POTENTIAL CHANGES IN AN INJURED REGION OF CARDIAC MUSCLE

Abstract

The potential changes in an injured region of ventricular muscle of the tortoise and dog heart were studied during rest and activity of the surrounding normal muscle. The reference level of potential was taken as the potential of uninjured resting ventricular muscle. It is shown that the negative potential of rest is replaced by a positive potential during activity, the injured region becoming positive to a degree which may be as great or greater than it was negative during the preceding stage of inactivity of the surrounding ventricular muscle. The near or complete absence of action potentials in an injured region points to the presence of some new source of potential in an injured region which is not present in uninjured heart muscle. With a Wiggers suction electrode the development of the injury potentials are followed in successive cycles. The fully developed potentials are established within a short period. The injury potentials recorded from unipolar leads, with one electrode on the injured surface, the other at a distant point, resemble closely those obtained from 2 contacts on the heart, one on an injured, the other on an uninjured surface. In bipolar leads from injured to uninjured surfaces on the heart, the large and prolonged positive potential developing in the injured region when the heart becomes active, nearly or completely obscures the normal action potential developing in the uninjured portions of the muscle. The potential distr. across an injured region on the quiescent tortoise ventricle shows no region which is positive with respect to uninjured quiescent muscle. The potential is uniform up to the margin of the injured areas, becomes rather abruptly negative and remains negative and approximately constant until the opposite marginal tissue is reached, returning to its original value beyond the injury. This distr. of potential accords with that of 2 concentric rings, the outside ring containing positive, the inside ring negative charges. This orientation of charges is reversed when the surrounding muscle becomes active.