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Acute and long term outcomes of catheter ablation using remote magnetic navigation for the treatment of electrical storm in patients with severe ischemic heart failure
International Journal of Cardiology 183 (2015) 11–16
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International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Acute and long term outcomes of catheter ablation using remote magnetic navigation for the treatment of electrical storm in patients with severe ischemic heart failure Qi Jin a,b, Peter Karl Jacobsen a, Steen Pehrson a, Xu Chen a,⁎ a b
Department of Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
a r t i c l e
i n f o
Article history: Received 19 October 2014 Received in revised form 3 January 2015 Accepted 25 January 2015 Available online 27 January 2015 Keywords: Electrical storm Remote magnetic navigation Ventricular tachycardia
a b s t r a c t Background: Catheter ablation with remote magnetic navigation (RMN) can offer some advantages compared to manual techniques. However, the relevant clinical evidence for how RMN-guided ablation affects electrical storm (ES) due to ventricular tachycardia (VT) in patients with severe ischemic heart failure (SIHF) is still limited. Methods: Forty consecutive SIHF patients (left ventricular ejection fraction, 21 ± 6.9%) presenting with ES underwent ablation using RMN. All the patients received implantable cardioverter-defibrillators (ICDs) either before or after ablation. Acute ablation success was defined as noninducibility of any sustained monophasic VT at the end of the procedure. Long-term analysis addressed VT recurrence, ICD therapies and all-cause death. ES was acutely suppressed by ablation in all patients. Results: Acute ablation success was obtained in 32 of 40 (80%) patients. The procedure time and fluoroscopy time were 105 ± 27 min and 7.5 ± 4.8 min respectively. No major complications occurred during procedures. During a mean follow-up of 17.4 months, 19 patients (47.5%) remained free of VT recurrence. The percentage of patients receiving ICD shocks after ablation was lower than before ablation (30% vs 69%, P b 0.01). The mean number of ICD shocks per individual per year was reduced from 4.3 before ablation to 1.9 after ablation (P b 0.05). Ten patients died during follow-up. Conclusions: Acute catheter ablation with RMN is safe and effective to suppress ES in SIHF patients. RMN-guided catheter ablation can prevent VT recurrence and significantly reduce ICD shocks, suggesting that this strategy can be used as an alternative therapy for VT storm in SIHF patients with ICDs. © 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Electrical storm (ES) due to ventricular tachycardia (VT) in patients with ischemic heart failure (IHF) is difficult to control with medical therapy as well as with implantable cardioverter-defibrillator (ICD), and is associated with poor short- and long-term prognoses [1–3]. Previous studies have shown that manual catheter ablation targeting the tachycardia substrate may overcome electrical instability [4,5] and can effectively suppress ES and reduce VT recurrence [6–8]. However, some regions of ventricular anatomy are difficult to reach by catheter using manual navigation, and compromised catheter positioning may lead to insufficient lesion formation [9]. Manipulating a catheter in some positions has also been associated with an increase in the risk of major procedure-related complications, including pericardial effusion or tamponade [10]. Mapping and ablation using a remote magnetic navigation (RMN) may offer advantages during VT procedure compared ⁎ Corresponding author at: Medical Department B 2014, The Heart Centre, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100 Copenhagen, Denmark. E-mail address: [email protected] (X. Chen).
http://dx.doi.org/10.1016/j.ijcard.2015.01.066 0167-5273/© 2015 Elsevier Ireland Ltd. All rights reserved.
to manual techniques [11–13]. Moreover, especially for severe IHF (SIHF) patients with left ventricular ejection fraction (LVEF) less than 30%, available experience on long-term outcomes of ES treated by acute catheter ablation with RMN is still limited. In the current study, we prospectively assessed the efficacy and safety of acute catheter ablation using RMN for drug-refractory ES in patients with SIHF. Furthermore, we analyzed the impact of RMN-guided catheter ablation on the long-term outcomes including VT recurrence, ICD therapies and survival rate. Therefore, the goal of this study was to provide the clinical evidence to support RMN-guided ablation as an alternative approach to manually performed ablation widely used in the treatment of ES in SIHF patients. 2. Methods 2.1. Study population In this prospective observational study, forty patients with a confirmed diagnosis of ES due to VT were consecutively included at the Rigshospitalet, University of Copenhagen between January 2008 and February 2014. All patients signed an informed consent before the procedure. ES was defined as the occurrence of three or more episodes of sustained
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VT, separated by 5 min, during a 24 h period or the presence of incessant VT (defined as persistent sustained VT or continuous episodes of VT separated by brief bouts of normal rhythm) [14]. SIHF was defined as ischemic heart disease with severe left ventricular dysfunction (LVEF ≤ 30%). Intravenous antiarrhythmic therapies, including amiodarone or other drugs, would be administrated and be adjusted if necessary in the interval before ablation. But intravenous antiarrhythmic therapy was withheld immediately before procedure. Due to the relative urgency of the ablation procedure, it was not possible to withdraw oral antiarrhythmic drugs, such as amiodarone, for 5 half-lives before the procedure. Also, blood electrolytes were measured immediately after admission and were corrected into normal range before ablation. A coronary angiogram was performed if acute ischemia was a potential cause of arrhythmia. Acute ischemic events were excluded in the present study. In this study, all patients had evidence of monomorphic VT on a 12-lead ECG and/or stored ICD electrograms. Eight patients with ICDs before ablation had only stored ICD electrograms because ICD therapies terminated these spontaneous VTs. Patient characteristics are summarized in Table 1. The population was predominantly male (37/40, 87.5%) with a mean age of 66 ± 9.2 years. The average LVEF was 21%. Meanwhile, 65% patients had low LVEF and clinical heart failure (NYHA classification ≥ III). Thirty-two patients were on amiodarone therapy before the ablation. About one third of patients had multiple monomorphic VTs recorded by ECG or ICD with a mean number of 1.35 ± 0.52 per patient (Table 1). Average VT cycle length (VT-CL) was 393 ms. A total of 36/40 (90%) patients had an ICD implanted. The number of ICD anti-tachycardia pacing (ICD-ATP) and ICD shocks per year in individuals was 66 ± 81 and 4.3 ± 5.0, respectively, before ablation. 17% (6/36) of patients experienced ventricular fibrillation (VF, indicated by ICD-stored electrograms) which was terminated by ICD shocks before ablation. Others underwent ICD shocks because ATP cannot terminate sustained VTs or degenerate to VF. In the 36 patients with ICD implantation before ablation, 5 underwent inappropriate ATP therapy, and only 2 patients received inappropriate shocks. 2.2. Electrophysiological study A 6 F steerable catheter (Inquiry, St Jude Medical, Inc.) and a 5 F quadripolar catheter (Medtronic, Inc) were positioned within the coronary sinus and at the apex of the right ventricle via the left femoral vein. A transseptal puncture was performed in the LAO radiographic position during pressure monitoring. Left atrial access was confirmed by an appropriate left atrial pressure waveform and fluoroscopic position. An open-irrigated magnetic ablation catheter (Navistar Thermocool-RMT, Biosense Webster Inc.) was introduced into the left ventricular (LV) cavity through a steerable sheath (Agilis, St. Jude Medical Inc.). A single bolus of 50–100 IU/kg body weight of heparin was administrated after transseptal puncture. Additional heparin was administrated to maintain an activated clotting time between 250 and 300 s as required. Surface ECG and endocardial electrograms were continuously monitored and recorded. ICD therapies were turned off and the device programmed to a VVI mode. The whole procedure on each patient was recorded by Odyssey system (Stereotaxis Inc).
applied to induce VT at multiple RV/LV sites with the 500-, and 400-ms drive cycle with up to 3 extrastimuli decrementally to 200 ms or ventricular refractoriness. If incessant VT was still present after catheter placement, activation and substrate mapping were performed simultaneously. In patients with poorly tolerated VT in the clinical setting, restrict activation mapping was performed after substrate mapping in sinus rhythm. Bipolar isovoltage maps of LV were constructed to delineate the scar and border zone areas. Areas with potential amplitudes ≥1.5 mV were defined as normal and those with amplitudes between 0.5 mV and 1.5 mV as border zone [14]. The scar area was defined during sinus rhythm by electrograms with an amplitude ≤ 0.5 mV. Regions with fragmented, abnormal electrograms and late potentials were annotated using color tags. Points with QRS morphology during pace-mapping identical to those seen during documented VT were also annotated. Entrainment-mapping techniques were applied trying to characterize the arrhythmic circuit in patients with well tolerated VTs. Radiofrequency energy was delivered in the temperature control mode with target tissue temperature of less than 45–48 °C. Power was set at 30–40 W with a flush rate of 10–25 mL/min. Radiofrequency lesions were delivered either during VT or during sinus rhythm in the regions identified or judged to be critical for the sustenance of clinical or inducible VTs. After VT, whether induced or incessant, was terminated by ablation, further ablation targeting local late potential during sinus rhythm was performed. After the catheter ablation, the same stimulation protocol mentioned above was applied to induce the tachycardia. Any induced sustained monomorphic VT was targeted with further ablation, and the inducible protocol of VT was repeated subsequently until no further VT was inducible. 2.5. Complications Complications were divided into two categories: major and minor. Major complications included cardiac tamponade, acute myocardial infarction, stroke, major bleeding and exacerbation of heart failure. Minor complications were defined as pericarditis and inguinal haematoma. 2.6. Study endpoints The procedural endpoint was ablation of any clinical and non-clinical inducible VTs. VT morphology was defined as “clinical” if it had been documented previously by a 12-lead electrocardiogram [7]. Nonclinical VTs were defined as those presenting different morphology and/or cycle length from any spontaneous episode documented in 12-lead ECG and/or stored ICD electrograms. Therefore, complete successful ablation was defined as the inability to reinduce any VT except polymorphic VT or ventricular fibrillation (VF). The primary study endpoint was the time to first recurrence of any sustained VT after ablation. The secondary endpoints were ICD shocks and all-cause death after ablation. 2.7. Follow-up
The ablation catheter was navigated with the CARTO RMT system (Biosense Webster) and the RMN Niobe II system or Niobe ES (Stereotaxis Inc., St. Louis, Missouri) to perform 3D LV electroanatomic mapping and ablation. The CARTO RMT system transmitted real-time catheter tip location and orientation to the magnetic navigation system. This information was displayed on the Navigant fluoroscopic reference screen, which enabled continuous real-time monitoring of catheter tip position without refreshing the fluoroscopic images.
All patients without a previous ICD implant were implanted before discharge. After ablation, ICD therapies were reprogrammed with active VT and VF zones. The first VT detection zone was programmed to include the slowest documented VT to prevent VT below detection. Patients were monitored at least 48 h in-hospital before discharge. After VT ablation, patients are typically seen at 1 month, and every 3 months afterwards to assess VT recurrences or were followed using remote monitoring systems. VT recurrence after hospital discharge was evaluated by careful ICD interrogation at each visit or by remote monitoring. Any sustained VT during follow-up, whether symptomatic, treated by ICD or not, was considered a recurrence of VT.
2.4. Mapping and ablation strategy
2.8. Statistical analysis
Substrate mapping followed by activation mapping was performed in patients with initial sinus rhythm and well tolerated VT. A programmed stimulation protocol was
Continuous variables were expressed with mean ± SD, and categorical variables as a percentage. An unpaired Student's t-test was used to compare the continuous variables from two groups. Categorical data were analyzed using chi-square test analysis or Fisher exact test where appropriate. For the long-term outcomes, survival functions were estimated by Kaplan–Meier analysis. A value of P b 0.05 was considered statistically significant. SPSS v19.0 statistical package was used for analysis.
2.3. Remote magnetic navigation system
Table 1 Baseline characteristic of patients. Characteristic
Total
No. of patients Age (year) Sex: male/female, n (%) LVEF (%) NYHA II/III + IV, n (%) PCI/CABG, n Amiodarone therapy before ablation (yes/no) Clinical multiple VTs, n (%) Clinical VTs per patient (#) Clinical VT-CL, ms ICD recipients: ICD-VVI/ICD-DDD/CRT-D, n Before ablation After ablation ICD ATP per patient per year ICD shock per patient per year
40 66 ± 9.2 37/3 (92.5%/7.5%) 21 ± 6.9 14/26 (35%/65%) 15/22 32/8 13 (32.5%) 1.35 ± 0.52 393 ± 86 14/7/15 16/9/15 66 ± 81 4.3 ± 5.0
PCI, percutaneous coronary intervention; CABG, coronary artery bypass grafting; ATP, anti-tachycardiac pacing.
3. Results 3.1. Acute outcomes of catheter ablation with RMN LV endocardial mapping was performed via transseptal approach in all patients. All the monomorphic sustained VTs were targeted for ablation. Fig. 1 shows an example of substrate mapping and ablation in a patient with anterior wall myocardial infarction. A total of 84 VTs were induced in this studied population with a mean number of 2.1 ± 1.0 induced VTs per patient. In this patient group, at least one type of VT, whether clinical or non-clinical, could be induced in each of the patients during the procedure. The frequency of multiple induced VTs during the procedure was higher than that documented in clinical settings (26/40 vs 13/40, P b 0.01) (Tables 1 and 2). The average CL of
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Fig. 1. An example of substrate mapping in a patient with anterior wall myocardial infarction. This SIHF patient (78 years old) with LVEF 25% experienced 3 ICD shocks and 20 ICD ATPs within 24 h before ablation. In substrate mapping (middle upper panel) the scar region (red area) was defined as areas with bipolar local electrogram ≤0.5 mV and the normal myocardium (purple area) was defined as areas with a bipolar local electrogram ≥1.5 mV. Middle lower panel shows that CARTO RMT system can transfer real-time catheter tip location and orientation to RMN. The red and pink dots represent the ablation lesions. The blue dots represent late potential locations, and the white circles represent the locations of successful termination of clinical sustained VT (VT 1, ECG on the right panel) and non-clinical sustained VT (VT 2, ECG on the left panel). In this case, further ablation targeting possible protected isthmus, regions with late potentials and fractionated potentials is applied after induced VTs are ablated. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
inducible clinical and non-clinical VTs was not significantly different from the clinical VT-CL (374 ± 84 ms, 393 ± 86 ms, P N 0.05). The VTs in 95% (38/40) patients were successfully ablated after the first ablation, and thus, ES was eliminated in these patients during the observation period in hospital. Successful ablation of any inducible monomorphic sustained VTs (clinical and non-clinical VTs) was achieved in 32 (80%) patients (Table 2). Acute complete success rate was not different between the patients with and without amiodarone before the ablation (26/32 vs 6/8, P = 0.92). Two patients still had VT after the procedure, but the ES was controlled with a combination of ablation and additional medication. No procedure was converted from RMN to manual in this study. Procedural outcomes of catheter ablation with RMN were listed in Table 2. The total procedure and fluoroscopy times were 105 ± 27 min and 7.5 ± 4.8 min, respectively. The duration of total RF ablation time was 16.5 ± 8.8 min. Table 2 Electrophysiological and procedural outcomes of acute catheter ablation. Parameters
Results
Multiple induced VTs, n (%) Inducible VTs per patient (#) Induced VT-CL (mean ± SD), ms Acute success of catheter ablation Non-inducibility of any VT Non-inducibility of clinical VT Failure Procedure time (mean ± SD), min Fluoroscopy time (mean ± SD), min RF ablation time (mean ± SD), min
26 (65%) 2.1 ± 1.0 374 ± 84
RF, radiofrequency.
32 (80%) 6 (15%) 2 (5%) 105 ± 27 7.5 ± 4.8 16.5 ± 8.8
There were no major complications, including cardiac tamponade, thromboembolic events or major bleeding, in this studied population. None of the patients underwent acute exacerbation of heart failure during or after catheter ablation. One patient required re-placement of right atrial lead of ICD. 3.2. Long-term outcomes of catheter ablation with RMN During a mean follow-up of 17.4 ± 16.9 months, 19 patients (47.5%) had no recurrence of sustained VT, and did not receive any ICD therapies. A Kaplan–Meier curve of time-to first recurrence of sustained VT is shown in Fig. 2. Of the 19 patients free of VT recurrence, 17/19 (89%) patients experienced acute successful ablation without inducing clinical and non-clinical VTs. VT recurrence rate in patients with just low LVEF was similar to those with low LVEF and clinical heart failure (43% vs 58%, P = 0.37). Also, the VT recurrence rate was not different between the patients with and without amiodarone before the ablation (15/32 vs 6/8, P = 0.30). During the follow-up period, the percentage of patients receiving ICD shocks after ablation procedure was significantly lower than that before ablation (30% vs 69% P b 0.01). The number of ICD shocks in individuals per year after ablation decreased by 56% compared to before ablation (1.9 ± 5.6 vs 4.3 ± 5.0, P b 0.05). A Kaplan–Meier survival free of ICD shock curve is illustrated in Fig. 3. Meanwhile, the number of ICD-ATP in individuals per year was decreased from 66 ± 81 episodes before ablation to 14 ± 30 episodes after ablation (P b 0.01). However, the percentages of inappropriate ICD-ATP and ICD shock in each patient after ablation procedure were not different from that before ablation (13% vs 14%, P = 0.87; 5.5% vs 2.5%, P = 0.93, respectively). A total of ten patients (25%) died after ablation. There were no procedure-related deaths. One patient died of cardiogenic shock and
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4.1. Acute outcomes of ES ablation with RMN: efficacy and safety
Fig. 2. Kaplan–Meier time-to-first recurrence of sustained VT curve.
severe congestive heart failure (LVEF = 10%, NYHA Class IV before ablation) after CABG surgery during hospitalization. Another nine patients died during follow-up. Of the 9 patients, 7 out of 9 died of end-stage heart failure. The average LVEF of these seven patients was 20% ± 7.5% before ablation. Another two patients died of ischemic stroke and cerebral hemorrhage respectively. The mortality of just low LVEF patients did not differ from the patients with low LVEF and clinical heart failure (2/14 vs 8/26, P = 0.44). The mean survival time of ten dead patients from first ablation to death was 19.4 months. 4. Discussion RMN has become a broadly accepted technique to treat various cardiac arrhythmias, including ischemic VT [12,15–17]. To the best of our knowledge, this is the first single-center description of how catheter ablation with RMN affects the short- and long-term clinical outcomes of ES in SIHF patients. The main findings of the present study are as follows. 1) Catheter ablation with RMN was an acutely effective and safe method for suppressing drug-refractory ES in patients with severe left ventricular dysfunction. 2) Fluoroscopy time and procedural time were markedly reduced by ablation with RMN compared to published data of manual ablation. 3) Long-term followup with strict ICD interrogation showed that RMN-guided catheter ablation can effectively prevent VT recurrence and significantly reduce ICD shocks, suggesting that the technique can be used as an alternative therapy for VT storm and potentially improve the quality of life for SIHF patients with ICDs.
Fig. 3. Kaplan–Meier time-to-first ICD shock curve.
To date, ES remains a challenging condition to manage despite the availability of various management techniques [18]. Most arrhythmic episodes (86–97%) during ES consist of scar-related monomorphic VT [2,19], which makes it feasible for catheter ablation to control ES. Accordingly, catheter ablation with manual navigation has been reported to suppress ES by ablating VT with complete success rate of up to 72% [7]. However, the complex anatomy of the endocardial scar, multiple potential reentrant pathways and different initiators possibly influence the success rate of ventricular arrhythmias with manual ablation [4,20]. Also, compromised catheter positioning for ablation may result in insufficient lesion formation [9]. Catheter ablation guided by RMN has the potential to overcome these challenges. A case–control study has documented that acute success rate of VT ablation with RMN was higher than with manual navigation in structural normal hearts (83% vs 61%). The use of RMN to ablate VT in patients with ischemic heart disease has been associated with success rates ranging from 71 to 82% [12,15, 17]. In the current study, the acute success rate of VT ablation reached 80%. Although the use of RMN in our study was not compared to manual navigation, the relatively higher success rate provided further clinical evidence of acute efficacy for suppressing drug-resistant ES due to VT as a “rescue” treatment in this severity of IHF. Major complication rates during VT ablation in patients with ischemic heart disease have ranged from 1 to 11.1% [11,21]. In our patients catheter ablation with RMN was performed without major periprocedural complications although the average LVEF was markedly reduced. The result is consistent with other studies about the excellent safety record of the atraumatic flexible catheter employed with RMN. Also, a relatively reduced procedure time in our study (105 ± 27 min) may have contributed to the low frequency of complications. In addition, epicardial mapping and ablation which could increase the possibility of complication were not performed in this study. Furthermore, LV access from transseptal route in this study can avoid the possibility of aortic valve injury. 4.2. Long-term outcomes of SIHF-ES ablation with RMN In earlier reports, approximately 40–70% and 10% of patients with ICDs respectively experienced VT recurrence and ES during follow-up [22,23]. Catheter ablation has been reported to acutely control ES, however, the evidence for the long-term effect of catheter ablation with RMN on ES was insufficient. The current study aims to describe how catheter ablation with RMN affects the long-term outcomes of ES in SIHF patients with regularly clinical and ICD follow-up, including VT recurrence, ICD therapies and survival rate. In this study, freedom from any VT was observed in 47.5% of SIHF patients by the end of the follow-up (mean, 17.4 months). The long-term outcome of this study is comparable to already published data in the biggest multicenter trials. In the Multicenter Thermocool Ventricular Tachycardia Ablation trial, the reported VT recurrence was 47% at 6 months in the patients with a history of HF in 62% [24]. In the multicenter, prospective, randomized Ventricular Tachycardia Ablation in Coronary Heart Disease (VTACH) study, 47% of patients were free from VT recurrence in the ablation patients with the mean of LVEF in 34% during the 2-year follow-up [25]. Our study provided new evidence that catheter ablation with RMN for the treatment of ES can play a secondary prophylactic role in VT recurrence even in SIHF patients (average LVEF 21%). ICDs have emerged as the major therapy for protecting patients from sudden death, but multiple ICD shocks, particularly when ≥5 shocks are delivered, would worsen quality of life and are associated with increased mortality [26]. In the present study, the number of ICD shocks and ICD ATPs in individuals per year after ablation was decreased by 56% and by 79% respectively compared to before ablation. The incidence of ICD shock in each patient after ablation was significantly reduced (30% vs 69%, P b 0.01). However, 25% patients died during follow-up
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even though ICD shocks were reduced from 4.3 before ablation to 1.9 after ablation. The results in our study together with those of other groups suggest that catheter ablation of VT reduces ICD therapies, and thus, possibly improves quality of life. However, at present, this strategy has not been shown to influence on mortality rates [14,27,28]. Therefore, further multicenter, prospective, randomized clinical trials are needed to evaluate the effect of RMN-controlled ES ablation on mortality in SIHF patients. 4.3. Limitations There are several limitations in the current study. First, although this ablation technique was performed in consecutive patients prospectively and analyzed the short- and long-term outcomes in patients with ES treated by catheter ablation with RMN, this study was not designed to directly compare catheter ablation with other forms of treatment for ES. Therefore, the study cannot prove that catheter ablation with RMN is superior to other therapies. In addition, epicardial ablation was not performed in this study. Although endocardial ablation is often sufficient to eliminate local abnormal ventricular activities from epicardium and may be used first to reduce the risk of epicardial ablation [29], advanced epicardial ablation can possibly increase the acute success rate of ES due to VT in a proportion of patients with ischemic heart disease. 5. Conclusions Catheter ablation with RMN is safe and acutely effective to control ES due to VT with minimal fluoroscopy exposure. RMN-guided catheter ablation can prevent VT recurrence and significantly reduce ICD therapies which potentially improve the quality of life in SIHF patients suffering from ES. This study provided new evidence to support RMN-guided ablation as an alternative approach to manually performed ablation in the treatment of VT storm in patients with ischemic heart disease. Disclosures None. Conflict of interest The authors report no relationships that could be construed as a conflict of interest. Acknowledgments The authors wish to thank the technical staff of the Cardiac Catheterization Laboratory for their help. References [1] F. Guerra, M. Shkoza, L. Scappini, M. Flori, A. Capucci, Role of electrical storm as a mortality and morbidity risk factor and its clinical predictors: a meta-analysis, Europace 16 (2014) 347–353. [2] S.H. Hohnloser, H.R. Al-Khalidi, C.M. Pratt, J.M. Brum, D.S. Tatla, P. Tchou, P. Dorian, Investigators SHIEwA, Electrical storm in patients with an implantable defibrillator: incidence, features, and preventive therapy: insights from a randomized trial, Eur. Heart J. 27 (2006) 3027–3032. [3] A. Arya, M. Haghjoo, M.R. Dehghani, A.F. Fazelifar, M.H. Nikoo, A. Bagherzadeh, M.A. Sadr-Ameli, Prevalence and predictors of electrical storm in patients with implantable cardioverter-defibrillator, Am. J. Cardiol. 97 (2006) 389–392. [4] J. Schreieck, B. Zrenner, I. Deisenhofer, C. Schmitt, Rescue ablation of electrical storm in patients with ischemic cardiomyopathy: a potential-guided ablation approach by modifying substrate of intractable, unmappable ventricular tachycardias, Heart Rhythm. 2 (2005) 10–14. [5] B.S. Alzand, C.C. Timmermans, H.J. Wellens, R. Dennert, S.A. Philippens, P.J. Portegijs, L.M. Rodriguez, Unmappable ventricular tachycardia after an old myocardial infarction. Long-term results of substrate modification in patients with an implantable cardioverter defibrillator, J. Interv. Card. Electrophysiol. 31 (2011) 149–156.
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Electrophysiol. 7 (2014) 414–423. [22] D.P. Zipes, D. Roberts, Results of the international study of the implantable pacemaker cardioverter-defibrillator. A comparison of epicardial and endocardial lead systems. The pacemaker–cardioverter-defibrillator investigators, Circulation 92 (1995) 59–65. [23] S.C. Credner, T. Klingenheben, O. Mauss, C. Sticherling, S.H. Hohnloser, Electrical storm in patients with transvenous implantable cardioverter-defibrillators: incidence, management and prognostic implications, J. Am. Coll. Cardiol. 32 (1998) 1909–1915. [24] W.G. Stevenson, D.J. Wilber, A. Natale, W.M. Jackman, F.E. Marchlinski, T. Talbert, M.D. Gonzalez, S.J. Worley, E.G. Daoud, C. Hwang, C. Schuger, T.E. Bump, M. Jazayeri, G.F. Tomassoni, H.A. Kopelman, K. Soejima, H. Nakagawa, V.T.A.T.I. Multicenter Thermocool, Irrigated radiofrequency catheter ablation guided by electroanatomic mapping for recurrent ventricular tachycardia after myocardial infarction: the multicenter thermocool ventricular tachycardia ablation trial, Circulation 118 (2008) 2773–2782. [25] K.H. Kuck, A. Schaumann, L. Eckardt, S. Willems, R. Ventura, E. Delacretaz, H.F. Pitschner, J. Kautzner, B. Schumacher, P.S. Hansen, group Vs, Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial, Lancet 375 (2010) 31–40. [26] S.B. Dunbar, C.M. Dougherty, S.F. Sears, D.L. Carroll, N.E. Goldstein, D.B. Mark, G. McDaniel, S.J. Pressler, E. Schron, P. Wang, V.L. Zeigler, American Heart Association
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[28] J. Mallidi, G.N. Nadkarni, R.D. Berger, H. Calkins, S. Nazarian, Meta-analysis of catheter ablation as an adjunct to medical therapy for treatment of ventricular tachycardia in patients with structural heart disease, Heart Rhythm. 8 (2011) 503–510. [29] Y. Komatsu, M. Daly, F. Sacher, H. Cochet, A. Denis, N. Derval, L. Jesel, S. Zellerhoff, H.S. Lim, A. Jadidi, I. Nault, A. Shah, L. Roten, P. Pascale, D. Scherr, V. AurillacLavignolle, M. Hocini, M. Haissaguerre, P. Jais, Endocardial ablation to eliminate epicardial arrhythmia substrate in scar-related ventricular tachycardia, J. Am. Coll. Cardiol. 63 (2014) 1416–1426.
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Acute and long term outcomes of catheter ablation using remote magnetic navigation for the treatment of electrical storm in patients with severe ischemic heart failure Qi Jin a,b, Peter Karl Jacobsen a, Steen Pehrson a, Xu Chen a,⁎ a b
Department of Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
a r t i c l e
i n f o
Article history: Received 19 October 2014 Received in revised form 3 January 2015 Accepted 25 January 2015 Available online 27 January 2015 Keywords: Electrical storm Remote magnetic navigation Ventricular tachycardia
a b s t r a c t Background: Catheter ablation with remote magnetic navigation (RMN) can offer some advantages compared to manual techniques. However, the relevant clinical evidence for how RMN-guided ablation affects electrical storm (ES) due to ventricular tachycardia (VT) in patients with severe ischemic heart failure (SIHF) is still limited. Methods: Forty consecutive SIHF patients (left ventricular ejection fraction, 21 ± 6.9%) presenting with ES underwent ablation using RMN. All the patients received implantable cardioverter-defibrillators (ICDs) either before or after ablation. Acute ablation success was defined as noninducibility of any sustained monophasic VT at the end of the procedure. Long-term analysis addressed VT recurrence, ICD therapies and all-cause death. ES was acutely suppressed by ablation in all patients. Results: Acute ablation success was obtained in 32 of 40 (80%) patients. The procedure time and fluoroscopy time were 105 ± 27 min and 7.5 ± 4.8 min respectively. No major complications occurred during procedures. During a mean follow-up of 17.4 months, 19 patients (47.5%) remained free of VT recurrence. The percentage of patients receiving ICD shocks after ablation was lower than before ablation (30% vs 69%, P b 0.01). The mean number of ICD shocks per individual per year was reduced from 4.3 before ablation to 1.9 after ablation (P b 0.05). Ten patients died during follow-up. Conclusions: Acute catheter ablation with RMN is safe and effective to suppress ES in SIHF patients. RMN-guided catheter ablation can prevent VT recurrence and significantly reduce ICD shocks, suggesting that this strategy can be used as an alternative therapy for VT storm in SIHF patients with ICDs. © 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Electrical storm (ES) due to ventricular tachycardia (VT) in patients with ischemic heart failure (IHF) is difficult to control with medical therapy as well as with implantable cardioverter-defibrillator (ICD), and is associated with poor short- and long-term prognoses [1–3]. Previous studies have shown that manual catheter ablation targeting the tachycardia substrate may overcome electrical instability [4,5] and can effectively suppress ES and reduce VT recurrence [6–8]. However, some regions of ventricular anatomy are difficult to reach by catheter using manual navigation, and compromised catheter positioning may lead to insufficient lesion formation [9]. Manipulating a catheter in some positions has also been associated with an increase in the risk of major procedure-related complications, including pericardial effusion or tamponade [10]. Mapping and ablation using a remote magnetic navigation (RMN) may offer advantages during VT procedure compared ⁎ Corresponding author at: Medical Department B 2014, The Heart Centre, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100 Copenhagen, Denmark. E-mail address: [email protected] (X. Chen).
http://dx.doi.org/10.1016/j.ijcard.2015.01.066 0167-5273/© 2015 Elsevier Ireland Ltd. All rights reserved.
to manual techniques [11–13]. Moreover, especially for severe IHF (SIHF) patients with left ventricular ejection fraction (LVEF) less than 30%, available experience on long-term outcomes of ES treated by acute catheter ablation with RMN is still limited. In the current study, we prospectively assessed the efficacy and safety of acute catheter ablation using RMN for drug-refractory ES in patients with SIHF. Furthermore, we analyzed the impact of RMN-guided catheter ablation on the long-term outcomes including VT recurrence, ICD therapies and survival rate. Therefore, the goal of this study was to provide the clinical evidence to support RMN-guided ablation as an alternative approach to manually performed ablation widely used in the treatment of ES in SIHF patients. 2. Methods 2.1. Study population In this prospective observational study, forty patients with a confirmed diagnosis of ES due to VT were consecutively included at the Rigshospitalet, University of Copenhagen between January 2008 and February 2014. All patients signed an informed consent before the procedure. ES was defined as the occurrence of three or more episodes of sustained
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VT, separated by 5 min, during a 24 h period or the presence of incessant VT (defined as persistent sustained VT or continuous episodes of VT separated by brief bouts of normal rhythm) [14]. SIHF was defined as ischemic heart disease with severe left ventricular dysfunction (LVEF ≤ 30%). Intravenous antiarrhythmic therapies, including amiodarone or other drugs, would be administrated and be adjusted if necessary in the interval before ablation. But intravenous antiarrhythmic therapy was withheld immediately before procedure. Due to the relative urgency of the ablation procedure, it was not possible to withdraw oral antiarrhythmic drugs, such as amiodarone, for 5 half-lives before the procedure. Also, blood electrolytes were measured immediately after admission and were corrected into normal range before ablation. A coronary angiogram was performed if acute ischemia was a potential cause of arrhythmia. Acute ischemic events were excluded in the present study. In this study, all patients had evidence of monomorphic VT on a 12-lead ECG and/or stored ICD electrograms. Eight patients with ICDs before ablation had only stored ICD electrograms because ICD therapies terminated these spontaneous VTs. Patient characteristics are summarized in Table 1. The population was predominantly male (37/40, 87.5%) with a mean age of 66 ± 9.2 years. The average LVEF was 21%. Meanwhile, 65% patients had low LVEF and clinical heart failure (NYHA classification ≥ III). Thirty-two patients were on amiodarone therapy before the ablation. About one third of patients had multiple monomorphic VTs recorded by ECG or ICD with a mean number of 1.35 ± 0.52 per patient (Table 1). Average VT cycle length (VT-CL) was 393 ms. A total of 36/40 (90%) patients had an ICD implanted. The number of ICD anti-tachycardia pacing (ICD-ATP) and ICD shocks per year in individuals was 66 ± 81 and 4.3 ± 5.0, respectively, before ablation. 17% (6/36) of patients experienced ventricular fibrillation (VF, indicated by ICD-stored electrograms) which was terminated by ICD shocks before ablation. Others underwent ICD shocks because ATP cannot terminate sustained VTs or degenerate to VF. In the 36 patients with ICD implantation before ablation, 5 underwent inappropriate ATP therapy, and only 2 patients received inappropriate shocks. 2.2. Electrophysiological study A 6 F steerable catheter (Inquiry, St Jude Medical, Inc.) and a 5 F quadripolar catheter (Medtronic, Inc) were positioned within the coronary sinus and at the apex of the right ventricle via the left femoral vein. A transseptal puncture was performed in the LAO radiographic position during pressure monitoring. Left atrial access was confirmed by an appropriate left atrial pressure waveform and fluoroscopic position. An open-irrigated magnetic ablation catheter (Navistar Thermocool-RMT, Biosense Webster Inc.) was introduced into the left ventricular (LV) cavity through a steerable sheath (Agilis, St. Jude Medical Inc.). A single bolus of 50–100 IU/kg body weight of heparin was administrated after transseptal puncture. Additional heparin was administrated to maintain an activated clotting time between 250 and 300 s as required. Surface ECG and endocardial electrograms were continuously monitored and recorded. ICD therapies were turned off and the device programmed to a VVI mode. The whole procedure on each patient was recorded by Odyssey system (Stereotaxis Inc).
applied to induce VT at multiple RV/LV sites with the 500-, and 400-ms drive cycle with up to 3 extrastimuli decrementally to 200 ms or ventricular refractoriness. If incessant VT was still present after catheter placement, activation and substrate mapping were performed simultaneously. In patients with poorly tolerated VT in the clinical setting, restrict activation mapping was performed after substrate mapping in sinus rhythm. Bipolar isovoltage maps of LV were constructed to delineate the scar and border zone areas. Areas with potential amplitudes ≥1.5 mV were defined as normal and those with amplitudes between 0.5 mV and 1.5 mV as border zone [14]. The scar area was defined during sinus rhythm by electrograms with an amplitude ≤ 0.5 mV. Regions with fragmented, abnormal electrograms and late potentials were annotated using color tags. Points with QRS morphology during pace-mapping identical to those seen during documented VT were also annotated. Entrainment-mapping techniques were applied trying to characterize the arrhythmic circuit in patients with well tolerated VTs. Radiofrequency energy was delivered in the temperature control mode with target tissue temperature of less than 45–48 °C. Power was set at 30–40 W with a flush rate of 10–25 mL/min. Radiofrequency lesions were delivered either during VT or during sinus rhythm in the regions identified or judged to be critical for the sustenance of clinical or inducible VTs. After VT, whether induced or incessant, was terminated by ablation, further ablation targeting local late potential during sinus rhythm was performed. After the catheter ablation, the same stimulation protocol mentioned above was applied to induce the tachycardia. Any induced sustained monomorphic VT was targeted with further ablation, and the inducible protocol of VT was repeated subsequently until no further VT was inducible. 2.5. Complications Complications were divided into two categories: major and minor. Major complications included cardiac tamponade, acute myocardial infarction, stroke, major bleeding and exacerbation of heart failure. Minor complications were defined as pericarditis and inguinal haematoma. 2.6. Study endpoints The procedural endpoint was ablation of any clinical and non-clinical inducible VTs. VT morphology was defined as “clinical” if it had been documented previously by a 12-lead electrocardiogram [7]. Nonclinical VTs were defined as those presenting different morphology and/or cycle length from any spontaneous episode documented in 12-lead ECG and/or stored ICD electrograms. Therefore, complete successful ablation was defined as the inability to reinduce any VT except polymorphic VT or ventricular fibrillation (VF). The primary study endpoint was the time to first recurrence of any sustained VT after ablation. The secondary endpoints were ICD shocks and all-cause death after ablation. 2.7. Follow-up
The ablation catheter was navigated with the CARTO RMT system (Biosense Webster) and the RMN Niobe II system or Niobe ES (Stereotaxis Inc., St. Louis, Missouri) to perform 3D LV electroanatomic mapping and ablation. The CARTO RMT system transmitted real-time catheter tip location and orientation to the magnetic navigation system. This information was displayed on the Navigant fluoroscopic reference screen, which enabled continuous real-time monitoring of catheter tip position without refreshing the fluoroscopic images.
All patients without a previous ICD implant were implanted before discharge. After ablation, ICD therapies were reprogrammed with active VT and VF zones. The first VT detection zone was programmed to include the slowest documented VT to prevent VT below detection. Patients were monitored at least 48 h in-hospital before discharge. After VT ablation, patients are typically seen at 1 month, and every 3 months afterwards to assess VT recurrences or were followed using remote monitoring systems. VT recurrence after hospital discharge was evaluated by careful ICD interrogation at each visit or by remote monitoring. Any sustained VT during follow-up, whether symptomatic, treated by ICD or not, was considered a recurrence of VT.
2.4. Mapping and ablation strategy
2.8. Statistical analysis
Substrate mapping followed by activation mapping was performed in patients with initial sinus rhythm and well tolerated VT. A programmed stimulation protocol was
Continuous variables were expressed with mean ± SD, and categorical variables as a percentage. An unpaired Student's t-test was used to compare the continuous variables from two groups. Categorical data were analyzed using chi-square test analysis or Fisher exact test where appropriate. For the long-term outcomes, survival functions were estimated by Kaplan–Meier analysis. A value of P b 0.05 was considered statistically significant. SPSS v19.0 statistical package was used for analysis.
2.3. Remote magnetic navigation system
Table 1 Baseline characteristic of patients. Characteristic
Total
No. of patients Age (year) Sex: male/female, n (%) LVEF (%) NYHA II/III + IV, n (%) PCI/CABG, n Amiodarone therapy before ablation (yes/no) Clinical multiple VTs, n (%) Clinical VTs per patient (#) Clinical VT-CL, ms ICD recipients: ICD-VVI/ICD-DDD/CRT-D, n Before ablation After ablation ICD ATP per patient per year ICD shock per patient per year
40 66 ± 9.2 37/3 (92.5%/7.5%) 21 ± 6.9 14/26 (35%/65%) 15/22 32/8 13 (32.5%) 1.35 ± 0.52 393 ± 86 14/7/15 16/9/15 66 ± 81 4.3 ± 5.0
PCI, percutaneous coronary intervention; CABG, coronary artery bypass grafting; ATP, anti-tachycardiac pacing.
3. Results 3.1. Acute outcomes of catheter ablation with RMN LV endocardial mapping was performed via transseptal approach in all patients. All the monomorphic sustained VTs were targeted for ablation. Fig. 1 shows an example of substrate mapping and ablation in a patient with anterior wall myocardial infarction. A total of 84 VTs were induced in this studied population with a mean number of 2.1 ± 1.0 induced VTs per patient. In this patient group, at least one type of VT, whether clinical or non-clinical, could be induced in each of the patients during the procedure. The frequency of multiple induced VTs during the procedure was higher than that documented in clinical settings (26/40 vs 13/40, P b 0.01) (Tables 1 and 2). The average CL of
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Fig. 1. An example of substrate mapping in a patient with anterior wall myocardial infarction. This SIHF patient (78 years old) with LVEF 25% experienced 3 ICD shocks and 20 ICD ATPs within 24 h before ablation. In substrate mapping (middle upper panel) the scar region (red area) was defined as areas with bipolar local electrogram ≤0.5 mV and the normal myocardium (purple area) was defined as areas with a bipolar local electrogram ≥1.5 mV. Middle lower panel shows that CARTO RMT system can transfer real-time catheter tip location and orientation to RMN. The red and pink dots represent the ablation lesions. The blue dots represent late potential locations, and the white circles represent the locations of successful termination of clinical sustained VT (VT 1, ECG on the right panel) and non-clinical sustained VT (VT 2, ECG on the left panel). In this case, further ablation targeting possible protected isthmus, regions with late potentials and fractionated potentials is applied after induced VTs are ablated. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
inducible clinical and non-clinical VTs was not significantly different from the clinical VT-CL (374 ± 84 ms, 393 ± 86 ms, P N 0.05). The VTs in 95% (38/40) patients were successfully ablated after the first ablation, and thus, ES was eliminated in these patients during the observation period in hospital. Successful ablation of any inducible monomorphic sustained VTs (clinical and non-clinical VTs) was achieved in 32 (80%) patients (Table 2). Acute complete success rate was not different between the patients with and without amiodarone before the ablation (26/32 vs 6/8, P = 0.92). Two patients still had VT after the procedure, but the ES was controlled with a combination of ablation and additional medication. No procedure was converted from RMN to manual in this study. Procedural outcomes of catheter ablation with RMN were listed in Table 2. The total procedure and fluoroscopy times were 105 ± 27 min and 7.5 ± 4.8 min, respectively. The duration of total RF ablation time was 16.5 ± 8.8 min. Table 2 Electrophysiological and procedural outcomes of acute catheter ablation. Parameters
Results
Multiple induced VTs, n (%) Inducible VTs per patient (#) Induced VT-CL (mean ± SD), ms Acute success of catheter ablation Non-inducibility of any VT Non-inducibility of clinical VT Failure Procedure time (mean ± SD), min Fluoroscopy time (mean ± SD), min RF ablation time (mean ± SD), min
26 (65%) 2.1 ± 1.0 374 ± 84
RF, radiofrequency.
32 (80%) 6 (15%) 2 (5%) 105 ± 27 7.5 ± 4.8 16.5 ± 8.8
There were no major complications, including cardiac tamponade, thromboembolic events or major bleeding, in this studied population. None of the patients underwent acute exacerbation of heart failure during or after catheter ablation. One patient required re-placement of right atrial lead of ICD. 3.2. Long-term outcomes of catheter ablation with RMN During a mean follow-up of 17.4 ± 16.9 months, 19 patients (47.5%) had no recurrence of sustained VT, and did not receive any ICD therapies. A Kaplan–Meier curve of time-to first recurrence of sustained VT is shown in Fig. 2. Of the 19 patients free of VT recurrence, 17/19 (89%) patients experienced acute successful ablation without inducing clinical and non-clinical VTs. VT recurrence rate in patients with just low LVEF was similar to those with low LVEF and clinical heart failure (43% vs 58%, P = 0.37). Also, the VT recurrence rate was not different between the patients with and without amiodarone before the ablation (15/32 vs 6/8, P = 0.30). During the follow-up period, the percentage of patients receiving ICD shocks after ablation procedure was significantly lower than that before ablation (30% vs 69% P b 0.01). The number of ICD shocks in individuals per year after ablation decreased by 56% compared to before ablation (1.9 ± 5.6 vs 4.3 ± 5.0, P b 0.05). A Kaplan–Meier survival free of ICD shock curve is illustrated in Fig. 3. Meanwhile, the number of ICD-ATP in individuals per year was decreased from 66 ± 81 episodes before ablation to 14 ± 30 episodes after ablation (P b 0.01). However, the percentages of inappropriate ICD-ATP and ICD shock in each patient after ablation procedure were not different from that before ablation (13% vs 14%, P = 0.87; 5.5% vs 2.5%, P = 0.93, respectively). A total of ten patients (25%) died after ablation. There were no procedure-related deaths. One patient died of cardiogenic shock and
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4.1. Acute outcomes of ES ablation with RMN: efficacy and safety
Fig. 2. Kaplan–Meier time-to-first recurrence of sustained VT curve.
severe congestive heart failure (LVEF = 10%, NYHA Class IV before ablation) after CABG surgery during hospitalization. Another nine patients died during follow-up. Of the 9 patients, 7 out of 9 died of end-stage heart failure. The average LVEF of these seven patients was 20% ± 7.5% before ablation. Another two patients died of ischemic stroke and cerebral hemorrhage respectively. The mortality of just low LVEF patients did not differ from the patients with low LVEF and clinical heart failure (2/14 vs 8/26, P = 0.44). The mean survival time of ten dead patients from first ablation to death was 19.4 months. 4. Discussion RMN has become a broadly accepted technique to treat various cardiac arrhythmias, including ischemic VT [12,15–17]. To the best of our knowledge, this is the first single-center description of how catheter ablation with RMN affects the short- and long-term clinical outcomes of ES in SIHF patients. The main findings of the present study are as follows. 1) Catheter ablation with RMN was an acutely effective and safe method for suppressing drug-refractory ES in patients with severe left ventricular dysfunction. 2) Fluoroscopy time and procedural time were markedly reduced by ablation with RMN compared to published data of manual ablation. 3) Long-term followup with strict ICD interrogation showed that RMN-guided catheter ablation can effectively prevent VT recurrence and significantly reduce ICD shocks, suggesting that the technique can be used as an alternative therapy for VT storm and potentially improve the quality of life for SIHF patients with ICDs.
Fig. 3. Kaplan–Meier time-to-first ICD shock curve.
To date, ES remains a challenging condition to manage despite the availability of various management techniques [18]. Most arrhythmic episodes (86–97%) during ES consist of scar-related monomorphic VT [2,19], which makes it feasible for catheter ablation to control ES. Accordingly, catheter ablation with manual navigation has been reported to suppress ES by ablating VT with complete success rate of up to 72% [7]. However, the complex anatomy of the endocardial scar, multiple potential reentrant pathways and different initiators possibly influence the success rate of ventricular arrhythmias with manual ablation [4,20]. Also, compromised catheter positioning for ablation may result in insufficient lesion formation [9]. Catheter ablation guided by RMN has the potential to overcome these challenges. A case–control study has documented that acute success rate of VT ablation with RMN was higher than with manual navigation in structural normal hearts (83% vs 61%). The use of RMN to ablate VT in patients with ischemic heart disease has been associated with success rates ranging from 71 to 82% [12,15, 17]. In the current study, the acute success rate of VT ablation reached 80%. Although the use of RMN in our study was not compared to manual navigation, the relatively higher success rate provided further clinical evidence of acute efficacy for suppressing drug-resistant ES due to VT as a “rescue” treatment in this severity of IHF. Major complication rates during VT ablation in patients with ischemic heart disease have ranged from 1 to 11.1% [11,21]. In our patients catheter ablation with RMN was performed without major periprocedural complications although the average LVEF was markedly reduced. The result is consistent with other studies about the excellent safety record of the atraumatic flexible catheter employed with RMN. Also, a relatively reduced procedure time in our study (105 ± 27 min) may have contributed to the low frequency of complications. In addition, epicardial mapping and ablation which could increase the possibility of complication were not performed in this study. Furthermore, LV access from transseptal route in this study can avoid the possibility of aortic valve injury. 4.2. Long-term outcomes of SIHF-ES ablation with RMN In earlier reports, approximately 40–70% and 10% of patients with ICDs respectively experienced VT recurrence and ES during follow-up [22,23]. Catheter ablation has been reported to acutely control ES, however, the evidence for the long-term effect of catheter ablation with RMN on ES was insufficient. The current study aims to describe how catheter ablation with RMN affects the long-term outcomes of ES in SIHF patients with regularly clinical and ICD follow-up, including VT recurrence, ICD therapies and survival rate. In this study, freedom from any VT was observed in 47.5% of SIHF patients by the end of the follow-up (mean, 17.4 months). The long-term outcome of this study is comparable to already published data in the biggest multicenter trials. In the Multicenter Thermocool Ventricular Tachycardia Ablation trial, the reported VT recurrence was 47% at 6 months in the patients with a history of HF in 62% [24]. In the multicenter, prospective, randomized Ventricular Tachycardia Ablation in Coronary Heart Disease (VTACH) study, 47% of patients were free from VT recurrence in the ablation patients with the mean of LVEF in 34% during the 2-year follow-up [25]. Our study provided new evidence that catheter ablation with RMN for the treatment of ES can play a secondary prophylactic role in VT recurrence even in SIHF patients (average LVEF 21%). ICDs have emerged as the major therapy for protecting patients from sudden death, but multiple ICD shocks, particularly when ≥5 shocks are delivered, would worsen quality of life and are associated with increased mortality [26]. In the present study, the number of ICD shocks and ICD ATPs in individuals per year after ablation was decreased by 56% and by 79% respectively compared to before ablation. The incidence of ICD shock in each patient after ablation was significantly reduced (30% vs 69%, P b 0.01). However, 25% patients died during follow-up
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even though ICD shocks were reduced from 4.3 before ablation to 1.9 after ablation. The results in our study together with those of other groups suggest that catheter ablation of VT reduces ICD therapies, and thus, possibly improves quality of life. However, at present, this strategy has not been shown to influence on mortality rates [14,27,28]. Therefore, further multicenter, prospective, randomized clinical trials are needed to evaluate the effect of RMN-controlled ES ablation on mortality in SIHF patients. 4.3. Limitations There are several limitations in the current study. First, although this ablation technique was performed in consecutive patients prospectively and analyzed the short- and long-term outcomes in patients with ES treated by catheter ablation with RMN, this study was not designed to directly compare catheter ablation with other forms of treatment for ES. Therefore, the study cannot prove that catheter ablation with RMN is superior to other therapies. In addition, epicardial ablation was not performed in this study. Although endocardial ablation is often sufficient to eliminate local abnormal ventricular activities from epicardium and may be used first to reduce the risk of epicardial ablation [29], advanced epicardial ablation can possibly increase the acute success rate of ES due to VT in a proportion of patients with ischemic heart disease. 5. Conclusions Catheter ablation with RMN is safe and acutely effective to control ES due to VT with minimal fluoroscopy exposure. RMN-guided catheter ablation can prevent VT recurrence and significantly reduce ICD therapies which potentially improve the quality of life in SIHF patients suffering from ES. This study provided new evidence to support RMN-guided ablation as an alternative approach to manually performed ablation in the treatment of VT storm in patients with ischemic heart disease. Disclosures None. Conflict of interest The authors report no relationships that could be construed as a conflict of interest. Acknowledgments The authors wish to thank the technical staff of the Cardiac Catheterization Laboratory for their help. References [1] F. Guerra, M. Shkoza, L. Scappini, M. Flori, A. Capucci, Role of electrical storm as a mortality and morbidity risk factor and its clinical predictors: a meta-analysis, Europace 16 (2014) 347–353. [2] S.H. Hohnloser, H.R. Al-Khalidi, C.M. Pratt, J.M. Brum, D.S. Tatla, P. Tchou, P. Dorian, Investigators SHIEwA, Electrical storm in patients with an implantable defibrillator: incidence, features, and preventive therapy: insights from a randomized trial, Eur. Heart J. 27 (2006) 3027–3032. [3] A. Arya, M. Haghjoo, M.R. Dehghani, A.F. Fazelifar, M.H. Nikoo, A. Bagherzadeh, M.A. Sadr-Ameli, Prevalence and predictors of electrical storm in patients with implantable cardioverter-defibrillator, Am. J. Cardiol. 97 (2006) 389–392. [4] J. Schreieck, B. Zrenner, I. Deisenhofer, C. Schmitt, Rescue ablation of electrical storm in patients with ischemic cardiomyopathy: a potential-guided ablation approach by modifying substrate of intractable, unmappable ventricular tachycardias, Heart Rhythm. 2 (2005) 10–14. [5] B.S. Alzand, C.C. Timmermans, H.J. Wellens, R. Dennert, S.A. Philippens, P.J. Portegijs, L.M. Rodriguez, Unmappable ventricular tachycardia after an old myocardial infarction. Long-term results of substrate modification in patients with an implantable cardioverter defibrillator, J. Interv. Card. Electrophysiol. 31 (2011) 149–156.
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