Far-field stimulation of cardiac tissue

Summary

This article outlines the mechanisms involved in far-field stimulation of cardiac tissue by the applied strong electric field, such as in cardioversion and defibrillation. In contrast to near-field stimulation which represents excitation of tissue in the vicinity of the cathode, far-field stimulation is defined as stimulation that results in tissue excitation away from the cathode. Conditions under which far-field stimulation occurs are often complex and non-intuitive. The paper discusses the structural features of the myocardium and the characteristics of the applied electric field that contribute to far-field stimulation. Analytical expressions and results from computer simulations are included to demonstrate the role of applied-field and tissue-structure features to far-field stimulation of the myocardium. The paper also presents arguments pertaining to the effect of the shock to tissue in fibrillation.