Intramyocardial current flow in acute coronary occlusion in the canine heart

Data from numerous experimental infarction studies indicate that rapid myocardial cell depolarization following ischemia causes the flow of injury currents. These currents were measured in the canine myocardium by monitoring voltage gradients across infarct boundaries using silver chloride plunge electrodes, followed by placement of a 100 omega resistor between the electrodes and again measuring the voltage gradients. Current flow was calculated from these measurements with the following results: 1) TQ currents developed within 15 seconds after occlusion and persisted for 120 to 150 minutes, often attaining a magnitude of 1 microA. 2) ST currents also developed within 15 seconds and attained 2 to 3 microA within 15 to 30 minutes, then usually subsided to some degree. 3) T currents were biphasic and attained 2 to 5 microA. Initially, current flowed from normal to ischemic myocardium but usually reversed within 30 minutes after occlusion. 4) The current flow was often disproportionate to the voltage gradient between 120 and 180 minutes after occlusion, possibly indicating electrical uncoupling of the infarcting cells from normal cells. These data indicate that intramyocardial current flow develops early after acute coronary occlusion. These currents may be sufficient to induce reexcitation.