ECG leads V1H to V6H and V1L to V6L

ECG leads V1H to V6H and V1L to V6L

ECG leads V1H to V6H are recorded one intercostal space above the conventional position, and leads V1L to V6L are recorded one intercostal space below. This means that V1H is recorded from 3rd intercostal space at the right sternal edge and V1L is recorded from 5th intercostal space at the right sternal edge. Rest of the leads follow in the usual sequence in a correspondingly higher or lower intercostal space. V1H is also sometimes called as 3V1 and V1L as 5V1, the initial number indicating the space from which the first lead in the sequence is recorded. So the conventional V1 is 4V1.
V1L to V6L are useful when the heart is shifted down as in emphysema. In emphysema, conventional leads (V1 to V6) will mimic V1H to V6H. V1H to V6H are also known as high precordial leads or high chest leads. High chest leads are sometimes useful in detecting high lateral wall infarction.