Comparison of novel intrinsic versus conventional antitachycardia pacing for ventricular tachycardia among implantable cardioverter-defibrillator recipients.

INTRODUCTION: Intrinsic antitachycardia pacing (iATP) is a novel automated antitachycardia pacing (ATP) that provides individual treatment to terminate ventricular tachycardia (VT). However, the clinical efficacy of iATP in comparison with conventional ATP is unknown. We aim to compare the termination rate of VT between iATP and conventional ATP in patients with implantable cardioverter-defibrillators using a unique setting of different sequential orders of both ATP algorisms. METHODS: Patients with the iATP algorithm were assigned to iATP-first and conventional ATP-first groups sequentially. In the iATP-first group, a maximum of seven iATP sequences were delivered, followed by conventional burst and ramp pacing. In contrast, in the conventional ATP-first group, two bursts and ramp pacing were initially programmed, followed by iATP sequences. We compared the success rates of VT termination in the first and secondary programmed ATP zones between the two groups. RESULTS: Fifty-eight and 56 patients were enrolled in the iATP-first and conventional ATP-first groups, and 67 and 44 VTs were analyzed in each group, respectively. At the first single ATP therapy, success rates were 64% and 70% in the iATP and conventional groups, respectively. At the end of the first iATP treatment zone, the success rate increased from 64% to 85%. Moreover, secondary iATP therapy following the failure of conventional ATPs increased the success rate from 80% to 93%. There was a significant benefit of alternative iATP for VT termination compared to secondary conventional ATP (100% vs. 33%, p = .028). CONCLUSIONS: iATP may be beneficial as a secondary therapy after failure of conventional ATP to terminate VT.

Characteristics of successful termination of atrial fibrillation by atrial antitachycardia pacing in patients with cardiac implantable electronic devices.

Asymptomatic paroxysmal atrial fibrillation (AF) is often found in patients implanted with cardiac implantable electronic devices (CIEDs). Second-generation atrial antitachycardia pacing (A-ATP) is effective in managing AF in patients implanted with CIEDs. The purpose of this study was to evaluate the efficacy and safety of A-ATP in patients implanted with CIEDs. This was a single-center retrospective study involving 91 patients (male 46 patients, mean age 74 ± 9 years) implanted with Reactive A-ATP equipped devices (84 patients with pacemakers, 6 with ICDs, and 1 with a CRT-D). The AF burden, rate of AF termination, and details of the activation of the A-ATP were analyzed in each patient. During a mean follow-up period of 21 ± 13 months, A-ATP was activated in 45 of 91 patients (49.5%). No patients had adverse events. Although the efficacy of the A-ATP varied among the patients, the median rate of AF termination was 44%. In comparison to the A-ATP start time, "0 min" had a higher AF termination rate by the A-ATP (39.4% vs. 24.4%, P = 0.011). The rate of termination by the A-ATP was high for AF with a long cycle length and a relatively regular rhythm. A-ATP successfully terminated AF episodes in some patients implanted with CIEDs. The optimal settings of the A-ATP will be determined in future studies.

Efficacy of intrinsic antitachycardia pacing for ventricular tachycardia refractory to conventional burst pacing: A case series.

Intrinsic antitachycardia pacing (iATP) is a novel automated ventricular ATP algorithm that designs ATP sequences based on the analysis of prior failed ATP. Real-world data on the efficacy and safety of iATP are lacking. Among 124 ventricular tachycardia (VT) episodes in 130 consecutive patients (mean age at implantation: 63.8 ± 14.9 years; sex, 95 male and 35 female) for whom implantable cardioverter defibrillator or cardiac resynchronization therapy defibrillator equipped with iATP algorithm was implanted, we investigated the efficacy and safety of iATP for VT refractory to conventional burst pacing. Eight patients had a total of 17 episodes of iATP therapy after failed conventional burst pacing within 11.2 ± 6.6 months of follow-up. Eleven VT episodes (64.7%) in seven patients (87.5%) were successfully terminated by iATP, and only one patient (12.5%) experienced VT acceleration. iATP might be useful for VTs refractory to conventional burst pacing with a low risk of VT acceleration.

Antitachycardia pacing at the His bundle is safer than conventional right ventricular antitachycardia pacing in a canine myocardial ischemic injury model.

INTRODUCTION: Antitachycardia pacing (ATP) is used to terminate ventricular tachycardia (VT) by delivering rapid, low energy pacing to the right ventricle (RV). Unfortunately, ATP is not effective against all VT episodes and can result in adverse outcomes, such as VT acceleration and degeneration into ventricular fibrillation (VF). Improving ATP is therefore desirable. Our objective was to compare the efficacy and safety of ATP delivered at the His bundle to traditional ATP. METHODS: Six dogs were anesthetized and pacing leads were implanted in the RV and His bundle. The left anterior descending artery was occluded for 2 h to create an ischemic injury. In a study 4-7 days later, a 128-electrode sock was placed snugly around the ventricles and VT was induced using rapid pacing. ATP was delivered from either the His bundle or RV lead, then attempted at the other location if unsuccessful. Success rates and instances of VT acceleration and degeneration into VF were calculated. RESULTS: We induced 83 runs of VT and attempted ATP 128 times. RV ATP was successful in 36% of attempts; His ATP was successful in 38% of attempts. RV ATP resulted in significantly more adverse outcomes. RV and His ATP induced VT acceleration in 9% and 3% of trains, respectively, and induced degeneration into VF in 5% and 1% of trains, respectively. CONCLUSION: His bundle ATP is safer, but not significantly more effective, than RV ATP.

Efficacy of antitachycardia pacing for electrical storms in patients with implantable defibrillators.

INTRODUCTION: Although antitachycardia pacing (ATP) is effective in terminating ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators (ICDs), the efficacy of ATP during an electrical storm (ES) and the positive impact on all-cause mortality have not been fully elucidated. METHODS AND RESULTS: From 2010 to 2012, 1570 patients who underwent ICD implantation in 48 ICD centers in Japan were enrolled in the study and prospectively followed up. Patients with long QT syndrome, Brugada syndrome, and idiopathic ventricular fibrillation were excluded. The prevalence of shocks during ESs and impact on the all-cause mortality were evaluated. During a median follow-up of 28 months, there were 127 ESs in 84 patients. Of those 127 ESs, 80 ESs (63%) in 37 patients were treated by only ATP and the remaining 47 ESs in 47 patients required at least one shock. The lower ventricular rate of the initial arrhythmia during ES (odds ratio [OR]: 1.02 per unit; 95% confidence interval [CI]: 1.00-1.04; p = .02) and narrower QRS complex (OR: 1.03 per unit; 95% CI: 1.01-1.06; p < .01) were the independent predictors of ATP success during the ES. The patients treated with ATP alone tended to have lower all-cause mortality compared to those that required shocks during the ES (log-rank p = .10). CONCLUSIONS: ATP was effective in patients suffering from ESs as it avoided painful shocks in more than half of the cases. Patients who received only ATP during ES tended to have lower mortality compared to those who received the shock.

Comparison of burst versus ramp antitachycardia pacing therapy for ventricular tachycardia: A meta-analysis.

Current guidelines recommend at least one attempt of defibrillator antitachycardia pacing (ATP) therapy, showing preference for burst therapy. The objective of this study is to compare ramp versus burst ATP therapy proportion of success and acceleration in treating spontaneous or induced ventricular tachycardia (VT). The review protocol was previously published in PROSPERO. Data synthesis and measures of heterogeneity (I2 ) was performed by CMA® software v.3 comparing proportions in both groups. Sensitivity analysis was performed as subgroup or meta-regression according to quality, clinical characteristics, and differences in design. Thirteen studies including 30,117 VT episodes in 1672 patients were analyzed. There was no significant difference in the proportion of success between burst and ramp therapy in spontaneous VT (odds ratio = 1.116; 95% confidence interval [CI] = 0.788-1.579; I2 = 89%). There was no significant difference in the proportion of success between burst and ramp therapy in induced VT (odds ratio = 0.820; 95% CI = 0.468-1.437; I2 = 93%). No significant difference was found in the proportion of acceleration between burst and ramp in spontaneous VT (odds ratio = 0.792; 95% CI = 0.476-1.317; I2 = 83%). No significant difference was found in the proportion of acceleration between burst and ramp in induced VT (odds ratio = 1.234; 95% CI = 0.802-1.898; I2 = 55%). Sensitivity analysis did not change main results. There is no difference in success or in acceleration proportion between burst or ramp ATP therapy irrespective if the VT was spontaneous or induced. Future implantable cardioverter defibrillator programming guidelines should offer both ATP therapies without preference in one of them.

Renal denervation for the treatment of ventricular arrhythmias: A systematic review and meta-analysis.

INTRODUCTION: Ventricular arrhythmias (VAs) are a major cause of morbidity and mortality in patients with heart disease. Recent studies evaluated the effect of renal denervation (RDN) on the occurrence of VAs. We conducted a systematic review and meta-analysis to determine the efficacy and safety of this procedure. METHODS AND RESULTS: A systematic search of the literature was performed to identify studies that evaluated the use of RDN for the management of VAs. Primary outcomes were reduction in the number of VAs and implantable cardioverter-defibrillator (ICD) therapies. Secondary outcomes were changes in blood pressure and renal function. Ten studies (152 patients) were included in the meta-analysis. RDN was associated with a reduction in the number of VAs, antitachycardia pacing, ICD shocks, and overall ICD therapies of 3.53 events/patient/month (95% confidence interval [CI] = -5.48 to -1.57), 2.86 events/patient/month (95% CI = -4.09 to -1.63), 2.04 events/patient/month (95% CI = -2.12 to -1.97), and 2.68 events/patient/month (95% CI = -3.58 to -1.78), respectively. Periprocedural adverse events occurred in 1.23% of patients and no significant changes were seen in blood pressure or renal function. CONCLUSIONS: In patients with refractory VAs, RDN was associated with a reduction in the number of VAs and ICD therapies, and was shown to be a safe procedure.

Efficacy of antitachycardia pacing alert by remote monitoring of implantable cardioverter-defibrillators for out-of-hospital electrical storm.

BACKGROUND: Remote monitoring (RM) has been shown to reduce all-cause mortality in patients with implantable cardioverter-defibrillators or cardiac resynchronization therapy defibrillators (ICD/CRT-D). Not all devices transmit an alert for antitachycardia pacing (ATP) therapy, and it is unknown whether differences of RM alert affect the outcomes of electrical storm (ES). METHODS: We enrolled 42 patients with ICD/CRT-D whose out-of-hospital ES were detected by RM between 2013 and 2020. We divided their 54 episodes into two groups (ATP-alert-on; 22, ATP-alert-off; 32), and clinical outcomes were compared between the two groups. RESULTS: In 35 of 54 episodes of ES, ventricular tachycardia (VT) could be terminated within 24 h of ES onset just by ATP (ATP-alert-on: 14, ATP-alert-off: 21); however, many patients subsequently received shock delivery for VT. Among the 35 episodes, only in ATP-alert-on group, seven patients were prompted to visit our hospital without ICD shock through confirmation of ES by ATP-alert. Episodes that led to shock delivery 24 h or longer after the ES onset were significantly less common in the ATP-alert-on group (ATP-alert-on: 1/14, ATP-alert-off: 9/21, p = .03). Although there were no significant differences in the number of shock deliveries between episodes in the two groups, the number of ATP deliveries were significantly fewer in the ATP-alert-on group (12[7-26] vs. 29[16-53] in ATP-alert-off group, p = .03). Multivariate logistic regression analyses showed that the only ATP-alert significantly reduced ATP deliveries (HR = 0.14, 95%CI = 0.04-0.57, p = .003). CONCLUSION: Remote monitoring with an ATP-alert function during electrical storm may reduce appropriate ICD therapy through prompting early review.

Generic ICD programming and outcomes.

INTRODUCTION: Generic ICD programming, where shock-reduction programming is extrapolated from trials of one manufacturer to another, may reduce non-essential ICD therapies beyond that seen in randomized trials. However, the benefits and risks are unknown. The purpose of this retrospective cohort study was to evaluate the impact of a standardized programming protocol, based on generic programming, across manufacturers. METHODS: We included all new ICDs in a single center (2009-2019). In 2013 a standardized programming protocol based on generic programming was introduced, incorporating high detection rates (200 bpm for primary prevention) and long detection (30/40 or equivalent in VF zone) for all patients. Patients were classified into three groups based on implant programming: pre-guideline (PS), post-guideline and guideline compliant (GC) and post-guideline but not guideline compliant (NGC). The end-points were the first occurrence of any device therapy (ATP or shock), ICD shock, syncope and all-cause mortality. Survival analysis was used to evaluate outcomes. RESULTS: 1003 patients were included (mean follow-up 1519 ± 1005 days). In primary prevention patients (n = 583) freedom from ICD therapy (91.5% vs. 73.6%, p < .001) or shock (94.7% vs 84.8%, p = .02) were significantly higher in GC compared to PS patients, without significant increase in syncope or mortality. In secondary prevention patients (n = 420) freedom from any ICD therapy or any shock were non-significantly higher in GC compared to PS patients, without an increase in syncope or mortality. CONCLUSIONS: In primary prevention patients a standardized programming protocol, incorporating generic programming, reduced the burden of ICD therapy without an increase in adverse outcomes.

Predictors of appropriate shock after generator replacement in patients with an implantable cardioverter defibrillator.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) are indicated for the primary prevention of sudden cardiac death in patients with reduced left ventricular ejection fraction (LVEF). The ongoing risk/benefit profile of an ICD at generator replacement is unknown. This study aimed to identify predictors of appropriate ICD shocks and therapies after first ICD generator replacement, and its procedure-related complications. METHODS: We conducted a multicenter, retrospective cohort study including patients with primary prevention ICDs who underwent generator replacement between April 2005 and July 2015 at three Canadian centers. The primary and secondary outcomes were appropriate ICD shock and any appropriate ICD therapy, respectively. Procedure-related complication rates were also reported. RESULTS: Of the 219 patients in the cohort, 61 (28%) experienced an appropriate shock while 40 (18%) experienced appropriate antitachycardia pacing over a median follow up of 2.2 years. Independent predictors of appropriate ICD shocks included: LVEF at time of replacement (adjusted odds ratio [OR] 0.4 per 10% increase in LVEF, P < .001), a history of appropriate ICD shocks prior to replacement (OR 4.9, P < .001), and a history of inappropriate ICD shocks (OR 4.2, 95%, P < .002). Similar predictors were identified for the secondary outcome of any appropriate ICD therapy. Device-related complications were reported in 25 (11%) patients, with 1 (0.5%) resulting in death, 14 (6.3%) requiring site re-operation, and 6 (2.7%) requiring cardiac surgical management. CONCLUSION: Not all primary prevention ICD patients undergoing generator replacement will require appropriate device therapies afterwards. Generator replacement is associated with several risks that should be weighed against its anticipated benefit. A comprehensive assessment of the risk-benefit profile of patients undergoing generator replacement is warranted.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients: Executive summary.

Guidelines for the implantation of cardiac implantable electronic devices (CIEDs) have evolved since publication of the initial ACC/AHA pacemaker guidelines in 1984 [1]. CIEDs have evolved to include novel forms of cardiac pacing, the development of implantable cardioverter defibrillators (ICDs) and the introduction of devices for long term monitoring of heart rhythm and other physiologic parameters. In view of the increasing complexity of both devices and patients, practice guidelines, by necessity, have become increasingly specific. In 2018, the ACC/AHA/HRS published Guidelines on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay [2], which were specific recommendations for patients >18 years of age. This age-specific threshold was established in view of the differing indications for CIEDs in young patients as well as size-specific technology factors. Therefore, the following document was developed to update and further delineate indications for the use and management of CIEDs in pediatric patients, defined as ≤21 years of age, with recognition that there is often overlap in the care of patents between 18 and 21 years of age. This document is an abbreviated expert consensus statement (ECS) intended to focus primarily on the indications for CIEDs in the setting of specific disease/diagnostic categories. This document will also provide guidance regarding the management of lead systems and follow-up evaluation for pediatric patients with CIEDs. The recommendations are presented in an abbreviated modular format, with each section including the complete table of recommendations along with a brief synopsis of supportive text and select references to provide some context for the recommendations. This document is not intended to provide an exhaustive discussion of the basis for each of the recommendations, which are further addressed in the comprehensive PACES-CIED document [3], with further data easily accessible in electronic searches or textbooks.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

Increasing atrial fibrillation: What is the cause?

A 72-year-old woman with a history of paroxysmal atrial fibrillation (AF) and sinus node dysfunction is seen in clinic for routine follow-up.

Characteristics of ventricular tachyarrhythmias and their susceptibility to antitachycardia pacing termination in patients with ischemic and nonischemic cardiomyopathy: A patient-level meta-analysis of three large clinical trials.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) reduce all-cause mortality among cardiomyopathy patients. Whether or not antitachycardia pacing (ATP) is equally effective in ischemic (ICM) and nonischemic (NICM) cardiomyopathy patients remains poorly understood. We describe the distribution of monomorphic (MVT) and non-monomorphic (polymorphic ventricular tachycardia/ventricular fibrillation [PVT/VF]) ventricular tachyarrhythmias among ICM and NICM primary prevention patients. METHODS: This patient-level meta-analysis included primary prevention patients from the Shock-Less (n = 3519), PainFree SST (n = 1917), and PREPARE (n = 690) studies. Distribution of MVT and PVT/VF events were compared with χ2 tests. ATP success was estimated using a generalized estimating equation model to correct for multiple episodes for a patient between cohorts for slow (≥320 ms) and fast (240-310 ms) MVTs. RESULTS: Among 6126 patients, 714 (29% NICM, age 66 ± 13 years, female 18%, EF = 29 ± 12%) had a total of 4444 treated ventricular tachyarrhythmia episodes. The rate of individuals treated for MVT or PVT/VF was comparable between ICM (11.9%) and NICM (11.2%) over 21 ± 10 months. In addition, the distribution of MVT (76% ICM vs. 71% NICM) and PVT/VF (15% ICM vs. 20% NICM) was not significantly different (p = .28). Among MVT episodes, the average tachycardia cycle lengths (332 ± 58 ms ICM vs. 313 ± 40 ms NICM; p = .27) were similar, as was the likelihood of ATP-associated termination (74.6% ICM vs. 76.4% NICM; p = .58). Overall, ATP success was higher for slow (≥320 ms) MVT versus faster (240-310 ms) episodes (84.1% vs. 69%; p < .001). CONCLUSION: In a large cohort of primary prevention ICD patients, ICM and NICM patients have similar rates and proportions of MVT and PVT/VF episodes. ATP-associated termination of MVT was comparable between the two groups.

Do ICD diagnostics predict failure of ventricular tachycardia response to antitachycardia pacing and need for shock?

BACKGROUND: Among heart failure patients with implantable cardioverter defibrillators (ICDs), monomorphic ventricular tachycardia (MMVT) failing antitachycardia pacing (ATP) and terminated by shock renders higher mortality as compared to MMVT terminated by ATP only. It is unknown if the higher mortality in ATP failure reflects decompensated heart failure. OBJECTIVE: It was the purpose of the present study to determine if ICD heart failure diagnostics can predict the failure of ATP and the need to shock to terminate MMVT. METHODS: This was a single-center retrospective review of 103 consecutive patients with Medtronic ICDs who had MMVT and received ICD therapy. Heart failure diagnostics preceding each MMVT event were reviewed including atrial fibrillation burden, patient activity, night heart rate, heart rate variability, Optivol® fluid index, and MMVT heart rate. RESULTS: A total of 452 MMVT events were analyzed, of which 23% required shock. Compared to MMVT that responded to ATP, MMVT that failed ATP and required shock had significantly faster heart rates and higher atrial fibrillation burden. Patient activity, night heart rate, heart rate variability, and OptiVol® fluid index were similar between ATP responsive MMVT events and those that failed ATP. In a multivariate analysis adjusting for baseline characteristics, higher atrial fibrillation burden and lower patient activity were associated with ATP failure and shock termination. CONCLUSION: Device diagnostics associated with decompensated heart failure identified MMVT events that failed ATP and necessitated shock.

2019 HRS/EHRA/APHRS/LAHRS focused update to 2015 expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing.

The 2015 HRS/EHRA/APHRS/SOLAECE Expert Consensus Statement on Optimal Implantable Cardioverter-Defibrillator Programming and Testing provided guidance on bradycardia programming, tachycardia detection, tachycardia therapy, and defibrillation testing for implantable cardioverter-defibrillator (ICD) patient treatment. The 32 recommendations represented the consensus opinion of the writing group, graded by Class of Recommendation and Level of Evidence. In addition, Appendix B provided manufacturer-specific translations of these recommendations into clinical practice consistent with the recommendations within the parent document. In some instances, programming guided by quality evidence gained from studies performed in devices from some manufacturers was translated such that this programming was approximated in another manufacturer's ICD programming settings. The authors found that the data, although not formally tested, were strong, consistent, and generalizable beyond the specific manufacturer and model of ICD. As expected, because these recommendations represented strategic choices to balance risks, there have been reports in which adverse outcomes were documented with ICDs programmed to Appendix B recommendations. The recommendations have been reviewed and updated to minimize such adverse events. Notably, patients who do not receive unnecessary ICD therapy are not aware of being spared potential harm, whereas patients in whom their ICD failed to treat life-threatening arrhythmias have their event recorded in detail. The revised recommendations employ the principle that the randomized trials and large registry data should guide programming more than anecdotal evidence. These recommendations should not replace the opinion of the treating physician who has considered the patient's clinical status and desired outcome via a shared clinical decision-making process.

Arrhythmic episodes in patients implanted with a cardioverter-defibrillator - results from the Prospective Study on Predictive Quality with Preferencing PainFree ATP therapies (4P).

BACKGROUND: Little is known about the ICD performance using enhanced detection algorithms in unselected, non-trial patients. Performance of recent generation ICD equipped with SmartShock™ technology (SST) for detection and conversion of ventricular tachyarrhythmias (VTA) was investigated. METHODS: 4P was a prospective, multicenter, observational study conducted in 10 Swiss implanting centers. Patients with a Class I indication according to international guidelines were included and received an ICD with SST. ICD discrimination capability was assessed by evaluating SST performance; therapy efficacy was assessed by rate of VTA conversions by ATP and by rescue shocks. RESULTS: Overall, 196 patients were included in the analysis with a mean duration of follow-up of 27.7 months (452 patient-years of observation). Patient-specific rather than recommended programming was preferred. Device-detected episodes were frequent (5147 episodes in 146 patients, 74.5%). In 44 patients (22.4%), 1274 episodes were categorized as VTA; only 215 episodes were symptomatic. ATP was the first-line therapy and highly effective (99.9% success rate at the episode level, 100.0% at the patient level). Rescue shocks were rare (66 episodes in 28 patients); 7 shocks in 5 patients (2.6%) were inappropriate. Death and hospitalization rates were low. CONCLUSIONS: In a cohort of non-trial, unselected ICD patients, VTA episodes were frequent. The 4P results confirm the robustness of VTA detection by SST and the effectiveness of ATP treatment, hence limiting overall ICD shock burden.

Clinical predictors of antitachycardia pacing response in implantable cardioverter defibrillator patients.

BACKGROUND: Antitachycardia pacing (ATP) provides safe and painless termination of reentrant ventricular arrhythmias in patients with implantable cardioverter defibrillator (ICDs), improving their quality of life. Established predictors of ATP responsiveness are not well known; only longer ventricular tachycardia (VT) cycle length and higher ejection fraction have been found to predict ATP success. OBJECTIVE: To investigate clinical and ECG predictors of ATP response in ICD patients with monomorphic VT. METHODS: The ICD clinic database was searched for monomorphic VT events requiring ICD therapy in patients with ischemic or non-ischemic cardiomyopathy. Each patient's first ICD encounter for VT was assessed. Patient demographics, clinical characteristics, VT rate, and ATP responsiveness (always, sometimes, and never successful) were recorded. An ECG was analyzed for QRS morphology and duration. Data was assessed for predictors of ATP responsiveness. RESULTS: In 527 patients, characteristics associated with always successful ATP included ACE-I/ARB therapy and slower VT rate (never successful ATP 197 ± 28 bpm, sometimes successful ATP 190 ± 27 bpm, always successful ATP 183 ± 22 bpm, P < .0001). Secondary prevention indication, amiodarone therapy, and longer QRS duration were associated with ATP failure. After multivariate analysis, only faster VT rate and amiodarone therapy were predictive of ATP failure. CONCLUSIONS: Neither QRS morphology nor duration was predictive of ATP success. Slower VT rate was predictive of repeated ATP responsiveness. Amiodarone therapy, which is known to increase VT cycle length, interestingly was associated with ATP failure for unclear reasons. More individualized and possibly more aggressive ATP programming may be warranted in patients on amiodarone.

Safety and efficacy of anti-tachycardia pacing in patients with hypertrophic cardiomyopathy implanted with an ICD.

BACKGROUND: In hypertrophic cardiomyopathy (HCM) patients implanted with an implantable cardioverter defibrillator (ICD), clinical outcomes of antitachycardia pacing (ATP) have been poorly explored. In a retrospective analysis of a cohort of consecutive HCM patients implanted with an ICD, we aimed to assess the efficacy, safety, and clinical value of ATP. METHODS: The cohort of HCM patients implanted with a transvenous ICD and followed in our center was assessed for device intervention from implantation to last clinical follow-up. RESULTS: Overall 77 patients (45 males; mean age: 46 ± 16 years) were analyzed. After 67 ± 41 months, 24 patients had 49 ventricular tachycardia/fibrillation (VT/VF) appropriately treated (5.8% per year). Among 39 monomorphic VTs, ATP was effective in 27 (success rate: 69%). Mean time from VT onset to ATP delivery was 9.1 ± 4.9 s. The only clinical variable improving ATP success was use of beta-blockers (81% vs 50%; P = .04). Out of 12 ineffectively treated VTs, one was immediately shocked, four self-terminated after 18 ± 12 s, and seven (18%) were accelerated to a new VT. ATP was also delivered for 27 of 42 inappropriately detected episodes and induced two de novo VTs (7%). In the per patient analysis, 14 out 77 (18%) patients had one or more appropriate and effective ATP (3.4% per year), and only six (8%; 1.4% per year) received more than one ATP. CONCLUSION: ATP is moderately effective for the treatment of monomorphic VTs in HCM patients. However, the rate of appropriate ATP therapies is low, ATP is often prematurely delivered, and ATP-induced arrhythmia degeneration is of concern.