Letter to the editor
Very late recurrences after ablation of AVNRT
Per Insulander, MD PhD, Mats Jensen-Urstad, MD PhD
Dept of Cardiology at Karolinska Institutet and Karolinska University
Hospital
Corresponding author:
Per Insulander
Dept of Cardiology at Karolinska Institutet
Karolinska University Hospital, M85
S-141 86 Stockholm
Sweden
Tel +46 8 585 80000
Fax +46 8 585 86710
per.insulander@sll.se
Funding: none
Conflict of interest: none
We read with great interest the recently published article by Chaumont
et al. (1) regarding late recurrences in AVNRT after cryoablation. The
authors found that among 257 patients with AVNRT successfully ablated
with cryo energy, recurrences occurred in 24 subjects during a follow-up
of 38±27 months. Most of the recurrences occurred between 1- and 6-year
follow-up, with one-third recurrences occurring after the 3-year
follow-up. Seventeen patients demonstrated
the fast-slow or slow-slow
variants of AVNRT. In univariate analysis, procedure duration, number of
applications, transient PR prolongation or AV block (5 cases), and
Kock´s triangle anatomical variants were associated with AVNRT
recurrences. However, only the last characteristic was independently
associated with recurrence.
Some years ago, we addressed this issue in a larger cohort of patients
who underwent cryoablation of AVNRT (2). In all, we followed up 516
patients (mean age 50 years, range 13-89 years, 317 women) for a mean of
7.1 years (range 2-11.5 years). All were ablated with the 6 mm
Freezer-Extra catheter. In this cohort, 24 patients had the fast-slow or
slow-slow variants of AVNRT. Furthermore, transient AV block was
observed in 45 patients. The anatomic morphology of Kock´s triangle was
not regularly documented in this series. In all, 54 patients had
recurrences.
In contrast to the finding of Chaumont et al., atypical variants of
AVNRT were related to recurrence in our series, but transient AV block
and energy duration were not. In agreement with Chaumont et al., late
recurrences dominated. Of these, 19 occurred later than 1 year, 14
occurred later than 2 years, 8 occurred later than 3 years, and 6
occurred later than 4 years. One patient had recurrence after 9 years.
The issue of very late recurrences, 5-10 years after the index
procedure, also reported after RF ablation (3), is interesting.
In our opinion, recurrence of AVNRT due to AV nodal pathway reconduction
caused by suboptimal cryo or RF lesions is less likely so many years
after the index procedure. We think other explanations should be
discussed.
The ablation lesion per se may certainly evolve to constitute a new
substrate but would probably manifest itself earlier. We think that age
related effects should also be considered. Fibrous and fatty tissue
infiltration in cardiac nodal tissues has been described to start as
early as in subjects 35-40 years old (4). Furthermore, the sympathovagal
influence on the AV node changes with age, partly due to changes in the
proportion of beta-adrenergic receptors and to a decrease in vagal
influence, in turn altering AV nodal conduction and refractoriness
(5,6). Taken together, these age-related changes in AV nodal
electrophysiologic conditions could set the stage for a previously not
present substrate for AVNRT. It is not uncommon that AVNRT manifest
itself for the first time in remarkably high age. This may also be
explained by the previously mentioned age-related AV nodal changes.
Consequently, the occurrence of AVNRT many years after an ablation
procedure may perhaps not always implicate a recurrence but instead an
arrhythmia caused by a new substrate.
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References
- Caumont C, Mirolo A, Savouré A, Godin B, et al. Very long-term
outcomes after catheter ablation of AVNRT: How does cryoenergy differ
from radiofrequency? J Cardiovasc Electrophysiol.2020;32:3215-3222.
- Insulander P, Bastani H, Braunschweig F, Drca N, et al. Cryoablation
of atrioventricular nodal re-entrant tachycardia: 7-year follow-up in
515 patients-confirmed safety but very late recurrences occur.
Europace. 2017;19:1038-1042.
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