Body Surface Low-Level Potentials During Ventricular Repolarization with Analysis of the ST Segment

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Early ventricular repolarization was examined by measuring body surface maps in normal subjects, ages 1-60 years. Repolarization began with positive potentials. The time of appearance of these potentials from the onset of QRS increased with age. All normal subjects had positive ST segments on the anterior torso. Although the magnitude of the maximal ST-segment voltage varied from subject to subject, the maximal ST-segment voltage increased from early childhood into the twenties and thereafter decreased with age. The same age-related trend occurred during other phases of ventricular repolarization, i.e., the T wave and the U wave. Although the ST-segment maxima occurred in a circumscribed area near the heart in all adults, the normal ST-segment patterns varied in relation to the vertical distance over which low-level positive potentials extended on the left anterior torso. The ST-segment patterns differed greatly in the low-level potentials in areas distant to the heart. The ST-segment patterns indicate that the arrangement of ST-segment "current sources" is detectably different in normal adults. This variability suggests that the evaluation of ventricular ischemia might be enhanced by interpreting a questionably abnormal map (e.g., during exercise) compared with the patient's own baseline map. These results emphasize the importance of measuring the total cardiac electrical field on the body surface to account for the effects of the currents from all areas of the ventricles during the ST segment, rather than characterizing primarily the proximity effects as dohe with precordial maps

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