Safety and efficacy of the remote magnetic navigation for ablation of ventricular tachycardias—a systematic review
) Clinical Electrophysiology, Department of Cardiology
, Erasmus MC, Rotterdam,
Objective Remote magnetic navigation (RMN) is considered to be a solution for mapping and ablation of several arrhythmias. In this systematic review we aimed to assess the safety and efficacy of RMN in ablation of ventricular tachycardia (VT). Methods The National Library of Medicine's PubMed database was searched for articles containing any of a predetermined set of search terms that were published prior to November 1, 2011. Quality of evidence was rated using the GRADE system. Results The database search resulted in 11 relevant articles evaluating the usefulness of RMN. Three groups of VTs were studied: VT in patients with ischemic cardiomyopathy (ICMP), non-ischemic cardiomyopathy (NICMP) and structurally normal hearts (SNH). The use of RMN in patients with ICMP has been associated with success rates ranging from 71 to 80%. RMN has been shown to be a feasible and effective method for ablation of VT in NICMP and SNH patients. Success rates between 50% and 100% have been reported in NICMP populations. Rates ranging from 86% to 100% have been reported for SNH patients. The lowest rates of arrhythmia recurrence are reported for SNH patients (0-17%). In ICMP and NICMP, recurrence rates of 0-30% and 14-50%, respectively, have been reported. One patient experienced total heart block, and one patient experienced a thromboembolic event after RMN catheter ablation procedures. Conclusions RMN has been shown to be an effective and safe method for ablation of VT in various patient populations with low recurrence and complication rates. However, more comparative and randomized studies are necessary, and therefore the true value of RMN for VT ablation remains still unknown.
Treatment of ventricular tachycardia (VT) has gone through
great improvements in recent years . When drug
therapy is not effective, catheter ablation of VT can be an
effective alternative that has been shown to eliminate
ventricular tachycardias with high efficacy [4, 5]. Different
approaches can be used depending on the arrhythmias
origin: left endocardial, right endocardial and epicardial
approach . Accurate mapping of the area of interest can
be difficult to achieve due to complex anatomical structures
or structural heart diseases. Remote magnetic navigation
(RMN) is considered to be an effective tool for mapping
and ablation of arrhythmias that has the potential to
overcome some of these challenges [6, 7]. It is a navigation
system, which provides good catheter stability during
mapping and ablation procedures . While the
capabilities of manual navigation are limited by the fixed
curves of manual catheters, the magnetic catheters have a
flexible catheter design enabling them to access otherwise
difficult anatomy . The RMN-guided ablation catheter
is manipulated by two external magnetic fields situated on
either side of the patient. The catheter tip aligns with the
magnetic vector produced by the system, allowing the
operator to navigate the catheter from its distal tip.
Additionally, the RMN system allows the operator to store and reapply
specific magnetic vectors in order to facilitate repeated access
to difficult anatomy . Some data suggest that utilizing an
atraumatic catheter design results in less cardiac perforations
[13, 14]. Previous research has shown that RMN may allow
the operator to reduce fluoroscopy time . RMN has
been reported as a feasible tool for ablation of several types
of arrhythmias, including AV nodal and AV reentrant
tachycardias and atrial fibrillation . VT can occur in
patients with or without structural heart disease (SHD). SHD
can be a result of either ischemic cardiomyopathy (ICMP) or
non-ischemic cardiomyopathy (NICMP) . Scar-related
VT (SRVT) could have several causes such as myocardial
infarction (MI), dilated cardiomyopathy (DCMP),
arrhythmogenic RV cardiomyopathy (ARVC) and hypertrophic
cardiomyopathy (HCMP) . Idiopathic VT originated in most
cases from the outflow tract regions or the fascicles of the left
ventricle in patients with structurally normal hearts (SNH)
. VTs originating from the left ventricular outflow tract
(LVOT) and VT originating from above the pulmonary and
aortic valve are recognized more often than before .
This systematic review aims to provide an overview of
the safety and efficacy of RMN in VT ablation.
Our aim was to identify all articles that discuss the use of
RMN for VT ablation procedures. The National Library of
Medicines PubMed database was searched until November
1, 2011. The following predetermined set of search terms
Tachycardia, Ventricular[Mesh] AND Magnetics
[Mesh] AND Catheter Ablation[Mesh] OR
Ventricular[All Fields] AND Magnetic[All Fields] AND
Remote[All Fields] AND Ablation[All Fields].
The reference list of each returned article was examined for
additional studies that may have been missed in the PubMed
database search. All studies discussing use of RMN for VT
ablation in human were included.
2.1 GRADE system
All data from the included articles were analysed according
to the internationally developed GRADE system in order to
define the quality of the evidence . The overall quality
of the evidence was rated into four categories (high,
moderate, low, very low) using the criteria of GRADE.
From the studies that met the inclusion criteria, four factors
were considered in appraising the overall strength of the
evidence according the GRADE system: study design,
study quality, consistency of evidence and directness of
2.2 Data extracting process
Two authors independently reviewed the eligible articles and
extracted the following data: VT type, RMN catheter type,
acute success rate, manual crossover rate, follow-up time,
follow-up recurrence rate and procedural complications. The
authors then cross-checked their results to ensure accuracy. If
the authors did not reach complete agreement, the results were
discussed and a consensus opinion was reached.
2.3 Outcome measurement The studies on RMN-guided VT ablation were compared with respect to all extracted data.
Our PubMed search returned in 22 results based on the
predefined search method. Eleven of the returned articles
did not evaluate the use of RMN in VT and were
consequently excluded [21, 2837]. In all, data from 11
articlesseven clinical trials, three case reports and one
case serieswere assessed [6, 7, 11, 20, 22, 3843]. After
quality assessment according to the GRADE system, four
studies were considered as low evidence and seven as very
low evidence (Table 1). Three main VT subtypes were studied:
VT in ICMP, NICMP and SNH. Additionally, studies on
SRVT in patients with ICMP, NICMP or both are analyzed.
In Table 1 an overview of the extracted data is presented.
As the article by De Torres et al. did not report a recurrence
rate, we contacted the authors in order to obtain the missing
3.1 Overall success rate
Overall success rates ranged from 52% to 86% for studies
assessing VT ablation in ICMP, NICMP and SNH. Two
studies reported crossover to manual irrigated tip catheters
in 14% and 48% of procedures, respectively [22, 38].
Thirty-four of 65 ablation procedures (52%) by Di Biase et
al. (2009) utilized only non-irrigated tip RMN ablation
catheters. The remaining procedures required the use of
manual ablation catheters in order to achieve procedural
success. Di Biase et al. (2010) report manual crossover in
15 cases (14%).
3.2 Ischemic cardiomyopathy
For ablation of VT in ICMP, success rates ranging from 71% to
80% were achieved [6, 20, 39]. Arya et al. and Haghjoo et al.
report success rates of 80% using the irrigated RMN ablation
catheter. In both studies 20% of the cases resulted in partial
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success, defined as inducibility of non-clinical VT following
the ablation procedure [20, 39]. Manual crossover was never
necessary to achieve procedural success in these studies.
Aryana et al. report a 71% success rate for VT ablation in
patients with ICMP .
Di Biase et al. report an acute success rate of 36% for SRVT
ablation . This study combines the ICMP and NICMP
populations into a single cohort. In 64% of the procedures the
non-irrigated tip RMN ablation catheter was unable to
achieve acute success, so the procedure was crossed-over to
right bundle branch block (RBBB) . Two additional
patients developed groin hematomas . Another study
reports an uncomplicated bilateral lower-extremity deep
venous thrombosis in one patient . This thromboembolic
complication occurred during left-sided ablation with a
nonirrigated tip catheter, so the risk of similar events is likely to
be reduced by using irrigated tip RMN ablation catheters
. Aryana et al. report a case of right ulnar nerve palsy
after an epicardial RV mapping procedure. It is unclear
whether the palsy is caused by an embolic stroke or was a
result of long immobilization under general anesthesia .
3.3 Non-ischemic cardiomyopathy
3.7 Crossover to manual ablation
Aryana et al. evaluated the use of RMN for VT ablation in
patients with NICMP and report an acute success rate of 50% in
patients with cardiac sarcoidosis after two VT ablation
procedures . In patients with ARVC and DCMP acute
success was achieved in 100% and 50% of procedures,
respectively. Because of lack of VT inducibility, successful
catheter ablation could not be performed in HCMP population.
3.4 Structurally normal heart
Success rates for RMN ablation in patients with SNH vary from
86% to 100% [7, 11, 38, 4043]. Di Biase et al. report manual
crossover in 14% of cases. Thornton et al., Konstantinidou et
al., De Torres et al., Schwagten et al. and Burkhardt et al.
completed all cases without crossover to manual catheters.
3.5 Recurrence rates
Following acutely successful ablation procedures, 030%
of ICMP patients experienced recurrence [6, 20, 22, 39].
Recurrence rates ranging from 14% to 50% are reported for
the NICMP population [6, 22]. Recurrence rates ranged
from 0% to 17% for patients with SNH after VT ablation
procedures [11, 22, 4043]. Thornton et al. note one patient
(14%) who experienced non-sustained VT after an acutely
successful catheter ablation procedure. Because this patient
had sustained VT prior to ablation, the procedure was
considered as partial success .
Di Biase et al. reported an overall recurrence rate of 40%
in a mixed sample of patients treated with 4 mm RMN,
8 mm RMN and manual catheters. The same group reported
an overall recurrence rate of 15% in 2010. For the RMN
subgroup, VT recurrence was 14% and 27% for patients
that were crossed over to manual technique .
3.6 Complications Four complications were associated with VT ablation procedures. Di Biase et al. noted heart block in one patient with a
In this systematic review the use of RMN in ablation of VT
has been investigated. Several groups report use of RMN
ablation to treat patients with ICMP, but these results are quite
varied [6, 20, 38, 39]. Three groups reported favorable
success rates between 71% and 80%. Two of 15 ablation
procedures (13%) by Aryana et al. utilized only non-irrigated
tip RMN ablation catheters. The remaining procedures
required the use of manual irrigated tip ablation catheters in
order to achieve acute procedural success. Di Biase et al.,
however, achieved a rate of only 36% for SRVT ablation
procedures. This low success rate may not accurately reflect
the potential of RMN as the study employs only
nonirrigated RMN catheters and showed a low threshold for
manual crossover . The most recent trial by Di Biase et
al. (2010) with irrigation demonstrated a considerable lower
crossover rate of 14%. Previous research has shown that
catheter irrigation improves ablation efficacy and decreases
the risk of thrombotic events . However, very scarce data
are available on SRVT using an irrigated ablation catheter.
3.8 Idiopathic VT
RMN is most effective when used in patients with SNH and is
successful in 86% to 100% of these procedures [7, 11, 38, 40
43]. The usefulness of RMN in ablation of idiopathic VTs
has been investigated by several groups. Although they
evaluate RMN in a relatively small sample of patients, these
studies demonstrate the feasibility of RMN for successful
ablation of RVOT, LVOT, left fascicular and aortic cusp VT.
Still, more evidence is needed to assess the efficacy and
safety of RMN in different subtypes of idiopathic VT.
3.9 Future studies or areas of investigation
This review showed successful results in patients with ARVC,
DCMP and sarcoidosis . However, these groups included a
minimal number of patients, and more research is needed in
this patient population. Therefore, we call for more research
on the use of RMN in ablation of VT in NICMP.
The safety and efficacy of RMN in ablation of VT is
evaluated in multiple studies. Schwagten et al. report on the
superior capabilities of RMN in VT ablation . A higher rate
of acute success (97% vs. 81%, p=0.03) and lower rate of
arrhythmia recurrence (14% vs. 50%, p<0.01) were achieved
in RMN procedures compared to manual catheter ablation.
The use of RMN compared to manual procedures has
been evaluated for multiple arrhythmias, including VT .
Bauernfeind et al. evaluated the safety and long-term
efficacy of RMN in a large number of patients. These data
showed that the use of RMN reduced the occurrence of
major complications (0.34 vs 3.2%, p = 0.01) without
compromising efficacy compared to manual ablation.
Further, RMN was significantly more successful for VTs
(93 vs 72%, p < 0.05). In this population both SNH and SR
VT were studied; however, the superiority of RMN in SNH
VT was largely responsible for the difference. Di Biase et
al. (2010) stated that procedure times were longer using
RMN, although with decreased use of fluoroscopy. To
achieve similar results, a statistically greater number of RF
lesions needed to be applied in RMN group. However,
Bauernfeind et al. report both decreased procedure times
and fluoroscopy times using RMN. This could be explained
by the steep learning curve for the RMN system. This
demonstrates that new methods are needed to increase
efficacy of ablation compared to conventional manual
techniques. However, no randomized studies have been
executed to prove superiority.
3.10 Limitations of the study
In this review we evaluated the safety and efficacy of
RMN in VT ablation. Several studies show advantages of
RMN for VT ablation, although this is based on low
quality evidence according to the GRADE system. High
quality randomized studies are needed for more consistent
evidence to assess the efficacy and safety of RMN in
ablation of VT.
The available data on RMN suggests that it is an effective
and safe method for ablation of VT with relatively low
recurrence and complication rates. RMN has been used to
achieve successful outcomes in various patient populations
and VT subtypes. SNH VT appears to have the best
outcome using RMN in comparison to ICMP and NICMP
VT. In case of NICMP extremely limited data are available
for the effectiveness of RMN. Although these are promising
results, more comparative and randomized studies are
necessary to assess superiority. The true value of RMN
for VT ablation remains still unknown.
Disclosure Tamas Szili-Torok is a consultant of Stereotaxis, Inc., St.
Louis, MO, USA.
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