DISCUSSION
This study demonstrated that common RAFl ablation can be performed with
a single ablation catheter approach while still enabling CTI block
verification. In addition, we found that a difference of 70 ms between
PR interval assessed at lateral versus septal side of the line could
predict with a 100% sensitivity and specificity the presence of a
complete CTI block.
This approach has been recently proposed by Madaffari et al (10). They
introduced the possibility to validate CTI block using surface ECG PR
interval measured at septal and lateral part of the isthmus. We
confirmed their results on a larger series of patients (61 versus 31
patients). However, they used a cut-off of 80 ms of PR increase to
validate CTI block. Our cut-off of 70 ms clearly demonstrated as shown
in Figure 3 a 100 % of sensitivity and specificity. This slight
discrepancy was likely due to the variability of PR interval measurement
and the difference in PR interval measurement method. Indeed, we
measured PR interval from the atrial spike to the peak of QRS in lead II
as it appeared that this method was associated with less variability
compared to the beginning the QRS which can be in some cases
particularly difficult to assess. In addition in our study, the septal
delay was obtained by CS pacing whereas Madaffari et al were pacing from
the ablation catheter at 5 o’clock on the tricuspid annulus. We think
pacing from the CS ostium is more reproducible than pacing from the
septal CTI.
We think that this technic is accurate and could also reduce the cost of
this procedure. Indeed, CTI ablation is usually performed with 2 or 3
catheters and we estimate that the use of the single catheter approach
could reduce the procedure cost up to 30%. Consistent with this,
Pambrun et al (11) also used the single catheter ablation approach to
perform PVI with a high success rate and demonstrated a significant
reduction in the cost procedure. Further this strategy could potentially
reduce vascular complication rates and be used in the setting of venous
abnormalities when access is difficult to obtain.
In our approach, PR measurement is critical to validate the block and
this measurement can be complex to perform. Then, we excluded for this
technic, patients with PR longer than 240 ms at baseline or with
permanent atrial or ventricular pacing requirement. Moreover, the pacing
rate to measure PR interval is important and we recommend using atrial
pacing at 800 ms or 10 bpm faster than the patient spontaneous heart
rate if needed.
Finally, limitations associated with our technic include, the fact that
CTI block cannot be assessed during ablation as no atrial pacing is
performed during ablation, implicating the need to confirm the block
after CTI line ablation. This technic provides unidirectional (lateral
to medial) validation of the CTI block which appears to be sufficient in
the vast majority of cases; and allows for differential pacing
maneuvers. Yet, as with most technics used to validate block, a
functional block could potentially be misclassified as a complete block
when CTI line verification, waiting period or adenosine injection (12)
are not carefully performed.