# RV Apex vs Base Pacing

## Use

- Determine if retrograde conduction is via a septal accessory pathway (AP) or the AV node (AVN).
- Useful when SVT is not inducible or post-ablation to exclude continued retrograde AP conduction.

## Technique

- Using a deflectable catheter, position at apex and then at posterior base of RV in 30° RAO view.
- Ventricular pacing at each site at same pacing cycle length.
- Measure stimulus to atrium (S-A) at each site.

## Results

- S-A is shorter pacing at base compared with apex in patients with AP conduction only.
- S-A is longer pacing at base compared with apex in patients with retrograde AVN conduction only.
- Note that patients with combined retrograde AP and AV nodal conduction were excluded from the study population. However change in atrial activation sequence when pacing at the 2 sites suggests combined retrograde AP and AVN conduction.
- Note that only patients with posteroseptal APs were included in the study, though the technique is probably also applicable to patients with anteroseptal or para-Hisian APs, as long as basal pacing site is close to the AP.

## Reference

Martínez-Alday JD, Almendral J, Arenal A, et al. Identification of concealed posteroseptal Kent pathways by comparison of ventriculoatrial intervals from apical and posterobasal right ventricular sites. Circulation 1994; 89: 1060-1067. http://circ.ahajournals.org/content/89/3/1060.abstract?ijkey=33950406ac6141d4fb927e205814d0bd992c33c9&keytype2=tf_ipsecsha