Trends in the use of implantable cardioverter-defibrillators for prevention of sudden cardiac arrest: A South Korean nationwide population-based study

Identification of concealed cardiomyopathy using next-generation sequencing-based genetic testing in Korean patients initially diagnosed with idiopathic ventricular fibrillation

AIMS

Idiopathic ventricular fibrillation (IVF) is a disease in which the cause of ventricular fibrillation cannot be identified despite comprehensive clinical evaluation. This study aimed to investigate the clinical yield and implications of genetic testing for IVF.

METHODS AND RESULTS

This study was based on the multi-centre inherited arrhythmia syndrome registry in South Korea from 2014 to 2017. Next-generation sequencing-based genetic testing was performed that included 174 genes previously linked to cardiovascular disease. A total of 96 patients were clinically diagnosed with IVF. The mean age of the onset was 41.2 ± 12.7 years, and 79 patients were males (82.3%). Of these, 74 underwent genetic testing and four (5.4%) of the IVF probands had pathogenic or likely pathogenic variants (each having one of MYBPC3, MYH7, DSP, and TNNI3). All pathogenic or likely pathogenic variants were located in genes with definite evidence of a cardiomyopathy phenotype, either hypertrophic cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy.

CONCLUSION

Next-generation sequencing-based genetic testing identified pathogenic or likely pathogenic variants in 5.4% of patients initially diagnosed with IVF, suggesting that genetic testing with definite evidence genes of cardiomyopathy may enable molecular diagnosis in a minority of patients with IVF. Further clinical evaluation and follow-up of patients with IVF with positive genotypes are needed to unveil concealed phenotypes, such as the pre-clinical phase of cardiomyopathy.

Statement from the Asia Summit: Current state of arrhythmia care in Asia

On May 27, 2022, the Asia Pacific Heart Rhythm Society and the Heart Rhythm Society convened a meeting of leaders from different professional societies of healthcare providers committed to arrhythmia care from the Asia Pacific region. The overriding goals of the meeting were to discuss clinical and health policy issues that face each country for providing care for patients with electrophysiologic issues, share experiences and best practices, and discuss potential future solutions. Participants were asked to address a series of questions in preparation for the meeting. The format of the meeting was a series of individual country reports presented by the leaders from each of the professional societies followed by open discussion. The recorded presentations from the Asia Summit can be accessed at https://www.heartrhythm365.org/URL/asiasummit-22. Three major themes arose from the discussion. First, the major clinical problems faced by different countries vary. Although atrial fibrillation is common throughout the region, the most important issues also include more general issues such as hypertension, rheumatic heart disease, tobacco abuse, and management of potentially life-threatening problems such as sudden cardiac arrest or profound bradycardia. Second, there is significant variability in the access to advanced arrhythmia care throughout the region due to differences in workforce availability, resources, drug availability, and national health policies. Third, collaboration in the area already occurs between individual countries, but no systematic regional method for working together is present.

Clinical and Genetic Features of Korean Inherited Arrhythmia Probands

BACKGROUND AND OBJECTIVES

Inherited arrhythmia (IA) is a more common cause of sudden cardiac death in Asian population, but little is known about the genetic background of Asian IA probands. We aimed to investigate the clinical characteristics and analyze the genetic underpinnings of IA in a Korean cohort.

METHODS

This study was conducted in a multicenter cohort of the Korean IA Registry from 2014 to 2017. Genetic testing was performed using a next-generation sequencing panel including 174 causative genes of cardiovascular disease.

RESULTS

Among the 265 IA probands, idiopathic ventricular fibrillation (IVF) and Brugada Syndrome (BrS) was the most prevalent diseases (96 and 95 cases respectively), followed by long QT syndrome (LQTS, n=54). Two-hundred-sixteen probands underwent genetic testing, and 69 probands (31.9%) were detected with genetic variant, with yield of pathogenic or likely pathogenic variant as 6.4%. Left ventricular ejection fraction was significantly lower in genotype positive probands (54.7±11.3 vs. 59.3±9.2%, p=0.005). IVF probands showed highest yield of positive genotype (54.0%), followed by LQTS (23.8%), and BrS (19.5%).

CONCLUSIONS

There were significant differences in clinical characteristics and genetic yields among BrS, LQTS, and IVF. Genetic testing did not provide better yield for BrS and LQTS. On the other hand, in IVF, genetic testing using multiple gene panel might enable the molecular diagnosis of concealed genotype, which may alter future clinical diagnosis and management strategies.

Predictors for early cardiac death after discharge from successfully treated acute myocardial infarction

Background

The use of a cardioverter defibrillator for the primary prevention of sudden cardiac death is not recommended within 40 days after acute myocardial infarction (AMI). We investigated the predictors for early cardiac death among patients who were admitted for AMI and successfully discharged.

Methods

Consecutive patients with AMI were enrolled in a multicenter prospective registry. Among 10,719 patients with AMI, 554 patients with in-hospital death and 62 patients with early non-cardiac death were excluded. Early cardiac death was defined as a cardiac death within 90 days after index AMI.

Results

Early cardiac death after discharge occurred in 168/10,103 (1.7%) patients. A defibrillator was not implanted in all patients with early cardiac death. Killip class ≥3, chronic kidney disease stage ≥4, severe anemia, cardiopulmonary support usage, no dual antiplatelet therapy at discharge, and left ventricular ejection fraction (LVEF) ≤35% were independent predictors for early cardiac death. The incidence of early cardiac death according to the number of factors added to LVEF criteria in each patient was 3.03% for 0 factor, 8.11% for 1 factor, and 9.16% for ≥2 factors. Each model that sequentially added the factors in the presence of LVEF criteria showed a significant gradual increase in predictive accuracy and an improvement in reclassification capability. A model with all factors showed C-index 0.742 [95% CI 0.702-0.781], p < 0.001; IDI 0.024 [95% CI 0.015-0.033], p < 0.001; and NRI 0.644 [95% CI 0.492-0.795], p < 0.001.

Conclusion

We identified six predictors for early cardiac death after discharge from AMI. These predictors would help to discriminate high-risk patients over current LVEF criteria and to provide an individualized therapeutic approach in the subacute stage of AMI.

Hypertension and diabetes including their earlier stage are associated with increased risk of sudden cardiac arrest

Sudden cardiac arrest (SCA) is a medical disaster for both the victim and the society. Despite intrinsic limitations in the management of SCA, primary prevention has been overlooked and risk factors for SCA are not fully understood. We aimed to evaluate whether hypertension and diabetes mellitus (DM), including pre-hypertension and impaired fasting glucose (IFG), are associated with increased risk of SCA. We performed a nationwide population-based analysis using the Korean National Health Insurance Service. People who underwent a national health check-up in 2009 were enrolled. The risk of SCA was evaluated in people with hypertension and DM with a clinical follow-up through December 2018. A total of 4,056,423 people with 33,345,378 person-years of follow-up and 16,352 SCA events were examined. People with hypertension had 65.4% increased risk of SCA (adjusted hazard ratio [HR] = 1.654 [1.572–1.739]; p < 0.001). Pre-hypertension was also associated with 21.3% increased risk of SCA (adjusted HR = 1.213 [1.158–1.272]; p < 0.001). People who had IFG and DM showed 7.5% (adjusted HR = 1.075 [1.035–1.117]; p < 0.001) and 80.1% (adjusted HR = 1.801 [1.731–1.875]; p < 0.001) increased risk of SCA, respectively. People with DM who took anti-diabetic medication showed significantly lower risk of SCA compared with uncontrolled DM patients (fasting glucose ≥ 200 mg/dL) (adjusted HR = 0.625 [0.533–0.733]; p < 0.001). Coexistence of hypertension and DM was associated with an even higher risk of SCA (adjusted HR = 3.078 [2.877–3.293]; p < 0.001). In conclusion, the risk of SCA is significantly higher in people with hypertension and DM, including pre-hypertension and IFG. Adequate control of blood pressure and serum glucose can have a profound impact for the primary prevention of SCA in the general population.

The 10-Year Trend of Out-of-hospital Cardiac Arrests: a Korean Nationwide Population-Based Study

We aimed to evaluate the epidemiologic features and outcomes of non-traumatic out-of-hospital cardiac arrest (OHCA) on the basis of nationwide population-based data from Korean National Health Insurance System. This study showed the incidence of OHCA in Korea had increased during the last decade (48.2 per 100,000 person-years in 2008 to 66.7 in 2017). Coronary artery disease was the main cause (59.8%). The 1-year mortality rate tended to decline steadily. Despite the advances in medical care system, the incidence of OHCA has increased and mortality rate was still high.

Background and Objectives

It is crucial to understand the exact public health burden of out-of-hospital cardiac arrest (OHCA) cases; this is presently unknown since sufficient episodes are not reported in registry studies. We aimed to evaluate the epidemiologic features and outcomes of non-traumatic OHCA.

Methods

During January 2008 to December 2017, we enrolled 387,665 patients who had been assigned a code for sudden cardiac arrest or had undergone cardiopulmonary resuscitation in the emergency room using the Korean National Health Insurance Service database. Those whose arrest was of non-cardiac origin were excluded.

Results

The incidence of OHCA per 100,000 patients increased steadily from 48.2 in 2008 to, 53.8 in 2011, 60.1 in 2014, and 66.7 in 2017, with a 1-year survival rate of 8.2%. Age and sex-adjusted mortality rates showed a decreasing trend. The hazard ratio was 1.0015 in 2009, 0.9865 in 2012, 0.9769 in 2015, and 0.9629 in 2017 (p for trend <0.0001), with coronary artery disease-related OHCA accounting for 59.8% of the total. Subgroups with coronary artery disease-related OHCA were more likely to be older and have a higher prevalence of all related comorbidities, excluding malignancy, than those with non-coronary artery disease-related OHCA.

Conclusions

This nationwide population-based study showed that the incidence of OHCA in Korea had increased during the last decade. The post OHCA 1-year mortality rate showed a poor outcome but improved gradually.

Inherited arrhythmia syndrome predisposing to sudden cardiac death

Inherited arrhythmia (IA) is one of the main causes of sudden cardiac death (SCD) in young people, and is reported to be a more prevalent cause of SCD in Asia than in Western countries. IAs are a group of genetic disorders caused by mutations in genes encoding cardiac ion channels, leading to electrophysiological characteristics that often occur in the absence of structural abnormalities. Channelopathies, such as long QT syndrome and Brugada syndrome, carry a potential risk of life-threatening ventricular tachyarrhythmias that predispose to SCD, although early prediction and prevention of the risk remain challenging. Recent advances in genetic testing have facilitated risk stratification as well as a precise diagnosis for IA, despite ongoing debates about the implications. Herein, we provide epidemiological data, a pathophysiological overview, and the current clinical approach to IAs related to SCD. In addition, we review the general issues arising from genetic testing for IAs.

Implantable Cardioverter-defibrillator Utilization and Its Outcomes in Korea: Data from Korean Acute Heart Failure Registry

BACKGROUND

There are sparse data on the utilization rate of implantable cardioverter-defibrillator (ICD) and its beneficial effects in Korean patients with heart failure with reduced left ventricular ejection fraction (LVEF).

METHODS

Among 5,625 acute heart failure (AHF) patients from 10 tertiary university hospitals across Korea, 485 patients with reassessed LVEF ≤ 35% at least 3 months after the index admission were enrolled in this study. The ICD implantation during the follow-up was evaluated. Mortality was compared between patients with ICDs and age-, sex-, and follow-up duration matched control patients.

RESULTS

Among 485 patients potentially indicated for an ICD for primary prevention, only 56 patients (11.5%) underwent ICD implantation during the follow-up. Patients with ICD showed a significantly lower all-cause mortality compared with their matched control population: adjusted hazard ratio (HR) (95% confidence interval [CI]) = 0.39 (0.16-0.92), P = 0.032. The mortality rate was still lower in the ICD group after excluding patients with cardiac resynchronization therapy (adjusted HR [95% CI] = 0.09 [0.01-0.63], P = 0.015). According to the subgroup analysis for ischemic heart failure, there was a significantly lower all-cause mortality in the ICD group than in the no-ICD group (HR [95% CI] = 0.20 [0.06-0.72], P = 0.013), with a borderline statistical significance (interaction P = 0.069).

CONCLUSION

Follow-up data of this large, multicenter registry suggests a significant under-utilization of ICD in Korean heart failure patients with reduced LVEF. Survival analysis implies that previously proven survival benefit of ICD in clinical trials could be extrapolated to Korean patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01389843.

Incidence and etiology of sudden cardiac arrest in Koreans: A cohort from the national health insurance service database

The incidence of sudden cardiac arrest (SCA) in Asians is lower than that seen in Western populations, but there are few available data on the incidence and associated cardiac etiology of SCA in Asians. From 2002 to 2013, patients with SCA were analyzed using a cohort from the South Korean National Health Insurance Service (NHIS) coded database. Sudden unexplained death syndrome (SUDS) was defined as cryptogenic arrest, excluding that of non-cardiac origin, coronary artery disease (CAD), cardiomyopathy (CM), and valvular heart disease. During the 12-year study period, 5,973 patients (0.53%) from the total cohort of 1,125,691 had a cardiac arrest code. The overall incidence of arrest was 48.7 per 100,000 person-years (95% CI 16.6-18.0). The incidence of primary SCA excluding those of non-cardiac origin was 16.1 per 100,000 person-years (95% CI 15.4-16.8). It was higher in males than in females (18.1 vs. 14.1 per 100,000 person-years). CAD was the most common cause of SCA (59.4%), and followed by CM (13.9%). SUDS accounted for 14.7% of SCA events. The risk of SCA had increased gradually from over 25 years old. Heart failure, atrial fibrillation and hypertension are major factors associated with SCA incidence. Our findings outline epidemiologic data for SCA and the proportion of associated cardiac etiology leads SCA in a large population.

Exploring Advance Directive Perspectives and Associations with Preferences for End-of-Life Life-Sustaining Treatments among Patients with Implantable Cardioverter-Defibrillators

Deactivation of an implantable cardioverter-defibrillator (ICD) is a critical issue in the advance care planning (ACP) of ICD recipients; however, related perspectives have rarely been explored. Thus, this study aimed to provide an initial investigation of ICD recipients’ perceived susceptibility and barriers/benefits regarding ACP and/or advance directives (ADs), and associations of these modifiable factors with preferences for end-of-life life-sustaining treatments (LSTs) (cardiopulmonary resuscitation (CPR), ventilator support, hemodialysis, and hospice care). Using a descriptive correlational design, 48 ICD recipients (age, 50.1 years; male, 85.4%) completed survey questionnaires. “No burden on family” was the most highly valued (59.1%), followed by “comfortable death” (20.4%), and both (11.4%). LST preference was 43.8% for ventilator support, 45.8% for both hemodialysis and hospice care, and 54.2% for CPR. Perceived susceptibility to having unexpected end-of-life experiences increased the likelihood of preference for aggressive LSTs, with preferences increasing by 15% for CPR, 17% for ventilator support, and 23% for hemodialysis. A non-modifiable factor, older age, was the only predictor of increased preference for hospice care (odds ratio = 1.09, p = 0.016). Among the modifiable factors, a higher perceived susceptibility increased the likelihood of aggressive LST preferences. The findings imply that to facilitate informed decisions for LSTs, early ACP discussion could be helpful and enhance these modifiable factors.

Effect of physical and psychocognitive function and perceived health status on 12-month adverse cardiac events among implantable cardioverter-defibrillator recipients

BACKGROUND

Post-implant recovery in patients with implantable cardioverter-defibrillators (ICDs) is often compromised because of reduced physical and psycho-cognitive function and poor health perception, leading to short event-free survival.

OBJECTIVES

To examine the effects of psychocognitive function, health perception, and ICD-related factors on 12-month cardiac events among ICD patients.

METHODS

Using a prospective study design, ICD patients underwent baseline assessment and were followed for 12 months to assess cardiac events.

RESULTS

Cardiac events occurred in 14 patients (18.9%) (N = 74: age, 58 years; primary ICDs, 45.9%). Time after ICD implant (odds ratio [OR] = 1.002; p = .028) and executive function (OR = 1.021; p = .027) were significant predictors of 12-month cardiac events, while other physical and psychological indices were not.

CONCLUSIONS

Reduced executive function and longer time after implant predicted the events. Healthcare professionals need to assess executive function and provide treatment and support to improve executive function.

Defibrillation threshold testing during implantable cardioverter defibrillator implantation: 5-year follow-up

PURPOSE

Defibrillation threshold (DFT) testing is a routine practice in some Asian countries for patients receiving an implantable cardioverter defibrillator (ICD). However, there are few long-term data about the necessity of intraoperative DFT testing in an Asian population. We investigated the safety of DFT testing and the long-term clinical outcomes in Asian patients undergoing ICD implantation.

METHODS

All patients undergoing de novo transvenous ICD implantation were randomized to undergo periprocedural DFT testing. The study included 67 patients (50 males; 51.5 ± 16.9 years) who underwent ICD implantation with (n = 33) or without (n = 34) intraoperative DFT testing between March 2012 and February 2014. We compared first-shock success, composite safety end points (the sum of complications recorded at 30 days), arrhythmic death, and all-cause mortality.

RESULTS

The baseline clinical characteristics and the procedural-related adverse event rate (3.0% with DFT vs. 0% with non-DFT, p = 0.214) did not differ between groups. The programmed output of the first shock was lower in the DFT testing group (22.9 ± 4.4 J vs. 25.3 ± 5.4 J, p = 0.007). However, there were no significant differences between groups for all-cause mortality (12.1% vs. 17.6%, p = 0.526) or first-shock success rate for ventricular arrhythmia (100% vs. 88.2%, p = 0.471).

CONCLUSIONS

There were no between-group differences in periprocedural safety, complications, and long-term clinical outcomes. Our results suggest that DFT testing in Asian patients allows reduction of the programmed output of the first shock, but does not affect long-term clinical outcomes.