The Clinical Value of Chest Leads.
نویسنده
چکیده
In the growth of electrocardiography as a clinical method, British physiologists and physicians have played a more important role than those of any other nationality. Waller was the first to show that the electrical activities of the human heart could be recorded by leading from the extremities or from the surface of the chest. Mackenzie, although he did not deal directly with this subject, tremendously increased our knowledge of clinical disorders of the rate and rhythm of the heart beat and aroused a world-wide interest in this field. Thomas Lewis contributed more than any other man to the development of the principles and methods of analysis upon which the interpretation of the electrocardiogram is founded. Most of my own electrocardiographic studies have been the result of ideas derived from his investigations, and I am also deeply indebted to him for help and encouragement on many occasions. I consider it a very great honour to be asked to discuss an important aspect of clinical electrocardiography here in his native land and in this great city where his work was c*ne. It would have been a still greater pleasure to come here if he were still living and could take part in this discussion. It was the work of Lewis and Rothschild on the spread of the excitatory process that first aroused my interest in the possibility of exploring the anterior ventricular surface by placing one electrode on the precordium and the other far from the heart. The observations and ideas contained in their paper and notions derived from a study of the physical principles upon which the work of Einthoven and that of Waller on the electrical axis of the heart is clearly founded led to a series of investigations concerned with the character of the heart's electrical field. These investigations were first undertaken late in 1919 and were continued off and on through the early twenties. A preliminary report to the effect that prxcordial leads of the kind mentioned are semi-direct leads very similar to the unipolar direct leads first used by Lewis and Rothschild was published in 1926, but the systematic use of multiple leads of this sort at the University of Michigan dates from the summer of 1929. It was precipitated at that time by the observations on bundle branch block by Barker, Macleod, and Alexander, and was undertaken with the purpose of obtaining additional data bearing on their conclusions. A preliminary report of this work was published in 1930; the final report came out in 1932, and was nearly simultaneous with the paper on the use of a single chest lead in the diagnosis of infarction by Wolferth and Wood. Since that time the percentage of cases in which pracordial leads are employed has steadily increased. We have never taken precordial leads routinely. For the purpose of studying disturbances of the rate and rhythm of the heart beat, or of the time relations and sequence of auricular and ventricular activation, unipolar chest leads are only occasionally better than limb leads, and are not in general superior to bipolar chest leads of the kind used by Lewis in his studies of auricular fibrillation, and are much less useful than cesophageal leads. They have not thus far proved to have any special advantages in the study of the form of the auricular complex. On the other hand, chest leads and particularly unipolar leads from the pracordium, are indispensable for the detection and differentiation of abnormalities of the ventricular complex. They frequently disclose abnormalities of the QRS group, the T complex, or both, when the limb leads show either no deviation from the normal or none that have diagnostic significance. On this occasion, it will suffice to consider only those conditions in which the value of unipolar pracordial leads has been most clearly demonstrated. It should, of course, be clearly understood that clinical diagnosis should seldom, if ever, be made on the basis of electrocardiographic findings alone. To rely solely upon an interpretation of the electrocardiogram that is not supported by the case history or other clinical data after an adequate investigation has been made frequently means to run the risk of converting an essentially normal person into a psychoneurotic invalid. Pr,ecordial leads are of value, first of all, in the recognition of abnormalities affecting the intraventricular conduction of the cardiac impulse. They make it possible in the vast majority of the cases in which the QRS interval measures 0X12 second or more to ascertain whether one is dealing with right bundle branch block, left bundle branch block, arborization block, Wolff-Parkinson-White
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عنوان ژورنال:
- British heart journal
دوره 10 2 شماره
صفحات -
تاریخ انتشار 1948