Chronic total occlusion of an infarct-related artery: a new predictor of ventricular arrhythmias in primary prevention implantable cardioverter defibrillator patients.

Aims: The aim of this article is to evaluate the impact of a coronary chronic total occlusion in an infarct-related artery (IRA-CTO) on the occurrence of ventricular arrhythmias (VAs) in patients implanted with an implantable cardioverter defibrillator (ICD) for primary prevention. Methods and Results: The study includes a prospective cohort of 108 consecutive patients with ischaemic cardiomyopathy, in whom an ICD was implanted for primary prevention and a coronary angiography performed before ICD implantation. About 49 patients (45%) had a CTO and 34 (31%) had an IRA-CTO. Patients with IRA-CTO did not differ from the rest of the population in terms of basal characteristics and severity of cardiac disease. Median follow-up was 33 months (interquartile range 46). Infarct-related artery-CTO was associated with higher rates of any VA (53 vs. 26%, P = 0.006) and fast ventricular tachycardia (fast VT, cycle length <300 ms) or ventricular fibrillation (VF) (47 vs. 19%, P = 0.002). At multivariate Cox regression, IRA-CTO was the only independent predictor of any VA [hazard ratio (HR) 3.64, P = 0.002] and fast VT/VF (HR 3.36, P = 0.008). On the contrary, CTO not associated with a prior infarction in their territory did not increase the risk of VA. Infract-related artery-CTO was also an independent predictor of cardiac mortality or heart transplantation (HR 3.46, P = 0.022). Conclusion: In ischaemic patients implanted with an ICD for primary prevention, a CTO associated with a previous infarction in its territory is an independent predictor of VA and, especially, of fast VT/VF, identifying a subgroup of patients with a very high rate of arrhythmic events at follow-up.

Impact of previous cardiac surgery on long-term outcome of cavotricuspid isthmus-dependent atrial flutter ablation.

AIMS: The aim of this study was to determine the acute and long-term outcome of radiofrequency catheter ablation (RFCA) for cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) in adults with and without previous cardiac surgery (PCS), and predictors of these outcomes. Structural alterations of the anatomical substrate of the CTI-AFL are observed in post-operative patients, and these may have an impact on the acute success of the ablation and in the long-term. METHODS AND RESULTS: Clinical records of consecutive adults undergoing RFCA of CTI-AFL were analysed. Two main groups were considered: No PCS and PCS patients, who were further subdivided into acquired heart disease (AHD: ischaemic heart disease and valvular/mixed heart disease) and congenital heart disease [CHD: ostium secundum atrial septal defect (OS-ASD) and complex CHD]. Multivariate analysis identified clinical and procedural factors that predicted acute and long-term outcomes. A total of 666 patients (73% men, age 65 ± 12 years) were included: 307 of them with PCS. Ablation was successful in 647 patients (97%), 96% in the PCS group and 98% in the No PCS group (P = 0.13). Regression analysis showed that surgically corrected complex CHD was related to failure of the procedure [odds ratio 5.6; 95% confidence interval (CI) 1.6-18, P = 0.008]. After a follow-up of 45 ± 15 months, recurrences were observed in 90 patients (14%), more frequently in the PCS group: absolute risk of recurrence 18 vs. 10.5%, relative risk 1.71, 95% CI: 1.2-2.5, P = 0.006. Multivariate analysis indicated that the types of PCS [OS-ASD vs. No PCS: hazard ratio (HR) 2.57; 95% CI: 1.1-6.2, P = 0.03 and complex CHD vs. No PCS: HR 2.75; 95% CI: 1.41-5.48, P = 0.004], female gender (HR 1.55; 95% CI: 1.04-2.4, P = 0.048), and severe LV dysfunction (HR 1.36; 95% CI: 1.06-1.67, P = 0.04) were independent predictors of long-term recurrence. CONCLUSION: Radiofrequency catheter ablation of CTI-AFL after surgical correction of AHD and CHD is associated with high acute success rates. The severity of the structural alterations of the underlying heart disease and consequently the type of surgical correction correlates with higher risk for recurrence.

Shock Reduction With Multiple Bursts of Antitachycardia Pacing Therapies to Treat Fast Ventricular Tachyarrhythmias in Patients With Implantable Cardioverter Defibrillators: A Multicenter Study.

INTRODUCTION: An empirical sequence of burst antitachycardia pacing (ATP) is effective in terminating fast ventricular tachycardias (FVT) in patients with implantable cardioverter-defibrillators (ICDs). We aimed to determine whether multiple ATP bursts for termination of FVT results in shock reduction compared to a single ATP burst. METHODS AND RESULTS: We analyzed data from the Umbrella trial, a multicenter prospective observational study of ICD patients followed by the CareLink Monitoring System. We compared the safety and effectiveness of a single ATP burst (Group 1) with a strategy of successive ATP sequences (Group 2) for termination of FVT episodes (cycle lengths 250-320 milliseconds) before shock therapy. Over a mean follow-up of 35 months, a total of 650 FVT episodes were detected in 154 patients (mean cycle length: 299 ± 18 milliseconds). Effectiveness of the first burst ATP in Group 1 was 73% and shocks were required in 27% of episodes. Effectiveness of the first burst ATP in Group 2 was 77%, and this increased to 91% with the third or successive ATP bursts. Shocks were required in 9% of episodes in group 2, representing a 67% reduction in the need of high-energy shocks. Median duration of FVT episodes and mortality in both groups were similar. Multivariate analysis indicated that programming multiple ATP bursts (OR 3.4, 95%CI 1.7-6.8, P = 0.001) was an independent predictor of ATP effectiveness. CONCLUSION: This study provides first evidence that a strategy of multiple burst ATP sequences for termination of FVT episodes leads to a clinically meaningful reduction in the need for shocks.

The benefit of a second burst antitachycardia sequence for fast ventricular tachycardia in patients with implantable cardioverter defibrillators.

BACKGROUND: In patients with implantable cardioverter defibrillators (ICDs), an empirical burst of antitachycardia pacing (ATP) is moderately effective in terminating fast ventricular tachycardias (FVTs). It is unknown whether, in the case of failure of a first burst, a second burst attempt increases the efficacy of the intervention, without increasing morbidity. Our aim was to evaluate the safety and efficacy of a strategy of programming successive ATP sequences for FVT episodes. METHODS: A prospective study evaluated the safety and effectiveness of programming successive ATP sequences for termination of FVT episodes (cycle lengths [CLs] 250-320 ms) treated by one ATP sequence and, in the event of failure, by successive ATP attempts or shocks. RESULTS: Over a median follow-up of 54 months, 267 FVT episodes (mean CL of 295 ± 18 ms) were detected in 35 patients. Effectiveness of the first burst ATP was 64% (65% GEE-adjusted, where GEE is generalized estimating equation) and increased significantly to 83% (75% GEE-adjusted) with the second burst ATP sequence (P = 0.01). In the remaining 17% of FVT episodes with failure of the second ATP, successive bursts and shocks were required. Multivariate analysis showed that primary prevention ICD (odds ratio [OR] 5.3, 95% confidence interval [CI] 1.9-14.5, P = 0.001), sinus rhythm (OR 4.34, 95% CI 1.4-13.4, P = 0.01), nonischemic cardiomyopathy (OR 2.36, 95% CI 1.2-4.8, P = 0.02), and longer VT CL (OR 1.32, 95% CI 1.1-1.6, P = 0.002) were independently associated with effectiveness of the first or second burst pacing sequence. CONCLUSION: The addition of a second burst pacing attempt increases the effectiveness of ATP for FVT and, therefore, reduces the need for high-energy shocks.

Morphology of far-field electrograms and antitachycardia pacing effectiveness among fast ventricular tachycardias occurring in ICD patients: a multicenter study.

INTRODUCTION: Fast ventricular tachycardias (FVT) are less likely to be terminated by antitachycardia pacing (ATP). No information is available regarding the ability of far-field electrogram (Ff-EG) morphology (Ff-EGm) in predicting the result of the subsequent ATP. Our objective is to determine the relationship between Ff-EGm and ATP efficacy. METHODS AND RESULTS: In this multicenter study we analyzed 289 FVT (cycle length [CL]: 250-320 milliseconds) occurring consecutively in 52 ICD patients with Medtronic devices (LVEF: 37 ± 6; pacing site: right ventricular apex). FVT programming was standardized, including a single ATP burst as initial therapy. The configuration of Ff-EG was HVA versus HVB. FVTs were classified in QFVT or non-QFVT according to the presence or absence of a negative initial deflection in the Ff-EG. The mean CL was 291 ± 24 milliseconds. We observed 4 Ff-EGm: QS (n = 14, 5%), QR (n = 158, 55%), R (n = 93, 32%), and RS (n = 24, 8%). The ATP effectiveness was 80% (86% in QS, 85% in QR, 74% in R, 62% in RS). The frequency of successful ATP was higher in QFVT: 86 versus 71% (P = 0.002). By logistic regression analysis, a QFVT pattern (OR = 2.3; P = 0.015) remained as an independent predictor of effective ATP. ATP was safer in QFVTs, the frequencies of shock (14% vs 29%; P = 0.002), acceleration (5.1 vs 12.3%; P = 0.02), and syncope (4.6 vs 12.3%; P = 0.01) being lower. CONCLUSIONS: Since ATP is less effective in non-QFVTs, they are less well tolerated. Therefore, the substrate of non-QFVTs may need a specific treatment.

Trends in the use of electrical cardioversion for atrial fibrillation: influence of major trials and guidelines on clinical practice.

BACKGROUND: The purpose of the present study was to assess the trends in the use of ECV following published studies that had compared rhythm and rate control strategies on atrial fibrillation (AF), and the recommendations included in the current clinical practice guidelines. METHODS: The REVERCAT is a population-based assessment of the use of electrical cardioversion (ECV) in treating persistent AF in Catalonia (Spain). The initial survey was conducted in 2003 and the follow-up in 2010. RESULTS: We observed a decrease of 9% in the absolute numbers of ECV performed (436 in 2003 vs. 397 in 2010). This is equivalent to 27% when considering population increases over this period. The patients treated with ECV in 2010 were younger, had a lower prevalence of previous embolism, a higher prevalence of diabetes, and increased body weight. Underlying heart disease factors indicated, in 2010, a higher proportion of NYHA ≥ II and left ventricular ejection fraction <30%. We observed a reduction in the number of ECV performed in 16 of the 27 (67%) participating hospitals. However, there was an increase of 14% in the number of procedures performed in tertiary hospitals, and was related to the increasing use of ECV as a bridge to AF ablation. Considering the initial number of patients treated with ECV, the rate of sinus rhythm at 3 months was almost unchanged (58% in 2003 vs. 57% in 2010; p=0.9) despite the greater use of biphasic energy in 2010 and a similar prescription of anti-arrhythmic drugs. CONCLUSIONS: Although we observed a decrease in the number of ECVs performed over the 7 year period between the two studies, this technique remains a common option for treating patients with persistent AF. The change in the characteristics of candidate patients did not translate into better outcomes.

Fatal undersensing of ventricular fibrillation due to intermittent high-amplitude R waves.

A 48-year-old man was admitted after an episode of aborted sudden death with external defibrillation. An implantable cardioverter defibrillator implanted 2 years before for secondary prevention failed to sense properly an episode of ventricular fibrillation. Interrogation of the device showed large oscillatory changes of the amplitude of the local electrogram during ventricular fibrillation, causing undersensing and inappropriate refraining from shock therapy.

Atrial asystole during ventricular pacing following radiofrequency catheter ablation of accessory pathways.

Sinus node bradycardia or sinus node arrest is a documented phenomenon during radiofrequency catheter ablation. In addition, sinus node inhibition during ventricular pacing has been described as an infrequent occurrence in the course of diagnostic electrophysiology studies. The proposed mechanism in both situations is intense stimulation of vagal afferent pathways leading to a Bezold-Jarisch-like phenomenon. In the present report, we describe a series of three cases of atrial asystole during ventricular pacing following radiofrequency catheter ablation of accessory pathways. Potential pathophysiologic mechanisms are discussed.

Shock Reduction With Antitachycardia Pacing Before and During Charging for Fast Ventricular Tachycardias in Patients With Implantable Defibrillators.

INTRODUCTION AND OBJECTIVES: Fast ventricular tachycardias in the ventricular fibrillation zone in patients with an implantable cardioverter-defibrillator are susceptible to antitachycardia pacing (ATP) termination. Some manufacturers allow programming 2 ATP bursts: before charging (BC) and during (DC) charging. The aim of this study was to describe the safety and effectiveness of ATP BC and DC for fast ventricular tachycardias in the ventricular fibrillation zone in patients with an implantable cardioverter-defibrillator in daily clinical practice. METHODS: Data proceeded from the multicenter UMBRELLA trial, including implantable cardioverter-defibrillator patients followed up by the CareLink monitoring system. Fast ventricular tachycardias in the ventricular fibrillation zone until a cycle length of 200ms with ATP BC and/or ATP DC were included. RESULTS: We reviewed 542 episodes in 240 patients. Two ATP bursts (BC/DC) were programmed in 291 episodes (53.7%, 87 patients), while 251 episodes (46.3%, 153 patients) had 1 ATP burst only DC. The number of episodes terminated by 1 ATP DC was 139, representing 55.4% effectiveness (generalized estimating equation-adjusted 60.4%). There were 256 episodes terminated by 1 or 2 ATP (BC/DC), representing 88% effectiveness (generalized estimating equation-adjusted 79.3%); the OR for ATP effectiveness BC/DC vs DC was 2.5, 95%CI, 1.5-4.1; P <.001. Shocked episodes were 112 (45%) for ATP DC vs 35 (12%) for ATP BC/DC, representing an absolute reduction of 73%. The mean shocked episode duration was 16seconds for ATP DC vs 19seconds for ATP BC/DC (P=.07). CONCLUSIONS: The ATP DC in the ventricular fibrillation zone for fast ventricular tachycardia is moderately effective. Adding an ATP burst BC increases the overall effectiveness, reduces the need for shocks, and does not prolong episode duration.

Late Gadolinium Enhancement and the Risk for Ventricular Arrhythmias or Sudden Death in Dilated Cardiomyopathy: Systematic Review and Meta-Analysis.

OBJECTIVES: The aim of this study was to evaluate the association between late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging and ventricular arrhythmias or sudden cardiac death (SCD) in patients with dilated cardiomyopathy (DCM). BACKGROUND: Risk stratification for SCD in DCM needs to be improved. METHODS: A systematic review and meta-analysis were conducted. A systematic search of PubMed and Ovid was performed, and observational studies that analyzed the arrhythmic endpoint (sustained ventricular arrhythmia, appropriate implantable cardioverter-defibrillator [ICD] therapy, or SCD) in patients with DCM, stratified by the presence or absence of LGE, were included. RESULTS: Twenty-nine studies were included, accounting for 2,948 patients. The studies covered a wide spectrum of DCM, with a mean left ventricular ejection fraction between 20% and 43%. LGE was significantly associated with the arrhythmic endpoint both in the overall population (odds ratio: 4.3; p < 0.001) and when including only those studies that performed multivariate analysis (hazard ratio: 6.7; p < 0.001). The association between LGE and the arrhythmic endpoint remained significant among studies with mean left ventricular ejection fractions >35% (odds ratio: 5.2; p < 0.001) and was maximal in studies that included only patients with primary prevention ICDs (odds ratio: 7.8; p = 0.008). CONCLUSIONS: Across a wide spectrum of patients with DCM, LGE is strongly and independently associated with ventricular arrhythmia or SCD. LGE could be a powerful tool to improve risk stratification for SCD in patients with DCM. These results raise 2 major questions to be addressed in future studies: whether patients with LGE could benefit from primary prevention ICDs irrespective of their left ventricular ejection fractions, while patients without LGE might not need preventive ICDs despite having severe left ventricular dysfunction.

Atrial Fibrillation Ablation in Adults With Repaired Congenital Heart Disease.

The incidence of atrial fibrillation (AF) in congenital heart disease (CHD) adults has increased in the past decades due to a longer life expectancy of this population where the subjects are exposed to cardiac overflow, overpressure and structural changes for years. The literature regarding AF ablation in repaired CHD adults emphasizes the importance of intracardiac echocardiography (ICE) to perform the transseptal puncture and the ablation procedure in the left atrium (LA), both effectively and safely. In small case control studies, where the predominant congenital cardiomyopathy was the atrial septal defect, the most common strategy for ablation was antral isolation of the pulmonary veins showing results, at one year follow-up, similar to those in the general population. The positive results of AF ablation so far, in this specific population, widen the range of therapeutic options for a group of patients whose only chance has been pharmacological treatment, which has proved to be inefficacious in most of the cases and not free from adverse events.

Implantable Cardioverter-defibrillator Therapy for Hypertrophic Cardiomyopathy: Usefulness in Primary and Secondary Prevention.

INTRODUCTION AND OBJECTIVES: Hypertrophic cardiomyopathy is a frequent cause of sudden death. Clinical practice guidelines indicate defibrillator implantation for primary prevention in patients with 1 or more risk factors and for secondary prevention in patients with a history of aborted sudden death or sustained ventricular arrhythmias. The aim of the present study was to analyze the follow-up of patients who received an implantable defibrillator following the current guidelines in nonreferral centers for this disease. METHODS: This retrospective observational study included all patients who underwent defibrillator implantation between January 1996 and December 2012 in 3 centers in the province of Barcelona. RESULTS: The study included 69 patients (mean age [standard deviation], 44.8 [17] years; 79.3% men), 48 in primary prevention and 21 in secondary prevention. The mean number of risk factors per patient was 1.8 in the primary prevention group and 0.5 in the secondary prevention group (P=.029). The median follow-up duration was 40.5 months. The appropriate therapy rate was 32.7/100 patient-years in secondary prevention and 1.7/100 patient-years in primary prevention (P<.001). Overall mortality was 10.1%. Implant-related complications were experienced by 8.7% of patients, and 13% had inappropriate defibrillator discharges. CONCLUSIONS: In patients with a defibrillator for primary prevention, the appropriate therapy rate is extremely low, indicating the low predictive power of the current risk stratification criteria.

Long-Term Outcome After Ablation of Right Atrial Tachyarrhythmias After the Surgical Repair of Congenital and Acquired Heart Disease.

Atrial myopathy, atriotomies, and fibrotic scars are the pathophysiological substrate of lines of conduction block, promoting atrial macroreentry. The aim of this study was to determine the acute and long-term outcome of radiofrequency catheter ablation (RFCA) for right atrial tachyarrhythmia (AT) in adults after cardiac surgery for congenital heart disease (CHD) and acquired heart disease (AHD) and predictors of these outcomes. Clinical records of adults after surgery for heart disease undergoing RFCA of right-sided AT were analyzed retrospectively. Multivariate analyses identified clinical and procedural factors predicting acute and long-term outcomes. A total of 372 patients (69% men; age 61 ± 15 years) after surgical repair of CHD (n = 111) or AHD (n = 261) were studied. Cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) was observed in 300 patients and non-CTI-AFL in 72 patients. Ablation was successful in 349 cases (94%). During a mean follow-up of 51 ± 30 months, recurrences were observed in 24.5% of patients. Multivariate analysis showed that non-CTI-AFL (hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.1 to 2.9) and CHD (HR 1.75, 95% CI 1.07 to 2.9) were independent predictors of long-term recurrences. Multivariate analysis showed that female gender (HR 2.29, 95% CI 1.6 to 3.3), surgery for AHD (HR 95% 2.31, 95% CI 1.5 to 3.7), and left atrial dilatation (HR 2.1, 95% CI 1.3 to 3.2) were independent predictors of long-term atrial fibrillation. In conclusion, RFCA of right-sided AT after cardiac surgery is associated with high acute success rates and significant long-term recurrences. Non-CTI-dependent AFL and surgery for CHD are at higher risk of recurrence. Atrial fibrillation is common during follow-up, particularly in patients with AHD and enlarged left atrium.

Aortic perforation by active-fixation atrial pacing lead: an unusual but serious complication.

Perforation of a cardiac chamber is an infrequent but serious sequela of pacemaker lead implantation. An even rarer event is the perforation of the aorta by a protruding right atrial wire. We present here the first case in the medical literature of aortic perforation as a sequela to the implantation of a cardiac resynchronization therapy defibrillator. The patient was a 54-year-old man with idiopathic dilated cardiomyopathy who underwent the implantation of a defibrillator, with no apparent sequelae. Six hours after the procedure, he experienced cardiac tamponade and required urgent open-chest surgery. The pericardial effusion was found to be caused by mechanical friction of a protruding right atrial wire on the aortic root. The aortic root and the atrial wall were both repaired with Prolene suture, which achieved complete control of the bleeding. There was no need to reposition the atrial wire. The patient had a good postoperative recovery.

Taquicardias ventriculares monomórficas en pacientes con síndrome de Brugada tratados con quinidina: eficacia de la estimulación antitaquicardia / Antitachycardia pacing effectiveness for monomorphic ventricular tachycardia in brugada syndrome after quinidine administration

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Taquicardias ventriculares rápidas en pacientes con desfibrilador implantable: reducción de choques mediante terapia antitaquicárdica antes y durante la carga / Shock reduction with antitachycardia pacing before and during charging for fast ventricular tachycardias in patients with implantable defibrillators

Introducción y objetivos: Las taquicardias ventriculares rápidas en zona de fibrilación ventricular en pacientes con desfibriladores implantables son susceptibles de terminación mediante estimulación antitaquicárdica (EA). Algunos fabricantes permiten la programación de 2 ráfagas de EA: antes de la carga (AC) y durante la carga (DC). Nuestro objetivo es describir la efectividad y la seguridad de la EA AC y DC en las taquicardias ventriculares rápidas en zona de fibrilación ventricular en pacientes con desfibriladores implantables en la práctica clínica diaria. Métodos: Los datos proceden del ensayo multicéntrico UMBRELLA, y se incluyó a los pacientes portadores de desfibriladores implantables seguidos por el sistema de monitorización a distancia CareLink. Se incluyeron las taquicardias ventriculares rápidas en la zona de fibrilación ventricular hasta una longitud de ciclo de 200 ms y tratadas con EA AC y/o DC. Resultados: Se revisaron 542 episodios en 240 pacientes. Dos ráfagas de EA (AC/DC) se programaron en 291 episodios (el 53,7%, 87 pacientes) mientras que 251 (el 46,3%, 153 pacientes) tuvieron 1 sola EA DC. Los episodios terminados por 1 EA DC fueron 139: el 55,4% de eficacia (ajustado por las ecuaciones de estimación generalizada, el 60,4%). Los episodios terminados por 1 o 2 EA (AC/DC) fueron 256, el 88% de efectividad (ajustado por las ecuaciones de estimación generalizada, el 79,3%). La OR para la eficacia de la EA AC/DC frente a DC fue 2,5 (IC95%, 1,5-4,1; p < 0,001). Los episodios con descarga de alta energía fueron 112 (45%) con EA DC frente a 35 (12%) con EA AC/DC (reducción absoluta del 73%). La media de duración de los episodios con descarga fue de 16 s con EA DC frente a 19 s con EA AC/DC (p = 0,07). Conclusiones: La EA DC en la zona de fibrilación ventricular en taquicardias ventriculares rápidas es moderadamente eficaz. La adición de una ráfaga de EA AC aumenta la efectividad general, reduce la necesidad de descargas y no prolonga el episodio

Introduction and objectives: Fast ventricular tachycardias in the ventricular fibrillation zone in patients with an implantable cardioverter-defibrillator are susceptible to antitachycardia pacing (ATP) termination. Some manufacturers allow programming 2 ATP bursts: before charging (BC) and during (DC) charging. The aim of this study was to describe the safety and effectiveness of ATP BC and DC for fast ventricular tachycardias in the ventricular fibrillation zone in patients with an implantable cardioverter-defibrillator in daily clinical practice. Methods: Data proceeded from the multicenter UMBRELLA trial, including implantable cardioverter-defibrillator patients followed up by the CareLink monitoring system. Fast ventricular tachycardias in the ventricular fibrillation zone until a cycle length of 200 ms with ATP BC and/or ATP DC were included. Results: We reviewed 542 episodes in 240 patients. Two ATP bursts (BC/DC) were programmed in 291 episodes (53.7%, 87 patients), while 251 episodes (46.3%, 153 patients) had 1 ATP burst only DC. The number of episodes terminated by 1 ATP DC was 139, representing 55.4% effectiveness (generalized estimating equation-adjusted 60.4%). There were 256 episodes terminated by 1 or 2 ATP (BC/DC), representing 88% effectiveness (generalized estimating equation-adjusted 79.3%); the OR for ATP effectiveness BC/DC vs DC was 2.5, 95%CI, 1.5-4.1; P < .001. Shocked episodes were 112 (45%) for ATP DC vs 35 (12%) for ATP BC/DC, representing an absolute reduction of 73%. The mean shocked episode duration was 16 seconds for ATP DC vs 19 seconds for ATP BC/DC (P = .07). Conclusions: The ATP DC in the ventricular fibrillation zone for fast ventricular tachycardia is moderately effective. Adding an ATP burst BC increases the overall effectiveness, reduces the need for shocks, and does not prolong episode duration