Theoretically the circuit is:
1. Antegrade limb of the circuit goes through the verapamil sensitive zone,
2. The turn around site of the reentrant circuit occurs in the lower third of the septum.
3. Retrograde activation occurs over the posterior fascicle from apical to basal septum
But this is very difficult to see in activation mapping. Usually we see only the exit point of the circuit and this is all. The circuit must be guessed.
http://tinypic.com/r/xlfrxh/8
That's correct. You can see that the picture is basically the same in this paper: Circulation. 2002;105:462-9 (http://circ.ahajournals.org/content/105/4/462.full.pdf+html). Both limbs of the circuit seems to be close enough to not allow detailed electroanatomic activation mapping.
Very interesting topic. I am on the modeling side of the Purkinje network and this is very interesting from the modeling perspective.
I have a question though related to your discussion. When you collect your CARTO data, Is the patient showing VT during all the procedure? Is the circuit exactly the same at any heart beat? Since CARTO does interpolation between points acquired between different heart beats, data could be masked (averaged) easily. Maybe a non-contact simultaneous acquisition could shed some light into the complex mechanism.
For Rafael Sebastian: Thank you for your comment.
The patient is not showing VT during all the procedure.
1.Usually we start with an anatomical map in sinus rythm, we tag the mitral anulus the aortic valve, the His, the postero-inferior fascicle, the antero-superior fascicle.
2. Than we induce VT and study the arrhythmia during 15-20 minutes in order to obtain activation mapping.
3. After this we make points of ablation at the level of postero-inferior fascicle if the circuit is clear enough or even if it's not clear. It stops rapidly the arrhythmia.
Carto do not make interpolation between points in terms of local electrical signal. Each point has its own signal and between 2 points if we do not have a third one we do not know the exact local electrogram at this level. Surely if we look only for colors of activation mapping you are right and there is an averaged color.
Non contact mapping is an interesting approach but the local electrogram is not so clear as with a contact catheter. We do not have experience with non-contact.
Gabriel, what type of ablation catheter do you usually use for fVT? Irrigated one?
Yes, an irrigated catheter.
Because we have a Carto 3 system we use the Navistar Thermocool catheter.
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