Contemporary rates of appropriate shock therapy in patients who receive implantable device therapy in a real-world setting: From the Israeli ICD Registry

doi:10.1016/j.hrthm.2015.08.020

Heart Rhythm

Volume 12, Issue 12, December 2015, Pages 2426-2433

https://doi.org/10.1016/j.hrthm.2015.08.020 Get rights and content

Background

Implantable cardioverter-defibrillators (ICDs) have become the mainstay of preventive measures for sudden cardiac death (SCD). However, there are limited data on rates of appropriate life-saving ICD shock therapies in contemporary real-life settings.

Objective

The purpose of the study was to evaluate the rate of appropriate life-saving ICD shock therapies in a contemporary registry.

Methods

The Israeli ICD Registry includes all implants and other ICD operative procedures nationwide. The present study comprises 2349 consecutive cases who were enrolled in the Registry and prospectively followed up for information regarding survival, hospitalizations, and ICD therapies since 2010.

Results

Kaplan-Meier survival analysis showed that the rate of appropriate ICD shock therapy at 30-month follow-up was 2.6% among patients who received an ICD for primary prevention compared with 7.4% among those who received a device for secondary prevention (log-rank P < .001). Rates of appropriate ICD shocks among primary prevention patients were 1.1% at 1-year of follow-up and 2.6% at 30 months, whereas the corresponding rates in the secondary prevention group were 3.8% at 1 year and 7.4% at 30 months (log-rank P < .001). A total of 253 patients (4.8%) died during follow-up, 65% of noncardiac causes.

Conclusion

Rates of life-saving appropriate ICD shock therapies among patients implanted with a defibrillator for the primary prevention of SCD in a contemporary real-world setting are lower than reported previously. These findings suggest a need for improved risk stratification and patient selection in this population.

Introduction

During the past 2 decades, implantable cardioverter-defibrillators (ICDs) have become the mainstay of sudden cardiac death (SCD) prevention. A series of landmark clinical trials1, 2, 3, 4, 5, 6 have established its role in an expanding population at risk. On the basis of these data, ICD implantation was incorporated into the guidelines,7, 8 becoming a standard of care in survivors of aborted SCD, and more importantly, in patients with advanced left ventricular dysfunction for the purpose of primary prevention of SCD. There were more than 485,000 ICD implants reported in the ICD Registry of the National Cardiovascular Data Registry during 2006 to 2009 in the United States alone.⁹ The devices currently in use offer 2 types of therapies for termination of tachyarrhythmias: antitachycardia pacing (ATP) and shock. The MADIT-RIT trial (Reduction in Inappropriate Therapy and Mortality through ICD Programming)¹⁰ has recently shown that programming of device to therapy at less than 200 bpm is associated with increased risk for inappropriate therapies and all-cause mortality, which suggests that only higher-rate therapies (mostly associated with appropriate ICD shocks) are life-saving. We and others have shown this tendency in a real-life setting in previous reports.11, 12

Notably, the rate of appropriate ICD shocks in MADIT-RIT was only 4% during a mean follow-up period of 1.4 years; however, most of the data on the rate of appropriate ICD shock therapies among patients who receive an ICD for primary prevention are derived from clinical trials, whereas real-world contemporary data are scarce. Thus, it is possible that the clinical characteristics and outcomes of patients who are currently selected for primary device intervention and are programmed in shock-reducing modes are different from those enrolled in clinical trials. Accordingly, the aim of the present study was to assess the rate of appropriate device therapies, with a specific focus on appropriate ICD shocks, in a contemporary real-world setting of patients who were enrolled and prospectively followed up in the Israeli ICD Registry.

Section snippets

Study population

The Israeli ICD Database is a national prospective registry of all patients referred for implantation or replacement of an ICD or cardiac resynchronization therapy defibrillators (CRT-D).¹³ The registry was initiated in July 2010 and incorporated all 21 centers in Israel, with the collaboration of device manufacture representatives. The registry is approved by the local institutional review boards of all participating centers, and enrolled subjects provide written informed consent. Prospective

Results

Of the 2349 study patients, 75% received the device for the primary prevention of SCD. The baseline clinical characteristics of study patients by indication for device implantation are presented in Table 1. Predictably, there were major dissimilarities between primary and secondary prevention patients. The former tended to present with a lower functional status, higher rates of severe left ventricular dysfunction, and wider QRS intervals. Rates of nonischemic cardiomyopathy were also higher in

Discussion

In the present study, we present data on defibrillator therapy in a cohort of patients who received an implantable device in a contemporary real-world setting. Our findings suggest that patients who are currently implanted for a primary prevention indication receive a very low rate of appropriate life-saving ICD shocks after implantation (3% at 30 months of follow-up). Within this population, the total mortality rate was 14%, and only 37% were cardiac-related deaths. We, however, have no data

Conclusion

Our study showed a low rate of ICD therapies, which suggests that patient selection in the current real-life setting may differ from those included in studies. In addition, it emphasizes the need for further study directed at formulating better risk stratification methods to increase the benefits of device implantation.

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For patients with nonischemic cardiomyopathy (NICM), current guidelines recommend implantable cardioverter defibrillators (ICD) when left ventricular ejection fraction (LVEF) is ≤35%, but the DANISH trial failed to confirm that ICDs reduced all-cause mortality for such patients. Circumstantial evidence suggests that scar on CMR is predictive of sudden and arrhythmic death in this population. The presence of myocardial scar identified by cardiac magnetic resonance imaging (CMR) in patients with NICM and an LVEF ≤35% might identify patients at higher risk of sudden arrhythmic death, for whom an ICD is more likely to reduce all-cause mortality.
The BRITISH trial is a prospective, multicenter, randomized controlled trial aiming to enrol 1,252 patients with NICM and an LVEF ≤35%. Patients with a nonischemic scar on CMR will be randomized to either: (1) ICD, with or without cardiac resynchronization (CRT-D), or (2) implantable loop recorder (ILR) or cardiac resynchronization (CRT-P). Patients who are screened for the trial but are found not to be eligible, predominantly due to an absence of scar or those who decline to be randomized will be enrolled in an observational registry. The primary endpoint is all-cause mortality, which we plan to assess at 3 years after the last participant is randomized. Secondary endpoints include clinical outcomes, appropriate and inappropriate device therapies, symptom severity and well-being, device-related complications, and analysis of the primary endpoint by subgroups with other risk markers.
The BRITISH trial will assess whether the use of CMR-defined scar to direct ICD implantation in patients with NICM and an LVEF ≤35% is associated with a reduction in mortality.
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The effectiveness of primary prevention implantable cardioverter-defibrillators (ICDs) is well established. However, there are several unsolved problems related to ICD use for primary prevention in Asia, including ICD underuse, population differences in underlying heart disease, and the rate of appropriate ICD therapy compared with Western countries. Although the prevalence of ischemic cardiomyopathy in Asia is lower than in Europe and the United States, the mortality rate of Asian patients with ischemic heart disease has been increasing recently. As for the use of ICDs for primary prevention, there have been no randomized clinical trials, and limited data are available in Asia. This review focuses on the unmet needs related to ICD use for primary prevention in Asia.
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Sudden cardiac death (SCD) occurs unexpectedly and is usually a result of ventricular arrhythmia in patients with structural heart disease. The implantable cardioverter-defibrillator (ICD), with or without biventricular pacing, has been proven to be protective for heart failure patients with reduced ejection fraction of <35 % (HFrEF). This device therapy prevents SCD, with additional optimal medications, namely angiotensin-converting enzyme-inhibitors, angiotensin-II receptor-blockers, beta-blockers and mineralocorticoid receptor-antagonists. HFrEF patients present the majority of SCD incidents, as they are characterized by cardiac fibrosis, the main arrhythmogenic element. The introduction of angiotensin-receptor-neprilysin inhibitors, sodium-glucose co-transporter-2 inhibitors and guanylate-cyclase stimulators was associated with reduction of SCD. Additionally, clinical trials have evaluated the improved outcome of these new medications on left ventricular ejection fraction, arrhythmias and HFrEF. These beneficial effects could possibly lead to important changes in decision-making on ICD implantation for primary prevention in patients with HFrEF and reduce the need for device therapy. In this review, we highlight the pathophysiological mechanisms of the new drug agents, and evaluate the possible effect they could have on the role of device therapy as a primary prevention of SCD.
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: See list of participating medical centers in the online Appendix.

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Contemporary rates of appropriate shock therapy in patients who receive implantable device therapy in a real-world setting: From the Israeli ICD Registry

Background

Objective

Methods

Results

Conclusion

Introduction

Section snippets

Study population

Results

Discussion

Conclusion

Heart Rhythm

Heart Rhythm

Am J Cardiol

J Am Coll Cardiol

Heart Rhythm

J Am Coll Cardiol

JACC Cardiovascular Imaging

Multicenter Automatic Defibrillator Implantation Trial III. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction

New Engl J Med

Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure

New Engl J Med

Robles de Medina EO. Randomized study of implantable defibrillator as first-choice therapy versus conventional strategy in postinfarct sudden death survivors

Circulation