Abstract
Earlier studies in this laboratory demonstrated that warming or cooling portions of the external surface of the ventricles caused characteristic alterations in the T wave of the electrocardiogram. 1 The basis of these T wave changes was found to be alteration in the duration of one or the other of the two components of the electrocardiogram, i. e., of the dextro- or the levocardiogram. Cold prolonged and heat shortened the duration of these components. The following experiments were undertaken to determine the cause of these alterations in the duration of the dextro- and levocardiograms.
Electrograms and monophasic action potentials were studied in 5 dogs by the method previously described, 2 one lead being taken from the anterior surface of the right ventricle and the other from the anterior surface of the left ventricle. Negativity at the lead on the right ventricle gave an upward deflection of the beam. The influence of temperature was determined first on the electrogram, and then on the monophasic action potential. Variations in temperature were produced by applying a small tin chamber to the surface of the heart under one or the other electrode, and circulating through the chamber water at 5°C or 55°C.
The results of heating or cooling the surface of the heart under one or the other electrode are shown in Fig. 1. When the region under the right ventricle electrode was cooled, an upright end deflection was obtained, while when this region was warmed, the end-deflection was sharply inverted. The duration of the whole electrogram was prolonged when the heart was cooled, and was not materially altered by warming. Exactly opposite effects followed cooling and heating under the electrode on the left ventricle. Cooling produced a prolonged downward end-deflection, while heating produced an upward end-deflection of normal duration.
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