Differential Pacing

From Ask Dr Wiki

Differential Pacing for Septal Pathways

• Ventricular pacing is performed from two right ventricular positions, an apical site, and a posterobasal site. Figure 1. illustrates the position of the catheters.
• This test is used to assess whether retrograde conduction takes place over a posteroseptal accessory pathway or over the normal conduction system. VA intervals when pacing from apex are shorter compared to pacing at base unless a septal pathway is present.
• The Ventriculoatrial Index is the difference between pacing at the apex compared to pacing at the base. In figure 4 it is shown that when group A, patients with no AP are compared to group B, patients with an AP the ventriculoatrial index in group B always exceeded 10 milliseconds, a value for this index >10 milliseconds establishes the presence of a posteroseptal accessory pathway with 100% sensitivity, specificity, and positive predictive value.

Figure Gallery

Figure 1. Position of catheters during differential pacing

Figure 3. VA interval pacing from the apex in a patient with a septal pathway is 174 ms

Figure 2. VA interval pacing from the base in a patient with a septal pathway is 151 ms

Figure 4. Ventriculoatrial Index is 23 ms indicating that there is a septal pathway present

References

JD Martinez-Alday, J Almendral, A Arenal, JM Ormaetxe, A Pastor, JP Villacastin, O Medina, R Peinado and JL Delcan. Circulation. 1994;89:1060-1067.