Parahisian or high output / low output pacing

[Jessica]

What is parahisian or high output / low output pacing used for and how do I do it? 

[roy]

This pacing procedure, performed by pressing Ctrl-INS / Ctrl-DEL on the Current parameter on the Micropace, is used to differentially pace the underlying myocardium at the low output and a specific underlying structure such as the His bundle at the high output. Typical low and high currents may be 2mA and 10mA respectively.

[Michael]

In parahisian pacing this method is used to detect concealed septal accessory pathways, which may not be diagnosable by normal retrograde pacing from the RVA because they result in normal-looking concentric atrial activation indistinguishable from normal retrograde His conduction. Pacing over the His bundle with high output captures the His resulting in narrow complex and the low output captures the ventricle, identifiable by its wide complex. If the V-A interval is the same for both, a septal retrograde AP is present because normally, the V-A interval is longer for the Ventricle than His capture because activation has to travel down to the purkinje fibres and then back up the His bundle.