Chest, Vol 69, 762-768, Copyright © 1976 by American College of Chest Physicians

ARTICLES

Influence of alterations in the hematocrit upon the P wave and the QRS complex

K Ishikawa

The net effect of intracavitary blood mass on cardiac dipole is believed to augment its radial components and reduce the tangential components. Commonly known as the Brody effect, it results from the lower resistivity of intracavitary blood mass as compared to the surrounding tissues (the short-circuiting effect). Thus, an increase in hematocrit should reduce and a decrease in hematocrit augment the Brody effect. It has generally been assumed that the initial portion of the process of ventricular depolarization and the left maximal spatial vector (LMSV) represent the radial components, while the terminal portion of the process of ventricular depolarization and the right maximal spatial vector (RMSV) represents the tangential components of cardiac dipole. Furthermore, the atrial accession is believed to be tangential. Based on this Brody effect, it is anticipated that an improvement of anemia, as indicated by an increase in hematocrit, would tend to reduce the initial portion of the QRS, and LMSV, but enhance the terminal portion of the QRS, and the P-wave amplitude; however, the results of this study were not in agreement with such predictions. With an improvement of anemia, a significant number of cases showed no essential changes in these electrocardiographic factors or even showed reactions oppisite to the Brody effect. This probably indicates that there are many other factors which might modify the Brody effect.