NCIt definition : A unipolar electrocardiogram lead site; the electrode is placed on the anterior chest
wall midway between leads V2 and V4. In large and small animals, it is placed over
the dorsal spinous process of the 7th thoracic vertebra.;
Alternative definition : CDISC: A unipolar electrocardiogram lead site; the electrode is placed on the anterior
chest wall midway between leads V2 and V4. In large and small animals, it is placed
over the dorsal spinous process of the 7th thoracic vertebra. (NCI);