A Study on the Direction of Inscription of the Vectorcardiographic T-Loop in Left and Right Ventricular Hypertrophy

Abstract

(1) Frank lead vectorcardiogram was recorded in 30 normal persons and in 323 cases with hypertension and acquired and congenital heart disease. The T-loop was classified into 8 types according to the directions of inscription in 3 planar projections. Frequently observed types were examined with the direction of the maximal T vector.
(2) In majority of normal cases, the T-loop was inscribed counterclockwise in horizontal and clockwise in sagittal planes.
(3) In left ventricular hypertrophy, abnormal inscription of the T-loop was observed with abnormal rightward and superior deviation of its maximal vector and the T-loop oriented more than 120° in horizontal plane was usually accompanied by abnormal inscription. Percentage of abnormal inscription was higher in cases with cardiac complaints.
(4) In right ventricular hypertrophy, directional change of the T-loop was relatively small but changes in inscription of it were common. The T-loop was always inscribed abnormally in cases with abnormal inscription of the QRS-loop.
(5) The concept of the polar vector was found to be valuable in studying the inscription and the direction of the T-loop. Significance of changes in inscription of the T-loop was discussed.