Clinical electrocardiography . e Ligation of Coronary Arteries with Electrocardiographic Study, Arch. Int. Med., 1918, xxii, 8-27. 8. Smith, F. M.: Experimental Observations on the Atypical Q R S Waves of the Electrocardiogram of the Dog, Arch. Int. Med., 1920, xxvi, 205-220. 9. Waller, A. D., and Reid, E. W.: On the Action of the Excised Mammalian Heart, Phil. Trans. Roy. Soc, London, 1887, clxxviii, Willius, F. A.: Observations on Negativity of the Final Ventricular T Waveof the Electrocardiogram, Am. Jour. Med. Sc, 1920, clx, 844-865. CHAPTER X ABNORMALITIES OF THE P WAVE The au
Clinical electrocardiography . e Ligation of Coronary Arteries with Electrocardiographic Study, Arch. Int. Med., 1918, xxii, 8-27. 8. Smith, F. M.: Experimental Observations on the Atypical Q R S Waves of the Electrocardiogram of the Dog, Arch. Int. Med., 1920, xxvi, 205-220. 9. Waller, A. D., and Reid, E. W.: On the Action of the Excised Mammalian Heart, Phil. Trans. Roy. Soc, London, 1887, clxxviii, Willius, F. A.: Observations on Negativity of the Final Ventricular T Waveof the Electrocardiogram, Am. Jour. Med. Sc, 1920, clx, 844-865. CHAPTER X ABNORMALITIES OF THE P WAVE The auricular P wave, as I have stated in Chapter III, resultsfrom contraction of the auricle and from passage of the impulsethrough the auricle. The normal wave is rather peaked, of lowamplitude, and upright (positive). EXAGGERATED AMPLITUDE OF THE P WAVE The P wave is at times found to be of increased amplitude,even exceeding the amplitude of the T wave. This finding isusually present in Derivations II and III. White believes that. Fig. 114.—Exaggerated P wave in Derivations II and III. P waves more than 3 by 10—4 millivolts in amplitude or more second in duration almost always indicate auricular hyper-trophy. This statement requires modification, as I have observedthe exaggerated P wave in hyperthyroidism when necropsy has 135 136 CLINICAL ELECTROCARDIOGRAPHY failed to reveal hypertrophy of the auricles. Increase in auricularactivity through increase in rate or increase in contraction amplitudeis likewise capable of producing the exaggerated wave. It is fre-quently observed in mitral stenosis, in hyperthyroidism, and inneurotic individuals with tachycardia (Fig. 114). NOTCHING OF THE P WAVEAt times distinct notching of the apex or the descending por-tion of the P wave is observed, usually in those waves of exaggeratedamplitude and involving particularly Derivation II or III. Such
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