|Year : 2020 | Volume
| Issue : 1 | Page : 1-7
Implantable cardioverter defibrillators for sudden cardiac death prevention in China: A regional analysis from the improve SCA clinical trial
Yanchun Liang1, Shu Zhang2, Zhihui Zhang3, Farong Shen4, Jingfeng Wang5, Liangrong Zheng6, Baopeng Tang7, Yangang Su7, Mark L Brown8, Brian M Van Dorn8, Janet E O'Brien8, Dejia Huang9
1 Division of Cardiology, The General Hospital of Northern Theater Command, Shenyang, Liaoning Province, China
2 Department of Cardiovascular Medicine, Arrythmia Center, Fuwai Hospital Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
3 Department of Cardiovascular Medicine, The Third Xiangya Hospital of Central South University, Changsha, Hunan Province, China
4 Department of Cardiovascular Medicine, Zhejiang Greentown Cardiovascular Hospital, Hangzhou, Zhejiang Province, China
5 Department of Cardiovascular Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
6 Department of Cardiovascular Medicine, The First Affiliated Hospital, Zhejiang University, Hangzhou, Zhejiang Province, China
7 Department of Cardiovascular Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
8 Cardiac Rhythm Disease Management Clinical Research, Medtronic, Inc., Mounds View, MN, USA
9 Department of Cardiovascular Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
|Date of Submission||24-Sep-2020|
|Date of Decision||10-Oct-2020|
|Date of Acceptance||24-Nov-2020|
|Date of Web Publication||28-Jan-2021|
Dr. Dejia Huang
West China Hospital, Sichuan University, No. 37 Guo Xue St., Chengdu 610041, Sichuan Province
Source of Support: None, Conflict of Interest: None
Background: The improve sudden cardiac arrest (SCA) study was a nonrandomized prospective global study that identified a subset of primary prevention (PP) patients at an elevated risk for SCA labeled 1.5PP. These 1.5PP patients had one or more of the following additional risk factors: Syncope, nonsustained ventricular tachycardia, premature ventricular contractions >10/h, and left ventricular ejection fraction <25%. The purpose of this sub-analysis was to examine the China population cohort according to the improve SCA study's primary and secondary objectives. We aim to analyze the improve SCA study objective outcomes explicitly in the Chinese cohort to better understand the utility of PP implantable cardioverter-defibrillator (ICD) therapy in China. Subjects and Methods: The improve SCA study enrolled patients (n = 4222) during March 2014 and July 2017, including 87 sites in 17 countries from the geographies of Asia, Latin America, Eastern Europe, the Middle East, and Africa. In this analysis, the China cohort of improve SCA patients (n = 1654) was analyzed according to the objectives of the main study; the primary objective compared time to first appropriate ventricular tachycardia (VT) or ventricular fibrillation (VF) therapy between 1.5PP (n = 904) and secondary prevention (SP) patients (n = 470). All-cause mortality rates of 1.5PP with ICDs versus no implant, and an analysis of ischemic versus nonischemic results (n = 280) were also analyzed. PP patients without an additional risk factor were labeled 1.0PP (n = 280). Cox-proportional hazards model was used for hazard ratio (HR) calculations. This study was approved by the Ethics Committee of each participating institution and the associated national and local regulatory agencies, and registered with ClinicalTrials.gov (identifier: NCT02099721). Results: The time to first VT/VF therapy for 1.5PP was not within 30% of SP (HR = 0.42, 95% confidence interval [CI]: 0.31–0.56, P < 0.0001). However, there was a 49% reduction (HR = 0.51, 95% CI: 0.35–0.74, P = 0.0004) in all-cause mortality in the 1.5PP implanted versus nonimplanted patients, and a 70% reduction (HR = 0.30, 95% CI: 0.09–0.99, P = 0.05) in 1.0PP implanted patients. Nonischemic cardiomyopathy (NICM) 1.5PP patients showed a 51% reduction (HR = 0.49, 95% CI: 0.34–0.77, P = 0.0012) in all-cause mortality compared to those who did not receive an ICD implant. Conclusion: The China populations of 1.0PP and 1.5PP patients obtain a significant benefit with implantable defibrillation therapy.
Keywords: Implantable cardioverter defibrillators, mortality, nonischemic cardiomyopathy, primary prevention, secondary prevention, sudden cardiac arrest
|How to cite this article:|
Liang Y, Zhang S, Zhang Z, Shen F, Wang J, Zheng L, Tang B, Su Y, Brown ML, Van Dorn BM, O'Brien JE, Huang D. Implantable cardioverter defibrillators for sudden cardiac death prevention in China: A regional analysis from the improve SCA clinical trial. Int J Heart Rhythm 2020;5:1-7
|How to cite this URL:|
Liang Y, Zhang S, Zhang Z, Shen F, Wang J, Zheng L, Tang B, Su Y, Brown ML, Van Dorn BM, O'Brien JE, Huang D. Implantable cardioverter defibrillators for sudden cardiac death prevention in China: A regional analysis from the improve SCA clinical trial. Int J Heart Rhythm [serial online] 2020 [cited 2021 Sep 24];5:1-7. Available from: https://www.ijhronline.org/text.asp?2020/5/1/1/308167
| Introduction|| |
Utilization of implantable cardioverter defibrillators (ICDs) for the prevention of sudden cardiac death (SCD) remains low in China despite solid evidence of ICD therapy for both primary prevention (PP) and secondary prevention (SP) of SCD., SP refers to the use of implantable defibrillator therapy to prevent sudden cardiac arrest (SCA) in survivors of a prior SCA or sustained ventricular tachycardia (VT). PP refers to patients who are at risk for SCD but do not have a documented episode of sustained VT, ventricular fibrillation (VF), or resuscitated cardiac arrest.
Over the past three decades, the trend of cardiovascular diseases and SCD has increased significantly in China as a result of improved living standards, dramatic lifestyle changes, and an aging population. One of the obstacles to ICD utilization is a lack of local evidence to support reimbursement and therapy adoption by physicians and patients.,, The improve SCA study was a prospective, nonrandomized, nonblinded, multicenter, global study that was intended to study a sub-population of PP patients labeled 1.5PP. This sub-population consists of patients with a current indication for an ICD that is considered PP who have at least one of these additional risk factors: Syncope or pre-syncope, very low left ventricular ejection fraction (LVEF <25%), nonsustained VT (NSVT), and/or frequent premature ventricular contractions (PVCs). Therefore, 1.5PP patients identified with a specific additional risk factor were at a potentially elevated risk of SCD over PP patients.
The global improve SCA study included 3889 patients and evaluated time to first ICD therapy and mortality rates between SP and 1.5PP patient populations. There were 1193 SP and 1913 1.5PP patients included. The primary endpoint was a prespecified percentage comparison (within 30%) of time to first therapy between SP and 1.5PP patients. The secondary objective compared mortality rates between the 1.5PP ICD implanted and 1.5PP nonimplanted patients. In the global enrollment, time to first therapy between these 1.5PP and SP patients was not within the prespecified 30%, but 1.5PP implanted patients had a 49% adjusted relative risk reduction in all-cause mortality compared to those who did not receive an ICD. A majority of the global study cohort had nonischemic cardiomyopathy (NICM); therefore, the endpoints for ischemic versus NICM were also analyzed.
Data on SCD, heart failure treatment, and outcomes specific to the improve SCA study regions are limited. The majority of large-scale studies results are from the United States and Europe where Asian patients are not well represented. Recent global analysis on the mortality of heart failure patients at 1 year, including the regions of Africa, China, India, the Middle East, Southeast Asia, and South America found marked differences in their regional results., This study aimed to evaluate the improve SCA study objective outcomes explicitly in Chinese patients to better understand the utility of PP ICD therapy in China.
| Subjects and Methods|| |
Patients from China were enrolled in the improve SCA study from 35 hospitals [Table 1] between March 2014 and July 2017 and followed every 6 months, for a consecutive period of 24 months. Patients 18 years or older who met the American Heart Association, American College of Cardiology, Heart Rhythm Society (HRS) or European Society of Cardiology Class I guidelines for an ICD or cardiac resynchronization therapy defibrillator (CRT-D) implant were eligible for enrollment., The improve SCA study protocol and data analysis oversight were conducted by the steering committee in collaboration with the sponsor and instituted in accordance with the ethical principles of the Declaration of Helsinki. This study was approved by the Ethics Committee of each participating institution and the associated national and local regulatory agencies, and registered with ClinicalTrials.gov (identifier: NCT02099721). The improve SCA study methods have been previously published. All patients voluntarily and without incentive provided written informed consent before undergoing study procedures. The physicians and eligible patients made the therapy choice. The final implant decision was made by the patients and was not dictated by the study. Patients were implanted with an medtronic device and programmed to the same therapy parameters.
Changes were allowed (and recorded) if necessary due to the patient's medical condition throughout the follow-up period. Medication use was collected at the baseline visit but was not recorded at subsequent follow-up visits. PP patients were followed every 6 months for 24 months, reasons for nonimplant choices were collected and those patients were also followed every 6 months for 24 months. SP patients who did not receive a device would not contribute to the objectives of the study and therefore were exited form the study.
To ensure a wide distribution of data between the sites, the maximum enrollment per site was limited to 5% of the expected total study enrollment.
The improve SCA study was powered at 80% to demonstrate that the rate of VT/VF between 1.5 and secondary patients was within 30% assuming the difference in rates was 9%. More details can be found in the primary results manuscript. The study enrolled patients in numerous countries, and the sample size of patients in China was not predetermined.
Continuous variables are reported as the mean ± standard deviation two-sample t-tests and The Chi-square tests were used to compare the baseline characteristics. The primary objective of the improve SCA study was to determine if VT/VF therapy rates (defined as time to first appropriate VT/VF therapy) between 1.5PP and SP were within 30% (lower 95% confidence bound of hazard ratio (HR) of 1.5PP/SP is >0.7). All patients who were enrolled in China and received an ICD at any time in the study were included in the primary objective analysis. The endpoint of treated VT/VF episode was therapy by antitachycardia pacing (ATP) therapy or shock. Episodes were adjudicated by 2–3 reviewers, and only those adjudicated to be true VT/VF were included. Patients were followed from the date of implant and were censored on the date of their last device follow-up. The global study patients were followed for a mean of 20.8 ± 10.8 months. The China cohort of patients was followed through to the 24-month visit with a median follow-up time of 22.2 months.
Subject demographics were collected at baseline to analyze the differences that could potentially affect the endpoints. Due to the lack of randomization, the secondary objective analysis of mortality used Cox proportional hazards adjustment (adjusting for the following pre-specified factors: Age, sex, QRS duration, ischemic cardiomyopathy, left bundle branch block, NYHA, diabetes, LVEF, syncope qualifying as 1.5PP, NSVT qualifying as 1.5PP, and PVCs qualifying as 1.5PP). The adjusted and unadjusted P values and HRS are reported in each mortality analysis. Patients were followed from the date of implant or date of implant refusal and were censored at their last follow-up. Kaplan–Meier methods were used to produce incidence plots, and the curves within the plots were censored when fewer than 20 patients remained at risk. There were post-hoc comparisons between the 1.5PP and 1.0PP populations. The sample size for the overall trial was determined using a simulation program and was re-calculated midway through the study to achieve a statistical power of 90%. However, the trial was not powered for this subset of Chinese patients.
| Results|| |
Of the 1654 patients analyzed in the cohort study, 1207 (73.0%) were male and 447 (27.0%) were female. Other baseline characteristics between implanted and nonimplanted SP, 1.5PP, and 1.0PP patients are found in [Table 2]. In this China cohort, 1074 (64.9%) patients received an ICD or CRT-D system. Of the SP (n = 470) patients, 385 (81.9%) were implanted, and 85 were not implanted. Of the 1.5PP (n = 904) patients, 545 (60.3%) were implanted and 359 were not implanted. For the 1.0PP (n = 280) patients, 144 (51.4%) were implanted and 136 were not implanted [Figure 1].
|Figure 1: Patient enrollment flow of the China Cohort of the Improve SCA study CRT-D = Cardiac resynchronization therapy-defibrillator, ICD = implantable cardioverter defibrillator, LVEF = Left ventricular ejection fraction, MI = Myocardial infarct|
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Time to first VT/VF therapy
Of the China cohort, there were appropriately 2178 treated VT/VF device episodes treated with ATP and/or shock that had electrocardiograms (EGMs) available for adjudication.
The time to first appropriate VT/VF therapy for 1.5PP and SP was not within the 30% prespecified criteria for “similar” [[Figure 2], HR = 0.42, 95% confidence interval (CI): 0.31–0.56, P < 0.0001]. This result is consistent with the global study results. The difference in the time to first appropriate VT/VF therapy between 1.5PP and 1.0PP patients was not statistically significant for participants in China.
|Figure 2: Time to the first appropriate ventricular tachycardia/ventricular fibrillation (VT/VF) therapy for 1.0PP, 1.5PP, and SP subjects. Hazard ratios are adjusted for differences in baseline characteristics. CI = Confidence interval, PP = Primary prevention, SP = Secondary prevention|
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The estimated 2-year mortality rate for 1.5PP patients was 20.9% in the nonimplanted group and 12.1% in the ICD implanted group, resulting in a statistically significant reduction of 49% in all-cause mortality [[Figure 3]a, HR = 0.51, 95% CI: 0.35–0.74, P = 0.0004]. For 1.0PP patients, the estimated 2-year all-cause mortality rate was 11.2% in the nonimplanted group and 3.0% in the implanted group, representing a 70% risk reduction with ICD implant [[Figure 3]b, HR = 0.30, 95% CI: 0.09–0.99, P = 0.05]. In addition, there was a significant difference in mortality between the 1.0PP and 1.5PP nonimplanted groups (HR = 0.41, 95% CI: 0.22–0.77, P < 0.0001).
|Figure 3: Mortality summary. (a) Mortality of prespecified secondary objective: Comparison of the 2-year all-cause mortality rates between implanted and nonimplanted 1.5PP patients. (b) Post hoc analysis of mortality rates between implanted and nonimplanted 1.0PP patients. Hazard ratios and P values are adjusted for differences in baseline characteristics. ICD = Implantable cardioverter defibrillator, CRT-D = Cardiac resynchronization therapy-defibrillator, PP = Primary prevention, SP = Secondary prevention|
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Study endpoints in patients with nonischemic cardiomyopathy
Of these nonischemic patients in the study, 142 SP, 453 1.5PP, and 114 1.0PP received a device. The time to first VT/VF therapy in the patients with NICM was similar to the ischemic cardiomyopathy patients [[Figure 4]a, HR = 0.48, 95% CI: 0.33–0.70, P = 0.0002]. In nonischemic, 1.5PP patients, ICD therapy significantly reduced all-cause mortality by 51% [[Figure 4]b, HR 0.49, 95% CI: 0.31–0.75, P = 0.0012). In addition, mortality was reduced for both ischemic (by 47%) and nonischemic (by 53%) 1.0PP patients by implantation [Figure 5].
|Figure 4: Study endpoints in patients with nonischemic cardiomyopathy. (a) Post hoc analysis of time to first treated ventricular tachycardia/ventricular fibrillation (VT/VF) episodes in PP and SP patients with nonischemic cardiomyopathy. (b) Post hoc analysis of the mortality rates in patients with nonischemic cardiomyopathy. ICD = implantable cardioverter defibrillator. CI = Confidence interval, CRT-D = Cardiac resynchronization therapy-defibrillator, PP = Primary prevention, SP = Secondary prevention|
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|Figure 5: Mortality comparison between implanted and nonimplanted 1.0 and 1.5PP patients within the cardiomyopathy groups. Hazard ratios are adjusted for differences in baseline characteristics. CI = Confidence interval, ICM = Ischemic cardiomyopathy, NICM = Non-ischemic cardiomyopathy|
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| Discussion|| |
The mortality benefit of ICD therapy in PP has been well-established in the past with the Multicenter Automatic Defibrillator Implantation Trial (MADIT-II) and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) studies, among others.,, However, these data are not contemporaneous and the current ICD population with recent advances in medical and revascularization therapy may not receive the same benefit from ICD therapy. A previous study found that Chinese patients (n = 70) were at a similar risk of sudden and nonsudden cardiac death compared to the original MADIT-II subjects. Our data show that there is a benefit in a contemporaneous population, specifically pertaining to the China improve SCA patients.
This prospective analysis of over 1500 patients highlights several important points for the Chinese heart failure patient population, which has been cited to be 4.2 million people with 500,000 new cases diagnosed annually. First, ICD implantation conferred a 49% reduction in all-cause mortality in 1.5PP patients. Moreover, 1.0PP patients receiving an ICD had a 70% all-cause mortality reduction compared to those who did not receive an ICD. The primary and secondary endpoints of the China analysis were comparable to the global findings. Second, both ischemic and nonischemic 1.0PP patients achieved a significant all-cause mortality reduction of 47% and 53%, respectively, for those receiving an ICD compared to those who did not. Our data show the benefit of ICD therapy in PP of SCD in NICM. This is important data further validating the contemporary benefit and use of ICDs for SCA prevention. These are important findings which can contribute to improving the overall heart failure population health in China, and it differs from the results reported in the Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure (DANISH) analysis which did not show a significant benefit of ICD therapy for NICM PP patients. Observational studies have indicated that roughly half of European clinicians changed their PP ICD implantation practice due to the DANISH study data., However, the DANISH study enrolled patients exclusively in Denmark, and the primary outcome was death from any cause. More recent global analysis (n = 8399) also found no significant difference in the benefit (56% SCD risk reduction for ICD eligible patients) between ischemic (P < 0.001) and nonischemic (P = 0.02) patients.(20) The benefits for NICM PP patients regarding mortality, and readmission rates were also found to be superior to ICM patients with ICD therapy.
Cardiovascular and cerebrovascular disease has become the leading cause of mortality (for men and women) in China, and SCD was estimated to be over 544,000 deaths per 1.3 billion annually. Despite this SCD rate, the cardioverter defibrillator utilization was found to be 1.5 per 2.5 million people (in a previous study). In a global analysis, the Asia-Pacific region was found to have the lowest rate of ICD utilization (1.7%) and the highest rate of SCD. Underutilization of device life-saving therapies remains due to several factors. A 2017 survey study using the Asian Sudden Cardiac Death in Heart Failure registry (n = 5276) found that the top three reasons for declining device therapy in Asian regions were financial (28.8%), patient's belief of the ability to manage symptoms without devices (24.3%), and inefficiency of the device therapy (14.0%). The improve SCA study found the most common reason for refusal of device therapy to be financial (53.8%) and not believing in the device benefit (19.4%), indicating that these barriers to therapy are not being resolved. In the China cohort of the improve SCA study, 58.2% of PP patients (1.0PP and 1.5PP) received an ICD or CRT-D, which is much higher than the historic implant rate. The reasons for this higher implant rate are not known but are likely associated with the involvement of the physicians and patients in a clinical trial.
Broader awareness of the benefits of ICD implantation, as observed in the improve SCA study, is essential to overcome the barriers to decrease the SCA risk for Chinese patients. The underutilization of ICD therapy in this region for PP patients leaves a significant number of the eligible population at risk for SCA. Barriers to therapy adoption remain and need to be addressed. The 1.5PP criteria can serve as an additional tool to stratify PP patients for SCA prevention within this underserved area of medicine.
This sub-analysis of the China improve SCA study population shows the similarity of the China patient population results to the worldwide study outcomes. There are recognized limitations within this sub-analysis. This is a subset of a large nonrandomized global study, of which the sample size was calculated to achieve a statistical power of 90% for the entire study cohort, and the trial was not powered for this subset of Chinese patients. The decision for ICD implantation was at the discretion of the patient and/or physician, which introduces factors that may confound the overall results.
| Conclusion|| |
This sub-analysis examining the China sub-population of the Improve SCA Study data results demonstrate that ICDs/CRT-Ds confer a significant mortality benefit for PP patients in China, including NICM patients. These results of the China population are consistent with the global improve SCA study results. These data on ICD therapy for PP patients in China and the 1.5PP criteria can serve as an additional tool in SCA prevention using device therapy for this underserved area of medicine.
Institutional review board statement
This study was approved by the Ethics Committee of each participating institution and conducted in accordance with the Declaration of Helsinki, and the associated national and local regulatory agencies and registered with ClinicalTrials.gov (identifier: NCT02099721).
Declaration of patient consent
The authors certify that they have obtained all appropriate consent from patients. In the forms, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity forms.
Financial support and sponsorship
The improve SCA study and this analysis were financially supported by Medtronic, Inc.
Conflicts of interest
The author DH has received speaker/consultant fees from Boston Scientific, St. Jude Medical and was a principal investigator for the Improve SCA Study. YL, SZ, ZZ, FS, JW, LZ, BT, YS and DH did not receive any compensation for their contributions on this publication. MB, BV and JO are employees of Medtronic, Inc.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]