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Background: There are limited data on clinical and arrhythmic outcomes following a first ventricular tachyarrhythmia (VTA) in heart failure (HF) patients who receive a primary prevention implantable cardioverter-defibrillator (ICD)., Objective: To quantify the burden and identify risk factors for recurrent VTA in this population, and to evaluate the risk of all-cause mortality associated with recurrent VTA., Methods: The study comprised 789 patients who experienced VTA following primary prevention ICD implantation in 5 ICD trials (MADIT-II, MADIT-RISK, MADIT-CRT, MADIT-RIT, RAID). Landmark analysis was used to quantify the burden and identify predictors of recurrent VTA. Time-dependent analysis was used to evaluate the association of VTA recurrence with subsequent mortality., Results: Among the study patients, mean age was 63 years and 17% were women. The cumulative probability of experiencing at least one recurrent VTA episode at 3 years following a first VTA episode was 60%; the recurrent VTA burden after a first event over 3 years was 2.8 episodes per patient. The risk of recurrent VTA remained ≥56% at 3 years regardless of baseline clinical and echocardiographic risk factors. VTA recurrence was associated with a significant two-fold increased risk of subsequent all-cause mortality., Conclusions: Patients with a primary prevention ICD who experience an episode of VTA are at very high risk of recurrent VTA, regardless of baseline risk factors. Recurrent VTA is associated with a pronounced increase in the risk of death. These findings suggest a need for early intervention following a first VTA in patients who receive a primary prevention ICD., (Copyright © 2024. Published by Elsevier Inc.)

Background: Scarce data exist on the evolution of device-related thrombus (DRT) after left atrial appendage closure (LAAC)., Objectives: This study sought to assess the incidence, predictors, and clinical impact of persistent and recurrent DRT in LAAC recipients., Methods: Data were obtained from an international multicenter registry including 237 patients diagnosed with DRT after LAAC. Of these, 214 patients with a subsequent imaging examination after the initial diagnosis of DRT were included. Unfavorable evolution of DRT was defined as either persisting or recurrent DRT., Results: DRT resolved in 153 (71.5%) cases and persisted in 61 (28.5%) cases. Larger DRT size (OR per 1-mm increase: 1.08; 95% CI: 1.02-1.15; P = 0.009) and female (OR: 2.44; 95% CI: 1.12-5.26; P = 0.02) were independently associated with persistent DRT. After DRT resolution, 82 (53.6%) of 153 patients had repeated device imaging, with 14 (17.1%) cases diagnosed with recurrent DRT. Overall, 75 (35.0%) patients had unfavorable evolution of DRT, and the sole predictor was average thrombus size at initial diagnosis (OR per 1-mm increase: 1.09; 95% CI: 1.03-1.16; P = 0.003), with an optimal cutoff size of 7 mm (OR: 2.51; 95% CI: 1.39-4.52; P = 0.002). Unfavorable evolution of DRT was associated with a higher rate of thromboembolic events compared with resolved DRT (26.7% vs 15.1%; HR: 2.13; 95% CI: 1.15-3.94; P = 0.02)., Conclusions: About one-third of DRT events had an unfavorable evolution (either persisting or recurring), with a larger initial thrombus size (particularly >7 mm) portending an increased risk. Unfavorable evolution of DRT was associated with a 2-fold higher risk of thromboembolic events compared with resolved DRT., Competing Interests: Funding Support and Author Disclosures Dr Rodés-Cabau holds the Research Chair “Fondation Famille Jacques Larivière” for the Development of Structural Heart Disease Interventions (Laval University, Quebec City, Canada). He also has received institutional research grants from Boston Scientific. Dr Maarse has received an unrestricted grant from Boston Scientific. Dr Pérez de Prado has served as a proctor for Boston Scientific. Dr Gupta has served as a proctor for Abbott. Dr Sanchez has served as a speaker and proctor for Boston Scientific. Dr Wang has served as a consultant for Edwards Lifesciences, Boston Scientific, and Neochord; and received research grant support from Boston Scientific assigned to his employer, the Henry Ford Health System. Dr Demkow has served as a proctor for Abbott and Boston Scientific. Dr Alkhouli has served as a consultant for Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Women with congenital long QT syndrome (LQTS) experience increased cardiac event risk after the onset of adolescence, perhaps stemming from the known modulating effects of sex hormones on the cardiac potassium channels., Objective: We hypothesized that the effect of sex hormones on cardiac ion channel function may modify electrocardiographic (ECG) parameters associated with the propensity for ventricular tachyarrhythmias during the menstrual cycle in women with LQTS., Methods: We prospectively enrolled 65 women with congenital LQTS (type 1 LQTS [LQT1], n = 24 [36.9%]; type 2 LQTS [LQT2], n = 20 [30.8%]) and unaffected female relatives (n = 21 [32.3%]). Patients underwent three 7-day ECG recordings during their menstrual cycles. Simultaneous saliva testing of sex hormone levels was conducted on the first day of each 7-day ECG recording cycle., Results: The mean age was 35 ± 8 years, without a significant difference among the groups. In women with LQT2, linear mixed effects models showed significant inverse correlations of the corrected QT interval with progesterone levels (P < .001) and with the progesterone to estradiol ratio (P < .001). Inverse relationships of the R-R interval with estradiol levels (P = .003) and of the T-wave duration with testosterone levels (P = .014) were also observed in women with LQT2. In contrast, no significant associations were observed between ECG parameters and sex hormone levels in women with LQT1 or unaffected relatives., Conclusion: This is the first study to prospectively assess correlations between repolarization dynamics and sex hormone levels during the menstrual cycle in women with congenital LQTS. Our findings show genotype-specific unique corrected QT dynamics during the menstrual cycle that may affect the propensity for ventricular tachyarrhythmia in women with LQTS, particularly women with LQT2., (Copyright © 2022. Published by Elsevier Inc.)

Background: The new high-sensitivity cardiac troponin T (hs-cTnT) is now widely used in the United States., Objectives: We aimed to examine outcomes associated with the introduction of the new 5 th generation hs-cTnT assay among patients presenting to the emergency department (ED) with cardiovascular (CV) disorders., Methods: The study comprised 5377 patients presenting to the ED with CV disorders between January and September 2018. Outcomes included rates of direct ED discharge, cardiac testing/procedures, and mortality. CV indications for troponin testing were categorized as rule-out acute coronary syndrome (RO-ACS) and other-CV (O-CV)., Results: Mean age was 62 ± 17 years, and 47% were female. Demographics and medical history did not differ significantly between the troponin groups. The use of hs-cTnT was associated with increased rates of direct discharge from the ED in the RO-ACS (48% vs. 37%; p < 0.01), but not in the O-CV (25% vs. 25%) cohort. Cardiac tests/procedures were more often performed after hs-cTnT vs. cTnT testing in both cohorts (45% vs. 41% for RO-ACS, and 33% vs. 28% for O-CV; p < 0.05 for both). Multivariate analysis demonstrated that hs-cTnT was not associated with a significant increase in postdischarge mortality in both cohorts (RO-ACS: hazard ratio = 1.47 [p = 0.13], O-CV: hazard ratio = 0.97 [p = 0.87])., Conclusions: Among patients with RO-ACS, hs-cTnT implementation resulted in increased rates of direct home discharge from the ED, without a significant increase in postdischarge mortality. Among patients presenting with O-CV indication, hs-cTnT implementation resulted in increased rates of cardiac testing procedures without an effect of ED discharge rates or long-term mortality., (Copyright © 2022. Published by Elsevier Inc.)

Background: Use of oral contraceptives (OCs) may modulate the clinical course of women with congenital long QT syndrome (LQTS). The safety of OC use by sex hormone content has not been assessed in women with LQTS., Objective: We aimed to evaluate the association of OCs with the risk of cardiac events (CEs) in women with LQTS., Methods: Beginning in 2010, information on menarche onset, OC use, pregnancy, and menopause were obtained from women enrolled in the Rochester LQTS Registry. Type of OC was categorized as progestin-only, estrogen-only, or combined (estrogen/progestin). Andersen-Gill multivariate modeling was used to evaluate the association of time-dependent OC use with the burden of CE (total number of syncope, aborted cardiac arrest, and LQTS-related sudden cardiac death) from menarche onset through 40 years. Findings were adjusted for genotype, corrected QT duration, and time-dependent β-blocker therapy., Results: A total of 1659 women with LQTS followed through March 2021, of whom 370 (22%) were treated with an OC. During a cumulative follow-up of 35,797 years, there were a total of 2027 CE. Multivariate analysis showed that progestin-only OC was associated with a pronounced 2.8-fold (P = .01) increased risk of CEs in women who did not receive β-blocker therapy, while β-blockers were highly protective during progestin-only OC treatment (hazard ratio 0.22; P = .01; P = .006 for β-blocker-by-OC interaction). The risk associated with OC use without concomitant β-blocker treatment was pronounced in women with LQTS type 2., Conclusion: Our findings suggest that progestin-only OC should not be administered in women with LQTS without concomitant β-blocker therapy. OCs should be used with caution in women with LQTS type 2., (Copyright © 2021. Published by Elsevier Inc.)

Background: Cardiac resynchronization therapy-defibrillator (CRT-D) may reduce the incidence of first ventricular tachyarrhythmia (VTA) in patients with heart failure (HF) and left bundle branch block (LBBB)., Objective: The purpose of this study was to assess the effect of CRT-D on VTA burden in LBBB patients., Methods: We included 1281 patients with LBBB from MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy). VTA was defined as any treated or monitored sustained ventricular tachycardia (VT ≥180 bpm) or ventricular fibrillation (VF). Life-threatening VTA was defined as VT ≥200 bpm or VF. VTA recurrence was assessed using the Andersen-Gill model., Results: During a mean follow-up of 2.5 years, 964 VTA episodes occurred in 264 patients (21%). The VTA rate per 100 person-years was significantly lower in the CRT-D group compared with the implantable cardioverter-defibrillator (ICD) group (20 vs 34; P <.01). Multivariate analysis demonstrated that CRT-D treatment was associated with a 32% risk reduction for VTA recurrence (hazard ratio 0.68; 95% confidence interval 0.57-0.82; P <.001), 57% risk reduction for recurrent life-threatening VTA, 54% risk reduction for recurrent appropriate ICD shocks, and 25% risk reduction for the combined endpoint of VTA and death. The effect of CRT-D on VTA burden was consistent among all tested subgroups but was more pronounced among patients in New York Heart Association functional class I. Landmark analysis showed that at 2 years, the cumulative probability of death subsequent to year one was highest (16%) among patients who had ≥2 VTA events during their first year., Conclusion: In patients with LBBB and HF, early intervention with CRT-D reduces mortality, VTA burden, and frequency of multiple appropriate ICD shocks. VTA burden is a powerful predictor of subsequent mortality., (Copyright © 2021 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Alcohol septal ablation (ASA) in patients with hypertrophic cardiomyopathy (HCM) can lead to heart rhythm disturbances including complete heart block (CHB) and atrial and ventricular arrhythmias., Objective: We aimed to evaluate the utility of long-term arrhythmia monitoring with an implantable cardiac monitor (ICM) after ASA., Methods: Between February 2014 and March 2019, 56 patients with HCM undergoing ASA were enrolled in a prospective study and underwent ICM implantation. Kaplan-Meier survival analysis was used to assess the rate of ICM-detected arrhythmic events., Results: The mean age was 59 ± 11 years, and 20 (36%) were women. The median (25th, 75th percentile) resting left ventricular outflow tract gradient obtained by echocardiography was 43 (22, 81) mm Hg. Greater than 1 septal perforating artery was injected in 48 patients (86%). The Kaplan-Meier cumulative rate of ICM-detected arrhythmic events at 18 months of follow-up was 71%, with an event rate of 43% occurring within 3 months of ASA. The cumulative rate of the ICM-detected first atrial fibrillation event at 18 months was 37%, and the corresponding rate of CHB was 19%. All atrial fibrillation and CHB events were actionable, leading to the initiation of anticoagulation and pacemaker implantation, respectively. No baseline demographic or procedural variables were identified as independent predictors of an increased risk of developing ICM-detected arrhythmic events., Conclusion: After ASA, ICM is effective in capturing clinically actionable arrhythmic events in patients with HCM regardless of patient's baseline risk factors., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

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., (Published by Elsevier Inc.)

The present study demonstrates the synthesis of water-soluble fluorescent calix[4]arenes (6 and 7) and its application in living cell imaging for Hg 2+ detection at a low level. The synthesized fluorescent ligands 6 and 7 were characterized by 1 H NMR technique. The fluorescent study showed both water soluble ligands were Hg 2+ selective and follow photo-induced electron transfer (PET) process. From the fluorimeter titration experiment detection limit was calculated as 1.14×10 -5 and 3.42×10 -5 for ligand 6 and 7, respectively. From the Benesi-Hildebrand plot binding constant values were evaluated as 666.7 and 733.3M -1 for 6 and 7, respectively. The interactions between ligands 6 and 7 and Hg 2+ were also demonstrated in living cells, SW-620, using Fluorescent Cell Imager. While ligands 6 and 7 alone show fluorescent properties, they loss their action with the presence of Hg 2+ in SW-620 cells., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: There are limited data on the significance of left ventricular (LV) lead pacing polarity to predict clinical outcomes., Objectives: We aimed to determine the association between the LV lead pacing polarity for heart failure (HF) or death and ventricular tachyarrhythmias (VTA) in patients enrolled in MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy), receiving a cardiac resynchronization therapy device with implanted cardioverter-defibrillator (CRT-D)., Methods: We retrospectively analyzed LV pacing polarity. Patients with LV bipolar leads paced between LV ring and LV tip were identified as True Bipolar, while those with LV bipolar leads paced between LV tip or LV ring and right ventricular coil or unipolar leads were identified as Unipolar/Extended Bipolar. Kaplan-Meier survival analyses and multivariate Cox proportional hazards regression models were used., Results: Of the 969 patients, 421 had True Bipolar pacing while the remainder (n = 548) had Unipolar/Extended Bipolar pacing. Among patients with left bundle branch block (LBBB), True Bipolar pacing was associated with lower cumulative incidence of death (P = .022) and HF/death (P = .046) compared to those with Unipolar/Extended Bipolar LV pacing. After adjustment for clinical covariates, bipolar LV pacing in LBBB patients was associated with 54% lower risk for death (HR: 0.46; 95% CI: 0.24-0.88; P = .020) and 32% lower risk for HF/death (HR: 0.68; 95% CI: 0.46-1.00; P = .048) compared to Unipolar/Extended Bipolar LV pacing, but not in those with non-LBBB. No association was seen with risk of ventricular tachyarrhythmia., Conclusion: True Bipolar LV pacing configuration is associated with a significantly lower risk of HF/death and all-cause mortality in CRT-D patients with LBBB., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Patients with a left ventricular assist device (LVAD) are at high risk for ventricular tachyarrhythmias (VTAs)., Objective: We aimed to identify clinical predictors of VTAs and subsequent outcomes after VTA in ambulatory LVAD patients., Methods: A retrospective study of 149 patients with a continuous flow HeartMate II LVAD who survived to discharge from index hospitalization after LVAD implantation was performed from January 10, 2005, to September 3, 2013. A multivariate Cox model was used to assess clinical predictors of VTAs., Results: During a mean follow-up period of 2.1 ± 1.2 years, 41 patients (28%) experienced VTAs; 30 of these patients (71%) had ventricular tachycardia, and 11 (29%) had ventricular fibrillation. History of VTAs before LVAD (hazard ratio [HR] 3.06; 95% confidence interval [CI] 1.57-5.96; P = .001) and history of atrial fibrillation (AF) (HR 3.13; 95% CI 1.60-6.11; P = .008) were the most powerful predictors of VTAs after LVAD implantation. There were 19 deaths (46%) among patients with VTAs and 15 deaths (14%) among patients without VTAs (P < .001). In multivariate analysis, time-dependent VTAs after LVAD implantation were associated with a significantly higher risk of all-cause mortality when compared with those without VTAs (HR 7.28; 95% CI 3.50-15.15; P < .001)., Conclusion: In ambulatory LVAD patients, history of VTAs before LVAD implantation and history of AF predict VTAs after LVAD implantation. VTAs are associated with an increased risk of mortality. In such patients, aggressive measures to control VTAs and AF should be considered., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The QT interval is a risk marker for cardiac events such as torsades de pointes. However, QT measurements obtained from a 12-lead ECG during clinic hours may not capture the full extent of a patient's daily QT range., Objective: The purpose of this study was to evaluate the utility of 24-hour Holter ECG recording in patients with long QT syndrome (LQTS) to identify dynamic changes in the heart rate-corrected QT interval and to investigate methods of visualizing the resulting datasets., Methods: Beat-to-beat QTc (Bazett) intervals were automatically measured across 24-hour Holter recordings from 202 LQTS type 1, 89 type 2, and 14 type 3 genotyped patients and a reference group of 200 healthy individuals. We measured the percentage of beats with QTc greater than the gender-specific threshold (QTc ≥470 ms in women and QTc ≥450 ms in men). The percentage of beats with QTc prolongation was determined across the 24-hour recordings., Results: Based on the median percentage of heartbeats per patient with QTc prolongation, LQTS type 1 patients showed more frequent QTc prolongation during the day (~3 PM) than they did at night (~3 AM): 97% vs 48%, P ~10(-4) for men, and 68% vs 30%, P ~10(-5) for women. LQTS type 2 patients showed less frequent QTc prolongation during the day compared to nighttime: 87% vs 100%, P ~10(-4) for men, and 62% vs 100%, P ~10(-3) for women., Conclusion: In patients with genotype-positive LQTS, significant differences exist in the degree of daytime and nocturnal QTc prolongation. Holter monitoring using the "QT clock" concept may provide an easy, fast, and accurate method for assessing the true personalized burden of QTc prolongation., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Limited data exist regarding the proarrhythmic effects of smoking., Objective: To evaluate the relationship between smoking and the risk of first and recurrent ventricular tachyarrhythmias (VTAs) in patients with mild heart failure., Methods: The risk of a first and recurrent appropriate implantable cardioverter-defibrillator therapy for VTAs or death was compared between nonsmokers (n = 465), past smokers (n = 780), and current smokers (n = 197) in patients with ischemic and nonischemic cardiomyopathy who were enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy study., Results: The cumulative probability of a first VTA or death was significantly higher in current smokers than in past and nonsmokers (P < .001). Multivariate analysis showed that current smokers had a significantly higher risk of first ventricular tachycardia/ventricular fibrillation or death (hazard ratio [HR] 1.51; 95% confidence interval [CI] 1.14-2.01; P = .005) and a higher risk for first ventricular tachycardia/ventricular fibrillation episode (HR 1.54, 95% CI 1.12-2.13, P = .008) than did nonsmokers. Past smokers had a risk of first VTAs or death similar to that of nonsmokers (HR 1.01; 95% CI 0.80-1.27; P = .953). In comparison to nonsmokers, the risk of recurrent VTAs was significantly higher in the total cohort of patients (HR 1.54; 95% CI 1.21-1.95; P < .001) and in the subgroups of patients with ischemic and nonischemic cardiomyopathy (HR 1.48; 95% CI 1.03-2.13; P = .035)., Conclusions: Current smokers with left ventricular dysfunction and mild heart failure are at a significantly higher risk of VTAs or death than are past smokers and nonsmokers. Smoking is associated with a significant increase in the risk of recurrent VTAs in both patients with ischemic and nonischemic cardiomyopathy., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Cardiac resynchronization therapy (CRT) is increasingly recognized for its ability to reduce ventricular tachyarrhythmias, possibly associated with left ventricular reverse remodeling, but the role of the right ventricle (RV) in this process has not been examined., Objective: The purpose of this study was to investigate the relationship between ventricular tachyarrhythmias and change in RV dimensions in patients receiving CRT with a defibrillator (CRT-D)., Methods: Multivariate Cox proportional hazards regression modeling was used to assess the risk for fast (≥180 bpm) ventricular tachycardia/ventricular fibrillation (VT/VF) or death by baseline and follow-up RV size (defined as right ventricular end-diastolic area [RVEDA]) among 1495 patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT)., Results: Multivariate analysis showed that treatment with CRT-D was independently associated with a 27% (P = .003) reduction in the risk of VT/VF or death among patients with larger RVs (>first quartile RVEDA ≥13 mm(2)/m(2)) compared with implantable cardioverter-defibrillator (ICD)-only therapy, whereas in patients with smaller RVs there was no significant difference in the risk of VT/VF between the 2 treatment arms (hazard ratio = 1.00, P = .99). At 1-year follow-up, CRT-D patients displayed significantly greater reductions in RVEDA compared to ICD-only patients (P <.001), associated with a corresponding reduction in the risk of subsequent VT/VF or death (>first quartile reduction in RVEDA with CRT-D vs ICD-only: hazard ratio = 0.55, P <.001) independent of changes in left ventricular dimensions., Conclusion: Our findings suggest that the RV may have an important role in determining the antiarrhythmic effect of CRT independent of the effect of the device on the left ventricle., (© 2013 Heart Rhythm Society. All rights reserved.)

Background: Defibrillation threshold (DFT) testing is commonly practiced at the time of implantable cardioverter-defibrillator (ICD) implant. The clinical consequence of ICD shocks delivered during DFT testing is unknown., Objective: The purpose of this study was to determine the impact of ICD shocks and ICD shock energy level delivered during DFT testing in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) on clinical outcomes., Methods: Patients who underwent DFT testing within 1 month of device implant were categorized by the number of ICD shocks delivered during DFT testing (0, 1, 2, ≥3 shocks) and according to high vs low (>20 J vs ≤20 J) energy ICD shocks. Clinical outcomes consisting of heart failure (HF) or death, death alone, HF alone, and ventricular tachycardia or ventricular fibrillation were analyzed in each group., Results: DFT testing was performed in 1,659 patients within 1 month of device implant (1 shock in 365 patients, 2 shocks in 896 patients, 3+ shocks in 398 patients). High-energy ICD shocks were delivered in 609 patients. Increasing number of ICD shocks during DFT testing was not associated with an increase risk for the primary end-point of HF or death or for any of the secondary end-points of HF alone, VT/VF alone, or death. Delivery of high vs low-energy ICD shocks was not associated with adverse clinical outcomes., Conclusions: In patients with mild symptoms of HF, increasing number of ICD shocks and delivery of high energy ICD shocks during DFT testing was not associated with increased risk for HF or death or future VT/VF episodes., (Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)