Catheter ablation for atrial fibrillation

As I understand it, during catheter ablation in the atria, the 'problem' electrical cells are identified and then destroyed using rf heat. This brings to mind the followinq questions:
1.) Is there a problem with weakening of the atrium walls and are there any issues concerning scar tissue, such as loss of flexibility where ablation is performed that may cause problems later.
2.) What are the typical dimensions of the 'problem' areas in the atrium, how large is the burn area, and what is the resolution with which the probes can be placed, i.e. can problem areas be missed?
3.)Is there 'old' equipment and 'new' equipment in use at various institutions that perform this type of work (what do I need to ask?)
4.) What are the dangers (if any) in creating the opening from one atrium to the other that may be required to reach both atria.

Thanks for your time and help.

[Cleveland Clinic, MD]

1.) Is there a problem with weakening of the atrium walls and are there any issues concerning scar tissue, such as
     loss of flexibility where ablation is performed that may cause problems later.
A: Yes, there can be problems with scar tissue forming.  For this reason the smallest amount of ablation possible is used.

     2.) What are the typical dimensions of the 'problem' areas in the atrium, how large is the burn area, and what is the
     resolution with which the probes can be placed, i.e. can problem areas be missed?
A: The area is actually not in the atrium but in the pulmonary veins and is actually quite small.

     3.)Is there 'old' equipment and 'new' equipment in use at various institutions that perform this type of work (what
     do I need to ask?)
A: No.  This is such a new field there is only new equipment.

     4.) What are the dangers (if any) in creating the opening from one atrium to the other that may be required to
     reach both atria.
A: The opening is actually already there but is usually closed.  There is some risk that the hole will not close again properly following the porcedure but this is rare.

[LaurieAVNRT]

A related discussion, Discharge Summary Post Ablation was started.