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.