Calcium overload, "injury" current, and early ischaemic cardiac arrhythmias--a direct connection.

Intracellular calcium ions induce a depolarising inward current by reacting with specific sites on the inner surface of cardiac muscle cell membranes. Since intracellular calcium overload invariably occurs with myocardial ischaemia, it may be that the early electrophysiological manifestations of ischaemia, including cellular depolarisation, diastolic current flow, and early ischaemic arrhythmias, are directly mediated by calcium. A simple explanation for the effects of many drugs upon the electrical behaviour of ischaemic myocardium is proposed.