Long-Term Outcomes of Implantable Cardioverter-Defibrillator Therapy in the SCD-HeFT

New York Heart Association functional class and implantable cardioverter-defibrillator in non-ischaemic heart failure with reduced ejection fraction: Extended follow-up of the DANISH trial

AIMS

Current guidelines recommend implantable cardioverter-defibrillator (ICD) therapy in patients with heart failure, a left ventricular ejection fraction of ≤35%, and New York Heart Association (NYHA) class II-III. However, the evidence regarding the benefit of primary prevention ICD is less consistent in patients with NYHA class III. We investigated the long-term effects of primary prevention ICD implantation according to NYHA class in an extended follow-up study of the DANISH trial.

METHODS AND RESULTS

The DANISH trial randomized 1116 patients with non-ischaemic heart failure with reduced ejection fraction (HFrEF) to ICD implantation or usual care. Outcomes were analysed according to NYHA class at baseline (NYHA class II and III/IV). The primary outcome was all-cause mortality. Of the 1116 patients randomized in the DANISH trial, 597 (53.5%) were in NYHA class II at baseline, 505 (45.3%) in NYHA class III, and 14 (1.3%) in NYHA class IV. During a median follow-up of 9.5 years, NYHA class III/IV, compared with NYHA class II, were associated with a greater long-term rate of all-cause mortality (hazard ratio [HR] 1.52, 95% confidence interval [CI] 1.20-1.93) and cardiovascular death (HR 1.95 [1.47-2.60]). ICD implantation, compared with usual care, did not reduce the long-term rate of all-cause mortality (all participants: HR 0.89 [95% CI 0.74-1.08]; NYHA class II: HR 0.85 [0.64-1.13]; NYHA class III/IV: HR 0.89 [0.69-1.14]; pinteraction = 0.78) or cardiovascular death (all participants: HR 0.87 [95% CI 0.70-1.09]; NYHA class II: HR 0.78 [0.54-1.12]; NYHA class III/IV: HR 0.89 [0.67-1.19]; pinteraction = 0.58), irrespective of NYHA class. Similarly, NYHA class did not modify the beneficial effects of ICD implantation on sudden cardiovascular death (all participants: HR 0.60 [95% CI 0.40-0.92]; NYHA class II: HR 0.73 [0.40-1.36]; NYHA class III/IV: HR 0.52 [0.29-0.94]; pinteraction = 0.39).

CONCLUSIONS

In patients with non-ischaemic HFrEF, ICD implantation, compared with usual care, did not reduce the overall mortality rate, but it did reduce sudden cardiovascular death, regardless of baseline NYHA class.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00542945.

Left bundle branch block-induced dilated cardiomyopathy: Definitions, pathophysiology, and therapy

Left bundle branch block (LBBB) is a frequent finding in patients with heart failure (HF), particularly in those with dilated cardiomyopathy (DCM). LBBB has been commonly described as a consequence of DCM development. However, a total recovery of left ventricular (LV) function after cardiac resynchronization therapy (CRT), observed in patients with LBBB and DCM, has led to increasing acknowledgement of LBBB-induced dilated cardiomyopathy (LBBB-iDCM) as a specific pathological entity. Its recognition has important clinical implications, as LBBB-iDCM patients may benefit from an early CRT strategy rather than medical HF therapy only. At present, there are no definitive diagnostic criteria enabling the universal identification of LBBB-iDCM, and no defined therapeutic approach in this subgroup of patients. This review compiles the main findings about LBBB-iDCM pathophysiology and the current proposed diagnostic criteria and therapeutic approach.

Predicting long-term survival after de novo cardioverter-defibrillator implantation for primary prevention: A population based study

Background

Implantable cardioverter-defibrillators (ICDs) reduce the risk of sudden cardiac death in patients with left ventricular dysfunction. While short-term mortality benefit of ICD insertion has been established in landmark randomized controlled trials, little is known about the long-term outcomes of patients with ICDs in clinical practice. In this paper, we describe the long-term survival of patients following de novo ICD implantation for primary prevention in clinical practice and determine the factors which help predict survival after ICD implant.

Methods

Retrospective population-based study of all patients receiving a de novo ICD for primary prevention in Ontario, Canada from 2007 to 2011 using the Ontario ICD Database housed within ICES. Simple random selection was used to split the population into a derivation and internal validation cohort in a ratio of 2:1. Cox proportional hazards regression was used to determine predictors of interest and predict 10-year survival, model performance was assessed using calibration and validation.

Results

In the derivation cohort (n = 3399), mean age was 65.3 years (standard deviation [SD] = 11.0), 664 patients were female (19.5 %) and 2344 patients (69.0 %) had ischemic cardiomyopathy. Ten year survival was 45.7 % (95 % confidence interval [CI] 44.0 %-47.4 %). The final prediction model included age, sex, disease factors (ischemic vs nonischemic cardiomyopathy, left ventricular ejection fraction) and patient factors (symptoms, comorbidities), and biomarkers at the time of ICD assessment. This model had good discrimination and calibration in derivation (0.79, 95 % CI 0.77, 0.81) and validation samples (0.78, 95 % CI 0.76, 0.79).

Conclusions

A combination of demographic and clinical factors determined at baseline can be used to predict 10-year survival in patients with implantable cardioverter-defibrillators with good accuracy. Our findings help to identify individuals at risk of long-term mortality and may be useful in targeting future prevention strategies to enhance longevity in this high-risk population.

Characteristics of the phenotype of mixed cardiomyopathy in patients with implantable cardioverter-defibrillators

BACKGROUND OR PURPOSE

The prognosis of m ixed cardiomyopathy (CMP) in patients with implanted cardioverter-defibrillators (ICDs) has not been investigated. We aim to study the demographic, clinical, device therapies and survival characteristics of mixed CMP in a cohort of patients implanted with a defibrillator.

METHODS

The term mixed CMP was used to categorise patients with impaired left ventricular ejection fraction attributed to documented non-ischemic triggers with concomitant moderate coronary artery disease. This is a single center observational cohort of 526 patients with a mean follow-up of 8.7 ± 3.5 years.

RESULTS

There were 42.5% patients with ischemic cardiomyopathy (ICM), 26.9% with non-ischemic cardiomyopathy (NICM) and 30.6% with mixed CMP. Mixed CMP, compared to NICM, was associated with higher mean age (69.1 ± 9.6 years), atrial fibrillation (55.3%) and greater incidence of comorbidities. The proportion of patients with mixed CMP receiving device shocks was 23.6%, compared to 18.4% in NICM and 27% in ICM. The VT cycle length recorded in mixed CMP (281.6 ± 43.1 ms) was comparable with ICM (282.5 ± 44 ms; p = 0.9) and lesser than NICM (297.7 ± 48.7 ms; p = 0.1). All-cause mortality in mixed CMP (21.1%) was similar to ICM (20.1%; p = 0.8) and higher than NICM (15.6%; p = 0.2). The Kaplan-Meier curves revealed hazards of 1.57 (95% CI: 0.91, 2.68) for mixed CMP compared to NICM.

CONCLUSION

In a cohort of patients with ICD, the group with mixed CMP represents a phenotype predominantly comprised of the elderly with a higher incidence of comorbidities. Mixed CMP resembles ICM in terms of number of device shocks and VT cycle length. Trends of long-term prognosis of patients with mixed CMP are worse than NICM and similar to ICM.

Incidence, risk assessment and prevention of sudden cardiac death in cardiomyopathies

Cardiomyopathies are a significant contributor to cardiovascular morbidity and mortality, mainly due to the development of heart failure and increased risk of sudden cardiac death (SCD). Despite improvement in survival with contemporary treatment, SCD remains an important cause of mortality in cardiomyopathies. It occurs at a rate ranging between 0.15% and 0.7% per year (depending on the cardiomyopathy), which significantly surpasses SCD incidence in the age- and sex-matched general population. The risk of SCD is affected by multiple factors including the aetiology, genetic basis, age, sex, physical exertion, the extent of myocardial disease severity, conduction system abnormalities, and electrical instability, as measured by various metrics. Over the past decades, the knowledge on the mechanisms and risk factors for SCD has substantially improved, allowing for a better-informed risk stratification. However, unresolved issues still challenge the guidance of SCD prevention in patients with cardiomyopathies. In this review, we aim to provide an in-depth discussion of the contemporary concepts pertinent to understanding the burden, risk assessment and prevention of SCD in cardiomyopathies (dilated, non-dilated left ventricular, hypertrophic, arrhythmogenic right ventricular, and restrictive). The review first focuses on SCD incidence in cardiomyopathies and then summarizes established and emerging risk factors for life-threatening arrhythmias/SCD. Finally, it discusses validated approaches to the risk assessment and evidence-based measures for SCD prevention in cardiomyopathies, pointing to the gaps in evidence and areas of uncertainties that merit future clarification.

Predictors and Outcomes of Sudden Cardiac Arrest in Heart Failure With Preserved Ejection Fraction: A Nationwide Inpatient Sample Analysis

Sudden cardiac arrest (SCA) is the leading cause of cardiovascular mortality in heart failure with preserved ejection fraction (HFpEF), contributing to around 25% of deaths observed in pivotal HFpEF trials. However, predictors and outcomes of in-hospital SCA in HFpEF have not been well characterized. We queried the Nationwide Inpatient Sample (2016 to 2017) to identify adult hospitalizations with a diagnosis of HFpEF. Patients with acute or chronic conditions associated with SCA (e.g., acute myocardial infarction, acute pulmonary embolism, sarcoidosis) were excluded. We ascertained whether SCA occurred during these hospitalizations, identified predictors of SCA using multivariate logistic regression, and determined outcomes of SCA in HFpEF. Of 2,909,134 hospitalizations, SCA occurred in 1.48% (43,105). The mean age of the SCA group was 72.3 ± 12.4 years, 55.8% were women, and 66.4% were White. Presence of third-degree atrioventricular block (odds ratio [OR] 5.95, 95% confidence interval [CI] 5.31 to 6.67), left bundle branch block (OR 1.96, 95% CI 1.72 to 2.25), and liver disease (OR 1.87, 95% CI 1.73 to 2.02) were the leading predictors of SCA in HFpEF. After excluding patients with do-not-resuscitate status, the SCA group versus those without SCA had higher mortality (25.9% vs 1.6%), major bleeding complications (4.1% vs 1.7%), increased use of percutaneous coronary intervention (2.5% vs 0.7%), and mechanical circulatory assist device (1.2% vs 0.1%). These observational inpatient data suggest identifiable risk factors for SCA in HFpEF including cardiac arrhythmias. Further research is warranted to identify the best tools to risk-stratify patients with HFpEF to implement targeted SCA prevention strategies.

Risk of Arrhythmic Death in Patients With Nonischemic Cardiomyopathy: JACC Review Topic of the Week

Nonischemic cardiomyopathy (NICM) is common and patients are at significant risk for early mortality secondary to ventricular arrhythmias. Current guidelines recommend implantable cardioverter-defibrillator (ICD) therapy to decrease sudden cardiac death (SCD) in patients with heart failure and reduced left ventricular ejection fraction. However, in randomized clinical trials comprised solely of patients with NICM, primary prevention ICDs did not confer significant mortality benefit. Moreover, left ventricular ejection fraction has limited sensitivity and specificity for predicting SCD. Therefore, precise risk stratification algorithms are needed to define those at the highest risk of SCD. This review examines mechanisms of sudden arrhythmic death in patients with NICM, discusses the role of ICD therapy and treatment of heart failure for prevention of SCD in patients with NICM, examines the role of cardiac magnetic resonance imaging and computational modeling for SCD risk stratification, and proposes new strategies to guide future clinical trials on SCD risk assessment in patients with NICM.

Optimal left ventricular ejection fraction in risk stratification of patients with cardiac sarcoidosis

AIMS

Identifying patients with cardiac sarcoidosis (CS) who are at an increased risk of sudden cardiac death (SCD) poses a clinical challenge. We sought to identify the optimal cutoff for left ventricular ejection fraction (LVEF) in predicting ventricular arrhythmia (VA) and all-cause mortality and to identify clinical and imaging risk factors in patients with known CS.

METHODS AND RESULTS

This retrospective cohort included 273 patients with well-established CS. The primary endpoint was a composite of VA and all-cause mortality. A modified receiver operating curve analysis was utilized to identify the optimal cutoff for LVEF in predicting the primary composite endpoint. Cox proportional hazard regression analysis was used to identify independent risk factors of the outcomes. At median follow-up of 7.9 years, the rate of the primary endpoint was 38% (83 VAs and 32 all-cause deaths). The 5-year overall survival rate was 97%. The optimal cutoff LVEF for the primary composite endpoint was 42% in the entire cohort and in subjects without a history of VA. Younger age, history of VA, lower LVEF, and any presence of scar by cardiac magnetic resonance (CMR) imaging and/or positron emission tomography (PET) were found to be independent risk factors for the primary endpoint and for VA, whereas lower LVEF, baseline NT-proBNP, and any presence of scar were independent risk factor of all-cause mortality.

CONCLUSION

Among patients with CS, a mild reduction in LVEF of 42% was identified as the optimal cutoff for predicting VA and all-cause mortality. Prior VA and scar by CMR or PET are strong risk factors for future VA and all-cause mortality.

Age-stratified comparison of prognosis in cardiac resynchronization therapy with or without prophylactic defibrillator for nonischemic cardiomyopathy-a nationwide cohort study

AIMS

Prior studies have suggested that the benefit from primary preventive defibrillator treatment for patients with nonischemic cardiomyopathyy, treated with cardiac resynchronization therapy, may be age-dependent. We aimed to compare age-stratified mortality rates and mode of death in patients with nonischemic cardiomyopathy who are treated with either primary preventive cardiac resynchronization therapy with defibrillator (CRT-D) or CRT with pacemaker (CRT-P).

METHODS AND RESULTS

All patients with nonischemic cardiomyopathy and CRT-P or primary preventive CRT-D who were implanted in Sweden during the period 2005-2020 were included. Propensity scoring was used to create a matched cohort. Primary outcome was all-cause mortality within 5 years. In all, 4027 patients were included: 2334 with CRT-P and 1693 with CRT-D. Crude 5-year mortality was 635 (27%) vs. 246 (15%), P < 0.001. In Cox regression analysis, adjusted for clinically relevant covariables, CRT-D was independently associated with higher 5-year survival [0.72 (0.61-0.85), P < 0.001]. Cardiovascular mortality was similar between groups (62 vs. 64%, P = 0.64), but death from heart failure was more common in the CRT-D group (46 vs. 36%, P = 0.007). In the matched cohort (n = 2414), 5-year mortality was 21% (24 vs. 16%, P < 0.001). In age-stratified analyses, CRT-P was associated with higher mortality in age groups <60 years and 70-79 years, but there was no difference in age groups 60-69 years or 80-89 years.

CONCLUSION

In this nationwide registry-based study, patients with CRT-D had better 5-year survival compared to patients with CRT-P. The interaction between age and mortality reduction was not consistent, but patients with CRT-D aged <60 years had the largest absolute mortality reduction.

Coronary revascularization for heart failure with coronary artery disease: A systematic review and meta-analysis of randomized trials

AIMS

Coronary artery disease (CAD) is a common cause of heart failure (HF). Whether coronary revascularization improves outcomes in patients with HF receiving guideline-recommended pharmacological therapy (GRPT) remains uncertain; therefore, we conducted a systematic review and meta-analysis of relevant randomized controlled trials (RCTs).

METHODS AND RESULTS

We searched in public databases for RCTs published between 1 January 2001 and 22 November 2022, investigating the effects of coronary revascularization on morbidity and mortality in patients with chronic HF due to CAD. All-cause mortality was the primary outcome. We included five RCTs that enrolled, altogether, 2842 patients (most aged <65 years; 85% men; 67% with left ventricular ejection fraction ≤35%). Overall, compared to medical therapy alone, coronary revascularization was associated with a lower risk of all-cause mortality (hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.79-0.99; p = 0.0278) and cardiovascular mortality (HR 0.80, 95% CI 0.70-0.93; p = 0.0024) but not the composite of hospitalization for HF or all-cause mortality (HR 0.87, 95% CI 0.74-1.01; p = 0.0728). There were insufficient data to show whether the effects of coronary artery bypass graft surgery or percutaneous coronary intervention were similar or differed.

CONCLUSIONS

For patients with chronic HF and CAD enrolled in RCTs, the effect of coronary revascularization on all-cause mortality was statistically significant but neither substantial (HR 0.88) nor robust (upper 95% CI close to 1.0). RCTs were not blinded, which may bias reporting of the cause-specific reasons for hospitalization and mortality. Further trials are required to determine which patients with HF and CAD obtain a substantial benefit from coronary revascularization by either coronary artery bypass graft surgery or percutaneous coronary intervention.

MAgnetic resonance imaging based DUal lead cardiac Resynchronization therapy: A prospectIve Left Bundle Branch Pacing Study (MADURAI LBBP study)

BACKGROUND

Cardiac resynchronization therapy(CRT) is a class-I indication for LVEF≤35%, and heart failure(HF). LBBB associated nonischemic-cardiomyopathy (LB-NICM) with minimal or no scar by cardiac-magnetic-resonance(CMR) imaging may be associated with excellent prognosis following CRT. Left-bundle-branch-pacing(LBBP) can achieve excellent resynchronization in LBBB patients.

OBJECTIVES

Aim of our study was to prospectively assess feasibility and efficacy of LBBP with or without a defibrillator in patients with LB-NICM and LVEF ≤35%, risk stratified by CMR.

METHODS

Pts with LB-NICM, LVEF≤35% and HF were prospectively enrolled from 2019 to 2022. If the scar burden<10% by CMR, LBBP only (Group-I) and if ≥10%, LBBP+ICD(Group-II) was performed. Primary endpoints-1.Echocardiographic-response(ER)- ΔLVEF ≥15% at 6 months; 2.Composite of time to death, HFH or sustained VT/VF. Secondary endpoints-1.Echocardiographic-hyper-response(EHR-LVEF≥50%orΔLVEF ≥20%) at 6 and 12 months; 2.Indication for ICD-upgradation(persistent LVEF<35% at 12 months or sustained VT/VF) RESULTS: 120 patients were enrolled. CMR showed <10% scar-burden in 109 patients(90.8%). 4 patients opted for LBBP+ICD and withdrew. LBBP optimized-dual-chamber-pacemaker(LOT-DDD-P) was done in 101 patients and LOT-CRT-P in 4 patients(Group-I,n=105). Scar-burden ≥10% in 11 pts who underwent LBBP+ICD(Group-II). During mean-follow-up 21±12 months, primary endpoint of ER observed in 80%(68/85 pts) in Group-I vs 27%(3/11 pts) in Group-II(p-0.0001). Primary composite-endpoint of death,HFH or VT/VF occurred in 3.8% in group-I vs 33.3% in Group-II(p<0.0001). Secondary endpoint of EHR(LVEF≥50%) observed in 39.5%vs0%, 61.2%vs9.1% and 80%vs33.3% at 3, 6 and 12 months in group-I and group-II respectively.

CONCLUSION

CMR guided CRT using LOT-DDD-P appears to be a safe and feasible approach in LB-NICM and has the potential to reduce healthcare cost.

Cardiac MRI to Predict Sudden Cardiac Death Risk in Dilated Cardiomyopathy

Background Sudden cardiac death (SCD) is one of the leading causes of death in individuals with nonischemic dilated cardiomyopathy (DCM). However, the risk stratification of SCD events remains challenging in clinical practice. Purpose To determine whether myocardial tissue characterization with cardiac MRI could be used to predict SCD events and to explore a SCD stratification algorithm in nonischemic DCM. Materials and Methods In this prospective single-center study, adults with nonischemic DCM who underwent cardiac MRI between June 2012 and August 2020 were enrolled. SCD-related events included SCD, appropriate implantable cardioverter-defibrillator shock, and resuscitation after cardiac arrest. Competing risk regression analysis and Kaplan-Meier analysis were performed to identify the association of myocardial tissue characterization with outcomes. Results Among the 858 participants (mean age, 48 years; age range, 18-83 years; 603 men), 70 (8%) participants experienced SCD-related events during a median follow-up of 33.0 months. In multivariable competing risk analysis, late gadolinium enhancement (LGE) (hazard ratio [HR], 1.87; 95% CI: 1.07, 3.27; P = .03), native T1 (per 10-msec increase: HR, 1.07; 95% CI: 1.04, 1.11; P < .001), and extracellular volume fraction (per 3% increase: HR, 1.26; 95% CI: 1.11, 1.44; P < .001) were independent predictors of SCD-related events after adjustment of systolic blood pressure, atrial fibrillation, and left ventricular ejection fraction. An SCD risk stratification category was developed with a combination of native T1 and LGE. Participants with a native T1 value 4 or more SDs above the mean (1382 msec) had the highest annual SCD-related events rate of 9.3%, and participants with a native T1 value 2 SDs below the mean (1292 msec) and negative LGE had the lowest rate of 0.6%. This category showed good prediction ability (C statistic = 0.74) and could be used to discriminate SCD risk and competing heart failure risk. Conclusion Myocardial tissue characteristics derived from cardiac MRI were independent predictors of sudden cardiac death (SCD)-related events in individuals with nonischemic dilated cardiomyopathy and could be used to stratify participants according to different SCD risk categories. Clinical trial registration no. ChiCTR1800017058 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Sakuma in this issue.

Association of Late-Gadolinium Enhancement in Cardiac Magnetic Resonance with Mortality, Ventricular Arrhythmias, and Heart Failure in Patients with Non-Ischemic Cardiomyopathy: A Systematic Review and Meta-Analysis

Background

Late gadolinium enhancement (LGE) on cardiac magnetic resonance is a predictor of adverse events in patients with nonischemic cardiomyopathy (NICM).

Objective

This meta-analysis evaluated the correlation between LGE and mortality, ventricular arrhythmias (VAs) and sudden cardiac death (SCD), and heart failure (HF) outcomes.

Methods

A literature search was conducted for studies reporting the association between LGE in NICM and the study endpoints. The primary endpoint was mortality. Secondary endpoints included VA and SCD, HF hospitalization, improvement in left ventricular ejection fraction (LVEF) to >35%, and heart transplantation referral. The search was not restricted to time or publication status. The minimum follow-up duration was 1 year.

Results

A total of 46 studies and 10,548 NICM patients (4610 with LGE, 5938 without LGE) were included; mean follow-up was 3 years (range 13-71 months). LGE was associated with increased mortality (odds ratio [OR] 2.9; 95% confidence interval [CI] 2.3-3.8; P < .01) and VA and SCD (OR 4.6; 95% CI 3.5-6.0; P < .01). LGE was associated with an increased risk of HF hospitalization (OR 3.4; 95% CI 2.3-5.0; P < .01), referral for transplantation (OR 5.1; 95% CI 2.5-10.4; P < .01), and decreased incidence of LVEF improvement to >35% (OR 0.2; 95% CI 0.03-0.85; P = .03).

Conclusion

LGE in NICM patients is associated with increased mortality, VA and SCD, and HF hospitalization and heart transplantation referral during long-term follow up. Given these competing risks of mortality and HF progression, prospective randomized controlled trials are required to determine if LGE is useful for guiding prophylactic implantable cardioverter-defibrillator placement in NICM patients.

Racial and ethnic differences in implantable cardioverter-defibrillator patient selection, management, and outcomes

Racial and ethnic differences in treatment-cardiovascular and otherwise-have been documented in many aspects of the American health care system and can be seen in implantable cardioverter-defibrillator (ICD) patient selection, counseling, and management. ICDs have been demonstrated to be a powerful tool in the prevention of sudden cardiac death, yet uptake across all eligible patients has been modest. Although patients who do not identify as White are disproportionately eligible for ICDs in the United States, they are less likely to see specialists, be counseled on ICDs, and ultimately have an ICD implanted. This review explores racial and ethnic differences demonstrated in ICD patient selection, outcomes including shock effectiveness, and postimplantation monitoring for both primary and secondary prevention devices. It also highlights barriers for uptake at the health system, physician, and patient levels and suggests areas of further research needed to clarify the differences, illuminate the driving forces of these differences, and investigate strategies to address them.

The need for a subsequent transvenous system in patients implanted with subcutaneous implantable cardioverter-defibrillator

BACKGROUND

The absence of pacing capabilities may reduce the appeal of subcutaneous implantable cardioverter-defibrillator (S-ICD) devices for patients at risk for conduction disorders or with antitachycardia pacing (ATP)/cardiac resynchronization (CRT) requirements. Reports of rates of S-ICD to transvenous implantable cardioverter-defibrillator (TV-ICD) system switch in real-world scenarios are limited.

OBJECTIVE

The purpose of this study was to investigate the need for a subsequent transvenous (TV) device in patients implanted with an S-ICD and its predictors.

METHODS

All patients implanted with an S-ICD were enrolled from the multicenter, real-world iSUSI (International SUbcutaneouS Implantable cardioverter defibrillator) Registry. The need for a TV device and its clinical reason, and appropriate and inappropriate device therapies were assessed. Logistic regression with Firth penalization was used to assess the association between baseline and procedural characteristics and the overall need for a subsequent TV device.

RESULTS

A total of 1509 patients were enrolled (age 50.8 ± 15.8 years; 76.9% male; 32.0% ischemic; left ventricular ejection fraction 38% [30%-60%]). Over 26.5 [13.4-42.9] months, 155 (10.3%) and 144 (9.3%) patients experienced appropriate and inappropriate device therapies, respectively. Forty-one patients (2.7%) required a TV device (13 bradycardia; 10 need for CRT; 10 inappropriate shocks). Body mass index (BMI) >30 kg/m2 and chronic kidney disease (CKD) were associated with need for a TV device (odds ratio [OR] 2.57 [1.37-4.81], P = .003; and OR 2.67 [1.29-5.54], P = .008, respectively).

CONCLUSION

A low rate (2.7%) of conversion from S-ICD to a TV device was observed at follow-up, with need for antibradycardia pacing, ATP, or CRT being the main reasons. BMI >30 kg/m2 and CKD predicted all-cause need for a TV device.

Cost-Effectiveness of Cardioverter-Defibrillator Implantation in Kazakhstan

ABSTRACT

Cardiovascular disease is the leading cause of morbidity and mortality worldwide. The implementation of effective technologies such as Implantable cardioverter-defibrillator (ICD) for patients at risk of sudden cardiac death requires additional health system resources.

OBJECTIVE

To assess the economic effectiveness of ICD in comparison with conservative tactics for preventing life-threatening rhythm disturbances in Kazakhstan.

METHODS

A Markov model was built with a time horizon of 35 years. Mortality and utility data were obtained from the available literature. The economic parameters of the model are based on the approved tariffs for medical services in Kazakhstan and clinical protocols. Following WHO recommendations, a willingness to pay threshold of three times gross domestic product per capita was used to assess cost-effectiveness. A discount rate of 3.5% was applied to both costs and benefits. To deal with parameter uncertainties and to provide robust analysis, a probabilistic sensitivity analysis was performed, randomly varying all inputs subject to uncertainty assuming a statistical distribution.

RESULTS

The total costs in the primary prevention (PP) group by ICD implantation and in the control group were 8,903,786 tenges and 3,194,414 tenges, respectively. The discounted total quality-adjusted life-years saved (QALYs) in the ICD and control groups were 6.48 and 4.98, respectively. The indicator of incremental cost-effectiveness ratio amounted to3791604 tenge, which is below the willingness to pay threshold and indicates the cost-effectiveness of using ICD as a PP strategy in patients with sudden cardiac death risk factors in the health care of Kazakhstan.

CONCLUSION

The ICD for the primary prevention of the development of life-threatening rhythm disturbances and sudden cardiac death is a cost-effective health technology from the position of a payer in the health care system of Kazakhstan.

Coronary Artery Calcium for Risk Stratification of Sudden Cardiac Death: The Coronary Artery Calcium Consortium

BACKGROUND

Coronary artery calcium (CAC) is a marker of plaque burden. Whether CAC improves risk stratification for incident sudden cardiac death (SCD) beyond atherosclerotic cardiovascular disease (ASCVD) risk factors is unknown.

OBJECTIVES

SCD is a common initial manifestation of coronary heart disease (CHD); however, SCD risk prediction remains elusive.

METHODS

The authors studied 66,636 primary prevention patients from the CAC Consortium. Multivariable competing risks regression and C-statistics were used to assess the association between CAC and SCD, adjusting for demographics and traditional risk factors.

RESULTS

The mean age was 54.4 years, 33% were women, 11% were of non-White ethnicity, and 55% had CAC >0. A total of 211 SCD events (0.3%) were observed during a median follow-up of 10.6 years, 91% occurring among those with baseline CAC >0. Compared with CAC = 0, there was a stepwise higher risk (P trend < 0.001) in SCD for CAC 100 to 399 (subdistribution hazard ratio [SHR]: 2.8; 95% CI: 1.6-5.0), CAC 400 to 999 (SHR: 4.0; 95% CI: 2.2-7.3), and CAC >1,000 (SHR: 4.9; 95% CI: 2.6-9.9). CAC provided incremental improvements in the C-statistic for the prediction of SCD among individuals with a 10-year risk <7.5% (ΔC-statistic = +0.046; P = 0.02) and 7.5% to 20% (ΔC-statistic = +0.069; P = 0.003), which were larger when compared with persons with a 10-year risk >20% (ΔC-statistic = +0.01; P = 0.54).

CONCLUSIONS

Higher CAC burden strongly associates with incident SCD beyond traditional risk factors, particularly among primary prevention patients with low-intermediate risk. SCD risk stratification can be useful in the early stages of CHD through the measurement of CAC, identifying patients most likely to benefit from further downstream testing.

Arrhythmic risk prediction in arrhythmogenic right ventricular cardiomyopathy: external validation of the arrhythmogenic right ventricular cardiomyopathy risk calculator

AIMS

Arrhythmogenic right ventricular cardiomyopathy (ARVC) causes ventricular arrhythmias (VAs) and sudden cardiac death (SCD). In 2019, a risk prediction model that estimates the 5-year risk of incident VAs in ARVC was developed (ARVCrisk.com). This study aimed to externally validate this prediction model in a large international multicentre cohort and to compare its performance with the risk factor approach recommended for implantable cardioverter-defibrillator (ICD) use by published guidelines and expert consensus.

METHODS AND RESULTS

In a retrospective cohort of 429 individuals from 29 centres in North America and Europe, 103 (24%) experienced sustained VA during a median follow-up of 5.02 (2.05-7.90) years following diagnosis of ARVC. External validation yielded good discrimination [C-index of 0.70 (95% confidence interval-CI 0.65-0.75)] and calibration slope of 1.01 (95% CI 0.99-1.03). Compared with the three published consensus-based decision algorithms for ICD use in ARVC (Heart Rhythm Society consensus on arrhythmogenic cardiomyopathy, International Task Force consensus statement on the treatment of ARVC, and American Heart Association guidelines for VA and SCD), the risk calculator performed better with a superior net clinical benefit below risk threshold of 35%.

CONCLUSION

Using a large independent cohort of patients, this study shows that the ARVC risk model provides good prognostic information and outperforms other published decision algorithms for ICD use. These findings support the use of the model to facilitate shared decision making regarding ICD implantation in the primary prevention of SCD in ARVC.

A Comparative Study Between Amiodarone and Implantable Cardioverter-Defibrillator in Decreasing Mortality From Sudden Cardiac Death in High-Risk Patients: A Systematic Review and Meta-Analysis

Sudden cardiac death (SCD) is an unexpected death that occurs within one hour of symptom onset. In the United States, sudden cardiac death is considered the leading cause of natural death, accounting for 325,000 adult patients annually. SCD is more common in adult patients (above the mid-30s) and men. The risk factors that predict SCD are categorized into clinical, sociological, genetic, and psychological. To prevent the occurrence of SCD, several treatment options, especially antiarrhythmic drugs and implantable cardioverter-defibrillator (ICD), have been used.

A literature search from 2000 to 2022 was conducted on six electronic databases: PubMed, Cochrane Library, Web of Science, Embase, ScienceDirect, and Google Scholar. The search query used Boolean expressions and keywords such as amiodarone, implantable cardioverter-defibrillator, sudden cardiac death, cardiac arrest, arrhythmic death, and all-cause mortality. The articles identified from the literature search were screened using the eligibility criteria, resulting in eight articles relevant for inclusion in the review. A meta-analysis of data from six of the included studies showed that ICD was more effective in the reduction of SCD rates, with an SCD rate of 5.97% (n = 84/1,408) observed in the ICD group compared with an SCD rate of 11.81% (n = 168/1,423) observed in the amiodarone group. The results also show that ICD was more effective in reducing all-cause mortality compared with amiodarone (odds ratio (OR): 1.36; 95% confidence interval (CI): 1.06-1.74; I² = 57%; P = 0.03).

ICD treatment of high-risk patients was more effective in reducing SCD and all-cause mortality rates compared with amiodarone treatment. There is evidence that amiodarone can be used as an adjuvant treatment option, especially for patients who are not eligible for ICD treatment and those who face more adverse events. Evidence has also shown that using amiodarone with ICD treatment significantly improves survival rates compared to ICD treatment only.

CE: Guideline-Directed Cardiac Devices for Patients with Heart Failure

ABSTRACT

Heart failure affects over 6.2 million adults in the United States and is expected to affect over 8 million by 2030. The U.S. one-year mortality rate is almost 30% among Medicare beneficiaries. Technological advances have produced several new cardiac devices that are available for therapy and symptom management. This article reviews current device therapies for heart failure and uses a composite case to demonstrate how bedside nurses can help patients understand treatment options related to their disease process and care for them through this experience.

OUP accepted manuscript

More than 40 years after the first implantable cardioverter-defibrillator (ICD) implantation, sudden cardiac death (SCD) still accounts for more than five million deaths worldwide every year. Huge efforts in the field notwithstanding, it is now increasingly evident that the current strategy of long-term prevention based on left ventricular ejection fraction as the key selection criterion is actually of very limited impact, also because the largest absolute numbers of SCD are encountered in the general population not known to be at risk. It has been recently reemphasized that SCD is often not so sudden, with almost half of the victims experiencing typical warning symptoms preceding the event. Importantly, heeded and prompt medical attention can dramatically improve survival. Essentially, such timely action increases the chances of the SCD event being witnessed by emergency medical services and provides the opportunity for early intervention. In addition, newer technologies incorporating digital data acquisition, transfer between interconnected devices, and artificial intelligence, should allow dynamic, real-time monitoring of diverse parameters and therefore better identification of subjects at short-term SCD risk. Along with warning symptoms, these developments allow a new approach of near-term prevention based on the hours and minutes preceding SCD. In the present review, we challenge the current paradigm of mid- and long-term prevention using ICD in patients at the highest risk of SCD, and introduce a complementary concept applicable to the entire population that would aim to pre-empt SCD by timely detection and intervention within the minutes or hours prior to the event.

Predictors for Early Mortality in Patients with Implantable Cardiac Defibrillator for Heart Failure with Reduced Ejection Fraction

Implantable cardioverter defibrillators (ICD) are recommended in heart failure with reduced ejection fraction (HFrEF) patients to reduce arrhythmic deaths. This study aimed to identify risk factors associated with mortality within one-year following the ICD. The data from our hospital's electronic database system was extracted for patients who were implanted ICD secondary to HFrEF between 2009 and 2019. Overall, 1107 patients were included in the present analysis. Mortality rate at one-year following the device implantation was 4.7%. In multivariate analysis; age, atrial fibrillation, New York Heart Association classification >2, blood urea nitrogen, pro-brain natriuretic peptide and albumin independently predicted one year mortality.

Management of ventricular tachycardia in patients with ischaemic cardiomyopathy: contemporary armamentarium

Worldwide, ∼4 million people die from sudden cardiac death every year caused in more than half of the cases by ischaemic cardiomyopathy (ICM). Prevention of sudden cardiac death after myocardial infarction by implantation of a cardioverter-defibrillator (ICD) is the most common, even though not curative, therapy to date. Optimized ICD programming should be strived for in order to decrease the incidence of ICD interventions. Catheter ablation reduces the recurrence of ventricular tachycardias (VTs) and is an important adjunct to sole ICD-based treatment or pharmacological antiarrhythmic therapy in patients with ICM, as conclusively demonstrated by seven randomized controlled trials (RCTs) in the last two decades. However, none of the conducted trials was powered to reveal a survival benefit for ablated patients as compared to controls. Whereas thorough consideration of an early approach is necessary following two recent RCTs (PAUSE-SCD, BERLIN VT), catheter ablation is particularly recommended in patients with recurrent VT after ICD therapy. In this context, novel, pathophysiologically driven ablation strategies referring to deep morphological and functional substrate phenotyping based on high-resolution mapping and three-dimensional visualization of scars appear promising. Emerging concepts like sympathetic cardiac denervation as well as radioablation might expand the therapeutical armamentarium especially in patients with therapy-refractory VT. Randomized controlled trials are warranted and on the way to investigate how these translate into improved patient outcome. This review summarizes therapeutic strategies currently available for the prevention of VT recurrences, the optimal timing of applicability, and highlights future perspectives after a PAUSE in BERLIN.

Real-world evaluation of followup strategies after ICD therapies in patients with VT (REFINE-VT)

Implantable cardiac defibrillators (ICDs) can prevent sudden cardiac death, but the risk of recurrent ventricular arrhythmia (VA) and ICD shocks persist. Strategies to minimise such risks include medication optimisation, device programming and ventricular tachycardia (VT) ablation. Whether the choice of these interventions at follow-up are influenced by factors such as the type of arrhythmia or ICD therapy remains unclear. To investigate this, we evaluated ICD follow-up strategies in a real-world population with primary and secondary prevention ICDs. REFINE-VT (Real-world Evaluation of Follow-up strategies after Implantable cardiac-defibrillator therapies in patients with Ventricular Tachycardia) is an observational study of 514 ICD recipients recruited between 2018 and 2019. We found that 77 patients (15%) suffered significant VA and/or ICD therapies, of whom 26% experienced a second event; 31% received no intervention. We observed an inconsistent approach to the choice of strategies across different types of arrhythmias and ICD therapies. Odds of intervening were significantly higher if ICD shock was detected compared with anti-tachycardia pacing (odds ratio [OR] 8.4, 95% confidence interval [CI] 1.7 to 39.6, p=0.007). Even in patients with two events, the rate of escalation of antiarrhythmics or referral for VT ablation were as low as patients with single events. This is the first contemporary study evaluating how strategies that reduce the risk of recurrent ICD events are executed in a real-world population. Significant inconsistencies in the choice of interventions exist, supporting the need for a multi-disciplinary approach to provide evidence-based care to this population.

Comparable Efficacy in Ischemic and Non-Ischemic ICD Recipients for the Primary Prevention of Sudden Cardiac Death

(1) Background: In patients suffering from heart failure, the main causes of death are either hemodynamic failure, or ventricular arrhythmias. The only tool to significantly reduce arrhythmic sudden death is the implantable cardioverter defibrillator (ICD), but not all patients benefit to the same extent from these devices. (2) Methods: The primary outcome of this single-center study was defined as cardiovascular death in patients with ischemic and non-ischemic heart failure who have benefited from ICD therapy. The secondary outcomes were death from any cause, sudden cardiac death, ICD-related therapies (appropriate antitachycardia pacing or shock therapy for ventricular tachycardia or fibrillation) and recurrences of ventricular tachyarrhythmias. (3) Results: A total of 403 consecutive ICD recipients—symptomatic heart failure patients with ICD for the primary prevention of sudden cardiac death—were included retrospectively: 59% ischemic cardiomyopathy (ICMP) and 41% non-ischemic cardiomyopathy (NICMP) patients. Within a median follow-up period of 36 months, the incidence of cardiovascular mortality was not significantly different in patients with NICMP and ICMP: the primary outcome had occurred in 9 patients (5.4%) in the NICMP group and in 14 patients (5.9%) in the ICMP group (hazard ratio 1; 95% confidence interval (CI) 0.45 to 2.28; p = 0.97). All-cause mortality occurred in 14 of 166 patients (8.4%) in the NICMP group and 18 of 237 patients (7.6%) in the ICMP group. Sudden cardiac death occurred in two patients (1.2%) in the NICMP group and in four patients (1.7%) in the ICMP group (hazard ratio 0.71; 95% CI, 0.13 to 3.88; p = 0.69). The rate of appropriate device therapies was comparable in both groups. (4) Conclusions: In this study, ICD implantation for primary prevention of sudden cardiac death in patients with symptomatic systolic heart failure was associated with similar rates of cardiovascular and all-cause mortality in patients with ischemic heart disease, and in patients with heart failure from other causes. NICMP and ICMP showed comparable rates of recurrent ventricular tachyarrhythmias and appropriate ICD therapies.

Growth/differentiation factor-15 (GDF-15) as a predictor of serious arrhythmic events in patients with nonischemic dilated cardiomyopathy

INTRODUCTION

Cardiac biomarkers have been proposed as a new tool to improve risk stratification of serious arrhythmic events in patients with heart failure (HF) beyond estimates of left ventricular ejection fraction. Growth differentiation factor (GDF)-15, a stress-induced cytokine, has been found to correlate with markers of myocardial fibrosis and adverse clinical outcomes, but its role as a predictor of arrhythmic events in patients with nonischemic HF is uncertain.

METHODS AND RESULTS

A prospective observational study was conducted in 148 nonischemic patients with HF who underwent comprehensive clinical and laboratory evaluation, including measurement of serum GDF-15. The study endpoints were serious arrhythmic events (which included appropriate implantable cardioverter-defibrillator therapy and sudden cardiac death) and all-cause mortality. Mean age of the cohort was 54.8 ± 12.7 years, and mean left ventricular ejection fraction (LVEF) was 27.4% ± 7.5%. During a mean follow-up time of 42 months, arrhythmic events occurred in 28 patients (19%), and 40 patients (27%) died. An increase in serum GDF-15 (log-transformed) correlated linearly with a higher risk of serious arrhythmic events (HR 1.14, 95% CI 1.01-1.28, p = 0.03) even after adjustment for other potential clinical predictors (HR 1.16, 95% CI 1.02-1.32, p = 0.02). GDF-15 was also strongly and independently associated with all-cause mortality (HR 1.17, 1.05-1.31, p = 0.004).

CONCLUSION

In this cohort of nonischemic HF patients on optimized medical treatment, serum GDF-15 levels were independently associated with major arrhythmic events and overall mortality. This biomarker may add prognostic information to better stratify the risk of sudden death in this particular population.

Ring-like late gadolinium enhancement for predicting ventricular tachyarrhythmias in non-ischaemic dilated cardiomyopathy

AIMS

Myocardial fibrosis is associated with clinical ventricular tachyarrhythmia (VTA) events in patients with non-ischaemic dilated cardiomyopathy (DCM). Subepicardial or mid-wall ring-like late gadolinium enhancement (LGE) has received increasing attention in recent years. The aim of this study was to investigate the relationship between ring-like LGE and VTAs in DCM.

METHODS AND RESULTS

Patients diagnosed with non-ischaemic DCM who underwent cardiac magnetic resonance with LGE imaging at baseline were investigated. The composite outcome was the occurrence of VTAs defined as sustained ventricular tachycardia, ventricular fibrillation/flutter, aborted sudden cardiac death (SCD), SCD, and appropriate implantable cardioverter-defibrillator intervention. The final cohort comprised 157 patients, including 36 (22.9%) in no LGE group, 48 (30.6%) in focal LGE group, 40 (25.5%) in multi-focal LGE group, and 33 (21%) in ring-like LGE group. Ring-like LGE group patients were younger compared to focal and multi-focal LGE group (P < 0.001) with higher left ventricular ejection fraction (33.0% vs. 24.4% vs. 22.1%, P < 0.001). After a median of 13 ± 7 months follow-up, compared to patients with no LGE, the hazard ratios (HRs) with 95% confidence intervals (CIs) for VTAs were 2.90 (0.56-15.06), 5.55 (1.21-25.44), and 11.75 (2.66-51.92) for patients with focal LGE, multi-focal LGE, and ring-like LGE, respectively. After multivariable adjustment, ring-like LGE group remained associated with increased risk of VTAs (adjusted HR 10.00, 95% CI 1.54-64.98; P = 0.016) independent of the global LGE burden.

CONCLUSION

The ring-like pattern of LGE is independently associated with an increased risk of VTAs in patients with non-ischaemic DCM.

CMR-Based Risk Stratification of Sudden Cardiac Death and Use of Implantable Cardioverter-Defibrillator in Non-Ischemic Cardiomyopathy

Non-ischemic cardiomyopathy (NICM) is one of the most important entities for arrhythmias and sudden cardiac death (SCD). Previous studies suggest a lower benefit of implantable cardioverter–defibrillator (ICD) therapy in patients with NICM as compared to ischemic cardiomyopathy (ICM). Nevertheless, current guidelines do not differentiate between the two subgroups in recommending ICD implantation. Hence, risk stratification is required to determine the subgroup of patients with NICM who will likely benefit from ICD therapy. Various predictors have been proposed, among others genetic mutations, left-ventricular ejection fraction (LVEF), left-ventricular end-diastolic volume (LVEDD), and T-wave alternans (TWA). In addition to these parameters, cardiovascular magnetic resonance imaging (CMR) has the potential to further improve risk stratification. CMR allows the comprehensive analysis of cardiac function and myocardial tissue composition. A range of CMR parameters have been associated with SCD. Applicable examples include late gadolinium enhancement (LGE), T1 relaxation times, and myocardial strain. This review evaluates the epidemiological aspects of SCD in NICM, the role of CMR for risk stratification, and resulting indications for ICD implantation.

Rapid evidence-based sequencing of foundational drugs for heart failure and a reduced ejection fraction

Foundational therapy for heart failure and a reduced ejection fraction consists of a combination of an angiotensin receptor-neprilysin inhibitor, a beta-blocker, a mineralocorticoid receptor antagonist and a sodium-glucose co-transporter 2 (SGLT2) inhibitor. However, the conventional approach to the implementation is based on a historically-driven sequence that is not strongly evidence-based, typically requires ≥6 months, and frequently leads to major gaps in treatment. We propose a rapid sequencing strategy that is based on four principles. First, since drugs act rapidly to reduce morbidity and mortality, patients should be started on all four foundational treatments within 2-4 weeks. Second, since the efficacy of each foundational therapy is independent of treatment with the other drugs, priority can be determined by considerations of relative efficacy, safety and ease-of-use. Third, low starting doses of foundational drugs have substantial therapeutic benefits, and achievement of low doses of all four classes of drugs should take precedence over up-titration to target doses. Fourth, since drugs can influence the tolerability of other foundational agents, sequencing can be based on whether agents started earlier can enhance the safety of agents started simultaneously or later in the sequence. We propose an accelerated three-step approach, which consists of the simultaneous initiation of a beta-blocker and an SGLT2 inhibitor, followed 1-2 weeks later by the initiation of sacubitril/valsartan, and 1-2 weeks later by a mineralocorticoid receptor antagonist. The latter two steps can be re-ordered or compressed depending on patient circumstances. Rapid sequencing is a novel evidence-based strategy that has the potential to dramatically improve the implementation of treatments that reduce the morbidity and mortality of patients with heart failure and a reduced ejection fraction.

Analysis of causes of death in patients with implanted defibrillators

AIMS

Implantable cardioverter defibrillators (ICDs) are used for primary or secondary prevention of sudden cardiac death. We sought to clarify prognosis and causes of death after ICD implantation.

METHODS AND RESULTS

A total of 2743 patients with ICDs implanted during 1990-2020 were analyzed. Median age was 68.5 (59.6-74.6) years; 21% women, median left ventricular ejection fraction (LVEF) was 30 (23-35), 52% had an ischemic etiology and 77% had a primary preventive indication. Mortality rate after 10 years was 22, 44, 55, and 72% in the 1st, 2nd, 3rd, and 4^th age quartile, respectively. The calculated median sex and age adjusted loss of life years compared to the average German population was 9.7 (6.1-14.0) years. Prognosis was independently related to sex, age, LVEF, and glomerular filtration rate. 713 out of 852 deaths could be classified to a specific cause. Congestive heart failure (CHF) accounted for death in 214 (30%) and sudden death (SD) for 144 patients (20%). Postmortem interrogation of devices in 74 patients revealed VT/VF in 39 and no episodes in 35 patients. Cancer was identified as the cause of death in 121 patients (17% of cases), of which 36 were bronchial carcinomas. 73 (10%) of patients died due to infection. 67 patients (9%) died within 24 h of procedures. Compared to other causes, significantly more life years were lost associated with procedures and SD: 9.3 (5.7-12.9) versus 12.1 (7.4-15.2) and 11.9 (7.6-17.8) years.

CONCLUSION

Life expectancy of ICD patients is lower than for the general population. Mortality is predominantly due to CHF, but there is still a considerable rate of SD. The occurrence of cancers, most importantly bronchial carcinomas, and infections, warrants protective measures. Some deaths during procedures are possibly preventable. Patients with ICDs comprise a vulnerable cohort, and treatment has to be optimized in many directions to improve prognosis.

The Optimal Timing of Primary Prevention Implantable Cardioverter-Defibrillator Referral in the Rapidly Changing Medical Landscape

The use of implantable cardioverter-defibrillators (ICDs) significantly reduces the risk of mortality in patients with heart failure with reduced ejection fraction (HFrEF). Current guidelines, which are based on seminal clinical trials published nearly 2 decades ago, recommend that patients be on optimal medical therapy for HF for a minimum of 3 months before referral for prophylactic ICD. This waiting period allows for left ventricular reverse remodelling and improvement in HF symptoms, which may render primary prevention ICD implantation unnecessary. However, medical therapy for HFrEF has significantly evolved since the publication of these landmark trials. Given the plethora of medical therapy options now available for HFrEF, it is appropriate to reassess the duration of this waiting period. In the present review, we examine the landmark randomised trials in primary prevention of sudden cardiac death in patients with HFrEF, summarise the novel medical therapies (sacubitril-valsartan, sodium-glucose cotransporter 2 inhibitors, ivabradine, vericiguat, and omecamtiv mecarbil) that have emerged since the publication of those trials, discuss the optimal timing of ICD referral, and review subtypes of nonischemic cardiomyopathy where timing of ICD insertion is guided by alternative criteria. With the steps now needed to optimise medical therapy for HFrEF, in terms of both classes of drugs and doses of each agent, it can easily take up to 6 months to achieve optimisation. Following that, waiting periods of 3 months for ischemic cardiomyopathy and 6 months for nonischemic cardiomyopathy may be required to allow adequate reverse remodelling before reevaluating for ICD implantation.