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Successful ventricular tachycardia ablation in patients with electrical storm reduces recurrences and improves survival

Published:August 23, 2017DOI:https://doi.org/10.1016/j.hrthm.2017.08.022

      Objective

      The purpose of this study was to evaluate the characteristics and outcome of patients undergoing ablation after electrical storm (ES).

      Methods

      Clinical and procedural characteristics, ventricular tachycardia (VT) recurrence, and mortality rates from 1940 patients undergoing VT ablation were compared between patients with and without ES.

      Results

      The group of 677 patients with ES (34.9%) were older, were more frequently men, and had a lower ejection fraction, more advanced heart failure, and a higher prevalence of cardiovascular comorbidities as compared with those without ES (86.1% patients with ES had ≥2 comorbidities vs 71.4%; P < .001). Patients with ES had more inducible VTs (2.5 ± 1.8 vs 1.9 ± 1.9; P < .001), required longer procedures (296.1 ± 119.1 minutes vs 265.7 ± 110.3 minutes; P < .001), and had a higher in-hospital mortality (42 deaths [6.2%] vs 18 deaths [1.4%]; P < .001). At 1-year follow-up, patients with ES experienced a higher risk of VT recurrence and mortality (32.1% vs 22.6% and 20.1% vs 8.5%; long-rank, P < .001 for both). Among patients with ES, those without any inducible VT after ablation had a higher survival rate (86.3%) than did those with nonclinical VTs only (72.9%), those with clinical VTs inducible at programmed electrical stimulation (51.2%), and not-tested patients (65.0%) (long-rank, P < .001 for all). In multivariate analysis, ES remained an independent predictor of in-hospital mortality, VT recurrence, and 1-year mortality (P < .001).

      Conclusion

      Patients with ES have a high risk of VT recurrence and mortality. Patient and procedure characteristics are consistent with advanced cardiac disease and longer and more complex procedures. In patients with ES, acute procedural success is associated with a significant reduction in VT recurrence and improved 1-year survival.

      Keywords

      Introduction

      The use of implantable cardioverter-defibrillators (ICDs) and improvements in pharmacological therapies have improved survival in patients with impaired systolic function. ICD therapies can successfully terminate acute ventricular arrhythmias, but do not modify the arrhythmic substrate nor prevent subsequent ventricular tachycardia (VT) episodes. Electrical storm (ES) is a life-threatening arrhythmic emergency characterized by ≥3 VT or ventricular fibrillation (VF) episodes treated by the ICD within 24 hours.
      • Exner D.V.
      • Pinski S.L.
      • Wyse D.G.
      • Renfroe E.G.
      • Follmann D.
      • Gold M.
      • Beckman K.J.
      • Coromilas J.
      • Lancaster S.
      • Hallstrom A.P.
      Electrical storm presages nonsudden death: The Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.
      • Bansch D.
      • Bocker D.
      • Brunn J.
      • Weber M.
      • Breithardt G.
      • Block M.
      Clusters of ventricular tachycardias signify impaired survival in patients with idiopathic dilated cardiomyopathy and implantable cardioverter defibrillators.
      • Credner S.C.
      • Klingenheben T.
      • Mauss O.
      • Sticherling C.
      • Hohnloser S.H.
      Electrical storm in patients with transvenous implantable cardioverter-defibrillators: incidence, management and prognostic implications.
      Catheter ablation has been shown to reduce VT burden and appropriate ICD therapies in patients with structural heart disease.
      The aims of this study were to characterize the population of patients who required catheter ablation for the treatment of ES and to evaluate the impact of acute procedural success on VT recurrence and survival of those patients from the largest available up-to-date multicenter database.

      Methods

      Study design

      The International VT Ablation Center Collaborative Group (IVTCC) consists of 12 international sites that specialized in VT management with a developed protocol for data sharing.
      • Tung R.
      • Vaseghi M.
      • Frankel D.S.
      • et al.
      Freedom from recurrent ventricular tachycardia after catheter ablation is associated with improved survival in patients with structural heart disease: an International VT Ablation Center Collaborative Group Study.
      For 1940 patients, physicians reported whether they had already experienced ES; those patients were included in the present analysis. ES was defined as ≥3 VT/VF episodes within 24 hours. The study was approved by the institutional review boards of the respective participating centers.

      Ablation procedure

      Ablation procedure methodology of the IVTCC has already been described.
      • Tung R.
      • Vaseghi M.
      • Frankel D.S.
      • et al.
      Freedom from recurrent ventricular tachycardia after catheter ablation is associated with improved survival in patients with structural heart disease: an International VT Ablation Center Collaborative Group Study.
      Ablation was performed targeting VTs induced by programmed electrical stimulation (PES) and modifying the electrical substrate.
      • Arenal A.
      • Glez-Torrecilla E.
      • Ortiz M.
      • Villacastin J.
      • Fdez-Portales J.
      • Sousa E.
      • del Castillo S.
      • Perez de Isla L.
      • Jimenez J.
      • Almendral J.
      Ablation of electrograms with an isolated, delayed component as treatment of unmappable monomorphic ventricular tachycardias in patients with structural heart disease.
      • Vergara P.
      • Trevisi N.
      • Ricco A.
      • Petracca F.
      • Baratto F.
      • Cireddu M.
      • Bisceglia C.
      • Maccabelli G.
      • Della Bella P.
      Late potentials abolition as an additional technique for reduction of arrhythmia recurrence in scar related ventricular tachycardia ablation.
      After ablation, PES was repeated unless hemodynamic instability or prohibitive procedural duration.

      Clinical follow-up

      Patients were followed up by ICD interrogation at 3, 6, and 12 months. For patients not followed up at an IVTCC center, referring cardiologists were contacted and ICD interrogations reviewed. Remote control follow-ups were carefully checked for VT recurrence. Telephone interviews were also routinely performed with patients or family members. Recurrent VT/VF was defined as documented VT/VF lasting >30 seconds or any appropriate ICD therapy including antitachycardia pacing. Study end points were VT recurrence after the last ablation procedure, death, and heart transplant. Antiarrhythmic therapy after ablation was at the discretion of the treating physician.

      Statistical analysis

      Continuous variables are expressed as mean ± SD; the independent samples t test and Mann-Whitney U test was used to compare normally and nonnormally distributed continuous variables, respectively. Categorical variables are summarized as frequency and percentage and compared using the Pearson χ2 exact test.
      Univariate analysis was performed to evaluate the association of clinical and procedural variables in terms of VT recurrence and mortality. Kaplan-Meier survival curves were used to estimate freedom from recurrent VT, transplant, and death. The log-rank test was used to compare VT-free survival times of patients with and without ES, also stratified by the result of PES after ablation (no inducible VT [no-VT], only nonclinical VT [nc-VT], at least 1 VT inducible, clinical VT still inducible [c-VT], and PES not repeated [no-PES]); the same analysis was repeated within the group with ES.
      Cox regression analysis was performed to identify risk/protective factors for VT recurrence or death on the entire sample and also by considering patients with ES separately (see Supplemental Methods). Analyses were performed using R statistical software (R Development Core Team, 2016); the significance level was set at .05.

      Results

      A total of 1940 patients with structural heart disease who underwent VT ablation in 12 centers from the IVTCC were included in the present analysis; of those, 677 patients (34.9%) had an ES episode before the index ablation procedure. Patients with ES were older (64.4 ± 12.5 years vs 61.3 ± 13.6 years; P < .001), were more frequently men, and had a lower left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) class II or greater as compared with patients without ES. Patients with ES were also more frequently affected by cardiovascular comorbidities such as hypertension, hyperlipidemia, atrial fibrillation, diabetes, and chronic kidney disease and more frequently had an already implanted cardiac resynchronization therapy device; they more frequently had prior ablation, with a higher number of procedures than did patients with VT who presented without ES. The arrhythmia more frequently manifested with syncope in patients with ES. Patients undergoing VT ablation after ES were more likely to have been previously treated with antiarrhythmic drugs, in particular with class 1A and class 1B antiarrhythmic drugs, β-blockers, and amiodarone; they were also more frequently treated by a combination of ≥2 drugs. Detailed baseline patient characteristics are summarized in Table 1.
      Table 1Baseline characteristics of patients with and without ES
      CharacteristicNo stormESP
      Patients (%)1263 (65.1)677 (34.9)
      Age (y)61.3 ± 13.664.4 ± 12.5<.001
      Sex: male1084 (85.9)603 (89.1).048
      Ischemic cardiomyopathy641 (50.8)370 (54.7).1
      LVEF (%)35.2 ± 13.230.4 ± 13.4<.001
      NYHA class<.001
       I405 (33.0)144 (21.8)
       II473 (38.6)226 (34.2)
       III313 (25.5)216 (32.7)
       IV35 (2.9)74 (11.2)
      CRT294 (23.7)211 (32.2)<.001
      ≥1 previous ablation procedures488 (38.6)300 (40.6).015
      No. of previous VT ablation procedures0.5 ± 0.80.6 ± 0.9.022
      Syncope102 (16.0)74 (23.6).004
      Prior heart surgery358 (29.5)209 (32.0).3
      Hypertension617 (45.4)353 (40.2).038
      Hyperlipidemia634 (55.7)368 (62.7).005
      Atrial fibrillation285 (25.3)204 (33.2).001
      Diabetes227 (18.5)177 (26.8)<.001
      Chronic kidney disease328 (26.1)252 (37.5)<.001
      Creatinine level (mg/dL)1.2 ± 0.61.4 ± 0.9<.001
      Previous drug therapy
       Class 1A AAD17 (1.4)26 (4.1)<.001
       Class 1B AAD166 (14.0)155 (24.7)<.001
       Class 1C AAD57 (4.8)24 (3.8).3
       β-Blockers947 (76.2)563 (84.3)<.001
       Amiodarone605 (51.0)404 (64.3)<.001
       Sotalol161 (13.6)75 (11.9).3
       ≥2 AADs183 (15.4)154 (24.5)<.001
      Values are presented as mean ± SD or as n (%).
      AAD = antiarrhythmic drug; CRT = cardiac resynchronization therapy; ES = electrical storm; LVEF = left ventricular ejection fraction; NYHA = New York Heart Association; VT = ventricular tachycardia.

      Ventricular ablation procedure

      The group of 677 patients treated after ES had more VTs inducible by PES (2.5 ± 1.8 vs 1.9 ± 1.9; P < .001), requiring the delivery of more radiofrequency ablation (46.0 ± 32.4 minutes vs 35.2 ± 28.0 minutes; P < .001) and longer procedures (296.1 ± 119.1 minutes vs 265.7 ± 110.3 minutes; P < .001) than did patients without ES (Table 2). Patients with ES required mechanical hemodynamic support more frequently than did the others (61 patients [9.0%] vs 58 patients [4.6%]; P = .001). No significant differences in the rate of epicardial and combined endo-epicardial mapping were shown between the 2 groups of patients; at least 1 not mappable VT was induced in 296 patients with prior ES (56.8%) and in 466 patients without prior ES (55.5%) (P = .63).
      Table 2Procedural characteristics
      CharacteristicNo stormESP
      Patients (%)1263 (60.8)677 (32.8)
      Induced VTs per patient1.9 ± 1.92.5 ± 1.8<.001
       0175 (13.9)40 (5.9)
       1419 (33.2)188 (27.8)
       2283 (22.4)158 (23.3)
       3153 (12.1)106 (15.7)
       ≥4150 (32.2)156 (52.7)
      Total radiofrequency delivery time (min)35.2 ± 28.046.0 ± 32.4<.001
      Total procedure time (min)265.7 ± 110.3296.1 ± 119.1<.001
      Hemodynamic support50 (4.6)44 (9.0).001
      Endocardial + epicardial mapping329 (27.5)169 (27.1).6
      Only mappable VTs374 (44.5)225 (43.2).5
      Any mappable VT508 (60.5)320 (61.4).7
      Any unmappable VT466 (55.5)296 (56.8).6
      Acute ablation result
       Absence of any inducible VTs834 (71.2)395 (63.9).002
       Only nonclinical VT still inducible214 (18.3)140 (22.7).03
       Clinical VT still inducible86 (7.3)43 (7.0).915
       PES not repeated after ablation38 (3.2)40 (6.5).002
      Procedural complications77 (6.5)45 (7.3).5
      Death before hospital discharge18 (1.4)42 (6.2)<.001
      Values are presented as mean ± SD or as n (%).
      ES = electrical storm; NS = not significant; PES = programmed electrical stimulation; VT = ventricular tachycardia.
      PES was not repeated in more patients with ES (40 [6.5%] vs 38 [3.2%]; P = .001). Information about the result of PES after ablation was available for 1712 patients. Among patients in whom the acute outcome of the procedure was tested by PES, 395 patients with ES (63.9%) and 834 without ES (71.2%) (P = .0017) had no-VT; only nc-VT was more frequently inducible in patients with ES (140 [22.7%] vs 214 [18.3%]; P = .026); c-VT was observed in 43 patients with ES (7.0%) and in 86 patients without ES (7.3%) (P = .91).
      While the number of procedure-related complications was similar for patients with and without prior ES, patients with ES had a higher in-hospital mortality (35 deaths [5.2%] vs 17 deaths [1.3%]; P < .001). Among patients with ES, 9 (25.7%) died of recurrent VT after ablation, 13 (37.1%) had a cardiac death not related to VTs (heart failure in 12 patients [34.3%] and myocardial infarction in 1 patient [2.8%]), and 6 patients (17.15%) died of noncardiac causes; in 7 patients the cause of death was not reported; in-hospital death occurred in 8 patients with c-VT (20.5%) as compared with 21 (5.0%) of no-VT patients with ES (P < .001).
      In Cox proportional hazard modeling, after adjusting for covariates, ES was independently associated with higher acute hospital mortality (hazard ratio [HR] 2.89; 95% confidence interval [CI] 1.44–5.80).

      VT recurrences in patients with ES

      During the year after ablation, patients with ES experienced a higher risk of VT recurrence than did those without prior ES (32.1% vs 22.6%; long-rank, P < .001) (Figure 1). Among patients with no-VT, patients with ES had a worse VT-free survival as compared with those without ES (73.2% vs 80.1%; long-rank, P = .003); findings were similar for those with at least 1 VT inducible (61.2% vs 71.0%; long-rank, P = .028) or c-VT inducible (27.9% vs 62.8%; long-rank, P < .001) (Supplemental Figure 1). Among patients with ES, patients with nc-VT had a VT-free survival not significantly different from that of patients with no-VT (71.4% vs 73.2%; long-rank, P = .235); both classes had a better VT-free survival than did those with c-VT (27.9%; long-rank, P < .001 and P < .001, respectively) and no-PES patients (47.5%; long-rank, P = .011 and P < .001, respectively) (Figure 2).
      Figure thumbnail gr1
      Figure 1Kaplan-Meier curves of survival free from ventricular tachycardia (VT) recurrences in patients with and without electrical storm (ES).
      Figure thumbnail gr2
      Figure 2Kaplan-Meier curves of survival free from ventricular tachycardia (VT) recurrences in patients with electrical storm stratified by the results of acute programmed electrical stimulation after ablation. NS = not significant.
      In Cox proportional hazard modeling, after adjusting for covariates, ES was independently associated with a greater likelihood of VT recurrences (HR 1.23; 95% CI 0.98–1.535). In patients with ES, Cox proportional hazard modeling identified the result of PES after ablation, nonischemic cardiomyopathy (HR 1.534; 95% CI 1.081–2.178), LVEF (HR 0.977; 95% CI 0.964–0.991), and hypertension (HR 0.723; 95% CI 0.503–1.037) as associated with VT recurrences (Figure 3). The risk of VT recurrence decreased by 2.3% for each unit increase in LVEF. In patients with no-VT and patients with nc-VT, the risk of VT recurrence at 1 year decreased, respectively, by 76.9% (HR 0.231; 95% CI 0.138–0.386) and 74.8% (HR 0.252; 95% CI 0.140–0.453) relative to patients with c-VT.
      Figure thumbnail gr3
      Figure 3Hazard ratio plot of predictors of ventricular tachycardia (VT) recurrences by multivariate analysis in patients with electrical storm. Among the subgroup of patients with ES, in Cox proportional hazard modeling, the result of programmed electrical stimulation (PES) after ablation, nonischemic cardiomyopathy (NICM), left ventricular ejection fraction (LVEF), and hypertension (HTN) were predictors of ventricular tachycardia recurrences. ICM = ischemic cardiomyopathy.

      Mortality after ablation in patients with ES

      During the year after ablation, the rate of death in patients with ES was higher than in those without ES (20.1% vs 8.5%; long-rank, P < .001) (Figure 4). Patients with ES had a lower survival than did those without ES whenever no VT (86.3% vs 94.4%; long-rank, P < .001), at least 1 VT (67.8% vs 85.0%; long-rank, P < .001), nc-VT (72.9% vs 85.5%; long-rank, P = .007), or c-VT was still inducible (51.2% vs 83.7%; long-rank, P < .001) or no PES was performed after ablation (65.0% vs 84.2%; long-rank P = .046) (Supplemental Figure 2).
      Figure thumbnail gr4
      Figure 4Kaplan-Meier curves of survival in patients with and without electrical storm (ES).
      Among patients with ES, those with no-VT had a better survival than did patients with nc-VT, c-VT, and no-PES (86.3% vs 72.9%, 51.2%, and 65.0%; long-rank, P < .001 for all comparisons); patients with nc-VT had a better survival that did those with c-VT (long-rank, P < .001) (Figure 5).
      Figure thumbnail gr5
      Figure 5Kaplan-Meier curves of survival free from death in patients with electrical storm stratified by the results of acute programmed electrical stimulation after ablation. VT = ventricular tachycardia.
      In Cox proportional hazard modeling, after adjusting for covariates, ES was associated with an HR of 1.5 (95% CI 1.09–2.07) for mortality. Among the subgroup of patients with ES, in Cox proportional hazard modeling, the result of PES after ablation, advanced NYHA class, LVEF, and previously performed VT ablation (HR 1.575; 95% CI 1.018–2.435); diabetes mellitus (HR 1.549; 95% CI 0.994–2.414); and chronic kidney disease (HR 1.515; 95% CI 0.973–2.361) were associated with death (Figure 6). In particular, in patients with ES, the mortality risk decreased by 4.9% (HR 0.951; 95% CI 0.927–0.976) as LVEF increased by 1 unit. Moreover, although the effect is not significant, the mortality risk increased by 1.7% (HR 1.017; 95% CI 0.995–1.040) as age increased by 1 year. Patients with no-VT and those with nc-VT had a rate of death at 1 year of 81.4% (HR 0.186; 95% CI 0.093–0.371) and 41.9% (HR 0.581; 95% CI 0.291–1.162), respectively, relative to c-VT ones. Patients in NYHA class III and IV, respectively, had a risk of death at 1 year 2.608 (95% CI 0.994–6.844) and 2.918 (95% CI 1.028–8.284) times higher than those in NYHA class I.
      Figure thumbnail gr6
      Figure 6Hazard ratio plot of predictors of death by multivariate analysis in patients with electrical storm. Among the subgroup of patients with ES, in Cox proportional hazard modeling, the result of programmed electrical stimulation (PES) after ablation, left ventricular ejection fraction (LVEF), advanced New York Heart Association functional classification (NYHA), previously performed ventricular tachycardia (VT) ablation (Previous Abl), diabetes mellitus (DM), and chronic kidney disease (CKD) were selected by a stepwise procedure as predictors of death.
      Patients with ES and absence of VT recurrences after ablation had a better survival than did those with VT recurrences during follow-up (88.7% vs 61.3%; long-rank, P < .001); their survival, however, was lower than that of patients without both ES and VT recurrences (88.7% vs 94.6%; long-rank, P < .001).

      Discussion

      The present study describes the characteristics of the largest available series of patients with VT ablation for ES. These data showed that patients with ES are among the highest risk VT population with regard to recurrence and mortality. This is also the first study to evaluate the occurrence of comorbidities in a large cohort of patients with ES. Baseline and procedural characteristics are consistent with advanced substrates that present with ES. However, acute procedural success is associated with improved survival.
      Patients with ES represent a relatively small portion of patient enrolled in large studies of VT ablation and most of the previously published data are single-center small series or case reports. ES is a challenging condition that occurs in ∼10%–28% of patients with an ICD,
      • Exner D.V.
      • Pinski S.L.
      • Wyse D.G.
      • Renfroe E.G.
      • Follmann D.
      • Gold M.
      • Beckman K.J.
      • Coromilas J.
      • Lancaster S.
      • Hallstrom A.P.
      Electrical storm presages nonsudden death: The Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.
      • Bansch D.
      • Bocker D.
      • Brunn J.
      • Weber M.
      • Breithardt G.
      • Block M.
      Clusters of ventricular tachycardias signify impaired survival in patients with idiopathic dilated cardiomyopathy and implantable cardioverter defibrillators.
      • Credner S.C.
      • Klingenheben T.
      • Mauss O.
      • Sticherling C.
      • Hohnloser S.H.
      Electrical storm in patients with transvenous implantable cardioverter-defibrillators: incidence, management and prognostic implications.
      and it was associated with a 3.15-fold increase in the risk of death.
      • Guerra F.
      • Shkoza M.
      • Scappini L.
      • Flori M.
      • Capucci A.
      Role of electrical storm as a mortality and morbidity risk factor and its clinical predictors: a meta-analysis.
      The high mortality may be related to the compound effects of the arrhythmia, the delivery of several ICD shock in a short time frame, and advanced heart failure; the relative contributions of these factors to mortality remains a matter of debate.
      • Nayyar S.
      • Ganesan A.N.
      • Brooks A.G.
      • Sullivan T.
      • Roberts-Thomson K.C.
      • Sanders P.
      Venturing into ventricular arrhythmia storm: a systematic review and meta-analysis.
      It is well known that sudden death is tachyarrhythmia associated in two-thirds of the patients with an ICD.
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      • Steinman R.T.
      • Baga J.J.
      • Schuger C.D.
      Sudden death in implantable cardioverter-defibrillator recipients: clinical context, arrhythmic events and device responses.
      ICD shocks may cause myocardial damage and are associated with increased mortality
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      • Wilkoff B.L.
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      • Larsen G.K.
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      • Lambert W.E.
      • Chen Y.
      • Raitt M.H.
      Shocks burden and increased mortality in implantable cardioverter-defibrillator patients.
      • Poole J.E.
      • Johnson G.W.
      • Hellkamp A.S.
      • et al.
      Prognostic importance of defibrillator shocks in patients with heart failure.
      • Mitchell L.B.
      • Pineda E.A.
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      • Benditt D.G.
      Sudden death in patients with implantable cardioverter defibrillators: the importance of post-shock electromechanical dissociation.
      ; these factors act on fragile patients, whom we identified to be older, with a lower LVEF, more advanced heart failure status, and more cardiovascular comorbidities, as compared with patients without ES. In this study, we showed that the 1-year survival of patients with ES is 61.3% if they continue to experience VT episodes after ablation and it was 88.7% when ablation was successful without VT recurrences. This might suggest that the arrhythmic episodes have a prominent detrimental effect on patient’s survival and that the adverse impact can be mitigated by a successful VT ablation procedure. However, survival of patients with ES and absence of VT recurrences was lower than that of patients without either ES and VT recurrences, suggesting that nonarrhythmic factors still act on these patients and might lead to death. It is possible that a comprehensive approach including not only the arrhythmia ablation but also careful treatment of the comorbidities that are more common in patients with ES, such as advanced heart failure, hypertension, hyperlipidemia, atrial fibrillation, diabetes, and chronic kidney disease, might have a positive effect on survival.

      Timing of VT ablation

      ES was the condition more frequently considered as the main indication for ablation in the survey by Dagres et al.
      • Dagres N.
      • Varounis C.
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      • Sommer P.
      • Hindricks G.
      • Kremastinos D.T.
      Mortality after catheter ablation for atrial fibrillation compared with antiarrhythmic drug therapy: a meta-analysis of randomized trials.
      Several studies suggested that the outcome of ablation is better when performed earlier: in the study by Dinov et al,
      • Dinov B.
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      • Bertagnolli L.
      • Schirripa V.
      • Schoene K.
      • Sommer P.
      • Bollmann A.
      • Rolf S.
      • Hindricks G.
      Early referral for ablation of scar-related ventricular tachycardia is associated with improved acute and long-term outcomes: results from the Heart Center of Leipzig ventricular tachycardia registry.
      VT recurred less frequently in the early ablation strategy (catheter ablation within 30 days after the first documented VT episode: 37.3%) as compared with later interventions (>60%); similar results were shown by Frankel et al,
      • Frankel D.S.
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      • Robinson M.R.
      • Zado E.S.
      • Callans D.J.
      • Marchlinski F.E.
      Ventricular tachycardia ablation remains treatment of last resort in structural heart disease: argument for earlier intervention.
      who classified patients as “late referrals” if they had ≥2 VT episodes, with the first and most recent episodes separated by ≥1 month. In the VTACH trial,
      • Kuck K.H.
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      • Kautzner J.
      • Schumacher B.
      • Hansen P.S.
      Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
      early VT ablation before defibrillator implantation prolonged time to recurrence of VT; in the SMASH VT trial,
      • Reddy V.Y.
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      • Richardson A.W.
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      • Josephson M.E.
      Prophylactic catheter ablation for the prevention of defibrillator therapy.
      an early ablation was associated with a reduction of ICD shocks afterward.
      In our study, patients treated by ablation after ES were older than those without ES and more likely to have been previously treated with ≥1 antiarrhythmic drugs; the complexity of the procedure (more VTs inducible by PES before ablation, more radiofrequency delivery, more frequent hemodynamic support, and longer procedures times) and the mortality during the year after ablation were both higher in patients with ES. It appears, therefore, that ES is an event typical of the late phases in the history of patients with heart failure. It is conceivable that an ablation strategy in earlier phases of the patient’s history, before the occurrence of ES, might improve the quality of life and survival with lower technical procedure complexity; however, only randomized controlled trials could provide definitive conclusions on this issue.
      • Yokokawa M.
      • Kim H.M.
      • Baser K.
      • et al.
      Predictive value of programmed ventricular stimulation after catheter ablation of post-infarction ventricular tachycardia.
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      Troponin elevation in patients with various tachycardias and normal epicardial coronaries.

      End points for VT ablation in patients with ES

      In the present multicenter experience, the abolition of the clinical VT, although associated with VT recurrence risk <30% during mid-term follow-up, had only a vague effect on survival; although harder to be obtained, the end point of absence of any inducible VT was associated with the highest (86.3%) survival rate. This confirms previous results in postinfarction patients by Yokokawa et al,
      • Yokokawa M.
      • Kim H.M.
      • Baser K.
      • et al.
      Predictive value of programmed ventricular stimulation after catheter ablation of post-infarction ventricular tachycardia.
      who showed that absence of any VT inducibility postablation was independently associated with lower mortality.
      Patients with ES undergoing VT ablation had an in-hospital mortality 4 times higher than that of patients without prior ES. The higher acute mortality is evident in patients with advanced heart failure, those requiring periprocedural hemodynamic support, and those undergoing epicardial procedures. It cannot be excluded that repeated arrhythmia inductions might negatively affect the already impaired myocardium.
      • Kanjwal K.
      • Imran N.
      • Grubb B.
      • Kanjwal Y.
      Troponin elevation in patients with various tachycardias and normal epicardial coronaries.
      A strategy of substrate-based ablation can minimize the need for repetitive inductions of VT for mapping during ongoing arrhythmia.
      • Vergara P.
      • Trevisi N.
      • Ricco A.
      • Petracca F.
      • Baratto F.
      • Cireddu M.
      • Bisceglia C.
      • Maccabelli G.
      • Della Bella P.
      Late potentials abolition as an additional technique for reduction of arrhythmia recurrence in scar related ventricular tachycardia ablation.
      • Di Biase L.
      • Santangeli P.
      • Burkhardt D.J.
      • et al.
      Endo-epicardial homogenization of the scar versus limited substrate ablation for the treatment of electrical storms in patients with ischemic cardiomyopathy.
      • Jais P.
      • Maury P.
      • Khairy P.
      • et al.
      Elimination of local abnormal ventricular activities: a new end point for substrate modification in patients with scar-related ventricular tachycardia.
      • Tzou W.S.
      • Frankel D.S.
      • Hegeman T.
      • Supple G.E.
      • Garcia F.C.
      • Santangeli P.
      • Katz D.F.
      • Sauer W.H.
      • Marchlinski F.E.
      Core isolation of critical arrhythmia elements for treatment of multiple scar-based ventricular tachycardias.
      • Tung R.
      • Mathuria N.S.
      • Nagel R.
      • Mandapati R.
      • Buch E.F.
      • Bradfield J.S.
      • Vaseghi M.
      • Boyle N.G.
      • Shivkumar K.
      Impact of local ablation on interconnected channels within ventricular scar: mechanistic implications for substrate modification.
      In the VISTA trial,
      • Di Biase L.
      • Burkhardt J.D.
      • Lakkireddy D.
      • et al.
      Ablation of stable VTs versus substrate ablation in ischemic cardiomyopathy: the VISTA randomized multicenter trial.
      substrate targeted ablation was associated with lower VT recurrence (15.5%) as compared with ablation of only the clinical VT (48.3%); the combined incidence of rehospitalization and mortality was also better with substrate targeted ablation.

      Study limitations

      The participating centers in the IVTCC are high-volume ablation hospitals that serve as state- or nationwide referrals for VT ablation procedures. As such, it is possible that there is a referral bias that may limit the generalizability of our results. The IVTCC database did not include detailed information about the ventricular substrate (voltage maps and magnetic resonance imaging scans) or severity of comorbidities, thus precluding further analysis on the correlation between the arrhythmic disease, stage of heart failure, severity of comorbidities, and outcomes. Because of the retrospective multicenter nature of this study, some clinical and procedural characteristics were not available for analysis. Antiarrhythmic drug therapy was left to the discretion of the treating physicians, and it could influence outcomes.

      Conclusion

      Patients with ES have characteristics and comorbidities consistent with advanced heart failure substrates. They are among the highest risk population with regard to arrhythmia recurrences and mortality. However, acute ablation success is associated with better 1-year survival. Further studies are warranted to determine whether early use of ablation can improve the outcomes in this patient population.

      Appendix. Supplementary data

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      Linked Article

      • Erratum
        Heart RhythmVol. 15Issue 3
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          In the article titled “Successful ventricular tachycardia ablation in patients with electrical storm reduces recurrences and improves survival” by Pasquale Vergara, Roderick Tung, Marmar Vaseghi, et al that published in the January issue of Heart Rhythm (2018; 15: 48-55), Dr Frankel's name should have been written as David S. Frankel, MD. The error is regretted.
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