Implantable Cardioverter-Defibrillators at End of Battery Life

Predictors of appropriate therapies delivered by the implantable cardioverter-defibrillator in patients with coronary artery disease during long-term period

This prospective study aimed to investigate the ability of cardiac autonomic nervous system (CANS) activity assessment to predict appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with coronary artery disease (CAD) during long-term follow-up period. We enrolled patients with CAD and ICD implantation indications that included both secondary and primary prevention of sudden cardiac death. Before ICD implantation CANS was assessed by using heart rate variability (HRV), myocardium scintigraphy with 123I-meta-iodobenzylguanidine (123I-MIBG) and erythrocyte membranes β-adrenoreactivity (EMA). The study's primary endpoint was the documentation of appropriate ICD therapy. Of 45 (100.0%) patients, 15 (33.3%) had appropriate ICD therapy during 36 months follow-up period. Patients with appropriate ICD therapy were likely to have a higher summed 123I-MIBG score delayed (p < 0.001) and lower 123I-MIBG washout rate (p = 0.008) indicators. These parameters were independently associated with endpoint in univariable and multivariable logistic regression. We created a logistic equation and calculated a cut-off value. The resulting ROC curve revealed a discriminative ability with AUC of 0.933 (95% confidence interval 0.817-0.986; sensitivity 100.00%; specificity 93.33%). Combined CANS activity assessment is useful in prediction of appropriate ICD therapy in patients with CAD during long-term follow-up period after device implantation.

Patients' Perspectives Regarding Generator Exchanges of Implantable Cardioverter Defibrillators

BACKGROUND

Shared decision-making is mandated for patients receiving primary prevention implantable cardioverter defibrillators (ICDs). Less attention has been paid to generator exchange decisions, although at the time of generator exchange, patients' risk of sudden cardiac death, risk of procedural complications, quality of life, or prognosis may have changed. This study was designed to explore how patients make ICD generator exchange decisions.

METHODS

Emory Healthcare patients with primary prevention ICDs implanted from 2013 to 2021 were recruited to complete in-depth interviews exploring perspectives regarding generator exchanges. Interviews were conducted in 2021. Transcribed interviews were qualitatively coded using multilevel template analytic methods. To investigate benefit thresholds for pursuing generator exchanges, patients were presented standard-gamble type hypothetical scenarios where their ICD battery was depleted but their 5-year risk of sudden cardiac death at that time varied (10%, 5%, and 1%).

RESULTS

Fifty patients were interviewed; 18 had a prior generator exchange, 16 had received ICD therapy, and 17 had improved left ventricular ejection fraction. As sudden cardiac death risk decreased from 10% to 5% to 1%, the number of participants willing to undergo a generator exchange decreased from 48 to 42 to 33, respectively. Responses suggest that doctor's recommendations are likely to substantially impact patients' decision-making. Other drivers of decision-making included past experiences with ICD therapy and device implantation, as well as risk aversion. Therapeutic inertia and misconceptions about ICD therapy were common and represent substantive barriers to effective shared decision-making in this context.

CONCLUSIONS

Strong defaults may exist to continue therapy and exchange ICD generators. Updated risk stratification may facilitate shared decision-making and reduce generator exchanges in very low-risk patients, especially if these interventions are directed toward clinicians. Interventions targeting phenomena such as therapeutic inertia may be more impactful and warrant exploration in randomized trials.

Risk of ventricular arrhythmias following implantable cardioverter-defibrillator generator change in patients with recovered ejection fraction: Implications for shared decision-making

INTRODUCTION

Guidelines indicate primary-prevention implantable cardioverter-defibrillators (ICDs) for most patients with left ventricular ejection fraction (LVEF) ≤ 35%. Some patients' LVEFs improve during the life of their first ICD. In patients with recovered LVEF who never received appropriate ICD therapy, the utility of generator replacement upon battery depletion remains unclear. Here, we evaluate ICD therapy based on LVEF at the time of generator change, to educate shared decision-making regarding whether to replace the depleted ICD.

METHODS

We followed patients with a primary-prevention ICD who underwent generator change. Patients who received appropriate ICD therapy for ventricular tachycardia or ventricular fibrillation (VT/VF) before generator change were excluded. The primary endpoint was appropriate ICD therapy, adjusted for the competing risk of death.

RESULTS

Among 951 generator changes, 423 met inclusion criteria. During 3.4 ± 2.2 years follow-up, 78 (18%) received appropriate therapy for VT/VF. Compared to patients with recovered LVEF > 35% (n = 161 [38%]), those with LVEF ≤ 35% (n = 262 [62%]) were more likely to require ICD therapy (p = .002; Fine-Gray adjusted 5-year event rates: 12.7% vs. 25.0%). Receiver operating characteristic analysis revealed the optimal LVEF cutoff for VT/VF prediction to be 45%, the use of which further improved risk stratification (p < .001), with Fine-Gray adjusted 5-year rates 6.2% versus 25.1%.

CONCLUSION

Following ICD generator change, patients with primary-prevention ICDs and recovered LVEF have significantly lower risk of subsequent ventricular arrhythmias compared to those with persistent LVEF depression. Risk stratification at LVEF 45% offers significant additional negative predictive value over a 35% cutoff, without a significant loss in sensitivity. These data may be useful during shared decision-making at the time of ICD generator battery depletion.

Incidence and Predictors of Implantable Cardioverter-defibrillator Therapies After Generator Replacement-A Pooled Analysis of 31,640 Patients' Data

Among primary prevention implantable cardioverter-defibrillator (ICD) recipients, 75% do not experience any appropriate ICD therapies during their lifetime, and nearly 25% have improvements in their left ventricular ejection fraction (LVEF) during the lifespan of their first generator. The practice guidelines concerning this subgroup's clinical need for generator replacement (GR) remain unclear. We conducted a proportional meta-analysis to determine the incidence and predictors of ICD therapies after GR and compared this to the immediate and long-term complications. A systematic review of existing literature on ICD GR was performed. Selected studies were critically appraised using the Newcastle-Ottawa scale. Outcomes data were analyzed by random-effects modeling using R (R Foundation for Statistical Computing, Vienna, Austria), and covariate analyses were conducted using the restricted maximum likelihood function. A total of 31,640 patients across 20 studies were included in the meta-analysis with a median (range) follow-up of 2.9 (1.2-8.1) years. The incidences of total therapies, appropriate shocks, and anti-tachycardia pacing post-GR were approximately 8, 4, and 5 per 100 patient-years, respectively, corresponding to 22%, 12%, and 12% of patients of the total cohort, with a high level of heterogeneity across the studies. Greater anti-arrhythmic drug use and previous shocks were associated with ICD therapies post-GR. The all-cause mortality was approximately 6 per 100 patient-years, corresponding to 17% of the cohort. Diabetes mellitus, atrial fibrillation, ischemic cardiomyopathy, and the use of digoxin were predictors of all-cause mortality in the univariate analysis; however, none of these were found to be significant predictors in the multivariate analysis. The incidences of inappropriate shocks and other procedural complications were 2 and 2 per 100 patient-years, respectively, which corresponded to 6% and 4% of the entire cohort. Patients undergoing ICD GR continue to require therapy in a significant proportion of cases without any correlation with an improvement in LVEF. Further prospective studies are necessary to risk-stratify ICD patients undergoing GR.

Subcutaneous Versus Transvenous Implantable Defibrillator Therapy: A Systematic Review and Meta-Analysis of Randomized Trials and Propensity Score-Matched Studies

Background

Subcutaneous implantable cardioverter‐defibrillators (S‐ICDs) have been of great interest as an alternative to transvenous implantable cardioverter‐defibrillators (TV‐ICDs). No meta‐analyses synthesizing data from high‐quality studies have yet been published.

Methods and Results

An electronic literature search was conducted to retrieve randomized controlled trials or propensity score–matched studies comparing S‐ICD against TV‐ICD in patients with an implantable cardioverter‐defibrillator indication. The primary outcomes were device‐related complications and lead‐related complications. Secondary outcomes were inappropriate shocks, appropriate shock, all‐cause mortality, and infection. All outcomes were pooled under random‐effects meta‐analyses and reported as risk ratios (RRs) and 95% CIs. Kaplan–Meier curves of device‐related complications were digitized to retrieve individual patient data and pooled under a 1‐stage meta‐analysis using Cox models to determine hazard ratios (HRs) of patients undergoing S‐ICD versus TV‐ICD. A total of 5 studies (2387 patients) were retrieved. S‐ICD had a similar rate of device‐related complications compared with TV‐ICD (RR, 0.59 [95% CI, 0.33–1.04]; P=0.070), but a significantly lower lead‐related complication rate (RR, 0.14 [95% CI, 0.07–0.29]; P<0.0001). The individual patient data–based 1‐stage stratified Cox model for device‐related complications across 4 studies yielded no significant difference (shared‐frailty HR, 0.82 [95% CI, 0.61–1.09]; P=0.167), but visual inspection of pooled Kaplan–Meier curves suggested a divergence favoring S‐ICD. Secondary outcomes did not differ significantly between both modalities.

Conclusions

S‐ICD is clinically superior to TV‐ICD in terms of lead‐related complications while demonstrating comparable efficacy and safety. For device‐related complications, S‐ICD may be beneficial over TV‐ICD in the long term. These indicate that S‐ICD is likely a suitable substitute for TV‐ICD in patients requiring implantable cardioverter‐defibrillator implantation without a pacing indication.

Ongoing Risk of Ventricular Arrhythmias and All-Cause Mortality at Implantable Cardioverter Defibrillator Generator Change: A Systematic Review and Meta-Analysis

[Figure: see text].

Incidence of Ventricular Arrhythmias and 1-Year Predictors of Mortality in Patients Treated With Implantable Cardioverter-Defibrillator Undergoing Generator Replacement

Background

When implantable cardioverter defibrillator (ICD) battery is depleted most patients undergo generator replacement (GR) even in the absence of persistent ICD indication. The aim of this study was to assess the incidence of ventricular arrhythmias and the overall prognosis of patients with and without persistent ICD indication undergoing GR. Predictors of 1‐year mortality were also analyzed.

Methods and Results

Patients with structural heart disease implanted with primary prevention ICD undergoing GR were included. Patients were stratified based on the presence/absence of persistent ICD indication (left ventricular ejection fraction ≤35% at the time of GR and/or history of appropriate ICD therapies during the first generator's life). The study included 371 patients (82% male, 40% with ischemic heart disease). One third of patients (n=121) no longer met ICD indication at the time of GR. During a median follow‐up of 34 months after GR patients without persistent ICD indication showed a significantly lower incidence of appropriate ICD shocks (1.9% versus 16.2%, P<0.001) and ICD therapies. 1‐year mortality was also significantly lower in patients without persistent ICD indication (1% versus 8.3%, P=0.009). At multivariable analysis permanent atrial fibrillation, chronic advanced renal impairment, age >80, and persistent ICD indication were found to be significant predictors of 1‐year mortality.

Conclusions

Patients without persistent ICD indication at the time of GR show a low incidence of appropriate ICD therapies after GR. Persistent ICD indication, atrial fibrillation, advanced chronic renal disease, and age >80 are significant predictors of 1‐year mortality. Our findings enlighten the need of performing a comprehensive clinical reevaluation of ICD patients at the time of GR.

Ultrasound-Induced Wireless Energy Harvesting: From Materials Strategies to Functional Applications

Wireless energy harvesting represents an emerging technology that can be integrated into a variety of systems for biomedical, physical, and chemical functions. The miniaturization and ease of implementation are the main challenges for the development of wireless energy harvesting systems. Unlike most reported wireless energy harvesting technologies represented by electromagnetic coupling, the new generation of ultrasound-induced wireless energy harvesting (UWEH) that use propagating ultrasound waves to carry the available energy provides a strategy with higher resolution, deeper penetration, and more security, especially in nanodevices and implantable medical systems where a long-term stable power is required. Recently, advances in nanotechnologies, microelectronics, and biomedical systems are revolutionizing UWEH. In this article, an overview of recent developments in UWEH technologies that use a variety of material strategies and system designs based on the piezoelectric and capacitive energy harvesting mechanisms is provided. Practical applications are also presented, including wireless power for bio-implantable devices, direct cell/tissue electrical stimulations, wireless recording and communication in nervous systems, ultrasonic modulated drug delivery, self-powered acoustic sensors, and ultrasound-induced piezoelectric catalysis. Finally, perspectives and opportunities are also highlighted.

Association between the Charlson comorbidity index and outcomes after implantable cardioverter defibrillator generator replacement

BACKGROUND

Recipients of implantable cardioverter defibrillator (ICD) generator replacement with multiple medical comorbidities may be at higher risk of adverse outcomes that attenuate the benefit of ICD replacement. The aim of this investigation was to study the association between the Charlson comorbidity index (CCI) and outcomes after ICD generator replacement.

METHODS

All patients undergoing first ICD generator replacement at Mayo Clinic, Rochester and Beth Israel Deaconess Medical Center, Boston between 2001 and 2011 were identified. Outcomes included: (a) all-cause mortality, (b) appropriate ICD therapy, and (c) death prior to appropriate therapy. Multivariable Cox regression analysis was performed to assess association between CCI and outcomes.

RESULTS

We identified 1421 patients with mean age of 69.6 ± 12.1 years, 81% male and median (range) CCI of 3 (0-18). During a mean follow-up of 3.9 ± 3 years, 52% of patients died, 30.6% experienced an appropriate therapy, and 23.6% died without experiencing an appropriate therapy. In multivariable analysis, higher CCI score was associated with increased all-cause mortality (Hazard ratio, HR 1.10 [1.06-1.13] per 1 point increase in CCI, P < .001), death without prior appropriate therapy (HR 1.11 [1.07-1.15], P < .0001), but not associated with appropriate therapy (HR 1.01 [0.97-1.05], P = .53). Patients with CCI ≥5 had an annual risk of death of 12.2% compared to 8.7% annual rate of appropriate therapy.

CONCLUSIONS

CCI is predictive of mortality following ICD generator replacement. The benefit of ICD replacement in patients with CCI score ≥5 should be investigated in prospective studies.

ICD replacement in patients with intermediate left ventricular dysfunction under optimal medical treatment

BACKGROUND

Implantable cardioverter-defibrillators (ICD) have a pivotal role in preventing major arrhythmic events in patients with severely reduced left ventricular ejection fraction (LVEF). Device replacement strategy is still controversial in patients without severely reduced left ventricular ejection fraction (LVEF) at the end of battery life.

OBJECTIVE

To evaluate the long-term arrhythmic outcome of patients with ICD or and cardiac resynchronization therapy defibrillators (CRT-D) with normal or intermediate LVEF at the time of device replacement.

METHODS

All consecutive patients with reduced ejection fraction heart failure, both from ischemic and non-ischemic origin, implanted with ICD or CRT-D for primary prevention from 2002 to 2009, were considered. The study population included patients without previous ICD interventions and without severe dysfunction (i.e. LVEF ≥ 35%) 60 [53-65] months after implantation (average battery duration). The outcome measure was the occurrence of appropriate ICD interventions in the long-term.

RESULTS

Among the 255 patients (150 ICDs; 105 CRT-D) evaluated, 45 (18%) had LVEF ≥ 35% without ICD interventions 5-year follow-up after implantation (15 ICD [10%]; 30 CRT-D [29%]). In the long term, ICD interventions were 4 (27%) in the ICD group and 5 (17%) in the CRT-D group.

CONCLUSIONS

Despite the absence of severe left ventricular dysfunction at the time of battery replacement, a not negligible number of patients with ICD and CRT-D maintained a high risk of appropriate interventions in the long term, suggesting the opportunity of replacing the ICD regardless the amount of LV dysfunction.

Association of Implantable Cardioverter Defibrillators With Survival in Patients With and Without Improved Ejection Fraction: Secondary Analysis of the Sudden Cardiac Death in Heart Failure Trial

Importance

Improvement in left ventricular ejection fraction (EF) to >35% occurs in many patients with reduced EF at baseline. To our knowledge, whether implantable cardioverter defibrillator (ICD) therapy improves survival for these patients is unknown.

Objective

To examine the efficacy of ICD therapy in reducing risk of all-cause mortality and sudden cardiac death among patients with an EF ≤35% at baseline, with or without an improvement in EF to >35% during follow-up.

Design, Setting, and Participants

This retrospective analysis examined data collected in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), which randomly assigned 2521 patients to placebo, amiodarone, or ICD between 1997 and 2001. A subset of 1902 participants (75.4%) of the SCD-HeFT had a repeated assessment of EF a mean (SD) of 13.5 (6) months after randomization. We stratified these patients by EF ≤35% and >35% based on the first repeated EF measurement after randomization and compared all-cause mortality in 649 patients randomized to placebo vs 624 patients randomized to ICD. Follow-up started with the repeated EF assessment. Analysis was performed between January 2016 and July 2016.

Exposures

Implantable cardioverter-defibrillator therapy.

Main Outcomes and Measures

All-cause mortality and sudden cardiac death.

Results

Of the included 1273 patients, the mean (SD) age was 59 (12) years, and 977 (76.7%) were male and 1009 (79.3%) were white. Repeated EF was >35% in 186 participants (29.8%) randomized to ICD and 185 participants (28.5%) randomized to placebo. During a median follow-up of 30 months, the all-cause mortality rate was lower in the ICD vs placebo group, both in patients whose EF remained ≤35% (7.7 vs 10.7 per 100 person-year follow-up) and in those whose EF improved to >35% (2.6 vs 4.5 per 100 person-year follow-up). Compared with placebo, the adjusted hazard ratio for the effect of ICD on mortality was 0.64 (95% CI, 0.48-0.85) in patients with a repeated EF of ≤35% and 0.62 (95% CI, 0.29-1.30) in those with a repeated EF >35%. There was no interaction between treatment assignment and repeated EF for predicting mortality.

Conclusions and Relevance

Among participants in the SCD-HeFT who had a repeated EF assessment during the course of follow-up, those who had an improvement in EF to >35% accrued a similar relative reduction in mortality with ICD therapy as those whose EF remained ≤35%. Prospective randomized clinical trials are needed to test ICD efficacy in patients with an EF >35%.

Trial Registration

clinicaltrials.gov Identifier: NCT01114269.

[Continuation of ICD treatment at the time of device exchange without adequate treatment?]

INTRODUCTION

Due to improved treatment of heart failure, patients are older and have more comorbidities at the time of an elective device exchange. This leads to higher rates of complications and represents an opportunity for re-evaluation of the implantable cardioverter defibrillator (ICD) treatment.

OBJECTIVE

This article reviews the current literature regarding the indications for continued ICD therapy and device exchange in patients who have never received adequate treatment through the ICD.

MATERIAL AND METHODS

Patients with primarily prophylactic indications, who have not received adequate treatment and have shown significant improvement in the left ventricular ejection fraction (LVEF) >35%, have a significantly lower risk of ventricular arrythmia (VA) after device exchange. Although further ventricular events can occur in these patients, the continuation of ICD treatment should be individually discussed in cases of high age and increased comorbidities. In female patients with a non-ischemic cardiac myopathy and an almost normalized LVEF, mostly during cardiac resynchronization therapy (CRT), a discontinuation of ICD treatment or downgrading to CRT with pacemaker (CRT-P) treatment should be discussed.

CONCLUSION

At the time of an elective device exchange for primarily prophylactic indications, the possibility to discontinue ICD treatment can be discussed with patients who have not experienced adequate treatment. Additional factors, such as LVEF, age, sex and comorbidities of the patient should be taken into consideration in order to make an individualized decision. As prospective randomized studies are lacking, it is not possible to give generally valid recommendations.

When Is It Safe Not to Reimplant an Implantable Cardioverter Defibrillator at the Time of Battery Depletion?

The implantable cardioverter defibrillator (ICD) is a life-saving therapy in various patient populations. Although data on the outcomes of initial ICD implants are abundant, data on ICD replacements, especially in patients with improved left ventricular (LV) function, are scarce. Therefore, it is not known when it is safe to not replace an ICD that has reached the end of battery life. This article reviews data on patients with primary prevention ICDs who have improvement in left ventricular ejection fraction during follow-up and provides some guidance, based on the available evidence, related to circumstances when replacement of an ICD may be forgone.

Incorporating patients' preference diagnosis in implantable cardioverter defibrillator decision-making: a review of recent literature

PURPOSE OF REVIEW

Strong recommendations exist for implantable cardioverter defibrillators (ICD) in appropriately selected patients. Yet, patient preferences are not often incorporated when decisions about ICD therapy are made. Literature published since 2016 was reviewed aiming to discuss current advances and ongoing challenges with ICD decision-making in adults, discuss shared decision-making (SDM) as a strategy to incorporate preference diagnoses, summarize current evidence on effective interventions to facilitate SDM, and identify opportunities for research and practice.

RECENT FINDINGS

Advances in risk stratification can identify patients who will most and least likely benefit from the ICD. Interventions to support SDM are emerging. These interventions present options, the risks, and the benefits of each option, and elicit patients' values and preferences regarding possible outcomes.

SUMMARY

Appropriate patient selection for initial or continued ICD therapy is multifactorial. It requires accurate clinical diagnosis using careful risk stratification and accurate preference diagnosis based upon the patient's preferences. SDM aims to unite the elements that constitute these two equally important diagnoses. High-quality decision-making will be difficult to achieve if patients lack or misunderstand information, and if evolving patient preferences are not incorporated when making decisions.

The relationship between baseline and follow-up left ventricular ejection fraction with adverse events among primary prevention ICD patients

BACKGROUND

Left ventricular ejection fraction (LVEF) is used to select patients for primary prevention implantable cardioverter defibrillators (ICDs). The relationship between baseline and long-term follow-up LVEF and clinical outcomes among primary prevention ICD patients remains unclear.

METHODS

We studied 195 patients with a baseline LVEF ≤35% ≤6 months prior to ICD implantation and follow-up LVEF 1-3 years after ICD implantation without intervening left ventricular assist device (LVAD) or transplant. The co-primary study endpoints were: (1) a composite of time to death, LVAD, or transplant and (2) appropriate ICD therapy. We examined multivariable Cox proportional hazard models with a 3-year post-implant landmark view; the LVEF closest to the 3-year mark was considered the follow-up LVEF for analyses. Follow-up LVEF was examined using 2 definitions: (1) ≥10% improvement compared to baseline or (2) actual value of ≥40%.

RESULTS

Fifty patients (26%) had a LVEF improvement of ≥10% and 44 (23%) had a follow-up LVEF ≥40%. Neither baseline nor follow-up LVEF was significantly associated with the composite endpoint. In contrast, both baseline and follow-up LVEF were associated with risk for long-term ICD therapies, whether follow-up LVEF was modeled as a ≥10% absolute improvement (baseline LVEF HR 0.87, CI 0.91-0.93, P < .001; follow-up LVEF HR 0.18, CI 0.06-0.53, P = .002) or a ≥40% follow-up value (baseline LVEF HR 0.89, CI 0.83-0.96, P = .001, follow-up LVEF HR 0.26, CI 0.08-0.87, P = .03).

CONCLUSIONS

Among primary prevention ICD recipients, both baseline and follow-up LVEF were independently associated with long-term risk for appropriate ICD therapy, but they were not associated with time to the composite of LVAD, transplant, or death.

The subcutaneous implantable cardioverter defibrillator--review of the recent data

The subcutaneous implantable cardioverter defibrillators (SICD) is an alternative to the transvenous ICD for the prevention of sudden cardiac death (SCD). Multiple studies have shown that the SICD is safe and effective in treating ventricular arrhythmias. While earlier studies mainly enrolled younger patients with channelopathies, more recent reports included patients with “typical” indications for ICD therapy for the prevention of SCD. In this review we summarize the data available to date on the SICD while highlighting its pros and cons.

Editor-in-Chief's Top Picks From 2016: Part Two

Each week, I record audio summaries for every article in JACC, as well as an issue summary. While this process has been incredibly time-consuming, I have become quite familiar with every paper that we publish. Thus, I personally select papers (both original investigations and review articles) from 15 distinct specialties each year for your review. In addition to my personal choices, I have included manuscripts that have been the most accessed or downloaded on our websites, as well as those selected by the JACC Editorial Board members. In order to present the full breadth of this important research in a consumable fashion, we will present these manuscripts in this issue of JACC. Part One included the sections: Basic & Translational Research, Cardiac Failure, Cardiomyopathies/Myocardial & Pericardial Diseases, Congenital Heart Disease, Coronary Disease & Interventions, and CVD Prevention & Health Promotion. Part Two includes the sections: CV Medicine & Society, Hypertension, Imaging, Metabolic & Lipid Disorders, Rhythm Disorders, Valvular Heart Disease, and Vascular Medicine (1-84).

Meta-analysis of Risk of Ventricular Arrhythmias After Improvement in Left Ventricular Ejection Fraction During Follow-Up in Patients With Primary Prevention Implantable Cardioverter Defibrillators

Implantable cardioverter defibrillators (ICDs) reduce the risk of sudden cardiac death in patients with impaired left ventricular ejection fraction (LVEF). However, there are limited data on the long-term benefit of ICD therapy in patients whose LVEF subsequently improves. We conducted a meta-analysis to evaluate the effect of LVEF improvement on ICD therapy during follow-up. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were calculated using random-effects modeling. Sixteen studies with 3,959 patients were included in our analysis. Study arms were defined by LVEF improvement at follow-up (improved LVEF [>35%]: 1,622; low LVEF [≤35%] 2,337). Mean age (64.8 vs 64.9 years, p = 0.97) was similar, whereas men were overrepresented in the persistent low LVEF group (79% vs 72%, p <0.001). Appropriate ICD therapy rate was 9.7% (improved LVEF) versus 21.8% (low LVEF) over a median follow-up period of 2.9 years. In the meta-analysis, improved LVEF group had significantly lower (3.3% vs 7.2% per year IRR 0.52; CI 0.38 to 0.70; p <0.001) appropriate ICD therapies which was uniformly seen across all subgroups (ICD-only studies: IRR 0.59; p = 0.004) (cardiac resynchronization therapy-defibrillator-only studies: IRR 0.31; p = 0.002) (super-responder studies [mean LVEF > 45%]: IRR 0.53; p = 0.002). Inappropriate ICD therapy rates were, however, similar in both groups (3.01% vs 2.56% per year IRR 0.76; CI 0.43 to 1.36; p = 0.35). All-cause mortality rates in our meta-analysis favored (3.63% vs 8.23% per year IRR 0.49; CI 0.35 to 0.69; p <0.001) the improved LVEF group. In conclusion, our meta-analysis demonstrates that an improvement in LVEF is associated with a significantly reduced risk of ventricular arrhythmia and mortality. However, inappropriate ICD therapy rates remain similar.

Arrhythmic risk stratification in heart failure: Time for the next step?

BACKGROUND

Primary prevention of sudden cardiac death by means of implantable cardioverter-defibrillators constitutes the holy grail of arrhythmology. However, current risk stratification algorithms lead to suboptimal outcomes, by both allocating ICDs to patients not deriving any meaningful survival benefit and withholding them from those erroneously considered as low-risk for arrhythmic mortality.

METHODS

In the present review article we will attempt to present shortcomings of contemporary guidelines regarding sudden death prevention in ischemic and dilated cardiomyopathy patients and present available data suggesting encouraging results following implementation of multifactorial approaches, by using multiple modalities, both noninvasive and invasive. Invasive electrophysiological testing, namely programmed ventricular stimulation, will be discussed in greater length to highlight both its potential usefulness and currently ongoing multicenter studies aiming to provide evidence necessary to make the next step in sudden death risk stratification.

RESULTS

Promising findings have been reported by multiple study groups regarding novel strategies for both negative selection of low and positive selection of relatively preserved ejection fraction patients as candidates for ICD implantation.

CONCLUSIONS

The era of ejection fraction as the sole risk stratifier for arrhythmic risk in heart failure appears to be drawing to an end, especially if current underway large studies validate previous findings.