Time-limited cryomapping during tachycardia: improved long-term outcomes for cryoablation of AVNRT
J Interv Card Electrophysiol
Time-limited cryomapping during tachycardia: improved long-term outcomes for cryoablation of AVNRT
Paula L. S. Eryazici 0
Mansour Razminia 0
Oliver D'Silva 0
Jaime R. Chavez 0
Ferah D. Ciftci 0
Marianne Turner 0
Theodore Wang 0
Terry A. Zheutlin 0
Richard F. Kehoe 0
0 Advocate Illinois Masonic Medical Center , 3000 N. Halsted St., Suite 803, Chicago, IL 60657 , USA
Purpose Cryothermal ablation (CTA) for atrioventricular nodal reentrant tachycardia (AVNRT) is considered safer than radiofrequency ablation (RFA) since it eliminates the risk of inadvertent AV block. However, it has not been widely adopted due to high late recurrence rate (LRR). In an effort to improve LRR, we evaluated a new approach to cryothermal mapping (CTM): “time to tachycardia termination” (TTT). Methods This single-center study had 88 consecutive patients who underwent CTA using TTT for AVNRT. The CTA catheter was positioned in sinus rhythm at the posteroseptal tricuspid annulus, and then AVNRT was induced. The CTA target site was identified by prompt tachycardia termination in ≤20 s during CTM. Procedural success was defined as no inducible AVNRT and ≤1 single AV nodal echoes. Results Acute procedural success was achieved in 87 of 88 patients (98.9 %) and was similar to prior studies for both CTA and RFA. No permanent AV block was observed. LRR was 3.7 % at a mean follow-up of 19.7 months. LRR was equivalent to that commonly reported for RFA and improved when compared to conventional CTA. Conclusion TTT for CTA of AVNRT provides enhanced safety and similar long-term efficacy when compared to RFA. Based upon this experience, TTT provides an enhancement to conventional CTA that appears to result in improved longterm outcomes. In light of these findings, it seems reasonable to undertake additional randomized trials to determine
AVNRT; Cryoablation; Cryomapping; Time to effect; Time to tachycardia termination
whether RFA or CTA using TTT is the optimal approach for
the catheter ablation of AVNRT.
Radiofrequency (RF) catheter ablation is generally
considered the preferred treatment option for patients with
symptomatic atrioventricular nodal reentrant tachycardia
(AVNRT) [1–3]. While its use is associated with
excellent short and long-term success rates, a major
drawback is the risk of inadvertent permanent AV block.
This complication has been reported in up to 2.0 % of
patients [3–6] and leaves them pacemaker-dependent for
life. Given that patients with AVNRT are often young
 and free of structural heart disease, this can be a
Cryothermal ablation (CTA) is an alternative to
radiofrequency ablation (RFA) with a similar acute procedural
efficacy averaging 95 % that also offers the advantage of being
virtually devoid of the risk of permanent AV block. The initial
experience with CTA for AVNRT was reported in the
multicenter prospective FROSTY trial. None of the 103 patients
with AVNRT that underwent CTA developed inadvertent
AV block that required permanent pacemaker implantation
. Subsequent studies have confirmed this finding in over
1000 patients [8–13].
Despite this noteworthy safety advantage, CTA has not
been broadly adopted as the ablative technique of choice since
its use has been associated with a higher risk of late arrhythmia
recurrence [10, 13, 14], averaging 9–10 % for CTA compared
to only 3–4 % for RFA based on the most recent studies [2, 3,
The inherent safety of CTA derives primarily from the
reversibility of the cryothermal lesion during the first 30–60 s of
cooling when lesion temperature is limited to a nadir of
−30 °C. During this phase of cooling, the targeted tissue
becomes temporarily unable to conduct, providing the operator
assurance that irreversible CTA at that site will be effective
and unlikely to create permanent AV block. The process of
CTA target site selection is broadly referred to as cryothermal
mapping (CTM). A variety of CTM end-points have been
employed to determine whether a site is suitable for
permanent CTA. These include (1) interruption of slow pathway
conduction during CTM; (2) inability to reinduce AVNRT in
a previously inducible patient; and (3) termination of
sustained AVNRT during CTM.
In all previously reported large studies, however, the
exact method employed for CTM was uncontrolled and
left to the discretion of the investigator. Similarly, the time
allowed to achieve the desired CTM effect was
uncontrolled, often lengthy, and usually not reported. In some
studies, a target site could be deemed appropriate for
permanent CTA even when the desired effect occurred as late
as 80 s into CTM . Thus, it is possible that the higher
late recurrence rate (LRR) often reported in prior CTA
studies could be related to the CTM methodology
employed. As an example on how the details of the
CTM technique can actually have a significant impact
on outcomes, improved CTA results have been noted
when target site selection was guided by time-limited
CTM, a feature that has often been referred to as “time
to effect” [12, 16, 17].
The objective of our study was to determine if a more
rigorously applied time-limited criterion for CTM success,
namely time to tachycardia termination (TTT), would provide
improved LRR for adult patients undergoing CTA for
AVNRT. Based on the work of previous investigations [12,
16, 17], we defined a successful TTT as the termination of
AVNRT due to slow pathway block within 20 s of the onset
Given the excellent safety profile of CTA, if the LRR seen
with its use could be improved to match that of RFA, it is
reasonable to propose that CTA should become the modality
of choice for patients undergoing catheter ablation for
2.1 Study design and patient selection
This study enrolled patients with symptomatic AVNRT who
underwent CTA at our center between February 2005 and
June 2011. We attempted to evaluate the utility of TTT during
CTA in 94 consecutive patients. Sustained AVNRT was
successfully induced in 88 of these 94 patients (94 %). The utility
of TTT as a guide to CTM could therefore be evaluated in
these 88 patients, and they comprised our study population.
In the 6 patients in whom sustained AVNRT could not be
induced, conventional CTM techniques applied during atrial
extrastimulus testing was performed. In all 6 patients, CTA
was successful and none required transition to RFA.
This study was approved by our local institutional review
board. The data collected included patient demographics,
arrhythmia characteristics, electrophysiologic study results,
procedural details, complications, as well as acute and long-term
2.2 Electrophysiologic study and cryoablation procedure
CTA was performed with a 7-French 6-mm electrode tip
catheter (Freezor Xtra®, CryoCath Technologies,
Montreal, QC, Canada). In all patients, the target for
CTA was the AV nodal slow pathway, whether it was
utilized in the antegrade or retrograde direction.
Procedure duration was measured from the first venous
sheath placement until final sheath removal.
All procedures were performed by one of three operators. If
CTA was unsuccessful, ablative therapy was transitioned to
the RFA approach.
Electrophysiologic study included the placement of
multiple electrode catheters in the standard positions. After
recording baseline intervals, antegrade and retrograde properties
were assessed using standard atrial and ventricular pacing
and extrastimulus techniques. Up to three atrial extrastimuli
at multiple cycle lengths were employed. If sustained
tachycardia (≥90 s duration) could not be induced, repeat
stimulation was undertaken during isoproterenol infusion. The
reproducibility of tachycardia induction was confirmed by
requiring three separate inductions of ≥90 s duration. AVNRT as the
tachycardia mechanism was confirmed by previously
described standard techniques . Since December of 2010,
all ablations at our institution have been performed without
fluoroscopic guidance . Catheter positioning was guided
by an electro-anatomic mapping (EAM) system (EnSite
NavXTM, St. Jude Medical, St. Paul, MN, USA), Therefore,
fluoroscopy times are not reported.
2.3 Cryomapping and cryoablation techniques
After confirmation of the reproducible induction of sustained
AVNRT, the cryoablation catheter was positioned at the
posteromedial tricuspid annulus during sinus rhythm. A site
yielding a distal electrode recording with an A:V ratio of
approximately 1:3 and/or a local slow pathway electrogram was
considered suitable for CTM.
Sustained AVNRT was again induced. Potential target sites
for permanent CTA were identified by the ability to terminate
AVNRT with slow pathway block within 20 s of CTM
application. Once a suitable target was identified by tachycardia
termination, CTA was continued for a total application time
of 4 min targeting a peak negative temperature of −70 °C.
During CTA application, repeated attempts to induce
AVNRT and to assess the integrity of fast pathway conduction
were undertaken. If tachycardia remained non-inducible and
fast pathway function remained intact, 3 additional
“consolidating” lesions guided by EAM were applied immediately
adjacent to the successful site, in an effort to minimize the
extent of the posteroseptal area exposed to permanent injury.
During these “consolidating” applications, AV conduction
was closely monitored and repeated attempts to assess
inducibility were undertaken.
If sustained AVNRT could not be terminated within 20 s, a
different site would be selected for CTM. Additionally, if AV
conduction became impaired or re-induction of AVNRT
occurred, an alternate site for CTM was identified. If tachycardia
remained non-inducible after the last consolidation
application, a 30-min waiting period was required. Thereafter, a
repeat EP study before and after isoproterenol infusion was
undertaken. Procedural end-points for success were defined as
non-inducibility of AVNRT and a maximum of only single AV
nodal reentrant echoes.
Follow-up was obtained through outpatient clinic records as
well as phone call or mail responses to a questionnaire
specifically designed to assess for arrhythmia recurrence. For those
with tachycardia recurrence, follow-up time was measured as
the time in months from the ablation procedure to recurrence.
For those free of recurrence, follow-up was measured as time
from initial procedure to last contact. Six patients were lost to
follow-up and were excluded from the analysis of LRR.
2.5 Statistical analysis We compared our acute procedural success, LRR, and complication rates to those reported in the major trials on both
3.1 Clinical and demographic features
The clinical, demographic, and arrhythmic features of the
participants are summarized in Table 1. In total, 11 patients
(12.5 %) had structural heart disease including hypertensive
heart disease, left ventricular systolic dysfunction,
myxomatous mitral valve disease, mitral stenosis, aortic stenosis, right
chambers dilatation associated with moderate pulmonary
hypertension. Four patients had recurrence of AVNRT after prior
RFA, and an additional patient had recurrence of AVNRT after
a prior CTA undertaken at another institution.
3.2 Procedural outcomes
The EP study and CTA outcomes are summarized in Table 2.
Typical slow-fast AVNRT was observed in 79 patients
(90.2 %), while 9 exhibited either the fast-slow or slow-slow
varieties of AVNRT.
The number of CTM attempts before a successful TTT
(≤20 s) was achieved ranged from 1 to 32. Forty-four patients
(50.0 %) required ≤8 CTM attempts and 12 patients required
only one. More than 10 CTM attempts were needed in only 9
patients (10.2 %). Successful CTM was achieved in ≤10 s in
30 patients and in 11 to 20 s in the remaining 57 patients.
A successful CTA using our strict TTT criteria of less than
20 s was achieved in 87 of the 88 patients (98.9 %). For the
remaining 1 patient, the ablation modality was switched to
RFA, which was successful at the same procedure session.
In the 87 patients in whom CTA was successful, residual dual
nodal physiology with single echoes was observed in 43
patients and dual pathway physiology was completely
eliminated in the remaining 44 patients.
There were no early or late major procedural
complications. No permanent AV block occurred, but transient AV
block during CTM was noted in 8 patients (9.1 %) and
promptly resolved within 30–180 s upon immediate
rewarming. These sites were identified on the EAM system
and were avoided during subsequent CTA applications. No
further AV conduction disturbances were encountered.
Of the 87 patients in whom acute procedural success was
achieved, 6 were lost to follow-up. Of the remaining 81
patients, 3 (3.7 %) experienced a recurrence of AVNRT during
long-term follow-up. Time to recurrence ranged from 1 to
26 months (Table 3). The LRR is compared to the results of
other CTA trials in Table 4.
Table 1 Baseline
characteristics for CTA
using TTT (n = 88)
In this study, we report our center’s acute and long-term
procedural outcomes in 88 consecutive patients in whom we
could use TTT as the guide for CTM success for AVNRT.
CTA, as compared to RFA, offers patients enhanced safety
from procedurally related permanent AV block. Nonetheless,
CTA has not been the preferred method for ablation since its
use has been associated with a significantly higher risk of
LRR. In an effort to retain the safety advantage of CTA, we
evaluated the hypothesis that a reduction in LRR could be
achieved by more rigorously controlling the methodology of
CTM. The changes to CTM that we employed included (1)
performing CTM exclusively during sustained AVNRT and
(2) requiring tachycardia termination in ≤20 s during CTM.
Using this methodology for CTM, acute procedural success
was excellent (98.9 %) and at a mean follow-up of over
19.7 months, the LRR of only 3.7 % was comparable to the
best outcomes reported for patients undergoing RFA . The
results reported in this study suggest that strict control of the
methods used for CTM is essential to achieve improved LRR.
Furthermore, a possible explanation for the wide variation in
LRR often reported for CTA of AVNRT may well derive from
differences in the methodology employed for CTM (Table 4).
Procedural outcomes for CTA using TTT (n = 88)
Mean Follow-Up Duration (months)
4.2 Prior studies of CTA for AVNRT
Several prior studies of CTA for AVNRT have reported an
unacceptably high LRR which ranged from 8 % to as high
as 17 % [8–13]. Despite the use of apparently similar
techniques and study populations, an explanation for this variation
has been lacking. Some have attributed this variance to minor
differences in technique, such as the use of “supplemental”
CTA applications, or the use of larger sized catheter tips. It
had been hoped that the introduction of the larger 6-mm tip, by
providing larger and deeper lesions, would afford improved
LRR. However, as summarized in Table 4, recent studies
limited exclusively to the larger 6-mm tip have still reported LRR
that were unacceptably high when compared to RFA [8–13].
For example, in the largest and most recent of these, the
prospective randomized CYRANO trial, the clinical outcomes of
251 patients with AVNRT who underwent CTA with a 6-mm
catheter tip were compared to those observed in 258 patients
who were treated with standard RFA . While acute
procedural success was excellent in both groups, the LRR of 9.4 %
observed for the CTA patients was significantly higher than
the 4.4 % noted in the RFA group. As has been consistently
reported, no permanent AV block was reported for patients
randomized to CTA, while 3 patients (1 %) in the RFA group
developed persistent AV block—one of whom required
A full understanding of the CYRANO trial results, as well
as those reported for other studies involving CTA, requires a
careful examination of the precise methods utilized for the
important variable of CTM. Often the techniques employed
for CTM have been neither tightly controlled nor reported in
detail. Important differences in the techniques of CTM could
potentially explain why some studies have reported long-term
outcomes for CTA equivalent to those seen for RFA, while the
majority of trials have found RFA to be superior. Some
important considerations in the performance of CTM are
4.3 Specifics of CTM
The primary goal of CTM is to determine whether a specific
catheter location is optimal for a permanent CTA lesion from
the perspectives of both safety and efficacy. Of the many
variables that have been shown to influence the results of CTM,
Comparison of CTA using TTT to conventional CTA using 6-mm tip size
two have recently been shown to have direct bearing on the
likelihood of a long-term success. The first is the actual patient
rhythm during which CTM is applied. For example, cooling
during CTM can be applied during atrial pacing runs to assess
slow pathway (SP) function, as is commonly chosen, or
secondly, during induced sustained AVNRT. In the case of atrial
pacing, the effect of CTM on SP conduction is assessed by
repeated pacing runs directed at either inducing AVNRT or
confirming impairment or elimination of SP function. When
CTM is applied during induced sustained tachycardia,
termination of AVNRT is the determinant of CTM success. It is
likely that termination of AVNRT was a result of SP block
as opposed to AV nodal block in that the integrity of both
AV nodal and fast pathway conduction was confirmed
immediately upon the resumption of sinus rhythm and, additionally,
during subsequent atrial pacing runs applied shortly after
The second important variable in selecting an optimal
ablation site is time: specifically, time to effect (TTE) defined as
the duration of cooling to −30 ° C before the desired effect is
achieved. In virtually all prior randomized trials comparing
CTA and RFA, a TTE of up to 60 s was considered an
acceptable duration [7, 13]. In this approach, either the lack of
inducibility or the elimination/impairment of SP function,
within the specified time frame of test cooling, is considered a
favorable CTM result and indicates a site suitable for
permanent CTA. The TTE at a given test site is a measure of catheter
tip proximity to the targeted tissue. Given the smaller and
more discrete lesion size associated with CTA, the use of a
narrow window for TTE is likely to be indicative of greater
proximity to the SP and a higher probability of achieving
permanent interruption of SP function and long-term
In several recent studies, investigators have emphasized the
importance of TTE during CTM as a determinant of LRR [12,
17]. In 30 pediatric patients with SVTs and right sided
accessory pathways, Drago and colleagues were able to show a
lower LRR of only 5.9 % when TTE was less 10 s, compared
to greater than 20 % in those with a more prolonged TTE .
In a much larger study of 312 adults with slow-fast AVNRT,
Bastani and colleagues strictly controlled CTM by limiting
TTE to a maximum duration of 20 s. Acute procedural success
was 99 %, and, importantly, the LRR improved to 5.8 % at an
average follow-up of 6 years . The observed decrease in
LRR was in part attributed to the strict time criterion used to
define a successful CTM response.
The ability to determine a precise TTE can be further
enhanced by the performance of CTM during induced
tachycardia. This approach allows for an unambiguous determination
of TTE as indicated by the abrupt termination of tachycardia
due to failure of SP conduction. In contrast, the performance
of CTM during various atrial pacing maneuvers renders an
accurate determination of TTE more difficult because the
pacing maneuver itself consumes time. In addition, the ability to
achieve consistent SP conduction is often variable from one
pacing attempt to another, which further impedes the ability to
determine a precise TTE. Lastly, the presence of multiple SPs
is not infrequent and the prompt termination of tachycardia
ensures that the pathway supporting the tachycardia is in fact
the one being targeted for permanent CTA .
4.4 Additional contributors to improved LRR
While the most likely explanations for the improved LRR
observed in this study derive from the strict time-limited
criterion used to guide CTM results and the performance of
CTM during sustained AVNRT, other variables could have
contributed as well. Three consecutively applied
“consolidation” lesions were delivered. These applications were guided
by EAM and located as close as possible to the initial
successful site. In the CYRANO study, only one supplemental
application was used . The extent to which our additional
consolidative CTA applications or the use of EAM
contributed to our lower LRR is difficult to determine.
A remaining variable that could have influenced long-term
outcome is that we routinely employed isoproterenol
stimulation after an “apparently” successful initial CTA—even in
patients who did not require its use for the induction of
AVNRT in the baseline state. This additional step extended the
duration of post CTA observation and, thereby, could have
facilitated our ability to detect delayed recovery of SP
function. In this study, we did not determine the extent to which
this additional step led to further CTA applications.
4.5 Study limitations
The primary limitation of our study is that it is a single-center,
non-randomized trial. Additionally, our results are compared
to those reported in previous trials—some recent, but also
some more remote. Accordingly, it is possible that a patient
selection bias may have in some way contributed to the
favorable long-term outcome observed in our study population.
While the sample study size of our study was modest, all of
the 88 patients included in this study were consecutively
enrolled and reflect all patients with AVNRT referred to our
center for catheter ablation during the study interval.
Also, there are certain requirements inherent in the
approach we employed in this study. First, it requires that
patients exhibit, in a reproducible fashion, sustained AVNRT.
This step will often necessitate the use of isoproterenol
stimulation. In our experience, about 6–7 % of patients with
documented AVNRT will fail to exhibit sustained tachycardia at
the time of the procedure. In this situation, some other
approach to CTM will be required. In such patients, CTM can
usually be undertaken during atrial pacing maneuvers to
assess impairment of SP function as described above [12, 13].
While it may be more difficult to determine a precise TTE, this
approach can still be employed and used to achieve procedural
When compared to the CTA arm of the CYRANO trial, our
procedure time was on average 14 min longer. This slightly
longer procedure time can be largely accounted for by the 2
additional 4-min consolidating applications we employed and
the use of isoproterenol infusion in all patients at the
conclusion of the procedure. It is unlikely this small an extension of
procedure time would have any significant clinical impact.
Our study results suggest that CTA for AVNRT, contrary to
the widely held perception, need not be associated with a
higher likelihood of LRR. TTT represents a technical
refinement when compared to conventional CTM. The performance
of CTM during sustained AVNRT with the use of a strict TTT
criterion of ≤20 s may have been the essential step needed to
achieve this improvement. In fact, the LRR of only 3.7 %
noted in our study is comparable to the 4.4 % rate noted in
the recent CYRANO trial for RFA and is superior to the 9.4 %
rate these investigators observed in their CTA group. Our
findings, combined with those noted by others [12, 13],
suggest that future trials of CTA for AVNRT should employ
at least some of the strict CTM criteria used in our study.
These results will need to be confirmed, optimally in a
controlled randomized trial, before a formal recommendation
can be made. Admittedly, the risk of permanent AV block
when RFA is used in this setting is low (0.4–2.0 %).
However, given the large number of patients who are likely
to undergo RFA for AVNRT in the future, many may be
spared the risk of life-long permanent pacemaker dependence
if CTA becomes the preferred initial approach to catheter
ablation of AVNRT.
Compliance with ethical standards
Mansour Razminia is a consultant for St. Jude
Ethical approval All procedures performed in studies involving
human participants were in accordance with the ethical standards of the
institutional and/or national research committee and with the 1964
Helsinki declaration and its later amendments or comparable ethical
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1. Orejarena LA , Vidaillet Jr H , DeStefano F , Nordstrom DL , Vierkant RA , Smith PN , et al. Paroxysmal supraventricular tachycardia in the general population . J Am Coll Cardiol . 1998 ; 31 : 150 - 7 .
2. Blomström-Lundqvist C , Scheinman MM , Aliot EM , Alpert JS , Calkins H , Camm AJ , et al. European Society of Cardiology Committee , NASPE-Heart Rhythm Society: ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias-executive summary. A report of the American college of cardiology/American heart association task force on practice guidelines and the European society of cardiology committee for practice guidelines (writing committee to develop guidelines for the management of patients with supraventricular arrhythmias) developed in collaboration with NASPE-Heart Rhythm Society . J Am Coll Cardiol . 2003 ; 42 : 1493 - 531 .
3. Kavesh NG , Gosnell MR , Shorofsky SR , Gold MR . Comparison of power and temperature-guided radiofrequency modification of the atrioventricular node . Polaris Investigator Group. Am J Cardiol . 1997 ; 80 : 1444 - 7 .
4. Calkins H , Yong P , Miller JM , Olshansky B , Carlson M , Saul JP , et al. Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial . The Atakr Multicenter Investigators Group. Circulation . 1999 ; 99 : 262 - 70 .
5. Delise P , Sitta N , Zoppo F , Corò L , Verlato R , Mantovan R , et al. Radiofrequency ablation of atrioventricular nodal reentrant tachycardia: the risk of intraprocedural, late and long-term atrioventricular block. The Veneto Region multicenter experience . Ital Heart J . 2002 ; 3 : 715 - 20 .
6. Hindricks G . Incidence of complete atrioventricular block following attempted radiofrequency catheter modification of the atrioventricular node in 880 patients. Results of the multicenter European radiofrequency survey (MERFS) the working group on arrhythmias of the European society of cardiology . Eur Heart J . 1996 ; 17 : 82 - 8 .
7. Friedman PL , Dubuc M , Green MS , Jackman WM , Keane DT , Marinchak RA , et al. Catheter cryoablation of supraventricular tachycardia: results of the multicenter prospective “frosty” trial . Heart Rhythm . 2004 ; 1 : 129 - 38 .
8. Jensen-Urstad M , Tabrizi F , Kennebäck G , Wredlert C , Klang C , Insulander P. High success rate with cryomapping and cryoablation of atrioventricular nodal reentry tachycardia . Pacing Clin Electrophysiol . 2006 ; 29 : 487 - 9 .
9. Khairi P , Novak PG , Guerra PG , Greiss I , Macle L , Roy D , et al. Cryothermal slow pathway modification for atrioventricular nodal reentrant tachycardia . Europace . 2007 ; 10 : 909 - 14 .
10. De Sisti A , Tonet J , Barakett N , Lacotte J , Leclercq JF , Frank R. Transvenous cryo-ablation of the slow pathway for the treatment of atrioventricular nodal re-entrant tachycardia: a single-centre initial experience study . Europace . 2007 ; 9 : 401 - 6 .
11. Chan NY , Mok NS , Lau CL , Lo YK , Choy CC , Lau ST , et al. Treatment of atrioventricular nodal re-entrant tachycardia by cryoablation with a 6 mm-tip catheter vs . radiofrequency ablation. Europace . 2009 ; 11 : 1065 - 70 .
12. Bastani H , Schwieler J , Insulander P , Tabrizi F , Braunschweig F , Kennebäck G , et al. Acute and long-term outcome of cryoablation therapy of typical atrioventricular nodal reentrant tachycardia . Europace . 2009 ; 11 : 1077 - 82 .
13. Deisenhofer I , Zrenner B , Yin YH , Pitschner HF , Kuniss M , Grossmann G , et al. Cryoablation versus radiofrequency energy for the ablation of atrioventricular nodal reentrant tachycardia (the CYRANO study): results from a large multicenter prospective randomized trial . Circulation . 2010 ; 122 : 2239 - 45 .
14. Gupta D , Al-Lamee RK , Earley MJ , Kistler P , Harris SJ , Nathan AW , et al. Cryoablation compared with radiofrequency ablation for atrioventricular nodal re-entrant tachycardia: analysis of factors contributing to acute and follow-up outcome . Europace . 2006 ; 8 : 1022 - 6 .
15. Rivard L , Dubuc M , Guerra PG , Novak P , Roy D , Macle L , et al. Cryoablation outcomes for AV nodal reentrant tachycardia comparing 4-mm versus 6-mm electrode-tip catheters . Heart Rhythm . 2008 ; 5 : 230 - 4 .
16. Riccardi R , Gaita F , Caponi D , Grossi S , Scaglione M , Caruzzo E , et al. Percutaneous catheter cryothermal ablation of atrioventricular nodal reentrant tachycardia: efficacy and safety of a new ablation technique . Ital Heart J . 2003 ; 4 : 35 - 43 .
17. Drago F , Russo MS , Silvetti MS , De Santis A , Onofrio MT . ' Time to effect' during cryomapping: a parameter related to the long-term success of accessory pathways cryoablation in children . Europace . 2009 ; 11 : 630 - 4 .
18. Knight B , Ebinger M , Oral H , Kim M , Sticherling C , Pelosi F , et al. Diagnostic value of tachycardia features and pacing maneuvers during paroxysmal supraventricular tachycardia . J Am Coll Cardiol . 2000 ; 36 ( 2 ): 574 - 82 .
19. Razminia M , Manankil MF , Eryazici PL , Arrieta-Garcia C , Wang T , D'Silva OJ , et al. Nonfluoroscopic catheter ablation of cardiac arrhythmias in adults: feasibility, safety, and efficacy . J Cardiovasc Electrophysiol . 2012 ; 23 : 1078 - 86 .
20. Kardos A , Paprika D , Shalganov T , Vatasescu R , Foldesi C , Kornyei L , et al. Ice mapping during tachycardia in close proximity to the AV node is safe and offers advantages for transcatheter ablation procedures . Acta Cardiol . 2007 ; 62 : 587 - 91 .