Original Article. Complications of Catheter Ablation of Ventricular Tachycardia A Single-Center Experience

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1 Original Article Complications of Catheter Ablation of Ventricular Tachycardia A Single-Center Experience Petr Peichl, MD, PhD*; Dan Wichterle, MD, PhD*; Ludek Pavlu, MD*; Robert Cihak, MD, PhD; Bashar Aldhoon, MD, PhD; Josef Kautzner, MD, PhD Background Catheter ablation has become an established treatment modality for a broad spectrum of ventricular tachycardias (VTs). We analyzed incidence and predictors of major complications of VT ablation procedures in a highvolume expert center. Methods and Results We evaluated 548 consecutive patients who underwent 722 ablation procedures, 473 (65.5%) for structural heart disease VT in the period 2006 to There were 45 (6.2%) major complications observed in 44 patients. Access site vascular complications were the most frequent (3.6%). Three patients (0.4%) had cardiac tamponade/ hemopericardium, and 5 patients (0.7%) had a thromboembolic event. No procedural deaths occurred. Procedures for structural heart disease VT versus idiopathic VT had a significantly higher complication rate (8.0% versus 2.8%; P=0.006). Similarly, patients with electrical storm (10.1% versus 5.3%; P=0.04) and nonelective procedures (8.4% versus 3.5%; P=0.007) were at higher risk of complications. On multivariate analysis, age >70 years (P=0.01), serum creatinine >115 μmol/l (P=0.0003), and individual operator (P=0.0001) were the only independent predictors of complications. Overall 30-day mortality in the structural heart disease VT group reached 5.0% (patients) and 3.6% (procedures). Death was associated with early recurrence of VT/ventricular fibrillation (P=0.003) and ablation for electrical storm (P=0.02). Conclusions Complication rates for VT ablation are significantly lower in idiopathic VT or in elective procedures. Independent predictors of complications include age, renal insufficiency, and individual operator. Postprocedural mortality is predicted by early recurrence of VT/ventricular fibrillation and ablation for electrical storm. (Circ Arrhythm Electrophysiol. 2014;7: ) Over the last decade, catheter ablation has become an established treatment modality for a broad spectrum of ventricular tachycardias (VTs). 1 Although it is considered a curative procedure in idiopathic VTs, the situation is more complex in patients with structural heart disease (SHD). In the vast majority, catheter ablation is indicated as adjunctive treatment when therapies from implantable cardioverter-defibrillator occur, frequently in the setting of electrical storm. In addition, the substrate for VT in patients with SHD is usually complex and often requires more extensive ablation. As a result, the incidence of major procedure-related complications has been reported higher in the latter group. Two multicenter trials 2,3 that recruited consecutive VT patients after previous myocardial infarction demonstrated major complications in 8% and 10%, respectively. Periprocedural mortality reached 3.8% and 3.0%, respectively. Thus, a better understanding of procedural risks is important for selecting patients for catheter ablation for different types of VT. Clinical Perspective on p 690 Key Words: catheter ablation ventricular tachycardia The goal of this study was to review complication rates of VT ablation procedures in a high-volume expert center. To assess determinants of complications, clinical and procedural variables or their combination were analyzed. Methods The study included all consecutive VT catheter ablation procedures performed at our institution between August 2006 and December Occurrence of complications was evaluated <1 month after the procedure. The study was approved by the institutional review committee. Survival in all patients was obtained at 7 days from in-hospital notes and at 30 days from national citizen registry. Catheter Ablation Procedure In all elective patients with long-term anticoagulation therapy, the procedure was performed after a temporary interruption of warfarin therapy, which was bridged by low-molecular-weight heparin. During left heart procedures, intravenous heparin was administered to maintain the activated clotting time 300 seconds. After ablation, patients received antiplatelet therapy for minimum of 6 weeks or anticoagulation therapy in cases of extensive ablation in the left ventricle Received February 5, 2014; accepted May 13, From the Department of Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. *Drs Peichl, Wichterle, and Pavlu contributed equally to this work. Correspondence to Petr Peichl, MD, PhD, Department of Cardiology, Institute for Clinical and Experimental Medicine, Vídeňská 1958/9, Prague, Czech Republic. pepi@medicon.cz 2014 American Heart Association, Inc. Circ Arrhythm Electrophysiol is available at DOI: /CIRCEP

2 Peichl et al Complications of Ventricular Tachycardia Ablation 685 (LV). The procedure was performed predominantly under conscious sedation (midazolam and alfentanyl), except for patients who were either on mechanical ventilation because of frequent VTs and hemodynamical instability or undergoing epicardial mapping/ablation. Mapping and ablation strategy are described elsewhere. 1,4 Briefly, if the VT did not occur spontaneously, the programmed stimulation protocol from the 2 right ventricular (RV) sites and 3 extrastimuli was applied to induce clinical VT. In patients with idiopathic VTs, isoproterenol was used to provoke arrhythmia. Mapping was performed under fluoroscopy guidance and, in the majority of cases, with 3-dimensional electroanatomical mapping systems CARTO or CARTO-3 (Biosense Webster, Diamond Bar, CA) or EnSite NavX (St Jude Medical, St Paul, MN). In select patients, the procedure was facilitated by intracardiac echocardiography (Accunav; Siemens). For ablation, 3.5-mm, saline-irrigated tip ablation catheters (Navistar Thermocool or Celsius Thermocool; Biosense Webster) were used. In the few patients with focal idiopathic VT, nonirrigated 4-mm tip catheters were used. In patients with idiopathic VTs, a combination of activation mapping or pace-mapping was used to determine the arrhythmia origin. In patients with SHD-VT, substrate mapping was performed primarily during spontaneous rhythm or during RV pacing. Only in patients with hemodynamically tolerated or incessant VT was 3-dimensional activation mapping initiated during tachycardia, and entrainment maneuvers were used. Radiofrequency ablation strategy was adjusted depending on the mechanism of arrhythmia. In focal arrhythmias, radiofrequency current was applied at sites of earliest activation. In re-entrant arrhythmias, radiofrequency applications targeted primarily central or central-to-exit zones of slowly conducting channels. Deployment of the lesions was confirmed by subsequent noncapture at given sites. Additional lesions were applied in areas of late or fractionated potentials for arrhythmogenic substrate modification. The goal of ablation was to abolish all inducible VTs. Ablation was performed in power control mode with an irrigation flow of 30 ml/min. Power was set up to 20 to 40 W, depending on location and catheter contact, and was downregulated when catheter tip temperature rose >43ºC or with a rapid drop of impedance (>10 15Ω) during ablation. Radiofrequency energy was applied in the majority of cases for a maximum of 60 seconds per target site. In patients where an epicardial approach was used, coronary angiography was performed to avoid application of radiofrequency energy in the vicinity of the epicardial coronary vessels. In the region of aortic cusps, power output was set in the majority of cases at 25 W. All of these cases were guided by intracardiac echocardiography; no coronary angiography was needed to identify ostia of the coronary vessels. Definitions Major complications were defined as those resulting in long-term disability, requiring intervention or prolonging hospitalization. Statistics Continuous variables were expressed as means with SDs. For the purpose of risk prediction, they were dichotomized at clinically reasonable cutoff values. Categorical variables were expressed as percentages and compared by χ 2 test. Univariate association of baseline clinical and procedural characteristics with major complications was expressed as relative risk with an associated 95% confidence interval. Stepwise forward analysis of a multivariate regression model was used to assess the independent association of individual factors with complication rates. A composite scoring system based on quartile categorization of selected risk factors was used for predicting overall complication risk. A P value <0.05 was considered significant. All analyses were performed using the STATISTICA version 10 software (Statsoft, Inc, Tulsa, OK). Results A total of 722 procedures in 548 patients were analyzed. Ten of 208 (4.8%) and 7 of 340 (2.1%) patients with idiopathic and SHD arrhythmias, respectively, were lost for minimum follow-up of 30 days after the last ablation. However, the postprocedural 30-day death/alive status was verified in all patients. Baseline characteristics of the study population are summarized in Table 1. A total of 473 (65.5%) procedures were performed for SHD-VT and 249 (34.5%) procedures for idiopathic VT. Among SHD-VT patients, 29% were indicated for electrical storm and 4.2% for focally triggered polymorphic VT/ventricular fibrillation (VF). A total of 176 (24.4%) redo procedures were performed (126 first, 33 second, 12 third, 3 fourth, and 2 fifth repeat procedures) with a mean number of procedures of 1.32±0.70 per patient (range, 1 6 procedures per patient). Repeat procedures were less common in idiopathic VT versus SHD-VT subgroups with rates of 16.5% and 28.7%, respectively (P=0.0003). Catheter ablation was performed under conscious sedation in 94.5% of cases. Irrigated radiofrequency catheters were used in 97.0% of procedures. Intracardiac echocardiography was used to guide the procedure in 34.1% of ablations. Endocardial RV ablation was performed in 34.9% of procedures; endocardial LV ablation was performed in 67.6% of procedures. In 7.1% of procedures, ablation was performed in both ventricles. A transseptal approach for LV mapping/ ablation was used in 6.5% of procedures. Pericardial puncture access was performed in 4.4% of procedures. Table 1. Characteristics Baseline Characteristics Total (n=722) Idiopathic VT (n=249) SHD-VT (n=473) Age, y 58±15 50±16 62±13 Female sex 23.7% 49.4% 10.1% Weight, kg 85±16 84±18 86±15 BMI, kg/m ± ± ±4.3 Hypertension 49.2% 38.6% 54.8% Heart failure 57.1% 5.2% 84.4% Diabetes mellitus 18.4% 8.0% 23.9% Stroke/TIA 7.5% 1.2% 10.8% CAD 48.1% 6.4% 70.0% LVEF, % 41±16 58±6 33±12 LVEDd, mm 61±10 53±5 65±9 Serum creatinine, 103±42 81±19 113±46 μmol/l Electrical storm 19.3% 1.2% 28.8% Elective procedure 43.6% 83.9% 22.4% ICD 58.0% 4.8% 86.0% CRT 24.2% 0% 37.0% Repeat procedure 24.4% 16.5% 28.5% Number of sheaths 2.4± ± ±0.7 Arterial access 74.1% 50.6% 86.5% Epicardial access 4.4% 2.4% 5.5% Procedure time, min 196±67 173±69 207±62 Radiofrequency time, s 1083± ± ±986 Fluoroscopy time, min 14.6± ±9,6 15.8±8.4 Values are mean±sd (for continuous variables) and % (for categorical variables). BMI indicates body mass index; CAD, coronary artery disease; CRT, cardiac resynchronization therapy; ICD, implantable cardioverter-defibrillator; LVEDd, left ventricular (LV) end diastolic diameter; LVEF, LV ejection fraction; SHD, structural heart disease; TIA, transient ischemic attack; and VT, ventricular tachycardia.

3 686 Circ Arrhythm Electrophysiol August 2014 Complications There were 45 (6.2%) major procedure complications recorded in 44 patients. Vascular injury was the most frequent (3.6%; ie, 58% of all complications). Characteristics of complication types are listed in Table 2. Among life-threatening complications, 3 patients (0.4%) had cardiac tamponade/hemopericardium. In 2 patients, pericardiocentesis was required, and the patients recovered without sequelae; 1 patient was treated conservatively. Of note, all cases of perforation were related to mapping or ablation within the RV. Five patients (0.7%) presented with a thromboembolic event. Two of them had a stroke during LV mapping before ablation, related presumably either to unrecognized LV thrombus or dislodgement of atherosclerotic plaques in the aorta. There was 1 intraprocedural transient ischemic attack after steam pop within the LV. Another case of major systemic embolization to the lower extremity occurred the day after the procedure, and 1 transient ischemic attack occurred 5 days after the ablation. Electric conduction block during the ablation procedure occurred in 7 patients; 5 developed higher-degree atrioventricular block, 1 trifasicular block, and 1 left bundle branch block that ultimately resulted in progressive heart failure. The most common cause was the LV ablation at the left basal septum in Table 2. Type of Complication Major Complications Total (n=722) Idiopathic VT (n=249) SHD-VT (n=473) Death Perforation 3 (0.4%) 0 (0.0%) 3 (0.6%) Tamponade Hemopericardium Thromboembolic event 5 (0.7%) 1 (0.4%) 4 (0.8%) Stroke intraprocedural TIA intraprocedural TIA <7 d Systemic embolism (legs) Conduction system damage 7 (1.0%) 1 (0.4%) 6 (1.3%) AV block LBBB resulting in HF Other 4 (0.6%) 1(0.4%) 3 (0.6%) Pericarditis RV lead dysfunction CPR during the procedure Vascular access 26 (3.6%) 4 (1.6%) 22 (4.7%) Femoral pseudoaneurysm Femoral AVF Groin hematoma With surgical management With transfusion needed With conservative management Total 45 (6.2%) 7 (2.8%) 38 (8.0%) Values are counts (%). AV indicates atrioventricular; AVF, arteriovenous fistula; CPR, cardiopulmonary resuscitation; HF, heart failure; LBBB, left bundle branch block; RV, right ventricular; SHD, structural heart disease; TIA, transient ischemic event; and VT, ventricular tachycardia. patients with pre-existing conduction disorders. In 2 patients, atrioventricular block was intentionally created during repeat procedures because the recurrent VTs originated from the vicinity of the proximal part of left bundle branch. Predictors of Complications Major complications occurred in 2.8% versus 8.0% of ablations for idiopathic VT versus SHD-VT (P=0.006). Major vascular complication rates reached 1.6% versus 4.7% (P=0.04), respectively. No significant complications occurred in 32 cases of pericardial access. Significant univariate predictors of complications are summarized in Table 3. Besides clinical risk factors such as advanced age, depressed LV ejection fraction (LVEF), elevated serum creatinine, nonelective procedure, and procedure for electrical storm, 2 additional risk factors were identified. Complications were greater for certain operators. Overall, catheter ablations for VT were performed by 9 operators, but the majority of cases (90%) were executed by 1 of 4 experienced operators who had complication rates of 2.9%, 11.8%, 8.4%, and 4.0%. Two of them had higher-than-average complication rates and were further classified as high-risk operators. These operators performed 43% of procedures and were responsible for 73% of complications, with incidence of 10.6% as compared with 2.9% for the other operators (P=0.0002). Timing of the procedure was the second factor. Procedures that started after 2 pm (last quartile of starting time) were associated with a significantly higher complication rate of 10.1% versus 5.0% in other procedures (P=0.01) and accounted for 40.0% of all major complications. In multivariate analysis with dichotomized risk factors, only age, serum creatinine, and operator remained independent Table 3. Risk Factor Significant Univariate Predictors of Major Complications Complication Rate in Low-Risk Group, % Complication Rate in High-Risk Group, % Relative Risk 95% Confidence Interval P Value High-risk operator Age >70 y Electrical storm Arterial access Nonelective procedure Procedure start time after 2 pm SHD-VT Heart failure LVEF 25% LVEDd >60 mm ICD CRT Serum creatinine >115 μmol/l (>1.3 mg/dl) CRT indicates cardiac resynchronization therapy; ICD, implantable cardioverterdefibrillator; LVEDd, left ventricular (LV) end diastolic diameter; LVEF, LV ejection fraction; and SHD-VT, structural heart disease ventricular tachycardia.

4 Peichl et al Complications of Ventricular Tachycardia Ablation 687 predictors of complications (Table 4). When analysis was performed with risk factors as continuous variables, LVEF appeared to be an independent predictor. Using the practically applicable risk factors, the composite risk score (range 0 9) was calculated from age, LVEF, and serum creatinine strata as a sum of risk points (Figure). For age, 0, 1, 2, and 3 risk points were assigned for each quartile: <50, 50 to 59, 60 to 69, and 70 years, respectively. For LVEF, 3, 2, 1, and 0 risk points were assigned for each quartile: <25%, 26% to 39%, 40% to 59%, and 60%, respectively. For serum creatinine, 3 risk points were assigned for its upper quartile (>115 μmol/l) only. In the total population, clinical risk score reached 3.5±2.5 (range, 0 9; median, 3; interquartile range, 2 5) and was able to identify patients at risk of major complications independently of VT cause. Thirty-Day Postprocedural Mortality There was zero 30-day mortality in patients with idiopathic VT. In the subgroup with SHD-VT, 5 patients (1.5%) died <7 days after the procedure. Causes of death were progression of heart failure with intractable VTs in 2 patients, recurrence of myocardial infarction in 2 patients with known multivessel coronary disease not suitable to revascularization, and tamponade because of perforation of temporary pacing lead inserted 2 days after ablation in 1 patient. When analysis of mortality was Table 4. Risk Factor Multivariate Predictors of Major Complications Relative Risk 95% Confidence Interval P Value High-risk operator Serum creatinine >115 μmol/l (>1.3 mg/dl) Age >70 y extended to 30 days, 17 deaths were observed (13±9 days after ablation), resulting in early mortality rates of 3.6% per procedure and 5.0% per patient. In addition, 7 patients (2.1%) were implanted with mechanical assist devices within this period. In patients who died, the last procedure was performed for electrical storm in 10 of 17 (59%) patients as compared with the rest of the SHD-VT subgroup (25%; P=0.002). Nine of 17 (53%) patients experienced recurrent arrhythmia early (<30 days) after the last ablation compared with the other SHD-VT patients (17%; P=0.0001). More than 1 procedure was performed in 65% (11 of 17) patients who died compared with 26% of those who survived 30 days (P=0.004). Rates of major periprocedural complications during the last procedure did not differ between deceased and surviving patients at Figure. A to C, Risk for complications (mean and 95% confidence interval [CI]) depending on clinical factors (age, left ventricular ejection fraction [LVEF], and serum creatinine) categorized by their quartiles. D, Risk for complications by composite risk score (see text for details).

5 688 Circ Arrhythm Electrophysiol August day follow-up (11.8% versus 8.4%, respectively; P=0.63). On multivariate analysis, 2 independent predictors of 30-day mortality were identified: early VT/VF recurrence with relative risk of 4.2 (95% confidence interval, ; P=0.003) and ablation for electrical storm with relative risk of 3.3 (95% confidence interval, ; P=0.02). Discussion Our study provides an update on the incidence of complications associated with VT ablation performed in a high-volume expert center and including data from >6 years. The main findings of this comprehensive analysis may be summarized as follows: (1) the incidence of major complications of catheter ablation in patients with both idiopathic and SHD-VT was 6.2%; (2) patients with idiopathic VT had significantly fewer complications than those with SHD-VT, and similarly, elective procedures were associated with lower procedural risk; (3) major life-threatening complications such as tamponade or stroke occurred in <1%; (4) complications were commonly related to vascular access; (5) complication incidence was operator-dependent and higher in patients with advanced age, depressed LVEF, and renal disease; (6) in patients with SHD-VT, the 30-day mortality reached 5.0% (3.6% per procedure) and was predicted by early recurrence of VT/VF and ablation for electrical storm. Idiopathic VTs It is generally accepted that the risk of complications is very low when catheter ablation is performed in idiopathic VTs. In a large series from an expert center, 5 the risk of major complications was 3%. Our data are fully in line with this observation. Importantly, there were no cardiac perforations and only 1 transient ischemic attack. Such figures are reassuring when patients with prognostically benign VTs are indicated for catheter ablation. Structural Heart Disease In SHD, data on complication rates of catheter ablation for VT are less consistent because of the broad spectrum of underlying conditions and comorbidities, different strategies of mapping and ablation, and more frequent procedures in the setting of electrical storm. Generally, we can get an impression of complication rates from 2 sources. One is multicenter trials on catheter ablation for VT, and the other is experience from expert centers. The incidence of complications in 3 major multicenter trials on VT ablation varied between 6.4% and 10.0%. 2,3,6 In 2 trials, perioperative mortality of 2.7% and 3.8% was reported. In contrast, complication rates were apparently lower (with zero mortality) in studies on prophylactic catheter ablation in postinfarction populations. In the VTACH (Ventricular Tachycardia Ablation in Addition to Implantable Defibrillators in Coronary Heart Disease) trial, 7 two complications were observed among 46 subjects (3.7%). In the SMASH-VT (Substrate Mapping and Ablation in Sinus Rhythm to Halt Ventricular Tachycardia) trial, 8 3 complications among 61 patients were noted (4.9%). This indicates that prophylactic catheter ablation for VT is relatively safe, at least in postinfarction populations. Experience from single centers is usually related to small cohorts of patients, 9,10 and the incidence of major complications could be as high as 15%. 11 The risk may be increased when an epicardial approach is used 12,13 or percutaneous mechanical support is deployed. 14,15 Recently published high-volume expert center experience revealed a complication rate of 6%. 5 One perioperative death was recorded in this series. Cardiac tamponade was observed in 4 subjects (1.4%) and thromboembolic events in 2 (0.8%). A more recent publication from another high-volume expert center reported the results of catheter ablation for SHD-VT in the largest cohort of patients studied (634 procedures in 528 patients). 16 Major complications were observed in 7.5%, with 1 death because of electromechanical dissociation. Cardiac tamponade was recorded in 2.4%, and major vascular complications were noted in 4% of cases. Our data documenting a 8% major complication rate among 473 ablation procedures for SHD-VT are again comparable with the above single-center reports and more favorable as compared with multicenter findings. When analyzing individual complications, the risk of cardiac tamponade is one of the most important because it is lifethreatening. The occurrence of tamponade may reach 7.5%, 11 but generally is reported 1%. 3,6,16 Tokuda et al 17 reviewed 1152 consecutive procedures of VT ablation and found that more than half of the perforations occurred in the context of steam pop during radiofrequency ablation. Those cases were also more likely to require surgical repair. In our series, cardiac tamponade occurred less frequently and mostly in the context of catheter manipulation within the RV. This observation reflects our rather conservative strategy of using power output with an upper limit between 30 and 40 W. Predictors of Complications Advanced age, lower LVEF, and renal disease were identified as independent clinical predictors of complications. The predictive power of renal impairment is in line with findings of a large study by Bohnen et al 5 who identified serum creatinine >1.5 mg/dl to be the independent predictor of complications related to catheter ablation of different arrhythmias. Advanced age was not a predictor of complications in their study, nor in a study by Inada et al 18 who did not find significantly higher risk of complications in patients aged >75 years. Multivariate analysis further suggested that the operator is an important confounding factor. This is not surprising given different experience and skills of individual operators. On the contrary, the risk associated with specific operators has to be interpreted with caution. Despite the significance in multivariate analysis, the result may have been biased by unrecognized interactions between patient characteristics that were different for individual operators. Patients were not randomized between operators, and it is likely that patients at the highest risk were assigned to the most experienced operators. This is underscored by the very low observed complication rate (1.4%) found in the group of 5 operators who performed a minority of procedures (total n=71). Thirty-Day Mortality The early mortality rate after the procedure in patients with SHD-VT is not negligible. Catheter ablation and resulting myocardial damage may have been proarrhythmic, which could have contributed to subsequent VT storm or worsening

6 Peichl et al Complications of Ventricular Tachycardia Ablation 689 of heart failure. However, in severely ill patients with advanced heart failure and electrical storm, it is often difficult to differentiate between complications that are more or less related to the procedure and other adverse events because of the natural course of the disease or inability to prevent arrhythmia recurrences. In this respect, it is important to emphasize that the risk of catheter ablation in SHD is strongly dependent on patient population. For select patient populations with elective procedures, the risk of complications seems to be lower, with no 30-day mortality. 6 8 However, a higher risk of complications and mortality was reported in a large series of consecutive patients, including those with electrical storm. The 7-day mortality in the Thermocool trial 3 was 3%. In a series by Della Bella et al, 16 the in-hospital mortality (mean 8±3 days after the procedure) reached 1.9%, which is comparable to a 7-day mortality of 1.5% in our patients after SHD-VT ablation. The 30-day mortality in our cohort was predicted by early recurrence of VT/VF necessitating repeat procedures and ablation for electrical storm. This is in concordance with a study by Carbucicchio et al 19 who found that recurrent storm despite catheter ablation is strongly associated with increased cardiac mortality. Limitations The study has several limitations. First, it is a single-center, retrospective, observational study. Second, although there were no periprocedural deaths, postprocedural mortality was not negligible. It must be acknowledged that prolonged procedures, saline overload because of ablation using open irrigation, postprocedural anemia, and worsening of renal function might have contributed to heart failure progression and early mortality. Because of the observational nature of our study, it was not possible to differentiate whether recurrent VTs were a harbinger or a causal precursor of adverse outcome. Only further prospective studies will allow determination of whether any measures (eg, hemodynamic support) can improve prognosis in these patients. Conclusions In this series of cases, the VT ablation complication rate is significantly lower in idiopathic VT or in elective procedures. The main clinical predictors of complications include advanced age, depressed LV systolic function, and renal disease. In addition, complications of VT ablation are strongly operator-dependent. Ablation for electrical storm and early recurrence of VT/VF are the main predictors of 30-day postprocedural mortality. Sources of Funding This study was in part supported by a research grant no. MZO of the Ministry of Health of the Czech Republic (Research in Cardiovascular Diseases, Diabetes Mellitus, and Transplantation of Life-Preserving Organs). Disclosures J. Kautzner is a member of advisory board for Biosense Webster, Boston Scientific, Medtronic, and St Jude Medical. He received speaker honoraria from Biosense Webster, Biotronik, Boston Scientific, GE Healthcare, Hansen Medical, Medtronic, Siemens Healthcare, and St Jude Medical. The other authors report no conflicts. References 1. Aliot EM, Stevenson WG, Almendral-Garrote JM, Bogun F, Calkins CH, Delacretaz E, Bella PD, Hindricks G, Jaïs P, Josephson ME, Kautzner J, Kay GN, Kuck KH, Lerman BB, Marchlinski F, Reddy V, Schalij MJ, Schilling R, Soejima K, Wilber D; European Heart Rhythm Association; European Society of Cardiology; Heart Rhythm Society. 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7 690 Circ Arrhythm Electrophysiol August Della Bella P, Baratto F, Tsiachris D, Trevisi N, Vergara P, Bisceglia C, Petracca F, Carbucicchio C, Benussi S, Maisano F, Alfieri O, Pappalardo F, Zangrillo A, Maccabelli G. Management of ventricular tachycardia in the setting of a dedicated unit for the treatment of complex ventricular arrhythmias: long-term outcome after ablation. Circulation. 2013;127: Tokuda M, Kojodjojo P, Epstein LM, Koplan BA, Michaud GF, Tedrow UB, Stevenson WG, John RM. Outcomes of cardiac perforation complicating catheter ablation of ventricular arrhythmias. Circ Arrhythm Electrophysiol. 2011;4: Inada K, Roberts-Thomson KC, Seiler J, Steven D, Tedrow UB, Koplan BA, Stevenson WG. Mortality and safety of catheter ablation for antiarrhythmic drug-refractory ventricular tachycardia in elderly patients with coronary artery disease. Heart Rhythm. 2010;7: Carbucicchio C, Santamaria M, Trevisi N, Maccabelli G, Giraldi F, Fassini G, Riva S, Moltrasio M, Cireddu M, Veglia F, Della Bella P. Catheter ablation for the treatment of electrical storm in patients with implantable cardioverter-defibrillators: short- and long-term outcomes in a prospective single-center study. Circulation. 2008;117: Clinical Perspective Catheter ablation is an established treatment modality for a broad spectrum of ventricular tachycardias (VTs). Although it is considered a curative procedure in idiopathic VTs, outcomes are not generally as good in structural heart disease. In structural heart disease, catheter ablation is predominantly used as an adjunctive treatment for recurrent VT in patients with implantable cardioverter-defibrillator and is often the treatment of choice for incessant VT or in electrical storms. Our study provides an update on the incidence of complications associated with VT ablation performed in a high-volume expert center. This series of cases confirmed that the complication rate in idiopathic VT is very low, and it is higher in patients with structural heart disease. The most common complications are related to vascular access. Life-threatening complications, such as tamponade or stroke, are rare. Predictors of complications include age, renal insufficiency, and individual operator. Although there was no 30-day mortality for idiopathic VTs, it reaches 5% in patients with structural heart disease and is predicted by early recurrence of VT/ventricular fibrillation and ablation for electrical storm. These data can help inform treatment decisions and generally support the use of catheter ablation for VT.