Model studies on the effect of the intracardiac blood on the electrocardiogram

Perfused dog bladders to simulate the intracardiac blood mass were placed in an electrolytic tank in the shape of an elliptical cylinder. An artificial dipole was placed adjacent to the preparation, and wall and limb potentials were measured. Measurements were made with the dipole axis tangential, radial, or at intermediate angles to the bladder wall. In one group of experiments the leads were measured for ratios of bladder fluid to tank fluid of from about 0.14 to 1.20. In the second series of experiments the ratio was kept constant at 0.15, and field potentials were measured as a function of the distance between the dipole and the bladder. The results show that the contribution of a dipole component to the potential at a given electrode depends on the ratio of the resistivity of the blood to the resistivity of myocardial and thorax tissue, the distance of the dipole from the cavity, its direction relative to the cavity wall, as well as on the orientation of the dipole with respect to the electrode