Monophasic Electrical Response Produced by the Contraction of Injured Heart Muscle

Abstract

The electrical responses produced by injured heart muscle are of great interest not only because of their important bearing upon the interpretation of the electrical phenomena exhibited by excitable tissues generally, but because of their relation to the electrocardiographic changes that follow coronary thrombosis in man. We here report briefly experiments relating to the electrical responses produced by the injured heart beating in situ. When one of 2 non-polarizable electrodes connected to the terminals of the string galvanometer is placed in contact with a burned region on the epicardial surface of the exposed turtle's heart and the other in contact with the subcutaneous tissues at a point distant from the heart, the ventricular complex of the curve recorded is essentially monophasic in outline. The monophasic character of the response is due to the disappearance during systole of the injury-current flowing during diastole. The direction of the deflection indicates that during ventricular systole the cardiac or exploring electrode is relatively positive with respect to the distant or indifferent electrode. Curves of the same type are obtained by leading from the exposed and freshly injured surface of the mammalian auricle or mammalian ventricle to a distant point. In all such experiments we have connected the electrodes to the galvanometer in such a way that relative negativity of the exploring electrode yields an upward deflection in the completed record. In the curves obtained by leading from an injured to a distant region, ventricular systole is, therefore, represented by a monophasic deflection directed downward. If a monophasic response is obtained, in the manner described, from the ventral surface of the turtle's heart by means of an electrode in which contact with the heart is made by a wick that extends 3 or 4 mm. beyond the insulated shaft of the electrode, flooding the heart with normal saline or with Ringer's solution so that the surface is immersed to a depth of 5 or 10 mm., greatly reduces the amplitude of the curve but does not materially alter its form.