Josephson Clinical Cardiac Electrophysiology

Historical Perspectives


The study of the heart as an electrical organ has fascinated physiologists and physicians for over 150 years. Matteucci 1 studied electrical current in pigeon hearts, and Kölliker and Müller 2 studied discrete electrical activity in association with each cardiac contraction in the frog. Study of the human elec trocardiogram awaited the discoveries of Waller 3 and, most importantly, Einthoven, 4 whose use and development of the string galvanometer permitted the standardization and wide spread use of that instrument. Almost simultaneously, anato mists and pathologists were tracing the atrioventricular (A-V) conduction system. Many of the pathways, both normal and abnormal, still bear the names of the men who described them. This group of men included His, 5 who discovered the muscle bundle joining the atrial and ventricular septae that is known as the common A-V bundle or the bundle of His. During the first half of the 20th century, clinical electro cardiography gained widespread acceptance, and in feats of deductive reasoning, numerous electrocardiographers con tributed to the understanding of how the cardiac impulse in humans is generated and conducted. Those researchers were, however, limited to observation of atrial (P wave) and ventricular (QRS complex) depolarizations and their relation ships to one another made at a relatively slow recording speed (25 mm/sec) during spontaneous rhythms. Nevertheless, com bining those carefully made observations of the anatomists and the concepts developed in the physiology laboratory, these researchers accurately described, or at least hypothesized, many of the important concepts of modern electrophysiology. These included such concepts as slow conduction, concealed conduction, A-V block, and the general area of arrhythmo genesis, including abnormal impulse formation and reentry. Some of this history was reviewed by Langendorf. 6 Even the mechanism of preexcitation and circus movement tachycar dia were accurately described and diagrammed by Wolferth and Wood from the University of Pennsylvania in 1933. 7 The diagrams in that manuscript are as accurate today as they were hypothetical in 1933. Much of what has followed the innova tive work of investigators in the first half of the century has confirmed the brilliance of their investigations. In the 1940s and 1950s, when cardiac catheterization was emerging, it became increasingly apparent that luminal cath eters could be placed intravascularly by a variety of routes and safely passed to almost any region of the heart, where they could remain for a substantial period of time. Alanis et al 8 recorded the His bundle potential in an isolated perfused ani mal heart, and Kottmeier et al 9 recorded the His bundle poten tial in humans during open heart surgery. Giraud et al 10 were the first to record electrical activity from the His bundle by a catheter; however, it was the report of Scherlag et al, 11 detail

ing the electrode catheter techniques in dogs and humans, to reproducibly record His bundle electrogram, which paved the way for the extraordinary investigations that led to modern cardiac electrophysiology. At about the same time Durrer et al in Amsterdam and Coumel and his associates in Paris independently devel oped the technique of programmed electrical stimulation of the heart in 1967. 12,13 This began the first decade of clinical cardiac electrophysiology. Although the early years of intra cardiac recording in humans were dominated by descriptive work exploring the presence and timing of His bundle activa tion (and that of a few other intracardiac sites) in a variety of spontaneously occurring physiologic and pathologic states, a quantum leap occurred when the technique of programmed stimulation was combined with intracardiac recordings by Wellens. 14 Use of these techniques furthered our understand ing of the functional component of the A-V specialized con ducting system, including the refractory periods of the atrium, A-V node, His bundle, Purkinje system, and ventricles, which enabled us to assess the effects of pharmacologic agents on these parameters, to induce and terminate a variety of tachyarrhythmias, and, in a major way, led to a greater under standing of the electrophysiology of the human heart. Shortly thereafter, enthusiasm and inquisitiveness led to placement of an increasing number of catheters for recording and stimu lation to different locations with the heart, first in the atria and thereafter in the ventricle. This led to the development of endocardial catheter mapping techniques to define the loca tion of bypass tracts and the mechanisms of supraventricular tachyarrhythmias. 15,16 Beginning in the mid-1970s, Josephson and his colleagues at the University of Pennsylvania were the first to use vigor ous, systematic, multisite programmed stimulation in the study of sustained ventricular tachycardia (VT) resulting from myocardial infarction. 17-19 Subsequent investigators sought to establish a better understanding of the methodology used in the electrophysiology study to induce arrhythmias. Several studies validated the sensitivity and specificity of programmed stimulation for induction of uniform tachycardias, and the nonspecificity of polymorphic arrhythmias induced with vig orous programmed stimulation was recognized. 19,20 In the same time period, Josephson et al 21-23 developed the technique of endocardial catheter mapping of VT, which for the first time demonstrated the safety and significance of plac ing catheters in the left ventricle. This led to the recognition of the subendocardial origin of the majority of ventricular tachyarrhythmias associated with coronary artery disease and the development of subendocardial resection as a therapeutic cure for this arrhythmia. 24

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