Clinical electrocardiography . rnating auricular premature contraction (Exsys.) arising at apoint in the auricular musculature distant from the sino-auricular node. The Pwave is negative (inverted). Electrocardiogram in Derivation II. becomes negative (inverted). Proof that the negative P wave isindicative of a change in the pace-maker is found in the work of 60 CLINICAL ELECTROCARDIOGRAPHY Lewis, von Hoesslin, Einthoven, Fahr and de Waart, Wilson, andCarter and Wedd. Figure 25 illustrates this type of prematureauricular contraction. White and Stevens have called attention to the fact that att
Clinical electrocardiography . rnating auricular premature contraction (Exsys.) arising at apoint in the auricular musculature distant from the sino-auricular node. The Pwave is negative (inverted). Electrocardiogram in Derivation II. becomes negative (inverted). Proof that the negative P wave isindicative of a change in the pace-maker is found in the work of 60 CLINICAL ELECTROCARDIOGRAPHY Lewis, von Hoesslin, Einthoven, Fahr and de Waart, Wilson, andCarter and Wedd. Figure 25 illustrates this type of prematureauricular contraction. White and Stevens have called attention to the fact that attimes premature auricular contractions show aberrant ventricularresponses. They showed that the greater the prematurity of theauricular beats, the greater is the likelihood of aberration of theresponding ventricular complex. An example of such a case isfound in Fig. 26. Auricular premature contractions are at times observed pre-ceding or following paroxysms of auricular tachycardia, auricularflutter, and auricular Fig. 26.—Auricular premature contraction with aberrant ventricular response. Nodal or Junctional Premature Contractions.—Premature con-tractions arising in the auriculoventricular junctional tissues arereferred to as nodal. They may arise in the node or bundle. Inthe resulting electrocardiograms one or more of several character-istics are present: 1. Owing to the intermediate region of ectopic impulse forma-tion both auricles and ventricles may contract this status the P wave is not apparent in the abnormal complex,but occurs synchronous with the R wave, giving a greater amplitudeto the latter (Fig. 27). In Fig. 28 the absence of the P wave andthe increased amplitude of the R wave of the premature complexmay be noted. The ventricular complex is usually unaltered, CARDIAC ARHYTHMIAS 6l sxsys Fig. 27.—-Schematic graph of nodal premature contractions. P-R interval 0.
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