Diseases of the chest and the principles of physical diagnosis . this time and is due to the downward rebound of the auriculo-ventricular tissues to their normal position. The second negative depression y is due to the opening of theauriculo-ventricular valves. CHAPTER XV CARDIAC ARRHYTHMIA Recent additions to our knowledge of cardiac anatomy and physi-ology have thrown much valuable light upon our conception of heartdisease, and have placed cardiac diagnosis and therapy upon a muchmore accurate scientific basis. As a result of these advances the studyof cardiac irregularities has been greatly
Diseases of the chest and the principles of physical diagnosis . this time and is due to the downward rebound of the auriculo-ventricular tissues to their normal position. The second negative depression y is due to the opening of theauriculo-ventricular valves. CHAPTER XV CARDIAC ARRHYTHMIA Recent additions to our knowledge of cardiac anatomy and physi-ology have thrown much valuable light upon our conception of heartdisease, and have placed cardiac diagnosis and therapy upon a muchmore accurate scientific basis. As a result of these advances the studyof cardiac irregularities has been greatly simplified, and the classifica-tion of these conditions has changed from the hopeless jumble whichexisted a few years ago, to a small and relatively simple grouping. NORMAL RHYTHM The stimulus which causes the heart to contract arises in the sino-auricular node, a small collection of specialized right auricular tissuewhich lies in the sulcus terminalis just below the fork formed betweenthe superior surface of the auricular appendix and the superior Fig. 137.—Xormal phlebogram. Blood-pressure .S. 130, D. 78 mm. Hg. Note the regu-lar sequence of the a, c, v waves bearing a definite time relationship to the brachialarterial waves. The conduction time ( a-c interval) is normal. The impulse is conducted from the auricles to the ventricles by meansof the auriculo-ventricular bundle (His bundle), a network of specializedtissue which begins in the right posterior margin of the base of theinterauricular septum (the auriculo-ventricular or Tawaras node) andnarrowing to form a bundle of fibers, leads through the interventricularseptum to the ventricles. Before entering these structures it dividesinto two branches (a right and a left) and again spreads out into a net-work which is distributed to the papillary muscles and to the ventricularwalls, and causes a contraction of these structures. Normal cardiac contraction is due to the fact that this organ possessesthe functions o
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