Ablation of posteroseptal pathways

Slant can be used to uncover AP potential.
Pathway potentials can be located by mapping aortic annulus just like the mapping of the mitral and tricuspid annulus.
IVUS probe can be put in the artery close to the site of ablation. Look for bubbles on IVUS and terminate the ablation as soon as bubbles are seen.
Coronary sinus diverticulum can be targeted deep within as well as at the neck. Ablation within will have the advantage of not closing of the diverticulum with thrombus. But most often we end up by a circumferential ablation at the mouth of the diverticulum because of multiple connections. PDA is more likely to be damaged deep in the coronary diverticulum. But the artery most likely to be damaged is the branch which hooks around. Cryo is a good option to avoid damage to coronary arteries.
If sudden PR lenghthening occurs while ablating within the coronary sinus, it could be damage to AV nodal damage or damage to the vagal ganglia in the posterior pyramidal space. The latter would manifest with associated slowing of the sinus rate. It is seldom due to AV nodal damage. If you are bold enough, you can try giving atropine and continuing the ablation (if the rate picks up, indicating gangliar involvement), which will differentiate between injury to the artery vs gangliar involvement.
Coronary sinus isolation is a very difficult procedure to do.