#+TITLE:     RV Apex vs Base Pacing
#+AUTHOR:    David Mann
#+EMAIL:     mannd@epstudiossoftware.com
#+DATE:      [2014-10-20 Mon]
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* 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
