Table 4:

Troubleshooting The Difficult Case

- Basket Catheter Sizing and Positioning	- Select basket based on left atrial rather than right atrial size.
	- Select basket based on measuring the distance from trans-septal crossing to Coumadin ridge
	- Select a more anterior trans-septal puncture, to advance the basket posteriorly into the left atrium
	- If in doubt, undersize rather than oversize the basket
- Unable to identify focal sources on a FIRM map.	- Assess for proper basket catheter size and position. See figure 5
	- Maximize signal fidelity by catheter opposition; ensure adequate filtering and unipolar reference.
	- Choose another time slice within the epoch, since AF drivers may fluctuate then re-appear in the same location. Alternatively, collect another epoch.
	- Play movie initially fast, to localize general region of rotation or focal activity, then slow movie down. For focal source, play movie in reverse to show activation ‘collapse’ to an origin.
	- Consider sources outside the mapping area.
	- Evaluate regions of under sampling, adjust basket positioning, and re-sample.
	- Choose an alternative spline to “cut and open”.
- Inability to eliminate Rotor or Focal Source Despite FIRM ablation	- Ensure adequate ablation at targeted sites by lack of capture with high output pacing.
	- Utilize additional ablation if needed, taking into account standard safety considerations e.g. near the esophagus or phrenic nerves.
	- Repeat FIRM map. Sources may become clearer with elimination of other sources.
	- Evaluate regions of under sampling, adjust basket positioning, and re-sample.
	- Consider sources outside the mapping area.