Abstract
His bundle electrocardiography has enhanced our knowledge of cardiac electrophysiology. The catheter technique for recording potentials from the specialized conducting tissues is most useful in determining the site (or sites) of atrioventricular and ventriculoatrial delays and blocks. Various types of ventricular preexcitation resulting from conduction through Kent, Mahaim and James bundles are adequately identified with this method. In some cases it provides the only means of differentiation between supraventricular and ventricular arrhythmias. A secondary gain obtained from His bundle recordings is the evaluation of the electrophysiologic effects of various drugs. Information thus obtained is not only academically important but also clinically useful, since it is a significant factor in establishing the proper therapy.