The normal electrocardiogram.
نویسنده
چکیده
O NE of the most difficult tasks which confronts the w orker in the life sciences is to define a normal. The difficulty is compounded when the measurement to be made is affected by many variables which differ in importance from time to time. These remarks apply to the electrocardiographer, and to the normal electrocardiogram. Some variables which affect the electrocardiogram are quite well known. They include phase of respiration, heart rate, recent ingestion of food, position and age of the subject. Equalization of the first four is usually achieved by recording the curve during quiet respiration with the subject in a basal state, usually recumbent; effects of age are solved by devising norms for different age groups. Other variables are less well known. Technical errors of various kinds must be guarded against. One of these, excessive electrode jelly which makes contact with jelly at adjacent points, has been shown' to cause considerable distortion of deflections of precordial leads, particularly inversion of the T waves farther to the left than is actually the case. The possibility of distortion of the electrocardiogram by the recording device is usually ignored. The electrocardiogram is made up of a series of transients and intervals. The fidelity with which these are reproduced will depend on the frequency characteristics and the timing accuracy of the instrument used. Despite this basic physical tenet, it is rare to see a paper on
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عنوان ژورنال:
- Circulation
دوره 8 6 شماره
صفحات -
تاریخ انتشار 1953