Catheter Ablation characteristics
A total of 301 RF applications were delivered (mean 4.5 ± 4.5 lesions
per patient) with an average RF duration of 28.2 ± 18.8 seconds per
lesion. Junctional rhythm was observed during 178 (59.1%) RF
applications. Effective RF application resulting in slow pathway
modification or elimination occurred after 66 (37%) RF applications
with JR in all. Slow pathway modification was not achieved by any RF
application which did not result in JR (Table 1). One (1.5%) patient
with readily inducible AVNRT had 2 echo beats after 15 RF applications
for a total of 7.95 minutes RF. No further RF was applied as AVNRT was
no longer sustained and the catheter position was in close proximity to
the compact AV node.
Effective RF applications were significantly longer in duration (38.5 ±
25.6 vs ineffective: 26.9 ± 18.4seconds, p = 0.002, Table 1) and ranged
from 5 to 60 seconds. Successful slow pathway ablation was achieved in 6
patients with RF applications less than 10 seconds. The fastest (406 ±
152ms vs 438 ± 179ms, p=0.2), median (587 ± 150ms vs 611 ± 193ms p=0.4)
cycle length of the junctional rhythm and proportion of junctional
rhythm (43.2 ± 28.4% vs 36.3 ± 23.7% p=0.1) observed during RF
application was not significantly different between effective and
ineffective lesions. Complete loss of slow pathway conduction after
catheter ablation occurred in 30 (45.5%) patients. The median cycle
length of JR was significantly faster during RF applications that
resulted in complete loss of slow pathway (546 ± 128ms) compared with
slow PW modification and those that did not affect slow pathway
conduction (613 ± 185ms, p=0.02).
Cycle length of the junctional rhythm observed during RF application was
compared between effective and ineffective lesion for individual
patient. First RF application with junctional response was effective in
28 (42%) patients with a median cycle length of 604 ± 180ms. Among the
38 (57.6%) patients who had >1 RF, 2.7 ± 2.6 ineffective
lesions with junctional response was performed prior to the successful
lesion.
Transient AV block occurred in 1 (1.5%) which resolved within 60
seconds of cessation of RFA. There were no cases of persistent AV block
or of any patients with a >10msec increment in the AH
interval. JA block was observed during faster JR in 19 (28%) patients
during RF application. RF application was terminated immediately if JA
block was seen with no prolongation of the AH interval in the next
conducted beat (Figure 2). Fourteen of 19(73.7%) RF applications
associated with JA block were successful with AVNRT no longer inducible
including complete loss of slow pathway conduction in 10 (52.6%). See
Table 1.
Following successful RF application, difference in AV nodal Wenckebach
threshold was not statistically significant (373 ± 75ms pre to 365 ±
99ms post RF (p=0.8). Fast pathway ERP shortened from 347 ± 64 to 319 ±
84ms, p = 0.003.
The average procedure duration was 78.0 ± 35.5 minutes with an average
fluoroscopy time of 8.4 ± 5.6minutes. There were no acute complications.
At a median follow up of 1.4 ± 0.7 years, 66 (98.5%) had no further
documented SVT. One (1.5%) patient presented with an early recurrence
after an initial procedure which had achieved the acute endpoint after
an RF time of 45 seconds with a cycle length of junctional rhythm during
RF as short as 350ms. A second procedure demonstrated inducible AVNRT
with RF resulting in adequate modification of slow pathway conduction
with no further recurrence.