Major advances have taken place in clinical cardiac electrophysiology during the past six years. Previously, students of arrythmia derived their knowledge from two principal sources, the animal laboratory and the electrocardiograms of patients. Inductive electrocardiographic analysis, particularly when coupled to experimentally derived electrophysiological principles, lead to development of major concepts of how and why arrhythmias occurred. However, the inability to test hypotheses in the human heart was a major limitation.
In the late 1960s and early 1970s, tools have been developed for proving and disproving hypotheses derived from inductive reasoning. These include the following: (1) the development of a simple catheter technique for recording of His bundle electrogram.1 The previously silent P-R interval on the surface ECG became amenable to study. Recording of His bundle electrograms allowed demonstration of the site of a conduction disturbance, and permitted the determination of whether an ectopic beat was of supraventricular or ventricular