Understanding the pathophysiologic mechanisms leading to ventricular arrhythmias seems indispensable for rational treatment. However, a detailed study of these mechanisms in the intact human heart is not possible at present. Therefore, we have to transpose knowledge obtained from observations on single cells, isolated muscle strips, and animal hearts to the human heart, with the inherent danger of making incorrect extrapolations. The recent introduction of programmed electrical stimulation of the heart gives us the opportunity to bridge a part of the gap by studying some aspects of the mechanisms of arrhythmias directly in the human heart. The purpose of this article is to review the possibilities and limitations of this technique to study ventricular tachycardia in man.
As recently reviewed by Scherf and Schott,1 Bigger,2 and Watanabe and Dreifus,3 cardiac arrhythmias can result from different electrophysiologic mechanisms. These mechanisms can be classified as (1) abnormalities in impulse formation,