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.