Changes in heart dipole moment after surgical correction of atrial septal defect

Relative influence of intracardiac blood hematocrit and volume on the electrocardiogram

Theoretical and experimental model studies on the effects of intracardiac blood have indicated that voltages due to a radial dipole are smaller than have been found in in-vivo experiments. The possible reasons for these differences have been examined. It is concluded that the lungs may tend to increase voltages over the anterior and posterior thoracic walls because of a current-channeling effect. This effect depends on the direction of cardiac excitation relative to the lungs. Voltages on the lateral and postero-lateral sides of the thorax are reduced because of the relatively large mass of the lungs in these regions. Changes in intracardiac blood volume for a constant hematocrit have less effect than changes in hematocrit per se.

The difference vector: assessment of effects of changes or interventions

Vector dipole moments were measured on young pigs before and one week after ligation of the left anterior descending coronary artery. Vectors were obtained for the three peaks of vector spatial magnitude, M. Preoperative, postoperative, and difference vectors were measured for each peak. If excitation is normal except through the infarcted tissue, the difference vector should be more closely related to the infarct because the normal excitation cancels out. It was found that the postoperative vector was changed by the infarct but that the difference vector was a better indication of infarction. This paper was designed to introduce the method using experimental data for a small number of pigs.