Utility of an Externalized Temporary Transvenous Implantable Cardioverter-defibrillator System in the Setting of Ventricular Tachycardia Storm and Concurrent Device Infection Requiring Extraction.

With the expanding use of cardiac implantable electronic device (CIED) therapy, intravascular device infections are becoming more common. In the case of transvenous implantable cardioverter-defibrillator (ICD) infections requiring extraction for bacterial clearance, there remains no standard method to deliver temporary ICD therapy following device removal. We present a case of persistent bacteremia complicated by monomorphic ventricular tachycardia (VT) electrical storm where biventricular ICD system extraction was performed and a temporary transvenous dual-coil lead with an externalized ICD generator was used to treat VT episodes prior to the re-implantation of a new permanent system. This case demonstrates the utility of a temporary externalized transvenous ICD system in the successful detection and pace-termination of VT, thereby reducing episodes of painful and potentially harmful external defibrillator shocks during the treatment of CIED infection.

Implantable Cardioverter Defibrillator Tachycardia Therapies: Past, Present and Future Directions.

Implantable cardioverter defibrillators (ICDs) have a long history and have progressed significantly since the 1980s. They have become an essential part of the prevention of sudden cardiac death, with a proven survival benefit in selected patient groups. However, with more recent trials and with the introduction of contemporary heart failure therapy, there is a renewed interest and new questions regarding the role of a primary prevention ICD, especially in patients with heart failure of non-ischaemic aetiology. This review looks at the history and evolution of ICDs, appraises the traditional evidence for ICDs and looks at issues relating to patient selection, risk stratification, competing risk, future directions and a proposed contemporary ICD decision framework.

Transition mechanisms from atrial flutter to atrial fibrillation during anti-tachycardia pacing therapy.

BACKGROUND: Atrial anti-tachycardia pacing (aATP) has been shown to be effective for the termination of atrial tachyarrhythmias, but its success rate is still not high enough. OBJECTIVE: The main objective of this study was to investigate the mechanisms of atrial flutter (AFL) termination by aATP and the transition from AFL to atrial fibrillation (AF) during aATP. METHODS: We developed a multi-scale model of the human atrium based on magnetic resonance images and examined the atrial electrophysiology of AFL during aATP with a ramp protocol. RESULTS: In successful cases of aATP, paced excitation entered the excitable gap and collided with the leading edge of the reentrant wave front. Furthermore, the excitation propagating in the opposite direction collided with the trailing edge of the reentrant wave to terminate AFL. The second collision was made possible by the distribution of the wave propagation velocity in the atria. The detailed analysis revealed that the slowing of propagation velocity occurred at the exit of the sub-Eustachian isthmus, probably due to source-sink mismatch. During the transition from AFL to AF, the excitation collided with the refractory zone of the preceding wave and broke into multiple wave fronts to induce AF. A similar observation was made for the transition from AF to sinus rhythm. In both cases, the complex anatomy of the atria played an essential role. CONCLUSION: The complex anatomy of atria plays an essential role in the maintenance of stable AFL and its termination by aATP, which were revealed by the realistic three-dimensional simulation model.

Case report: successful termination of ventricular tachycardia by intrinsic anti-tachycardia pacing beyond conventional anti-tachycardia pacing.

Background: Anti-tachycardia pacing (ATP) is a pain-free alternative to defibrillation shock for monomorphic ventricular tachycardia (VT). Intrinsic ATP (iATP) is a novel algorithm of auto-programmed ATP. However, the advantage of iATP over conventional ATP in clinical cases is still unknown. Case summary: A 49-year-old man with no significant past medical history was transferred to our institution with sudden-onset fatigue from working on a farm. A 12-lead electrocardiogram showed monomorphic sustained wide QRS tachycardia with a right bundle branch block pattern and superior axis deviation with a cycle length (CL) of 300 ms. Sustained monomorphic VT originating from the left ventricle due to underlying vasospastic angina was diagnosed by contrast-enhanced cardiac magnetic resonance imaging, coronary angiography, and the acetylcholine stress test, and implantable cardioverter defibrillator implantation was performed. Nine months later, a clinical VT episode with a CL of 300 ms was observed, which could not be terminated by three sequences of conventional burst pacing. Ventricular tachycardia was finally terminated by a third iATP sequence without any acceleration. Discussion: Although standard burst pacing by conventional ATP reached the VT circuit, it failed to terminate the VT. Using the post-pacing interval, iATP automatically calculated the appropriate number of S1 pulses required to reach the VT circuit. In iATP, the S2 pulses are delivered with a calculated coupling interval based on the estimated effective refractory period during tachycardia. In this case, iATP might have led to less aggressive S1 stimulation, followed by aggressive S2 stimulation, which probably helped terminate the VT without any acceleration.

Prolonged T-peak to T-end Interval Predicts Implantable Cardioverter Defibrillator Therapy in Patients With Cardiac Sarcoidosis.

BACKGROUND: The association between the T-peak to T-end interval (Tp-e) and ventricular arrhythmia (VA) events in cardiac sarcoidosis (CS) is unknown. The purpose of this study was to investigate whether Tp-e was associated with VA events in CS patients with implantable cardioverter defibrillators (ICDs) or cardiac resynchronization therapy defibrillators (CRT-Ds).Methods and Results: We retrospectively studied 50 patients (16 men; mean [±SD] age 56.3±10.5 years) with CS and ICD/CRT-D. The maximum Tp-e in the precordial leads recorded by a 12-lead electrocardiogram after ICD/CRT-D implantation was evaluated. The clinical endpoint was defined as appropriate ICD therapy. During a median follow-up period of 85.0 months, 22 patients underwent appropriate therapy and 10 patients died. Kaplan-Meier analysis revealed that the probability of the clinical endpoint was 28.3% at 2 years and 35.3% at 4 years. The optimal cut-off value of the Tp-e for the prediction of the clinical endpoint was 91 ms, with a sensitivity of 72.7% and a specificity of 87.0% (area under the curve=0.81). Multivariate Cox regression analysis showed that Tp-e ≥91 ms (hazard ratio [HR] 5.10; 95% confidence interval [CI] 1.99-13.1; P<0.001) and a histological diagnosis of CS (HR 3.84; 95% CI 1.28-11.5; P=0.016) were significantly associated with the clinical endpoint. CONCLUSIONS: Tp-e ≥91 ms was a significant predictor of VA events in patients with CS and ICD/CRT-D.

Cost-effectiveness analysis of cardiac implantable electronic devices with reactive atrial-based antitachycardia pacing.

AIMS: Reactive atrial-based anti-tachycardia pacing (rATP) in pacemakers (PMs) and cardiac resynchronization therapy defibrillators (CRT-Ds) has been reported to prevent progression of atrial fibrillation, and this reduced progression is expected to decrease the risk of complications such as stroke and heart failure (HF). This study aimed to assess the cost-effectiveness of rATP in PMs and CRT-Ds in the Japanese public health insurance system. METHODS AND RESULTS: We developed a Markov model comprising five states: bradycardia, post-stroke, mild HF, severe HF, and death. For devices with rATP and control devices without rATP, we compared the incremental cost-effectiveness ratio (ICER) from the payer's perspective. Costs were estimated from healthcare resource utilisation data in a Japanese claims database. We evaluated model uncertainty by analysing two scenarios for each device. The ICER was 763 729 JPY/QALY (5616 EUR/QALY) for PMs and 1,393 280 JPY/QALY (10 245 EUR/QALY) for CRT-Ds. In all scenarios, ICERs were below 5 million JPY/QALY (36 765 EUR/QALY), supporting robustness of the results. CONCLUSION: According to a willingness to pay threshold of 5 million JPY/QALY, the devices with rATP were cost-effective compared with control devices without rATP, showing that the higher reimbursement price of the functional categories with rATP is justified from a healthcare economic perspective.

Optimization of anti-tachycardia pacing efficacy through scar-specific delivery and minimization of re-initiation: a virtual study on a cohort of infarcted porcine hearts.

AIMS: Anti-tachycardia pacing (ATP) is a reliable electrotherapy to painlessly terminate ventricular tachycardia (VT). However, ATP is often ineffective, particularly for fast VTs. The efficacy may be enhanced by optimized delivery closer to the re-entrant circuit driving the VT. This study aims to compare ATP efficacy for different delivery locations with respect to the re-entrant circuit, and further optimize ATP by minimizing failure through re-initiation. METHODS AND RESULTS: Seventy-three sustained VTs were induced in a cohort of seven infarcted porcine ventricular computational models, largely dominated by a single re-entrant pathway. The efficacy of burst ATP delivered from three locations proximal to the re-entrant circuit (septum) and three distal locations (lateral/posterior left ventricle) was compared. Re-initiation episodes were used to develop an algorithm utilizing correlations between successive sensed electrogram morphologies to automatically truncate ATP pulse delivery. Anti-tachycardia pacing was more efficacious at terminating slow compared with fast VTs (65 vs. 46%, P = 0.000039). A separate analysis of slow VTs showed that the efficacy was significantly higher when delivered from distal compared with proximal locations (distal 72%, proximal 59%), being reversed for fast VTs (distal 41%, proximal 51%). Application of our early termination detection algorithm (ETDA) accurately detected VT termination in 79% of re-initiated cases, improving the overall efficacy for proximal delivery with delivery inside the critical isthmus (CI) itself being overall most effective. CONCLUSION: Anti-tachycardia pacing delivery proximal to the re-entrant circuit is more effective at terminating fast VTs, but less so slow VTs, due to frequent re-initiation. Attenuating re-initiation, through ETDA, increases the efficacy of delivery within the CI for all VTs.

Inappropriate Subcutaneous Implantable Cardioverter Defibrillator Shocks Secondary to Cardiac Remodeling: A Unique Case of T Wave Oversensing.

Implantable cardioverter defibrillators (ICD) are used for the primary and secondary prevention of sudden cardiac death (SCD). Currently, two different modalities of ICDs are in use: transvenous (TV) and subcutaneous (S-ICD). The use of S-ICDs has been driven by several potential benefits of this technology: preservation of central venous vasculature, no risk of vascular or myocardial injury during implant, easier explanation, and lower risk of systemic infections. Inappropriate shocks are defined as shocks delivered for non-life-threatening arrhythmias or because of oversensing. Here, we present a case of a 58-year-old man who began experiencing inappropriate shocks three years after S-ICD placement. Careful analysis of the ICD showed T wave oversensing with no malfunction of the device. The shocks persisted even after reprogramming, leading to subsequent ICD removal and loop recorder implantation. The onset of shock episodes coincided with the improvement of left ventricular ejection fraction (LVEF). To the best of our knowledge, this is the first published report of cardiac remodeling leading to uncorrectable T wave oversensing that subsequently required S-ICD explant. This represents a potentially important limitation of S-ICD technology, especially as S-ICD use rises and medical therapy for cardiomyopathy continues to improve.

Patient-activated anti-tachycardia pacing in adult congenital heart disease.

INTRODUCTION: In adults with congenital heart disease, intra-atrial reentrant tachycardia (IART) is a common arrhythmia that causes significant morbidity and mortality. One treatment option for IART is antitachycardia pacing. Atrial antitachycardia pacing algorithms deliver therapy for IART with ≥2:1 conduction, but most algorithms will not recognize IART with 1:1 conduction. Temporary Patient Activated Rx (TPARx) is Medtronic software that can be installed in antitachycardia pacemakers allowing patients to deliver therapies on demand for IART with 1:1 conduction. METHODS: Retrospective chart review at a single institution of all patients who had TPARx installed into their pacemaker. RESULTS: Four adults with single ventricle congenital heart disease and IART underwent Fontan conversion, arrhythmia surgery, and placement of an epicardial dual-chamber antitachycardia pacemaker. They had recurrent IART with a long cycle length and 1:1 conduction that failed to trigger antitachycardia pacing therapies. TPARx software was programmed into their pacemakers to allow recognition and treatment of IART with 1:1 conduction. Mean follow-up duration after TPARx programming was 4.9 years. Each patient received at least one successful antitachycardia pacing therapy via TPARx - range 0.4-26 treated IART episodes per year. There were no atrial or ventricular arrhythmias induced with antitachycardia pacing. Two patients were able to discontinue anticoagulation after TPARx installation. CONCLUSION: This series demonstrates the use of TPARx software as part of a long-term IART management strategy in select patients with IART who have failed more conventional therapies.

Utility of Simultaneous Biatrial Atrial Anti-Tachycardia Pacing for the Termination of Atrial Fibrillation during Catheter Ablation of Atrial Fibrillation.

BACKGROUND: Atrial anti-tachycardia pacing (A-ATP) of the right atrium (RA) has been shown to decrease the burden of atrial fibrillation (AF) in patients with dual-chamber pacemakers. The aim of this study is to identify the novel predictors of effective A-ATP for terminating AF in patients with AF undergoing catheter ablation. METHODS: This study included 41 consecutive patients undergoing a first ablation procedure for paroxysmal (PAF: n = 21) or persistent (PEF: n = 20) AF. We prospectively evaluated predictors of AF termination after A-ATP. The coefficient of variation (CoV = SD/mean × 100) of the dominant frequencies (DFs) was calculated to evaluate the variability in atrial activation. RESULTS: AF was terminated by A-ATP in 29% of PAF and 5% of PEF patients. In these patients, simultaneous high-rate pacing from the RA and the coronary sinus (CS) terminated AF in 71% of patients, in whom the mean AF cycle length (CL) before A-ATP was longer (214 ± 23 vs. 177 ± 35 ms, p = 0.02) and became slower after A-ATP (234 ± 37 vs. 176 ± 32 ms, p < 0.01), compared to unsuccessful patients. The CoV of the DFs before A-ATP were lower in both RA (6.2 ± 2.0 vs. 15.3 ± 7.9, p = 0.02) and CS (11.0 ± 7.9 vs. 24.3 ± 9.3, p < 0.01) in successful patients. CONCLUSIONS: Simultaneous biatrial A-ATP from the RA and CS could terminate AF in patients with PAF. The predictors for successful termination include longer AF CL and higher AF stability.

Intrinsic anti-tachycardia pacing terminated ventricular tachycardia resistant to traditional anti-tachycardia pacing.

Implantable cardioverter-defibrillators (ICDs) serve to reduce the risk of sudden death; however, ICD shocks worsen patient prognosis. Therefore, attempts have been made to terminate life-threatening arrhythmias without ICD shocks. A 71-year-old man with non-ischemic cardiomyopathy, who previously underwent cardiac resynchronization therapy-defibrillator (CRT-D) placement, was hospitalized for ventricular tachyarrhythmia (VT) that was refractory to traditional anti-tachycardia pacing (ATP). Endocardial and epicardial ablation failed to prevent VT recurrence. Since the CRT-D battery was exhausted, it was replaced with a Cobalt™ XT HF CRT-D (Medtronic, Minneapolis, MN, USA), and the intrinsic ATP (iATP) algorithm was employed. Although VT recurred frequently, recurrent VTs were terminated by the iATP, which created a conduction block in the circuit without VT acceleration or shock. This is the first reported case wherein an iATP algorithm was effective against VT resistant to traditional anti-tachycardia pacing. This novel ATP algorithm has the potential to terminate refractory VT without ICD shocks and provide a better prognosis.

Management of hemodynamically stable wide QRS complex tachycardia in patients with implantable cardioverter defibrillators.

Management of hemodynamically stable, incessant wide QRS complex tachycardia (WCT) in patients who already have an implantable cardioverter defibrillator (ICD) is challenging. First-line treatment is performed by medical staff who have no knowledge on programmed ICD therapy settings and there is always some concern for unexpected ICD shock. In these patients, a structured approach is necessary from presentation to therapy. The present review provides a systematic approach in four distinct phases to guide any physician involved in the management of these patients: PHASE I: assessment of hemodynamic status and use of the magnet to temporarily suspend ICD therapies, especially shocks; identification of possible arrhythmia triggers; risk stratification in case of electrical storm (ES). PHASE II: The preparation phase includes reversal of potential arrhythmia "triggers", mild patient sedation, and patient monitoring for therapy delivery. Based on resource availability and competences, the most adequate therapeutic approach is chosen. This choice depends on whether a device specialist is readily available or not. In the case of ES in a "high-risk" patient an accelerated patient management protocol is advocated, which considers urgent ventricular tachycardia transcatheter ablation with or without mechanical cardiocirculatory support. PHASE III: Therapeutic phase is based on the use of intravenous anti-arrhythmic drugs mostly indicated in this clinical context are presented. Device interrogation is very important in this phase when sustained monomorphic VT diagnosis is confirmed, then ICD ATP algorithms, based on underlying VT cycle length, are proposed. In high-risk patients with intractable ES, intensive patient management considers MCS and transcatheter ablation. PHASE IV: The patient is hospitalized for further diagnostics and management aimed at preventing arrhythmia recurrences.

Reverse RAMP (REVRAMP) pacing: A novel anti tachycardia pacing technique.

Anti-tachycardia pacing (ATP) is frequently used to terminate ventricular tachycardia (VT), however it is not always successful and may accelerate VT requiring defibrillation. REVRAMP is a novel concept of ATP that involves delivering pacing at a faster rate than VT, but instead of abruptly terminating pacing after eight beats, pacing is gradually slowed until VT continues or normal rhythm is restored. In a pilot study we show that REVRAMP can restore normal rhythm, and that if REVRAMP is unsuccessful, VT is not accelerated.

An in-silico assessment of efficacy of two novel intra-cardiac electrode configurations versus traditional anti-tachycardia pacing therapy for terminating sustained ventricular tachycardia.

The implanted cardioverter defibrillator (ICD) is an effective direct therapy for the treatment of cardiac arrhythmias, including ventricular tachycardia (VT). Anti-tachycardia pacing (ATP) is often applied by the ICD as the first mode of therapy, but is often found to be ineffective, particularly for fast VTs. In such cases, strong, painful and damaging backup defibrillation shocks are applied by the device. Here, we propose two novel electrode configurations: "bipolar" and "transmural" which both combine the concept of targeted shock delivery with the advantage of reduced energy required for VT termination. We perform an in silico study to evaluate the efficacy of VT termination by applying one single (low-energy) monophasic shock from each novel configuration, comparing with conventional ATP therapy. Both bipolar and transmural configurations are able to achieve a higher efficacy (93% and 85%) than ATP (45%), with energy delivered similar to and two orders of magnitudes smaller than conventional ICD defibrillation shocks, respectively. Specifically, the transmural configuration (which applies the shock vector directly across the scar substrate sustaining the VT) is most efficient, requiring typically less than 1 J shock energy to achieve a high efficacy. The efficacy of both bipolar and transmural configurations are higher when applied to slow VTs (100% and 97%) compared to fast VTs (57% and 29%). Both novel electrode configurations introduced are able to improve electrotherapy efficacy while reducing the overall number of required therapies and need for strong backup shocks.

Non-transvenous ICD therapy: current status and beyond.

Subcutaneous implantable cardioverter/defibrillators (S-ICDs) have been developed to offer ICD treatment to patients without venous access to the heart and to overcome complications associated with transvenous leads, particularly lead fracture/insulation defects and endocarditis. Several studies and registries have demonstrated the feasibility and safety of S­ICD in different groups of patients. Further developments in S­ICD technology involve the combination with devices that can provide anti-bradycardia and anti-tachycardia pacing if needed. The extravascular ICD (EV-ICD) is a new system that similarly offers ICD therapy without a transvenous lead but uses a substernal instead of a subcutaneous lead to facilitate detection of ventricular fibrillation and to provide anti-tachycardia and also temporary anti-bradycardia pacing. The first animal but also clinical data on EV-ICDs have been published. This review discusses the current state, potential advantages and limitations, and future research of both S­ICD and EV-ICD.

RR interval variability in the evaluation of ventricular tachycardia and effects of implantable cardioverter defibrillator therapy.

BACKGROUND: An implantable cardioverter defibrillator (ICD) is the most reliable therapeutic device for preventing sudden cardiac death in patients with sustained ventricular tachycardia (VT). Regarding its effectiveness, targeted VT is defined based on the tachyarrhythmia cycle length. However, variations in RR interval variability of VTs may occur. Few studies have reported on VT characteristics and effects of ICD therapy according to the RR interval variability. We aimed to identify the clinical characteristics of VTs and ICD therapy effects according to the RR interval variability. METHODS: We analyzed 821 VT episodes in 69 patients with ICDs or cardiac resynchronization therapy defibrillators. VTs were classified as irregular when the difference between two successive beats was >20 ms in at least one of 10 RR intervals; otherwise, they were classified as regular. We evaluated successful termination using anti-tachycardia pacing (ATP)/shock therapy, spontaneous termination, and acceleration between regular and irregular VTs. The RR interval variability reproducibility rates were evaluated. RESULTS: Regular VT was significantly more successfully terminated than irregular VT by ATP. No significant difference was found in shock therapy or VT acceleration between the regular and irregular VTs. Spontaneous termination occurred significantly more often in irregular than in regular VT cases. The reproducibility rates of RR interval variability in each episode and in all episodes were 89% and 73%, respectively. CONCLUSIONS: ATP therapy showed greater effectiveness for regular than for irregular VT. Spontaneous termination was more common in irregular than in regular VT. RR interval variability of VTs seems to be reproducible.

Intracardiac atrial overdrive pacing as an alternative to extracorporeal membrane oxygenation in the treatment of cardiogenic shock due to drug refractory and incessant persistent junctional reciprocating tachycardia in a 7-month-old infant.

In the case of prolonged, undiagnosed persistent junctional reciprocating tachycardia in infants, compensatory mechanisms are exhausted leading to heart failure. However, when cardioverted to sinus rhythm patients often deteriorate due to cardiac output dependency on the higher rates. Extracorporeal membrane oxygenation (ECMO) is often used to stabilize their hemodynamic status. A 7-month-old female infant was admitted in cardiogenic shock due to drug refractory supraventricular tachycardia (SVT). Pharmacological cardioversion to sinus rhythm with heart rate (HR) of 90 bpm was achieved but resulted in hemodynamic deterioration and early recurrence of arrhythmia. Right atrial overdrive pacing (ODP) wire was introduced through femoral vein and allowed to override the tachycardia with 2:1 A:V block and HR of 160 bpm. ODP was continued for 24 h allowing to wean off the inotropic support. We postulate that ODP can be a safe and less invasive alternative to ECMO in stabilizing infants with cardiogenic shock due to intractable SVTs.

Successful termination of ventricular tachycardia with intrinsic anti-tachycardia pacing.

Intrinsic anti-tachycardia pacing (iATP) is a novel automated ATP algorithm that employs post-pacing interval (PPI) to design the next ATP sequence based on an analysis of the prior failed ATP sequence. A patient with hypertrophic cardiomyopathy received an implantable cardioverter-defibrillator (ICD) (Cobalt™ XT DR, Medtronic, Minneapolis, MN, USA) following an episode of syncope due to macro-reentrant ventricular tachycardia (VT) (right bundle branch block configuration, cycle length [CL] 280 ms). The VF zone was set to VTCL <300 ms and iATP therapy was prescribed before and during capacitor charging. The iATP was initiated when VT recurred 3 months later. The first attempt with an assumption of 150 ms propagation time from the pacing site to the VT circuit (9 pulses) could not reset the VT, leaving a PPI of 650 ms. A subsequent attempt involving 20 pulses with an assumption of 250 ms propagation time terminated the VT. Failure to reach the circuit is a major cause of unsuccessful ATP. In this regard, iATP is expected to have theoretical advantages over empirical and traditional ATP therapies. To the best of our knowledge, this is the first intracardiac electrogram illustrating how automated precision ATP terminates VT in a clinical setting.

ATP - A friend with benefits.

Anti-tachycardia pacing (ATP) has gained widespread acceptance to treat ventricular tachyarrhythmias and prevent implantable defibrillator shocks. A 63-year-old lady with nonischemic cardiomyopathy underwent insertion of a primary prevention biventricular implantable cardioverter defibrillator (BIV-ICD). Post implant she was found to have recurrent episodes of atrioventricular nodal re-entry tachycardia (AVNRT) based on device electrograms. In this report, we describe the use of anti-tachycardia pacing to manage this tachycardia.

Patient-by-patient basis anti-tachycardia pacing for fast ventricular tachycardia with structural heart diseases.

BACKGROUND: Anti-tachycardia pacing (ATP) delivered from an implantable device is an important tool to terminate ventricular tachycardia (VT). But its real-world efficacy for fast VT has not been fully studied. METHODS: Using the database of Nippon-storm study, effect of patient-by-patient basis ATP programming for fast VT (≥188 bpm) was assessed for the patients with structural heart diseases. Fast VTs were divided into three groups depending on heart rate (HR); Group A was 188-209 bpm, and Group-B and Group-C were 210-239 bpm and ≥240 bpm, respectively. RESULTS: During a median follow-up of 28 months, 202 fast VT episodes (209 ± 19 bpm) were demonstrated in the 85 patients. ATP terminated 151 of the 202 episodes (74.8%) in total. The success rate of the ATP was not different among the three groups: 73.3% in Group A, 80.6% in Group B, and 66.7% in Group C. ATP success rate of >50% and >70% was 77.6% and 64.7% of the patients, respectively. Left ventricular ejection fraction (LVEF) was significantly higher in the patients with rather than without successful ATP therapy, and receiver operating characteristic (ROC) analysis revealed that LVEF of 23% was the optimal cut-off value. ATP was less effective in patients taking amiodarone, but etiology of the structural heart diseases, indication of the device implantation, and all Electrocardiogram (ECG) parameters were not useful predictors for successful ATP therapy. CONCLUSIONS: ATP highly terminated fast VT with wide HR ranges in patients with structural heart diseases, and should be considered as the first-line therapy for fast VT except for patients with very low LVEF.