, is an indication that the ventricular contraction has been propagated from fixed * P and K arc upward movements when the galvanometric connections are so arranged that if the right arm contact is replaced by the zinc terminal of a copper-zinc couple, and the left leg contact is replaced by the copper terminal, an upward deflection results.