Multicenter automatic defibrillator implantation trial: reduce inappropriate therapy (MADIT-RIT): background, rationale, and clinical protocol

Rationale and study protocol for the BRITISH randomized trial (Using cardiovascular magnetic resonance identified scar as the benchmark risk indication tool for implantable cardioverter defibrillators in patients with nonischemic cardiomyopathy and severe systolic heart failure)

BACKGROUND

For patients with nonischemic cardiomyopathy (NICM), current guidelines recommend implantable cardioverter defibrillators (ICD) when left ventricular ejection fraction (LVEF) is ≤35%, but the DANISH trial failed to confirm that ICDs reduced all-cause mortality for such patients. Circumstantial evidence suggests that scar on CMR is predictive of sudden and arrhythmic death in this population. The presence of myocardial scar identified by cardiac magnetic resonance imaging (CMR) in patients with NICM and an LVEF ≤35% might identify patients at higher risk of sudden arrhythmic death, for whom an ICD is more likely to reduce all-cause mortality.

METHODS/DESIGN

The BRITISH trial is a prospective, multicenter, randomized controlled trial aiming to enrol 1,252 patients with NICM and an LVEF ≤35%. Patients with a nonischemic scar on CMR will be randomized to either: (1) ICD, with or without cardiac resynchronization (CRT-D), or (2) implantable loop recorder (ILR) or cardiac resynchronization (CRT-P). Patients who are screened for the trial but are found not to be eligible, predominantly due to an absence of scar or those who decline to be randomized will be enrolled in an observational registry. The primary endpoint is all-cause mortality, which we plan to assess at 3 years after the last participant is randomized. Secondary endpoints include clinical outcomes, appropriate and inappropriate device therapies, symptom severity and well-being, device-related complications, and analysis of the primary endpoint by subgroups with other risk markers.

CONCLUSION

The BRITISH trial will assess whether the use of CMR-defined scar to direct ICD implantation in patients with NICM and an LVEF ≤35% is associated with a reduction in mortality.

Tachycardia Therapy Outcomes of Ischemic Versus Nonischemic Cardiomyopathy on Cardiac Resynchronization Therapy: A Propensity Score-matched Analysis

Objective

This investigation aimed to investigate differences between dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM) patients treated with cardiac resynchronization therapy with defibrillator (CRT-D) for tachycardia therapy-related outcomes as well as mortality during follow-up of at least 1 year.

Methods

Seventy-eight patients with DCM (n = 42) and ICM (n = 36) with implantation or upgradation to CRT-D were included in this study and analyzed for incidence of non-sustained ventricular tachycardia (NSVT), non-sustained ventricular fibrillation (NSVF), defibrillator therapies, anti-tachycardia pacing (ATP), and mortality.

Results

DCM was the underlying etiology in 42 (53.84%) and ICM in 36 (46.15%). Time to first therapy was numerically longer in DCM than in ICM (9.5 ± 2.4 vs. 7.1 ± 3.2; P-value = 0.088). DCM patients had significantly higher therapy-free survival and mortality compared with ICM patients (OR (95%CI): 0.238 (0.155-0.424); log-rank P = 0.017) and (OR (95% CI): 0.612 (0.254-0.924); log-rank P = 0.029). ICM (HR (95%CI): 0.529 (0.243-0.925); P-value = 0.014) CAD (HR (95%CI): 0.326 (0.122-0.691): P-value = 0.003), and NSVT (HR (95%CI): 0.703 (0.513-0.849): P-value = 0.005) were demonstrated as independent predictors of the primary endpoint of appropriate therapy in CRT-D and ICM (HR (95%CI): 0.421 (0.321-0.524); P-value = 0.037), chronic kidney disease (CKD; HR (95%CI): 0.289 (0.198-0.380); P-value = 0.013), and CAD (HR (95%CI): 0.786 (0.531-0.967); P-value = 0.003) were predictors of mortality.

Conclusion

The clinical course of ICM and DCM cohorts who were treated with CRT-D differs significantly during follow-up, with increased tachycardia therapy and increased incidence of mortality in ICM patients.

The ATLAS Randomised Clinical Trial: What do the Superiority Results Mean for Subcutaneous ICD Therapy and Sudden Cardiac Death Prevention as a Whole?

This review sets out the key evidence comparing subcutaneous ICDs (S-ICDs) and transvenous ICDs and uses it to empower clinical cardiologists and those who implant ICDs to make optimum patient selections for S-ICD use. The evidence demonstrates that clinical trials performed until recently have proven the performance of S-ICDs. However, the latest data now available from the ATLAS randomised controlled trial have added new insights to this body of evidence. ATLAS demonstrates the superiority of S-ICDs over transvenous ICDs regarding lead-related complications, findings that point to promising opportunities for patients who are at risk of sudden cardiac death.

Primary results from the Japanese Heart Failure and Sudden Cardiac Death Prevention Trial (HINODE)

Aims

The HINODE study aimed to analyse rates of mortality, appropriately treated ventricular arrhythmias (VA), and heart failure in Japanese patients and compared with those in Western patients.

Methods and results

After treatment decisions following contemporary practice in Japan, patients were prospectively enrolled into four cohorts: (i) internal cardioverter‐defibrillator (ICD), (ii) cardiac resynchronization therapy (CRT) defibrillator (CRT‐D), (iii) standard medical therapy (‘non‐device’: ND), or (iv) pacing (indicated for CRT; received pacemaker or CRT pacing). Cohorts 1–3 required a left ventricular ejection fraction ≤35%, a history of heart failure, and a need for primary prevention of sudden cardiac death based on two to five previously identified risk factors. Endpoint outcomes were adjudicated by the independent committees. ICD and CRT‐D cohorts, considered as high‐voltage (HV) cohorts, were pooled for Kaplan–Meier analysis and propensity‐matched to Multicenter Automatic Defibrillator Implantation Trial‐Reduce Inappropriate Therapy (MADIT‐RIT) arm B and C patients. The study enrolled 354 patients followed for 19.6 ± 6.5 months, with a minimum of 12 months. Propensity‐matched HV cohorts showed comparable VA (P = 0.61) and mortality rates (P = 0.29) for HINODE and MADIT‐RIT. The ND cohort presented a high crossover rate to ICD therapy (6.1%, n = 7/115), and the CRT‐D cohort showed elevated mortality rates. The pacing cohort revealed that patients implanted with pacemakers had higher mortality (26.0%) than those with CRT‐Pacing (8.4%, P = 0.05).

Conclusions

The mortality and VA event rates of landmark trials are applicable to patients with primary prevention in Japan. Patients who did not receive guideline‐indicated CRT devices had poor outcomes.

Multiparameter Monitoring with a Wearable Cardioverter Defibrillator

A wearable cardioverter-defibrillator (WCD) is a temporary treatment option for patients at high risk for sudden cardiac death (SCD) and for patients who are temporarily not candidates for an implantable cardioverter defibrillator (ICD). In addition, the need for telemedical concepts in the detection and treatment of heart failure (HF) and its arrhythmias is growing. The WCD has evolved from a shock device detecting malignant ventricular arrhythmias (VA) and treating them with shocks to a heart-failure-monitoring device that captures physical activity and cardioacoustic biomarkers as surrogate parameters for HF to help the treating physician surveil and guide the HF therapy of each individual patient. In addition to its important role in preventing SCD, the WCD could become an important tool in heart failure treatment by helping prevent HF events by detecting imminent decompensation via remote monitoring and monitoring therapy success.

Rationale and design of the HINODE study: Heart failure indication and sudden cardiac death prevention trial Japan

BACKGROUND

Randomized trials in Western countries have provided evidence that prophylactic implantable cardioverter-defibrillator (ICD) therapy reduces mortality in heart failure (HF) patients with reduced left ventricular ejection fraction. However, the risk of life-threatening ventricular arrhythmias in Japanese HF patients sharing similar risk factors is still unknown.

METHODS

The Heart Failure Indication and Sudden Cardiac Death Prevention Trial Japan trial (NCT03185832) is a prospective, multicenter registry designed to collect data on ventricular arrhythmia, HF events, and mortality in Japanese HF patients. Japanese patients with HF and 2-5 predefined risk factors who were indicated for cardiac device implantation based on European Society of Cardiology guidelines were enrolled in four treatment arms: implantable cardioverter-defibrillator (ICD), cardiac resynchronization therapy defibrillator (CRT-D), HF pacing (PA; Pacemaker and cardiac resynchronization pacemaker), and nondevice (ND) cohorts and followed for a minimum of 12 months. Since it is anticipated that some baseline patient characteristics and risk factors will differ significantly from those reported in predominantly Western populations, event rates will be compared to a propensity-matched population from the MADIT RIT trial. Primary endpoints are composite rates of first appropriately treated ventricular arrhythmias (VA) or/and life-threatening VA symptoms for the ICD and CRT-D cohorts. For nondevice and PA cohorts, the primary outcome is all-cause mortality.

CONCLUSIONS

The Heart Failure Indication and Sudden Cardiac Death Prevention Trial Japan is a large prospective multicenter registry with defined device treatment cohorts and will provide data for risk stratification for cardiovascular events in Japanese HF patients.

Utility of cardiovascular implantable electronic device-derived patient activity to predict clinical outcomes

BACKGROUND

The role of cardiovascular implantable electronic device (CIED)-derived activity to predict implantable cardioverter-defibrillator (ICD) therapy or death is not known.

OBJECTIVE

We aimed to assess CIED-derived activity to predict clinical outcomes.

METHODS

In 1500 patients enrolled in MADIT-RIT, CIED-derived patient activity was acquired daily, then averaged for the first 30 days following randomization to predict inappropriate/appropriate therapy or death. Kaplan-Meier analysis and Cox proportional regression models were used to evaluate inappropriate/appropriate therapy, heart failure, or death by 30-day CIED-derived patient activity quintiles.

RESULTS

There were 1463 patients with CIED activity data (98%). Patients in the highest quintile (Q5) of activity (more active) had the highest rate of inappropriate therapy, 21% at 2 years, as compared to 7%-11% in the other 4 quintiles (P < .001), a 1.75 times higher risk (95% confidence interval [CI]: 1.23-2.50, P = .002). However, patients in the lowest quintile of activity (Q1, 1 hour/day) had the highest risk of mortality, 15% in 2 years, as compared to Q2-3 (1-2 hours/day, 8%-7% mortality), and Q4-5 (>2 hours/day, 2%-3% mortality) (P < .001). Patients with the lowest level of activity (Q1) had a 2.02 times higher risk of mortality (95% CI: 1.21-3.38, P = .007), and they had an 82% higher risk of heart failure hospitalization (95% CI: 1.28-2.57, P = .001).

CONCLUSIONS

High CIED-derived 30-day median patient activity predicted inappropriate therapy, while low patient activity predicted mortality and heart failure in ICD and cardiac resynchronization therapy with defibrillator patients enrolled in MADIT-RIT. Device-derived activity assessment could serve as a useful predictor of outcomes.

Systolic Blood Pressure and Risk for Ventricular Arrhythmia in Patients With an Implantable Cardioverter Defibrillator

Low systolic blood pressure (SBP) was previously suggested to be a marker for heart failure and mortality in patients with low left ventricular ejection fraction. We aimed to explore the association of SBP on risk of ventricular tachyarrhythmias (VTA) and atrial arrhythmias as well as appropriate and inappropriate Implantable Cardioverter Defibrillator (ICD) therapy. The study population comprised 1,481 of 1,500 (99%) patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial - Reduce Inappropriate Therapy trial. Multivariate Cox proportional hazards regression modeling was used to identify the association of baseline SBP (recorded prior to ICD implantation) with the risk of VTA > 170 beats/min during follow-up (primary end point) and atrial arrhythmia, appropriate and inappropriate ICD therapy, hospitalization and death (secondary end points). SBP was dichotomized at 120 mm Hg (approximate mean and median) and was also assessed as a continuous measure. Multivariate analysis showed that each 10 mm Hg decrement in SBP was associated with corresponding 11% increased risk for VTA (p = 0.008). Low SBP (≤120 mm Hg) was associated with a significant 58% (p = 0.002) increased risk for VTA ≥170 beats/min; 53% (p = 0.019) increased risk for VTA ≥200 beats/min; and 65% (p = 0.001) increased risk for appropriate ICD therapy, as compared with SBP >120 mm Hg. Low SBP was not associated with increased risk of atrial arrhythmias, and inappropriate ICD therapy. In conclusion, in MADIT-RIT, SBP (≤120 mm Hg) predicted higher rates of VTA. These findings suggest that SBP may be utilized for VTA risk stratification in candidates for primary ICD therapy.

Reassessing the role of antitachycardia pacing in fast ventricular arrhythmias in primary prevention implantable cardioverter-defibrillator recipients: Results from MADIT-RIT

BACKGROUND

In Multicenter Automatic Defibrillator Implantation Trial - Reduce Inappropriate Therapy (MADIT-RIT), high-rate cutoff (arm B) and delayed therapy (arm C) reduced the risk of inappropriate implantable cardioverter-defibrillator (ICD) interventions when compared with conventional programming (arm A); however, appropriate but unnecessary therapies were not evaluated.

OBJECTIVE

The purpose of this study was to assess the value of antitachycardia pacing (ATP) for fast ventricular arrhythmias (VAs) ≥ 200 beats/min in patients with primary prevention ICD.

METHODS

We compared ATP only, ATP and shock, and shock only rates in patients in MADIT-RIT treated for VAs ≥ 200 beats/min. The only difference between these randomized groups was the time delay between ventricular tachycardia detection and therapy (3.4 seconds vs 4.9 seconds vs 14.4 seconds).

RESULTS

In arm A, 11.5% patients had events, the initial therapy was ATP in 10.5% and shock in 1%, and the final therapy was ATP in 8% and shock in 3.5%. In arm B, 6.6% had events, 4.2% were initially treated with ATP and 2.4% with shock, and the final therapy was ATP in 2.8% and shock in 3.8%. In arm C, 4.7% had events, 2.5% were initially treated with ATP and 2.3% with shock, and the final therapy was ATP in 1.4% and shock in 3.3%. The final shock rate was similar in arm A vs arm B (3.5% vs 3.8%; P = .800) and in arm A vs arm C (3.5% vs 3.3%; P = .855) despite the marked discrepancy in initial ATP therapy utilization.

CONCLUSION

In MADIT-RIT, there was a significant reduction in ATP interventions with therapy delays due to spontaneous termination, with no difference in shock therapies, suggesting that earlier interventions for VAs ≥ 200 beats/min are likely unnecessary, leading to an overestimation of the value of ATP in primary prevention ICD recipients.

Circadian variation and seasonal distribution of implantable defibrillator detected new onset atrial fibrillation

BACKGROUND

We aimed to characterize the hourly, daily, and seasonally variations in the detection of new atrial fibrillation (AF) in heart failure patients implanted with a defibrillator.

METHODS

In 1309 patients enrolled in MADIT-RIT without AF at baseline, atrial arrhythmia data were analyzed from device interrogations. The circadian, weekly, and seasonal distribution of device detected AF was evaluated. The morning period was defined as 06:00-11:59, afternoon as 12:00-16:59, evening as 17:00-22:59, and the nighttime as 23:00-05:59.

RESULTS

During 17 months of follow-up, 66 (5%) patients developed new device-detected AF. AF patients were less likely to have ischemic cardiomyopathy and were more likely to have received an implantable cardioverter defibrillator rather than a cardiac resynchronization therapy with defibrillator. The highest number of AF occurred during the evening hours (25 patients [38%]) followed by a second peak in AF detection during the afternoon hours (21 patients [32%]). Importantly during the nighttime, new AF occurred only in three patients (4%). In comparison with the nighttime period, the odds ratio (OR) of developing AF during the evening time period was 8.5-fold higher (95% CI 7.3-9.7, P < .01). Detection of AF during the spring and winter seasons accounted for 67% of all new device-detected AF.

CONCLUSIONS

There is diurnal and seasonal variation in new onset AF. A double peak in the incidence of AF is observed during the afternoon and evening hours, and during the spring and winter seasons. This information may be useful when deciding when to screen at-risk patients for new AF.

Driving Restrictions and Early Arrhythmias in Patients Receiving a Primary-Prevention Implantable Cardioverter-Defibrillator (DREAM-ICD) Study

BACKGROUND

Current guidelines recommend 4 weeks of private driving restriction after implantation of a primary-prevention implantable cardioverter-defibrillator (ICD). These driving restrictions result in significant inconvenience and social implications. Advances in medical treatment and ICD programming have lowered the overall rate of device therapies. The objective of this study was to assess the incidence of ICD therapies at 30, 60, and 180 days after implantation.

METHODS

Driving Restrictions and Early Arrhythmias in Patients Receiving a Primary-Prevention Implantable Cardioverter-Defibrillator (DREAM-ICD) was a retrospective cohort study conducted at 2 Canadian university centres enrolling patients with new implantation of a primary-prevention ICD. Device programming was standardised according to current guidelines. A total of 803 patients were enrolled.

RESULTS

The cumulative rates of appropriate ICD therapies at 30, 60, and 180 days were 0.12%, 0.50%, and 0.75%, respectively. There was no syncope during the first 6 months. The median duration to the first appropriate ICD therapy was 208 (range 23-1109) days after implantation. The rate of inappropriate ICD therapies at 30 days was only 0.2%. Overall, < 13.6% of all appropriate ICD therapies occurred within the first 6 months after implantation.

CONCLUSIONS

The rate of appropriate ICD therapies within the first 30 days after device insertion is extremely low in contemporary primary prevention cohorts with guideline-concordant device programming. There was no increased risk for ventricular arrhythmia early after ICD insertion. The results of DREAM-ICD suggest the need for a revision of the existing driving restrictions for primary-prevention ICD recipients.

Relation between resting heart rate and the risk of ventricular tachyarrhythmias in MADIT-RIT

AIMS

To explore the association between resting heart rate (RHR) and ventricular tachyarrhythmias (VTA) events among patients who were enrolled in MADIT-RIT.

METHODS AND RESULTS

Multivariate Cox proportional hazards regression modelling was employed to evaluate the association between baseline RHR [dichotomized at the lower quartile (≤63 b.p.m.) and further assessed as a continuous measure] and the risk for any VTA, fast VTA (>200 b.p.m.), and appropriate implantable cardioverter-defibrillator (ICD) therapy, among 1500 patients who were enrolled in MADIT-RIT. Kaplan-Meier survival analysis showed that at 2 years of follow-up the rate of any VTA was significantly lower among patients with low baseline RHR (≤63 b.p.m.) as compared with faster RHR (11% vs. 19%, respectively; P = 0.001 for the overall difference during follow-up). Similar results were shown for the association with the rate of fast VTA (8% vs. 14%, respectively; P = 0.016), and appropriate ICD therapy (10% vs. 18%, respectively; P = 0.004). Multivariate analysis, after adjustment for medical therapy, showed that low baseline RHR was associated with a significant 45% (P = 0.002) reduction in the VTA risk as compared with faster baseline RHRs. When assessed as a continuous measure, each 10 b.p.m. decrement in RHR was associated with a corresponding 13% (P = 0.014) reduction in the VTA risk.

CONCLUSION

In MADIT-RIT, low RHR was independently associated with a lower risk for life-threatening arrhythmic events. These findings suggest a possible role for RHR for improved selection of candidates for ICD therapy.

Handling of Ventricular Fibrillation in the Emergency Setting

Ventricular fibrillation (VF) and sudden cardiac death (SCD) are predominantly caused by channelopathies and cardiomyopathies in youngsters and coronary heart disease in the elderly. Temporary factors, e.g., electrolyte imbalance, drug interactions, and substance abuses may play an additive role in arrhythmogenesis. Ectopic automaticity, triggered activity, and reentry mechanisms are known as important electrophysiological substrates for VF determining the antiarrhythmic therapies at the same time. Emergency need for electrical cardioversion is supported by the fact that every minute without defibrillation decreases survival rates by approximately 7%–10%. Thus, early defibrillation is an essential part of antiarrhythmic emergency management. Drug therapy has its relevance rather in the prevention of sudden cardiac death, where early recognition and treatment of the underlying disease has significant importance. Cardioprotective and antiarrhythmic effects of beta blockers in patients predisposed to sudden cardiac death were highlighted in numerous studies, hence nowadays these drugs are considered to be the cornerstones of the prevention and treatment of life-threatening ventricular arrhythmias. Nevertheless, other medical therapies have not been proven to be useful in the prevention of VF. Although amiodarone has shown positive results occasionally, this was not demonstrated to be consistent. Furthermore, the potential proarrhythmic effects of drugs may also limit their applicability. Based on these unfavorable observations we highlight the importance of arrhythmia prevention, where echocardiography, electrocardiography and laboratory testing play a significant role even in the emergency setting. In the following we provide a summary on the latest developments on cardiopulmonary resuscitation, and the evaluation and preventive treatment possibilities of patients with increased susceptibility to VF and SCD.

Predictors and outcomes of atrial tachyarrhythmia among patients with implantable defibrillators

BACKGROUND

Atrial tachyarrhythmias (ATAs) are common among heart failure (HF) patients.

OBJECTIVE

The purpose of this study was to assess predictors for the development of new ATA and its components (atrial fibrillation/flutter [AF], supraventricular tachycardia [SVT]), and their association with subsequent clinical outcomes.

METHODS

We assessed predictors for first and recurrent ATA, AF, and SVT among 1500 patients in MADIT-RIT (Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy). We also investigated the association of new ATA, AF, or SVT with subsequent ventricular arrhythmia (VA), adverse events (HF hospitalization, syncope, or death), or death by time-dependent analysis.

RESULTS

During 17 months of follow-up, 286 patients (19%) developed new ATA, of whom 92 (6%) had AF and 194 (12%) had SVT. Younger age (≤65 years), diastolic blood pressure ≥72 mm Hg, heart rate ≥63 bpm, absence of diabetes, and prior atrial arrhythmia were independent predictors of ATA. Prior atrial arrhythmia was the only predictor of AF (hazard ratio 3.14; P <.001). New ATA was associated with significantly increased risk for subsequent VA (HR 2.12; P <.001), increased adverse events (HR 1.42; P <.001), and death (HR 1.85; P = .038). New AF and new SVT were both independently associated with >2-fold increased risk for the development of subsequent VA (HR 2.21; P = .012l and HR 2.15; P <.001, respectively) and adverse events.

CONCLUSION

Among MADIT-RIT patients, younger age, absence of diabetes, higher blood pressure, higher heart rate, and prior atrial arrhythmia predicted device-detected ATA. Both AF and SVT were associated with increased risk for subsequent VA and adverse events. Aggressive management should be considered in HF patients who develop new-onset, device-detected ATA to improve clinical outcomes.

Effectiveness of high rate and delayed detection ICD programming by race: A MADIT-RIT substudy

INTRODUCTION

Data on inappropriate and appropriate ICD therapy, and efficacy of ICD programing strategies by race are limited.

METHODS

In MADIT-RIT, we evaluated the risk of ICD therapy by race, and the efficacy of high rate cut-off ventricular tachycardia (VT) zone ≥200 beats per minute (bpm) (Arm B), or 60 seconds delay in VT zone 170-199 bpm (Arm C), compared to 2.5 seconds delay at 170 bpm (Arm A) among black and white patients.

RESULTS

MADIT-RIT enrolled 272 (20%) black and 1119 (80%) white patients. The risk of inappropriate therapy was similar among blacks and whites, HR 1.25, 95% CI (0.82-1.93), P  =  0.30. High rate cut-off or delayed VT therapy was associated with significant reductions in inappropriate therapy among whites, Arm B versus Arm A, HR 0.15, 95% CI (0.08-0.29), P < 0.0001, Arm C versus Arm A, HR 0.19, 95% CI (0.11-0.33), P < 0.001, and black individuals Arm B versus Arm A, HR 0.24, 95% CI (0.01-0.56), P  =  0.0001, Arm C versus Arm A, HR 0.30, 95% CI (0.13-0.68), P  =  0.004, P interaction > 0.10). However, delayed VT therapy was associated with a trend toward greater reduction in appropriate therapy in black individuals, HR 0.08, 95% CI (0.03-0.27), P < 0.0001 relative to white individuals, HR 0.27, 95% CI (0.16-0.43), P < 0.0001, P interaction  =  0.077.

CONCLUSION

In MADIT-RIT, high rate and delayed detection ICD programming provided similar benefit with reductions in both inappropriate therapy and unnecessary appropriate therapy among black and white individuals. CLINICALTRIALS.

GOV IDENTIFIER

NCT00947310.

Impact of cardiac reverse remodeling after cardiac resynchronization therapy assessed by myocardial perfusion imaging on ventricular arrhythmia

BACKGROUND

Although cardiac resynchronization therapy (CRT) has been a useful treatment of heart failure, patients with CRT are still in risk of sudden cardiac death due to ventricular arrhythmia. The aim of this study was to investigate the impact of cardiac reverse remodeling after CRT on the prevalence of ventricular tachycardia or fibrillation (VT/VF).

METHODS AND RESULTS

Forty-one heart failure patients (26 men, age 66 ± 10 years), who were implanted with CRT for at least 12 months, were enrolled. All patients received myocardial perfusion imaging (MPI) under CRT pacing to evaluate left ventricle (LV) function, dyssynchrony, and scar. VT/VF episodes during the follow-up period after MPI were recorded by the CRT devices. Sixteen patients (N = 16/41, 39%) were found to have VT/VF. Multivariate Cox regression analysis and receiver operating characteristic curve analysis showed that five risk factors were significant predictors of VT/VF, including increased left ventricle ejection fraction (LVEF) by ≤7% after CRT, low LVEF after CRT (≤30%), change of intrinsic QRS duration (iQRSd) by ≤7 ms, wide iQRSd after CRT (≥121 ms), and high systolic dyssynchrony after CRT (phase standard deviation ≥45.6°). For those patients with all of the 5 risk factors, 85.7% or more developed VT/VF.

CONCLUSIONS

The characteristics of cardiac reverse remodeling after CRT as assessed by MPI are associated with the prevalence of ventricular arrhythmia.

Effects of implantable cardioverter/defibrillator shock and antitachycardia pacing on anxiety and quality of life: A MADIT-RIT substudy

Effects of implantable cardioverter/defibrillator (ICD) shocks and antitachycardia pacing (ATP) on anxiety and quality of life (QoL) in ICD patients are poorly understood.

METHODS

We evaluated changes in QoL from baseline to 9-month follow-up using the EQ-5D questionnaire in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT) (n=1,268). We assessed anxiety levels using the Florida Shock Anxiety Scale (1-10 score) in patients with appropriate or inappropriate shocks or ATP compared to those with no ICD therapy during the first 9 months postimplant. The analysis was stratified by number of ATP or shocks (0-1 vs ≥2) and adjusted for covariates.

RESULTS

In MADIT-RIT, 15 patients (1%) had ≥2 appropriate shocks, 38 (3%) had ≥2 appropriate ATPs. Two or more inappropriate shocks were delivered in 16 patients (1%); ≥2 inappropriate ATPs, in 70. In multivariable analysis, patients with ≥2 appropriate shocks had higher levels of shock-related anxiety than those with ≤1 appropriate shock (P<.01). Furthermore, ≥2 inappropriate shocks produced more anxiety than ≤1 inappropriate shock (P=.005). Consistently, ≥2 appropriate ATPs resulted in more anxiety than ≤1 (P=.028), whereas the number of inappropriate ATPs showed no association with anxiety levels (P=.997). However, there was no association between QoL and appropriate or inappropriate ATP/shock (all P values > .05).

CONCLUSIONS

In MADIT-RIT, ≥2 appropriate or inappropriate ICD shocks and ≥2 appropriate ATPs are associated with more anxiety at 9-month follow-up despite no significant changes in the assessment of global QoL by the EQ-5D questionnaire. Innovative ICD programming reducing inappropriate therapies may help deal with patient concerns about the device.

Efficacy and Limitations of Tachycardia Detection Interval Guided Reprogramming for Reduction of Inappropriate Shock in Implantable Cardioverter-Defibrillator Patients

The avoidance of inappropriate shock therapy is an important clinical issue in implantable cardioverter-defibrillator (ICD) patients. We retrospectively analyzed therapeutic events in ICD patients, and the effect of tachycardia detection interval (TDI) and tachycardia cycle length (TCL) guided reprograming on the reduction of inappropriate ICD therapy. The clinical determinants of after reprogramming were also evaluated.A total of 254 consecutive ICD patients were included in the study, and the incidence of antitachycardia therapy was evaluated during the follow-up period of 27.3 ± 18.7 months. When inappropriate antitachycardia therapy appeared, TDI was reprogrammed not to exceed the detected TCL and the patients continued to be followed-up. Various clinical parameters were compared between patients with and without inappropriate ICD therapy. During the initial follow-up period of 18.6 ± 15.6 months, ICD therapy occurred in 127/254 patients (50%) including inappropriate antitachycardia pacing (ATP) (12.9%) and shock (44.35%). Determinants of initial inappropriate therapy were dilated cardiomyopathy (DCM), history of therapeutic hypothermia, and QRS duration. Of the 61 patients with inappropriate therapy, 24 received TCL guided reprogramming. During the additional observation period of 17.0 ± 16.8 months, inappropriate therapy recurred in 5/24 patients (2 ATP, 3 shocks). The determinant of these inappropriate therapy events after reprogramming was the presence of supraventricular tachycardia.By applying simple TCL and TDI guided reprogramming, inappropriate therapy was reduced by 79%. The determinant of inappropriate therapy after reprogramming was the presence of supraventricular tachycardia.

Results of ENHANCED Implantable Cardioverter Defibrillator Programming to Reduce Therapies and Improve Quality of Life (from the ENHANCED-ICD Study)

Novel implantable cardioverter defibrillator (ICD) discrimination algorithms and programming strategies have significantly reduced the incidence of inappropriate shocks, but there are still gains to be made with respect to reducing appropriate but unnecessary antitachycardia pacing (ATP) and shocks. We examined whether programming a number of intervals to detect (NID) of 60/80 for ventricular tachyarrhythmia (VT)/ventricular fibrillation (VF) detection was safe and the impact of this strategy on (1) adverse events related to ICD shocks and syncopal events; (2) ATPs/shocks; and (3) patient-reported outcomes. The "ENHANCED Implantable Cardioverter Defibrillator programming to reduce therapies and improve quality of life" study (ENHANCED-ICD study) was a prospective, safety-monitoring study enrolling 60 primary and secondary prevention patients at the University Medical Center Utrecht. Patients implanted with any type of ICD with SmartShock technology and aged 18 to 80 years were eligible to participate. In all patients, a prolonged NID 60/80 was programmed. The cycle length for VT/fast VT/VF was 360/330/240 ms, respectively. Programming a NID 60/80 proved safe for ICD patients. Because of the new programming strategy, unnecessary ICD therapy was prevented in 10% of ENHANCED-ICD patients during a median follow-up period of 1.3 years. With respect to patient-reported outcomes, levels of distress were highest and perceived health status lowest at the time of implantation, which both gradually improved during follow-up. In conclusion, the ENHANCED-ICD study demonstrates that programming a NID 60/80 for VT/VF detection is safe for ICD patients and does not negatively impact their quality of life.

Novel ICD Programming and Inappropriate ICD Therapy in CRT-D Versus ICD Patients

Background—

The Multicenter Automatic Defibrillator Implantation Trial–Reduce Inappropriate therapy (MADIT-RIT) trial showed a significant reduction in inappropriate implantable cardioverter defibrillator (ICD) therapy in patients programmed to high-rate cut-off (Arm B) or delayed ventricular tachycardia therapy (Arm C), compared with conventional programming (Arm A). There is limited data on the effect of cardiac resynchronization therapy with a cardioverter defibrillator (CRT-D) on the effect of ICD programming. We aimed to elucidate the effect of CRT-D on ICD programming to reduce inappropriate ICD therapy in patients implanted with CRT-D or an ICD, enrolled in MADIT-RIT.

Methods and Results—

The primary end point of this study was the first inappropriate ICD therapy. Secondary end points were inappropriate anti-tachycardia pacing and inappropriate ICD shock. The study enrolled 742 (49%) patients with an ICD and 757 (51%) patients with a CRT-D. Patients implanted with a CRT-D had 62% lower risk of inappropriate ICD therapy than those with an ICD only (hazard ratio [HR] =0.38, 95% confidence interval: 0.25–0.57; P <0.001). High-rate cut-off or delayed ventricular tachycardia therapy programming significantly reduced the risk of inappropriate ICD therapy compared with conventional ICD programming in ICD (HR=0.14 [B versus A]; HR=0.21 [C versus A]) and CRT-D patients (HR=0.15 [B versus A]; HR=0.23 [C versus A]; P <0.001 for all). There was a significant reduction in inappropriate anti-tachycardia pacings in both group and a significant reduction in inappropriate ICD shock in CRT-D patients.

Conclusions—

Patients implanted with a CRT-D have lower risk of inappropriate ICD therapy than those with an ICD. Innovative ICD programming significantly reduces the risk of inappropriate ICD therapy in both ICD and CRT-D patients.

Clinical Trial Registration—

http: //clinicaltrials.gov ; Unique identifier: NCT00947310.

Reduction in Inappropriate ICD Therapy in MADIT-RIT Patients Without History of Atrial Tachyarrhythmia

BACKGROUND

There are limited data whether history of atrial tachyarrhythmia (AT) modifies the risk of inappropriate ICD therapy, or the efficacy of novel ICD programming to reduce inappropriate ICD therapy events.

METHODS

In MADIT-RIT, we investigated the effects of novel ICD programming with high-rate cut-off VT zone ≥ 200 bpm (arm B), or 60-second delayed therapy in the VT zone 170-199 bpm (arm C), compared to conventional programming VT zone>170 bpm (arm A) on first inappropriate ICD therapy in those with or those without AT prior to enrollment.

RESULTS

In patients with prior AT (n = 203, 14%) there was a higher risk of inappropriate ICD therapy (HR = 2.10, 95% CI: 1.38-3.20, P < 0.001), and inappropriate ICD shock (HR = 2.56, 95% CI: 1.38-4.74, P = 0.003) compared to those with no prior AT. The effects of innovative programming to reduce inappropriate ICD therapy with either high-rate cut-off or delayed VT therapy were similar in patients with prior AT (arm B vs. A HR = 0.11, P < 0.001, arm C vs. A HR = 0.17, P < 0.001), and also in patients without prior AT before enrollment (arm B vs. A HR = 0.15, P < 0.001, arm C vs. A HR = 0.24, P < 0.001, interaction P-values >0.10 for all).

CONCLUSIONS

Novel ICD programming with a high-rate cut-off or delayed therapy is equally beneficial to reduce inappropriate ICD therapy in patients with or without prior AT, despite the lower risk of inappropriate ICD therapy in patients without prior AT.

[Inappropriate ICD therapies: All problems solved with MADIT-RIT?]

The MADIT-RIT study represents a major trial in implantable cardioverter-defibrillator (ICD) therapy that was recently published. It highlights that different programming strategies (high rate cut-off or delayed therapy versus conventional) reduce inappropriate ICD therapies, leave syncope rates unaltered and can improve patient's survival. The study should motivate cardiologist and electrophysiologists to reconsider their individual programming strategies. However, as the study represents largely patients with ischemic or dilated cardiomyopathy for primary prevention of sudden cardiac death supplied with a dual chamber or cardiac resynchronisation therapy ICD, the results may not easily be transferable to other entities or other device types. Despite the success of the MADIT-RIT study efforts still need to be taken to further optimise device algorithms to avert inappropriate therapies. Optimised ICD therapy also includes the avoidance of unnecessary ICD shocks as well as the treatment of all aspects of the underlying cardiac disease.

Time-dependent risk reduction of ventricular tachyarrhythmias in cardiac resynchronization therapy patients: a MADIT-RIT sub-study

AIMS

Data on the time-dependent benefit of cardiac resynchronization therapy with defibrillator (CRT-D) compared with a dual-chamber implantable cardioverter-defibrillator (ICD) to reduce death or ventricular tachycardia (VT) or ventricular fibrillation (VF) are limited. We aimed to evaluate the time-related risk of death or sustained VT or VF in patients receiving CRT-D vs. ICD in the MADIT-RIT trial.

METHODS AND RESULTS

Kaplan-Meier survival analyses and multivariate Cox regression models were utilized to compare the incidence and the risk of death or sustained VT/VF in the CRT-D and ICD subgroups by the elapsed time after device implantation (6 months). Of the ICD (n = 742) and CRT-D (n = 757) patients enrolled, the risk of death was lower in CRT-D vs. in ICD early after device implantation [hazard ratio (HR) = 0.42, 95% confidence interval (CI): 0.17-1.03, P = 0.058] and beyond 6 months of follow-up (HR = 0.39, 95% CI: 0.21-0.73, P = 0.004), with the 6-month interaction P = 0.899. The overall risk of sustained VT/VF was reduced in CRT-D vs. ICD patients (HR = 0.73, 95% CI: 0.52-1.03, P = 0.07). However, the risk was similar in the first 6 months (HR = 1.00, 95% CI: 0.62-1.62, P = 0.988), and a lower risk emerged 6 months after CRT-D implantation (HR = 0.58, 95% CI: 0.38-0.88, P = 0.011), with the 6-month interaction P = 0.059.

CONCLUSION

The reduced mortality risk of CRT-D compared with an ICD alone began early after device implantation and was sustained during long-term follow-up; the reduced risk for ventricular tachyarrhythmias did not emerge until 6 months after device implantation.

CLINICAL TRIAL REGISTRATION

http://clinicaltrials.gov/ct2/show/NCT00947310.

ICD programming to reduce shocks and improve outcomes

Despite the clinical benefit of implantable cardioverter defibrillator (ICD), there is a high frequency of inappropriate ICD therapy associated with impaired quality of life, unwanted health care resource utilization, and adverse clinical outcome. Alternative strategies of ICD programming are needed to reduce the risk of inappropriate and "unnecessary" ICD therapies and to improve patient outcome. In this review, we provide an overview of the rate of inappropriate and appropriate ICD therapies in clinical trials and large registries as well as a review of current trials evaluating novel ICD programming to reduce inappropriate ICD therapy to avoid unnecessary ICD therapy. Based on recent studies including a large randomized trial, we recommend a simple programming approach involving high-rate device therapy beginning at 200 bpm with a 2.5 sec delay for it reduces inappropriate therapy, unnecessary therapy, and all-cause mortality in patients receiving ICD or CRT-D devices for primary prevention indications.

Mortality reduction in relation to implantable cardioverter defibrillator programming in the Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT)

BACKGROUND

The benefit of novel implantable cardioverter defibrillator (ICD) programming in reducing inappropriate ICD therapy and mortality was demonstrated in Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT). However, the cause of mortality reduction remains incompletely evaluated. We aimed to identify factors associated with mortality, with focus on ICD therapy and programming in the MADIT-RIT population.

METHODS AND RESULTS

In MADIT-RIT, 1500 patients with a primary prophylactic indication for ICD or cardiac resynchronization therapy with defibrillator were randomized to 1 of 3 different ICD programming arms: conventional programming (ventricular tachycardia zone ≥170 beats per minute), high-rate programming (ventricular tachycardia zone ≥200 beats per minute), and delayed programming (60-second delay before therapy ≥170 beats per minute). Multivariate Cox models were used to assess the influence of time-dependent appropriate and inappropriate ICD therapy (shock and antitachycardia pacing) and randomized programming arm on all-cause mortality. During an average follow-up of 1.4±0.6 years, 71 of 1500 (5%) patients died: cardiac in 40 patients (56.3%), noncardiac in 23 patients (32.4%), and unknown in 8 patients (11.3%). Appropriate shocks (hazard ratio, 6.32; 95% confidence interval, 3.13-12.75; P<0.001) and inappropriate therapy (hazard ratio, 2.61; 95% confidence interval, 1.28-5.31; P=0.01) were significantly associated with an increased mortality risk. There was no evidence of increased mortality risk in patients who experienced appropriate antitachycardia pacing only (hazard ratio, 1.02; 95% confidence interval, 0.36-2.88; P=0.98). Randomization to conventional programming was identified as an independent predictor of death when compared with patients randomized to high-rate programming (hazard ratio, 2.0; 95% confidence interval, 1.06-3.71; P=0.03).

CONCLUSIONS

In MADIT-RIT, appropriate shocks, inappropriate ICD therapy, and randomization to conventional ICD programming were independently associated with an increased mortality risk. Appropriate antitachycardia pacing was not related to an adverse outcome.

CLINICAL TRIAL REGISTRATION URL

clinicaltrials.gov Unique identifier: NCT00947310.

PR Interval Identifies Clinical Response in Patients With Non–Left Bundle Branch Block

Background—

In Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADIT-CRT), patients with non–left bundle branch block (LBBB; including right bundle branch block, intraventricular conduction delay) did not have clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D). We hypothesized that baseline PR interval modulates clinical response to CRT-D therapy in patients with non-LBBB.

Methods and Results—

Non-LBBB patients (n=537; 30%) were divided into 2 groups based on their baseline PR interval as normal (including minimally prolonged) PR (PR <230 ms) and prolonged PR (PR ≥230 ms). The primary end point was heart failure or death. Separate secondary end points included heart failure events and all-cause mortality. Cox proportional hazards regression models were used to compare risk of end point events by CRT-D to implantable cardioverter defibrillator therapy in the PR subgroups. There were 96 patients (22%) with a prolonged PR and 438 patients (78%) with a normal PR interval. In non-LBBB patients with a prolonged PR interval, CRT-D treatment was associated with a 73% reduction in the risk of heart failure/death (hazard ratio, 0.27; 95% confidence interval, 0.13–0.57; P <0.001) and 81% decrease in the risk of all-cause mortality (hazard ratio, 0.19; 95% confidence interval, 0.13–0.57; P <0.001) compared with implantable cardioverter defibrillator therapy. In non-LBBB patients with normal PR, CRT-D therapy was associated with a trend toward an increased risk of heart failure/death (hazard ratio, 1.45; 95% confidence interval, 0.96–2.19; P =0.078; interaction P <0.001) and a more than 2-fold higher mortality (hazard ratio, 2.14; 95% confidence interval, 1.12–4.09; P =0.022; interaction P <0.001) compared with implantable cardioverter defibrillator therapy.

Conclusions—

The data support the use of CRT-D in MADIT-CRT non-LBBB patients with a prolonged PR interval. In non-LBBB patients with a normal PR interval, implantation of a CRT-D may be deleterious.

Clinical Trial Registration—

http://clinicaltrials.gov ; Unique Identifier: NCT00180271.

Syncope in High-Risk Cardiomyopathy Patients With Implantable Defibrillators: Frequency, Risk Factors, Mechanisms, and Association With Mortality

Background—

There is a relative paucity of studies investigating the mechanisms of syncope among heart failure patients with implantable cardioverter-defibrillators, and it is controversial whether nonarrhythmogenic syncope is associated with increased mortality.

Methods and Results—

The Multicenter Automatic Defibrillator Implantation Trial–Reduce Inappropriate Therapy (MADIT-RIT) randomized 1500 patients to 3 different implantable cardioverter-defibrillator programming arms: (1) Conventional programming with therapy for ventricular tachycardia ≥170 bpm; (2) high-rate cutoff with therapy for ventricular tachycardia ≥200 bpm and a monitoring zone at 170 to 199 bpm, and (3) prolonged 60-second delay with a monitoring zone before therapy. Syncope was a prespecified safety end point that was adjudicated independently. Multivariable Cox models were used to identify risk factors associated with syncope and to analyze subsequent risk of mortality. During follow-up, 64 of 1500 patients (4.3%) had syncope. The incidence of syncope was similar across the 3 treatment arms. Prognostic factors for all-cause syncope included the presence of ischemic cardiomyopathy (hazard ratio [HR], 2.48; 95% confidence interval [CI], 1.42–4.34; P =0.002), previous ventricular arrhythmias (HR, 2.99; 95% CI, 1.18–7.59; P =0.021), left ventricular ejection fraction ≤25% (HR, 1.65; 95% CI, 0.98–2.77; P =0.059), and younger age (by 10 years; HR, 1.25; 95% CI, 1.00–1.52; P =0.046). Syncope was associated with increased risk of death regardless of its cause (arrhythmogenic syncope: HR, 4.51; 95% CI, 1.39–14.64, P =0.012; nonarrhythmogenic syncope: HR, 2.97; 95% CI, 1.07–8.28, P =0.038).

Conclusions—

Innovative programming of implantable cardioverter-defibrillators with therapy for ventricular tachycardia ≥200 bpm or a long delay is not associated with increased risk of arrhythmogenic or all-cause syncope, and syncope caused by slow ventricular tachycardias (<200 bpm) is a rare event. The clinical risk factors associated with syncope are related to increased cardiovascular risk profile, and syncope is associated with increased mortality irrespective of the cause.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00947310.

Influence of diabetes mellitus on inappropriate and appropriate implantable cardioverter-defibrillator therapy and mortality in the Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT) Trial

BACKGROUND

The relationship between diabetes mellitus and risk of inappropriate or appropriate therapy in patients receiving an implantable cardioverter-defibrillator (ICD) and resynchronization therapy has not been investigated thoroughly. The effect of innovative ICD programming on therapy delivery in these patients is unknown.

METHODS AND RESULTS

The Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT) randomized patients with a primary prophylactic ICD indication to 3 different types of ICD programming: conventional programming with a ventricular tachycardia zone of 170 to 199 bpm (arm A), high-rate cutoff with a ventricular tachycardia zone ≥200 bpm (arm B), or 60-second-delayed therapy (arm C). The end points of inappropriate therapy, appropriate therapy, and death were assessed among 485 patients with and 998 without diabetes mellitus. Innovative ICD programming reduced the risk of inappropriate therapy regardless of diabetes mellitus, although a trend toward a more pronounced effect of high-rate cutoff programming was seen in patients without diabetes mellitus (P for interaction=0.06). Diabetes mellitus was associated with a decreased risk of inappropriate therapy (hazard ratio, 0.54; 95% confidence interval, 0.36-0.80; P=0.002) and increased risk of appropriate therapy (hazard ratio, 1.58; 95% confidence interval, 1.17-2.14; P=0.003). In diabetic patients, there was significantly increased risk of death in those who had inappropriate therapy (hazard ratio, 4.17; 95% confidence interval, 1.52-11.40; P=0.005) and appropriate therapy (hazard ratio, 2.49; 95% confidence interval, 1.06-5.87; P=0.037) compared with those who did not.

CONCLUSIONS

Innovative high-rate cutoff or delayed ICD programming was associated with a reduction in inappropriate therapy in patients with and without diabetes mellitus. Diabetes mellitus was associated with lower risk of inappropriate therapy but higher risk of appropriate therapy. Appropriate and inappropriate ICD therapy was associated with increased mortality in diabetic patients.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT00947310.

Reduction in inappropriate therapy and mortality through ICD programming

BACKGROUND

The implantable cardioverter-defibrillator (ICD) is highly effective in reducing mortality among patients at risk for fatal arrhythmias, but inappropriate ICD activations are frequent, with potential adverse effects.

METHODS

We randomly assigned 1500 patients with a primary-prevention indication to receive an ICD with one of three programming configurations. The primary objective was to determine whether programmed high-rate therapy (with a 2.5-second delay before the initiation of therapy at a heart rate of ≥200 beats per minute) or delayed therapy (with a 60-second delay at 170 to 199 beats per minute, a 12-second delay at 200 to 249 beats per minute, and a 2.5-second delay at ≥250 beats per minute) was associated with a decrease in the number of patients with a first occurrence of inappropriate antitachycardia pacing or shocks, as compared with conventional programming (with a 2.5-second delay at 170 to 199 beats per minute and a 1.0-second delay at ≥200 beats per minute).

RESULTS

During an average follow-up of 1.4 years, high-rate therapy and delayed ICD therapy, as compared with conventional device programming, were associated with reductions in a first occurrence of inappropriate therapy (hazard ratio with high-rate therapy vs. conventional therapy, 0.21; 95% confidence interval [CI], 0.13 to 0.34; P<0.001; hazard ratio with delayed therapy vs. conventional therapy, 0.24; 95% CI, 0.15 to 0.40; P<0.001) and reductions in all-cause mortality (hazard ratio with high-rate therapy vs. conventional therapy, 0.45; 95% CI, 0.24 to 0.85; P=0.01; hazard ratio with delayed therapy vs. conventional therapy, 0.56; 95% CI, 0.30 to 1.02; P=0.06). There were no significant differences in procedure-related adverse events among the three treatment groups.

CONCLUSIONS

Programming of ICD therapies for tachyarrhythmias of 200 beats per minute or higher or with a prolonged delay in therapy at 170 beats per minute or higher, as compared with conventional programming, was associated with reductions in inappropriate therapy and all-cause mortality during long-term follow-up. (Funded by Boston Scientific; MADIT-RIT ClinicalTrials.gov number, NCT00947310.).