1995 年 33 巻 3 号 p. 266-274
An ideal reference for Unipolar electrocardiography is the electrode at infinity without any potential variations. Wilson's electrode was devised to approximate this ideal zero reference. Being constructed only from both arms and left leg, his device is quite practical and convenient. However, better approximation is conceivable with a connection of many electrodes on the body surface. In this communication, we propose two methods for the calculation of an ideal reference potential from potential distributions measured with any reference system. One of the methods was applied to certain clinical cases to confirm its consistency and to evalute the potential variation of Wilson's central terminal. In the first method, the potential φout for the space outside the body is determined such that it coincides with the measured potential distribution on the body surface within an unknown constant. This constant is then determined from the behavior of φout at infinity. The second method is based on the immersion of the body into an infinite homogeneous meium with the same conductivity as that of the body. Then, the outside conductivity is made to approach zero. The second method was applied to 60 clinical cases including normal persons and cases with myocardial infarction, bundle branch blocks and WPW syndrome. The results indicated that the maximal potential of Wilson's terminal was in the range of -0.4 to 0.2mV, which amounted to -10 to 5% of the surface voltage in most of the cases. These values are consistent with previous reports on the bath immersion of body and the others. In conclusion, this communication answers the fundamental question of unipolar electrocardiography on the sound theoretical bases.