Abnormalities of the S‐T segment—Part I

AbstractThe usual normal S‐T segment of the surface electrocardiogram (ECG) contributes little to the diagnostic procedure. When the S‐T segment is too long or too short, or when it is displaced upward or downward, it is commonly abnormal. Under such circumstances, an S‐T segment abnormality usually contributes considerable diagnostic information. When the Grant method of ECG interpretation is used, it is possible to perceive abnormalities of the S‐T segment that may otherwise be ignored or misinterpreted. This paper describes the method of identification and the significance of primary and secondary S‐T segment abnormalities. When a mean vector constructed for the S‐T segment displacement seen in 12 ECG leads is relatively parallel with a mean vector representing the T wave, it is, with a few exceptions, part of the repolarization process and is therefore part of the T wave. This may be called a secondary S‐T segment abnormality. When a mean vector constructed for the S‐T segment displacement seen in 12 ECG leads is not relatively parallel with a mean vector representing the T wave, it is, with a few exceptions, not part of the repolarization process and is therefore not part of the T wave. This may be called a primary S‐T segment abnormality.