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Prognostic Value of Time Dependent Voltage Abatement During Remote Magnetic Navigation Guided Ablation in Idiopathic Right Ventricular Outflow Tract Arrhythmias
Raluca Sirbu Prisecaru*, Leila Riahi, Yves De Greef, Dirk Stockman and Bruno Schwagten
ZNA Middelheim Cardiovascular Center, Antwerpen, Belgium
Submission: April 24, 2019; Published: May 17, 2019
*Corresponding author: Raluca Sirbu Prisecaru, Department of Cardiology Polisano Hospital Sibiu, Izvorului Street, Sibiu, Romania
How to cite this article:Raluca Sirbu Prisecaru, Leila Riahi, Yves De Greef, Dirk Stockman, Bruno Schwagten. Prognostic Value of Time Dependent Voltage
Abatement During Remote Magnetic Navigation Guided Ablation in Idiopathic Right Ventricular Outflow Tract Arrhythmias. J Cardiol & Cardiovasc Ther. 2019; 14(1):
555876. DOI: 10.19080/JOCCT.2019.14.555876
Prognostic value of time dependent voltage abatement during remote magnetic navigation guided ablation in idiopathic right ventricular outflow tract arrhythmias
Purpose: We set out to evaluate if time related voltage abatement (dV/dt) of ventricular electrograms (EGM) during catheter ablation of idiopathic right ventricular outflow tract (RVOT) arrhythmias using the Stereotaxis Niobe II system is an efficient marker of long-term procedural success.
Methods: Twenty-six consecutive patients with acute success of RVOT ablation for premature ventricular contractions (PVCs) and/ or ventricular tachycardia (VT) suggestive of RVOT origin were included. Late success was defined as freedom of ventricular ectopies originating from the RVOT after 3 months of follow up without antiarrhythmic drugs (AAD).
Results: After 3 months follow-up 20 of 26 patients (77%) remained free of symptoms and arrhythmias (group 1) and recurrences occurred in 6 patients (23%) (group 2). ’Warming up’ during RF applications occurred respectively in 85% and 83,33 % of patients (p=0,46), after a mean period (dt 2) of 4,72 ± 9,42 vs 10,75 ± 11,34 sec (p=0,045). The time intervals from the onset of RF delivery (t0) to significant voltage abatement (>90%) or reversal of EGM polarity (t1) between the two groups were: 9,11 ± 5,11 vs 32,16 ± 10,33 (p=0,00006). dV/dt1 was 95,44 ± 87,6 vs 23,5 ± 16,97μV/s (P=0,024).
Conclusion: Time related voltage abatement of ventricular EGM together with time interval from onset of RF ablation to significant voltage abatement (>90%) or reversal of EGM polarity and time interval from RF delivery to onset ‘warming up’ are possible predictors of long term success after RF ablation of idiopathic RVOT arrhythmias.
Keywords: Voltage abatement of ventricular EGM; RF ablation; Idiopathic RVOT arrhythmias
Abbrevations: EGM: Electrograms; RVOT: Right Ventricular Outflow Tract; PVCs: Premature Ventricular Contractions; VT: Ventricular Tachycardia; AAD: Antiarrhythmic Drugs; ARVD: Arrhythmogenic Right Ventricular Dysplasia; LV: Left Ventricular; RF: Radiofrequency
Arrhythmias originating from the right ventricular outflow tract (RVOT) tend to present as isolated premature ventricular complexes (PVCs), runs of non-sustained VT or sustained VT . Unless it is the initial sign of an arrhythmogenic right ventricular dysplasia (ARVD), the prognosis is generally good, with an excellent long-term survival. For symptomatic patients in whom β-adrenergic blockers, calcium channel blockers [2,3] or anti-arrhythmic drugs (AAD) class IC and III are ineffective  or not
desired and for patients in whom left ventricular (LV) dysfunction occurs [5-7] radiofrequency (RF) ablation is a safe and effective treatment option .
The acute success rate for ablation of RVOT ectopies in non-structural heart disease ranges from 65 to 97% [9-11]. When RF ablation is not successful [12-14], this can be due to intramural or epicardial origin of ectopies, occurrence of multiple morphologies of ectopic beats in the same patient or matching between the clinical VT and pace-map being less than 11 out of 12 leads.
Despite high acute success rates, there is a recurrence rate of
5-23% during a follow up to 2 years [15-17].
Endocardial activation time at the successful ablation site is
the only predictor of long-term tachycardia recurrence reported
in literature to our knowledge . Remote magnetic navigation
(RMN) mapping and ablation of RVOT ectopies guided by the
Stereotaxis Niobe II system (Stereotaxis, Inc., St Louis, MO, USA)
appears to be safe, fast and effective . The aim of our study was
to evaluate if time related voltage abatement (dV/dt) of ventricular
electrograms (EGM) during catheter ablation of idiopathic RVOT
arrhythmias guided by RMN is an efficient marker of long-term
Between July 2012 and January 2015, 26 patients with acute
success of RVOT ablation for premature ventricular contractions
(PVCs) and/or VT suggestive of RVOT origin were included in this
study. All patients provided written informed consent. Patients
were symptomatic and have been refractory to at least one AAD.
Transthoracic echocardiography was performed in all patients
for assessing right and left ventricle dimensions and left ventricle
PVCs were documented on the Lab System PRO™ EP recording
system (Bard Electrophysiology Division, Lowell, MA, USA).
All procedures were performed under local anesthesia. After
obtaining vascular access, one 8F sheath was positioned in the
right femoral vein. Navigation to the RVOT was performed utilizing
a 3,5 mm tip irrigated magnetic catheter (Navi Star RMT Thermo
Cool, Bio sense Webster, Diamond Bar, CA, USA). Detailed mapping
was performed with the CARTO 3D mapping system (Bio sense
Webster, Diamond Bar, CA, USA). The catheter movement within
the RVOT was guided remotely by the Stereotaxis Niobe II system.
An activation map was made for each patient in order to
determine the earliest local bipolar activation point (≥30 ms
from the onset of the QRS) (Figure 1). If PVCs were not occurring
frequently, Isoproterenol (15 to 30 mcg/min) was administered,
and if this did not successfully increase the amount of ectopic
beats, ablation was finally performed using pace mapping only.
Pacing with output just above the threshold targeted the most
optimal pace map (≥11/12 leads). After the focus of PVCs was
identified, RF delivery was applied with a maximal power of 40
W, maximal temperature of 48° C during 60 to 120 seconds and
catheter irrigation flow set at 17ml/min. Catheter stability was
analyzed semi quantitatively. If the ablation catheter displaced
during application, RF delivery was interrupted. Procedural
endpoint was the elimination of spontaneous clinical PVCs at
baseline and after Isoproterenol (15 mcg/min) infusion postablation.
A waiting period of 30 min was applied for all procedures.
The time interval from the onset of RF delivery (t0) to
significant voltage abatement (>90%) or reversal of EGM polarity
(t1), as well as ventricular EGM amplitude during baseline (V0)
and the new EGM amplitude during RF delivery at the moment
of significant voltage abatement or reversal of EGM polarity (V1),
were registered for each site of RF application. Thereafter, the
difference between EGM amplitude (dV=V0-V1) and the time
interval between t0-t1(dt1) were calculated for each site of RF
application. If warming up during RF occurred, time interval
from onset of RF ablation to warming up of the arrhythmia (dt2)
was also registered (Figure 2). Procedural time, radiofrequency
application time and fluoroscopy time were collected at the end
of the procedure.
AAD were discontinued after RF ablation. All patients
underwent follow-up at 1 and 3 months. Follow-up examinations
consisted of symptom-based evaluation, 12-lead ECG and 24-h
Holter-monitoring. Late success was defined as freedom of
ectopies identical to the preprocedural ectopies, without AAD at
3 months of follow-up.
Categorical variables are expressed as frequencies and
percentages. Continuous data are presented as mean value plus
standard deviation. Continuous variables were analysed with
a paired t-test. A P-value <0.05 was considered statistically
Data are summarized in Table 1. RVOT was identified as the
origin of the VES/VT in all 26 patients. Successful RVOT ablation
sites were identified using a combined activation and pacing map
in 19 patients (73%) and only a pacing map in 7 patients (27%).
Acute success was obtained in all patients. After a waiting time of
30 minutes, no patient presented PVC recurrence with the same
morphology as the clinical arrhythmia. Mean total procedural
time was 98,60 ±30,93min, mean total fluoroscopy time 2,97 ±
1,67 minutes and mean radiofrequency ablation time was 353,20
± 193,38 seconds. During and after the procedure, no pericardial
tamponade, cardiac perforation or other major adverse event
At 3 months of follow-up, 20 of 26 patients (76,92%) remained
free of symptoms and arrhythmias (group 1). During
a mean period of follow up thereafter of 13,55 ± 10,15 months,
these patients presented no recurrence. During the 3 months of
follow up, recurrences occurred with evidence of VES or/and VT
in 6 patients (group 2). Three out of 6 patients underwent a second
RF ablation. After 3 months of follow up after the second procedure,
all patients were free of arrhythmias and symptoms. In
one of these 3 patients, success was obtained after both right and
left sided ablation. There was no significant difference with regard
to clinical characteristics (gender, age) and several electrophysiological
findings (type of map, the location of ectopic focus and the
type of arrhythmia) between patients with long term successful
ablation and those with recurrence of arrhythmia (Table 2).
PVC, premature ventricular contraction; NSVT, non sustained
’Warming up’ during RF applications occurred respectively in
85% and 83,33 % of patients (p=0,46), after a mean time (dt 2)
of 4,72 ± 9,42 vs 10,75 ± 11,34 sec (p=0,045). The time intervals
from the onset of RF delivery (t0) to significant voltage abatement
(>90%) or reversal of EGM polarity (t1) between the two groups
were: 9,11 ± 5,11 vs 32,16 ± 10,33 (p=0,00006) and dV/dt1 was
95,44 ± 87,6 vs 23,5 ± 16,97 μV/s (P=0,024) (Table 3). Total RF
application times for the two groups were 351,5 ± 206,31 versus
370 ± 120,96 seconds (p=0,4).
*P<0,05 dt1, the time interval from the onset of RF delivery to significant
voltage abatement (>90%) or reversal of EGM polarity; dt2, time interval
from onset of RF ablation to warming up of the arrhythmia; dV/dt1, the
difference between EGM amplitude at the onset of RF application to
significant voltage abatement (>90%) or reversal of EGM polarity
corelated to the time interval dt1.
The rate of recurrence of 23,08% after a follow period of
13,55 ± 10,15 months is similar with those reported in literature.
The 76,92% success rate from the series suggests that long
term successful ablation of RVOT arrhythmia can be achieved in
patients who present during RF ablation with a short time interval
between onset of RF delivery (t0) to significant voltage abatement
(>90%) or reversal of EGM polarity (t1) and a higher value of
voltage abatement correlated to time interval between t0 and t1.
‘Warming up’ is not a predictor of procedural success in the
long run, even though shorter time intervals between the onset
of RF delivery and onset of warming up (dt2) trend towards
predicting long term success.
Successful transmural lesion formation during RF ablation
is the result of an ideal combination of contact force, catheter
stability, tissue temperature and wall thickness. The mechanisms
underlying long term recurrence of ventricular arrhythmias
originating from RVOT are unknown but are likely due to
inadequate lesion formation during the initial procedure. This
may be due to the inability of achieving transmural lesions caused
by poor catheter stability or insufficient wall contact creating
acute tissue edema causing only temporary suppression of
arrhythmias. In standard electrophysiological settings, changes
in EGM morphology are the only way of determining successful
transmural lesion formation. The speed at which this reduction
in EGM amplitude occurs, now seems to represent the most ideal
combination of wall contact, catheter precision and efficient
transmural lesion formation.
Several studies already proved the superiority of RMN guided
ablation of VT compared with manual navigation in terms of acute
success rate and procedure and fluoroscopy times . First, this
finding could be explained by the higher navigation capability,
even in difficult positions, due to the absence of pre-defined
catheter curves. Secondly, the positioning of the tip, the catheter
stability and contact are improved due to the constant magnetic
force directing the tip during application, allowing appropriate
lesion formation. Thirdly, RMN requires lower forces to maintain
stable tissue contact than conventional manual ablation while
creating equivalent lesions, making it also very suitable to be used
in thin walled regions such as the outflow tracts.
It has been previously reported that mural swelling develops
acutely in response to focal RF application. The swelling is
most marked at the site of RF delivery, but also tends to spread,
presumably through extension of interstitial edema through the
adjacent tissue, preventing optimal catheter tissue contact and
RF energy delivery. This tissue swelling persists throughout the
time of the ablation procedure and appears to resolve only within
weeks to months. So, while acute edema may result in temporary
suppression of arrhythmias, long term scarring may not have
been achieved, leading to recurrence. Therefore, it is paramount
to achieve adequate lesion formation as soon as possible during
the ablation procedure without causing too much ‘collateral
damage’ by edema formation.
This study has some limitations: the number of patients
included is relatively small and this is a nonrandomized,
retrospective study. However, since the dt1, dt2, dV/dt1, were
identified in our study as long-term outcome predictors post
RVOT ablation, we believe that further studies and investigations
are appropriate to confirm and establish a cut off value of dt1, dt2
and dV/dt1 as possible predictors of long-term success.
There was no significant difference of time of RF application
between our 2 groups, and thus the hypothesis, that some patients
are more prone to development of edema, exists.
Time related voltage abatement of ventricular EGM together
with time interval from onset of RF ablation to significant
voltage abatement (>90%) or reversal of EGM polarity and time
interval from onset of RF ablation to ‘warming up’ are possible
predictors of long-term success after RF ablation of idiopathic
RVOT arrhythmias. Presence of ‘warming up’ however is not
significantly correlated to procedural success in the long run.