Depolarizing-electrode monophasic curves and myocardial infarction ST shift

The in vivo monophasic curves of the potential variations between an intracellular microelectrode and a remote reference electrode show irregular upstrokes. These can be removed by subtracting from them the ECG recorded from a wire loop surrounding the microelectrode. Since similar irregularities are present in the upstrokes of monophasic curves obtained from potassium-ion depolarizing electrodes, the effect of a similar subtraction technique was tried. Again, sigmoid upstrokes were obtained. The role of the potassium ion is to render the membrane inexcitable at the electrode. The result is that the electrode follows the potential changes of the cell interior with a lag determined by a time constant due to the membrane resistance and the capacitance of the electrode to the rest of the animal. Since the ST changes in myocardial infarction can be considered low amplitude monophasic patterns superimposed on the ECG, and it has been found that the release of potassium from damaged muscle can produce monophasic patterns, it now seems possible to present a satisfactory explanation of such changes.