Europace Advance Access published online on November 4, 2008
Europace, doi:10.1093/europace/eun297
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Effects of inadvertent atrioventricular block on clinical outcomes during cryoablation of the slow pathway in the treatment of atrioventricular nodal re-entrant tachycardia
1 Rhythmology Department, Cardiology Institute, Pitié-Salpetrière Hospital, Paris, France; 2 Rhythmology Department, Hôpital Privé Paris Essonne, Arpajon, France
Aims: The study aimed at evaluating the long-term effects of transient atrioventricular (AV) block on clinical outcomes during atrioventricular nodal re-entrant tachycardia (AVNRT) cryoablation.
Methods and results: In 150 consecutive patients (39 ± 14 years, ineffective anti-arrhythmic drugs 1.9 ± 1.3), slow-pathway cryoablation for AVNRT was performed. A 7 Fr 6 mm-tip cryocatheter was used. After successful cryomapping (–30°C), defined as jump abolition or AV nodal refractory period prolongation, cryoablation (–80°C for 4 min) was applied if no AV block occurred. Atrioventricular nodal re-entrant tachycardia inducibility was checked after 30 min. Acute success (AVNRT non-inducibility) was achieved in 142 patients (95%). Overall, after a follow-up of 18 ± 10 months, 118 of 150 patients (79%) were recurrence-free (including 2 patients for whom the procedure was unsuccessful). Among successful procedures, 116 of 142 (82%) patients were recurrence-free. During cryoablation, inadvertent transient AV block of varying degrees occurred in 34 patients (22.7%), namely, increased PR in 17 patients and a 2nd–3rd AV block in the remaining 17. In 24 patients, AV block occurred at the last effective site (increased PR in 13 patients and a 2nd–3rd AV block in 11). In the study population as a whole, univariate predictors of recurrence in the follow-up were AVNRT inducibility (P < 0.001), increased PR at the last effective site (P < 0.001), residual jump (P < 0.02), and small Koch’s triangle (X-ray distance < 11 mm between the His and coronary sinus ostium catheters; P < 0.02). Atrioventricular nodal re-entrant tachycardia inducibility (P < 0.03), increased PR (P < 0.01), and small Koch’s triangle (P< 0.04) were independently significant. For attempts at the last effective site, 3 groups of patients were compared: 13 patients with increased PR duration (Group A), 11 with a 2nd–3rd AV block (Group B), and 126 without AV block (Group C). Cryo-application time was 277 ± 203 s in Group A, 75 ± 87 s in Group B, and 253 ± 135 s in Group C (A vs. B, P < 0.01; B vs. C, P < 0.001; and C vs. A, P= NS). There was no statistical difference among groups in the atriogram/ventriculogram amplitude ratio at the site of the last attempt, unsuccessful acute procedure, small Koch’s triangle, and residual jump. Actuarial incidence of recurrence-free status at 12 months was 38% in A, 82% in B, and 82% in C (A vs. B, P < 0.05; B vs. C, P = NS; and C vs. A, P < 0.001).
Conclusion: All AV blocks occurring during cryoablation were transient, confirming the safety of this method. An increased PR duration at the last effective site is associated with a higher recurrence rate, whereas a 2nd–3rd degree AV block has a recurrence rate similar to that of patients without AV block despite a shorter cryo-application time at the last site.
Key Words: Atrioventricular nodal re-entrant tachycardia, Cryoablation, Atrioventricular block
* Corresponding author. Tel: +33145409530. E-mail address: antoniodesisti{at}yahoo.fr
Manuscript submitted 5 July 2008. Accepted after revision 13 October 2008.