Clinical electrocardiography . ng the preponderanceof one ventricle over the other. The graphic criteria generally accepted as indicative of ven-tricular preponderance deal with changes in the amplitude anddirection of the R wave. Preponderance of the right ventricleis supposedly indicated by a downwardly directed R wave (S)in Derivation I and an upwardly directed R wave in DerivationIII. In preponderance of the left ventricle the reverse of thisstatus obtains (Figs. 97, 98). Einthoven, Fahr, and deWaart believe that the direction of theelectric axis of the heart corresponds roughly to the ana
Clinical electrocardiography . ng the preponderanceof one ventricle over the other. The graphic criteria generally accepted as indicative of ven-tricular preponderance deal with changes in the amplitude anddirection of the R wave. Preponderance of the right ventricleis supposedly indicated by a downwardly directed R wave (S)in Derivation I and an upwardly directed R wave in DerivationIII. In preponderance of the left ventricle the reverse of thisstatus obtains (Figs. 97, 98). Einthoven, Fahr, and deWaart believe that the direction of theelectric axis of the heart corresponds roughly to the anatomicaxis in normal hearts at an angle varying between 40° and 90°from the horizontal. Changes were observed in the axis in mechan-ical displacement of the heart by posture and by respiratory move-ments. Calculation of their angle a determined the electric axis 5 n6 CLINICAL ELECTROCARDIOGRAPHY of the heart, believed to be an index of ventricular balance. Anglesbetween 40° and 90° showed a normal balance, angles above 40°. Fig. 97.—Electrocardiogram of right ventricular preponderance. R wave directeddownward in Derivation I and upward in Derivation III.
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