Studies on unipolar leads

False coronary patterns in the infant electrocardiogram

Electrocardiographic patterns of myocardial infarction are rarely found in infancy and suggest, in the first place, an anomalous origin of the left coronary artery. Five infants with such electrocardiograms are reported. In all coronary heart disease could be ruled out, in 4 by autopsy and in 1 by the clinical course. Comparison of these 5 cases with previously reported cases with similar electrocardiograms and autopsy control revealed that coronary patterns in infancy occur in a true and false variety. Some distinguishing features are discussed.

Polarity and amplitude of the U wave of the electrocardiogram in relation to that of the T wave

The ratio of the amplitude of the QRS complex to the amplitude of the U wave varies in different leads of the same electrocardiogram. In the majority of electrocardiograms, the U wave has the same polarity as the T wave and the ratio of the U wave and T wave amplitude is relatively constant in all leads. The tallest positive U wave is usually observed in the area of leads V 2 to V 4 . The deepest negative U wave is usually observed in the area of leads V 5 to V 6 . Secondary changes of the T wave are very frequently accompanied by similar changes of the U wave. T-wave changes caused by myocardial infarction and digitalis are usually not accompanied by changes of the polarity of the U wave.

The electrocardiograms of 297 cases of hypertension were divided into 6 groups on the basis of the relationship between the polarity of the T wave and the U wave. Both waves were positive in all precordial leads in 48.1 per cent of the cases. Negative U waves were found in 21.8 per cent of the cases and these were predominantly in the leads with negative T waves. A negative T wave in the left precordial leads was accompanied most frequently by a negative, less frequently by an isoelectric, and least frequently by a positive, U wave. An inverted U wave in the presence of an upright T wave was found in only 2.8 per cent of the cases. A change from a negative to a positive or isoelectric U wave was observed after slowing of the heart rate, a drop in blood pressure, and nitroglycerin administration.

The effect of digitalis on the normal electrocardiogram

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The Nature of the RS-T Segment Displacement as Studied with Esophageal Leads

The electrocardiographic changes, with particular reference to the RS-T segment and T wave, in surface leads and in esophageal leads reflecting left ventricular cavity potentials, are studied in 7 persons with and without heart disease, before and after the administration of digitoxin. After the administration of digitoxin, the RS-T segment depression in precordial leads and in esophageal leads reflecting the potentials of the posterior surface of the left ventricle, are regularly associated with RS-T segment elevation in esophageal leads reflecting left ventricular cavity potentials. The possible roles played by myocardial involvement due to digitalis, modification of the monophasic curves, and the reduction of the human ventricular gradient are discussed.