NCIt definition : A unipolar electrocardiogram lead site; the electrode is placed at the fourth intercostal
space on the anterior chest wall (between ribs 4 and 5) to the right of the sternal
border. In small animals, it is placed at the right fifth intercostal space near the
sternum.;
Alternative definition : CDISC: A unipolar electrocardiogram lead site; the electrode is placed at the fourth
intercostal space on the anterior chest wall (between ribs 4 and 5) to the right of
the sternal border. In small animals, it is placed at the right fifth intercostal
space near the sternum. (NCI);