Ranolazine in High-Risk Patients With Implanted Cardioverter-Defibrillators: The RAID Trial

Association of device detected atrial and ventricular tachyarrhythmia with adverse events in patients with an implantable cardioverter-defibrillator

INTRODUCTION

Heart failure patients with a history of atrial fibrillation (AF) and ventricular tachycardia/ventricular fibrillation (VT/VF) are known to have worse outcomes. However, there are limited data on the temporal relationship between development of these arrhythmias and the risk of subsequent congestive heart failure (CHF) exacerbation and death.

METHODS

The study cohort comprised 5511 patients implanted with an implantable cardioverter-defibrillator (ICD) in landmark clinical trials (MADIT-II, MADIT-RISK, MADIT-CRT, MADIT-RIT, and RAID) who were in sinus rhythm at enrollment. Multivariate cox analysis was performed to evaluate the time-dependent association between development of in-trial device detected AF and VT/VF with subsequent CHF exacerbation and death.

RESULTS

Multivariate analysis showed that AF occurrence and VT/VF occurrence were both associated with a similar magnitude of risk for subsequent CHF exacerbation (HR = 1.73 and 1.87 respectively, p < .001 for both). In contrast, only in-trial VT/VF was associated with a significant > two-fold increase in the risk of subsequent mortality (HR = 2.13, p < .001) whereas AF occurrence was not associated with a significant mortality increase after adjustment for in-trial VT/VF (HR = 1.36, p = .096).

CONCLUSION

Our findings from a large cohort of ICD recipients enrolled in landmark clinical trials show that device detected AF and VT/VF can be used to identify patients with increased risk for CHF exacerbation and mortality. These findings suggest a need for early intervention in CHF patients who develop device-detected atrial and ventricular tachyarrhythmias.

Management of patients with an electrical storm or clustered ventricular arrhythmias: a clinical consensus statement of the European Heart Rhythm Association of the ESC-endorsed by the Asia-Pacific Heart Rhythm Society, Heart Rhythm Society, and Latin-American Heart Rhythm Society

Electrical storm (ES) is a state of electrical instability, manifesting as recurrent ventricular arrhythmias (VAs) over a short period of time (three or more episodes of sustained VA within 24 h, separated by at least 5 min, requiring termination by an intervention). The clinical presentation can vary, but ES is usually a cardiac emergency. Electrical storm mainly affects patients with structural or primary electrical heart disease, often with an implantable cardioverter-defibrillator (ICD). Management of ES requires a multi-faceted approach and the involvement of multi-disciplinary teams, but despite advanced treatment and often invasive procedures, it is associated with high morbidity and mortality. With an ageing population, longer survival of heart failure patients, and an increasing number of patients with ICD, the incidence of ES is expected to increase. This European Heart Rhythm Association clinical consensus statement focuses on pathophysiology, clinical presentation, diagnostic evaluation, and acute and long-term management of patients presenting with ES or clustered VA.

Heart failure and atrial fibrillation: Is atrial fibrillation ablation in heart failure pointless or mandatory?

A vast amount of now well-established clinical and epidemiological data indicates a close, interdependent, and symbiotic association between atrial fibrillation (AF) and heart failure (HF). Both AF and HF, when co-exist in a patient, have serious treatment and prognostic implications. Based on the prevailing knowledge of the topic, various societies have issued a number of guidelines regarding the management of patients with AF and HF. Overall, it is the rhythm control strategy that has shown beneficial effect over the rate control strategy with improvement in symptoms of AF and HF. While antiarrhythmic drugs (AADs) and catheter ablation (CA) may be utilized as rhythm control strategy for AF, both AADs and CA have limitations of their own. Furthermore, with the progress made in various pharmacotherapeutic agents in HF, one could question the utility of CA in HF (i.e., whether ablation is mandatory or pointless in patients who have HF). The purpose of this review is to discuss this very point, focusing on the beneficial, neutral, or detrimental outcome of CA based on the category and class of HF.

Are antiarrhythmic agents indicated in premature ventricular complex-induced cardiomyopathy and when?

INTRODUCTION

Premature ventricular complexes (PVCs) are the most common ventricular arrhythmia that are encountered in the clinical practice. Recent data suggests that high PVC burden may lead to the development of PVC-induced cardiomyopathy (PVC-CM) even in patients without structural heart disease. Treatment for effective suppression of PVCs, can reverse PVC-CM. Both antiarrhythmic drugs (AADs) and catheter ablation (CA) are recognized treatment modalities for any cardiac arrhythmias. However, with increasing preference of CA, the role of AADs needs further defining regarding their efficacy, safety, indications and patient selection to treat PVC-CM.

METHODS

To ascertain the role of AADs to treat PVC-CM; whether they are indicated to treat PVC-CM, and if so, when, we interrogated PubMed and other search engines for English language publications with key words premature ventricular complexes (PVCs), cardiomyopathy, anti-arrhythmic drugs, catheter ablation, and pharmacological agents. All publications were carefully reviewed and scrutinized by the authors for their inclusion in the review paper. For illustration of cases, ethical standard was observed as per the 1975 Declaration of Helsinki, and the patient was treated as per the prevailing standard of care. Informed consent was obtained from the patient for conducting the ablation procedure.

RESULTS

Our literature search specifically the pharmacological treatment of PVC-CM with AADs revealed significant paradigm shift in treatment approach for PVCs and PVC-induced cardiomyopathy. No major large, randomized control trials of AADs versus CA for PVC-CM were found. We found that beta-blockers and calcium channel blockers are particularly effective in the treatment of PVCs originating from right ventricular outflow tract. For Class Ic AADs - flecainide and propafenone, small clinical studies showed Class Ic AADs to be effective in PVC suppression, but their usage was not recommended in patients with significant coronary artery disease. Mexiletine was found to have modest effect on PVC suppression. Studies showed sotalol to significantly reduce PVCs frequency in patients receiving both low and high doses. Studies also showed amiodarone to have higher successful PVC suppression, but not recommended as a first-line treatment for patients with idiopathic PVCs in the absence of symptoms and left ventricular dysfunction. For dronedarone, no major clinical data were available.

CONCLUSIONS

Based on the available data in the literature, we conclude that AADs play important role in the treatment of PVC-induced cardiomyopathy. However, appropriate patient selection criteria are vitally important, and in general terms AADs are indicated or polymorphic PVCs, epicardial PVCs; and when CA procedure is contraindicated, or not feasible or failed.

Sex-Related Differences in Ventricular Tachyarrhythmia Events in Patients With Implantable Cardioverter-Defibrillator and Prior Ventricular Tachyarrhythmias

BACKGROUND

Data on the risk of ventricular tachycardia (VT), ventricular fibrillation (VF), and death by sex in patients with prior VT/VF are limited.

OBJECTIVES

This study aimed to assess sex-related differences in implantable cardioverter-defibrillator (ICD)-treated VT/VF events and death in patients implanted for secondary prevention or primary prevention ICD indications who experienced VT/VF before enrollment in the RAID (Ranolazine Implantable Cardioverter-Defibrillator) trial.

METHODS

Sex-related differences in the first and recurrent VT/VF requiring antitachycardia pacing or ICD shock and death were evaluated in 714 patients.

RESULTS

There were 124 women (17%) and 590 men observed during a mean follow-up of 26.81 ± 14.52 months. Compared to men, women were at a significantly lower risk of VT/VF/death (HR: 0.67; P = 0.029), VT/VF (HR: 0.68; P = 0.049), VT/VF treated with antitachycardia pacing (HR: 0.59; P = 0.019), and VT/VF treated with ICD shock (HR: 0.54; P = 0.035). The risk of recurrent VT/VF was also significantly lower in women (HR: 0.35; P < 0.001). HR for death was similar to the other endpoints (HR: 0.61; P = 0.162). In comparison to men, women presented with faster VT rates (196 ± 32 beats/min vs 177 ± 30 beats/min, respectively; P = 0.002), and faster shock-requiring VT/VF rates (258 ± 56 beats/min vs 227 ± 57 beats/min, respectively; P = 0.30). There was a significant interaction for the risk of VT/VF by race (P = 0.013) with White women having significantly lower risk than White men (HR: 0.36; P < 0.001), whereas Black women had a similar risk to Black men (HR: 1.06; P = 0.851).

CONCLUSIONS

Women with a history of prior VT/VF experienced a lower risk recurrent VT/VF requiring ICD therapy when compared to men. Black Women had a risk similar to men, whereas the lower risk for VT/VF in women was observed primarily in White women. (Ranolazine Implantable Cardioverter-Defibrillator Trial; NCT01215253).

QRS Morphology and the Risk of Ventricular Tachyarrhythmia in Cardiac Resynchronization Therapy Recipients

BACKGROUND

There are conflicting data on the effect of cardiac resynchronization therapy with a defibrillator (CRT-D) on the risk of life-threatening ventricular tachyarrhythmia in heart failure patients.

OBJECTIVES

The authors aimed to assess whether QRS morphology is associated with risk of ventricular arrhythmias in CRT recipients.

METHODS

The study population comprised 2,862 patients implanted with implantable cardioverter defibrillator (ICD)/CRT-D for primary prevention who were enrolled in 5 landmark primary prevention ICD trials (MADIT-II [Multicenter Automated Defibrillator Implantation Trial], MADIT-CRT [Multicenter Automated Defibrillator Implantation Trial-Cardiac Resynchronization Therapy], MADIT-RIT [Multicenter Automated Defibrillator Implantation Trial-Reduction in Inappropriate Therapy], MADIT-RISK [Multicenter Automated Defibrillator Implantation Trial-RISK], and RAID [Ranolazine in High-Risk Patients With Implanted Cardioverter Defibrillators]). Patients with QRS duration ≥130 ms were divided into 2 groups: those implanted with an ICD only vs CRT-D. The primary endpoint was fast ventricular tachycardia (VT)/ventricular fibrillation (VF) (defined as VT ≥200 beats/min or VF), accounting for the competing risk of death. Secondary endpoints included appropriate shocks, any sustained VT or VF, and the burden of fast VT/VF, assessed in a recurrent event analysis.

RESULTS

Among patients with left bundle branch block (n = 1,792), those with CRT-D (n = 1,112) experienced a significant 44% (P < 0.001) reduction in the risk of fast VT/VF compared with ICD-only patients (n = 680), a significantly lower burden of fast VT/VF (HR: 0.55; P = 0.001), with a reduced burden of appropriate shocks (HR: 0.44; P < 0.001). In contrast, among patients with non-left bundle branch block (NLBBB) (N = 1,070), CRT-D was not associated with reduction in fast VT/VF (HR: 1.33; P = 0.195). Furthermore, NLBBB patients with CRT-D experienced a statistically significant increase in the burden of fast VT/VF events compared with ICD-only patients (HR: 1.90; P = 0.013).

CONCLUSIONS

Our data suggest a potential proarrhythmic effect of CRT among patients with NLBBB. These data should be considered in patient selection for treatment with CRT.

The Role of Ranolazine in Heart Failure-Current Concepts

Heart failure is a complex clinical syndrome with a detrimental impact on mortality and morbidity. Energy substrate utilization and myocardial ion channel regulation have gained research interest especially after the introduction of sodium-glucose co-transporter 2 inhibitors in the treatment of heart failure. Ranolazine or N-(2,6-dimethylphenyl)-2-(4-[2-hydroxy-3-(2-methoxyphenoxy) propyl] piperazin-1-yl) acetamide hydrochloride is an active piperazine derivative which inhibits late sodium current thus minimizing calcium overload in the ischemic cardiomyocytes. Ranolazine also prevents fatty acid oxidation and favors glycose utilization ameliorating the "energy starvation" of the failing heart. Heart failure with preserved ejection fraction is characterized by diastolic impairment; according to the literature ranolazine could be beneficial in the management of increased left ventricular end-diastolic pressure, right ventricular systolic dysfunction and wall shear stress which is reflected by the high natriuretic peptides. Fewer data is evident regarding the effects of ranolazine in heart failure with reduced ejection fraction and mainly support the control of the sodium-calcium exchanger and function of sarcoendoplasmic reticulum calcium adenosine triphosphatase. Ranolazine's therapeutic mechanisms in myocardial ion channels and energy utilization are documented in patients with chronic coronary syndromes. Nevertheless, ranolazine might have a broader effect in the therapy of heart failure and further mechanistic research is required.

Effect of Carvedilol vs Metoprolol on Atrial and Ventricular Arrhythmias Among Implantable Cardioverter-Defibrillator Recipients

BACKGROUND

Both selective and nonselective beta-blockers are used to treat patients with heart failure (HF). However, the data on the association of beta-blocker type with risk of atrial arrhythmia and ventricular arrhythmia (VA) in HF patients with a primary prevention implantable cardioverter-defibrillator (ICD) are limited.

OBJECTIVES

This study sought to evaluate the effect of metoprolol vs carvedilol on the risk of atrial tachyarrhythmia (ATA) and VA in HF patients with an ICD.

METHODS

This study pooled primary prevention ICD recipients from 5 landmark ICD trials (MADIT-II, MADIT-CRT, MADIT-RIT, MADIT-RISK, and RAID). Fine and Gray multivariate regression models, stratified by study, were used to evaluate the risk of ATA, inappropriate ICD shocks, and fast VA (defined as ventricular tachycardia ≥200 beats/min or ventricular fibrillation) by beta-blocker type.

RESULTS

Among 4,194 patients, 2,920 (70%) were prescribed carvedilol and 1,274 (30%) metoprolol. The cumulative incidence of ATA at 3.5 years was 11% in patients treated with carvedilol vs 15% in patients taking metoprolol (P = 0.003). Multivariate analysis showed that carvedilol treatment was associated with a 35% reduction in the risk of ATA (HR: 0.65; 95% CI: 0.53-0.81; P < 0.001) when compared to metoprolol, and with a corresponding 35% reduction in the risk of inappropriate ICD shocks (HR: 0.65; 95% CI: 0.47-0.89; P = 0.008). Carvedilol vs metoprolol was also associated with a 16% reduction in the risk of fast VA. However, these findings did not reach statistical significance (HR: 0.84; 95% CI: 0.70-1.02; P = 0.085).

CONCLUSIONS

These findings suggests that HF patients with ICDs on carvedilol treatment experience a significantly lower risk of ATA and inappropriate ICD shocks when compared to treatment with metoprolol.

Primary prevention implantable cardioverter defibrillator in cardiac resynchronization therapy recipients with advanced chronic kidney disease

Introduction

The implantable cardioverter defibrillator (ICD) is effective for the prevention of sudden cardiac death (SCD) in patients with heart failure and a reduced ejection fraction (HFrEF). The benefit of the ICD in patients with advanced CKD, remains elusive. Moreover, the benefit of the ICD in patients with advanced chronic kidney disease (CKD) and HFrEF who are cardiac resynchronization therapy (CRT) recipients may be attenuated.

Hypothesis

We hypothesized that patients with CKD who are CRT recipients may derive less benefit from the ICD due to the competing risk of dying prior to experiencing an arrhythmia.

Methods

The study population included 1,015 patients receiving CRT with defibrillator (CRT-D) device for primary prevention of SCD who were enrolled in either (Multicenter Automated Defibrillator Implantation Trial) MADIT-CRT trial or the Ranolazine in High-Risk Patients with Implanted Cardioverter Defibrillator (RAID) trial. The cohort was divided into two groups based on the stage of CKD: those with Stage 1 to 3a KD, labeled as (S1-S3a)KD. The second group included patients with Stage 3b to stage 5 kidney disease, labeled as (S3b-S5)KD. The primary endpoint was any ventricular tachycardia (VT) or ventricular fibrillation (VF) (Any VT/VF).

Results

The cumulative incidence of Any VT/VF was 23.5% in patients with (S1-S3a)KD and 12.6% in those with (S3b-S5)KD (p < 0.001) The incidence of Death without Any VT/VF was 6.6% in patients with (S1-S3a)KD and 21.6% in patients with (S3b-S5)KD (p < 0.001). A Fine and Gray multivariate competing risk regression model showed that Patients with (S3b-S5)KD had a 43% less risk of experiencing Any VT/VF when compared to those with (S1-S3a)KD (HR = 0.56, 95% CI [0.33-0.94] p = 0.03. After two years of follow up, there was almost a 5-fold increased risk of Death without Any VT/VF among patients with (S3b-S5)KD when compared to those with (S1-S3a)KD [HR = 4.63, 95% CI (2.46-8.72), p for interaction with time = 0.012].

Conclusion

Due to their lower incidence of arrhythmias and higher risk of dying prior to experiencing an arrhythmia, the benefit of the ICD may be attenuated in CRT recipients with advanced CKD. Future prospective trials should evaluate whether CRT without a defibrillator may be more appropriate for these patients.

Arrhythmia and Survival Outcomes Among Black Patients and White Patients With a Primary Prevention Defibrillator

BACKGROUND

Black Americans have a higher risk of nonischemic cardiomyopathy (NICM) than White Americans. We aimed to evaluate differences in the risk of tachyarrhythmias among patients with an implantable cardioverter-defibrillator (ICD).

METHODS

The study population comprised 3895 ICD recipients in the United States enrolled in primary prevention ICD trials. Outcome measures included ventricular tachyarrhythmia (VTA), atrial tachyarrhythmia (ATA), ICD therapies, VTA burden (using Andersen-Gill recurrent event analysis), death, and the predicted benefit of the ICD. All events were adjudicated blindly. Outcomes were compared between self-reported Black patients versus White patients with cardiomyopathy (ischemic and NICM).

RESULTS

Black patients were more likely to be female (35% versus 22%) and younger (57±12 versus 62±12 years) with a higher frequency of comorbidities. In NICM, Black patients had a higher rate of first VTA, fast VTA, ATA, and appropriate and inappropriate ICD therapy (VTA ≥170 bpm, 32% versus 20%; VTA ≥200 bpm, 22% versus 14%; ATA, 25% versus 12%; appropriate therapy, 30% versus 20%; and inappropriate therapy, 25% versus 11%; P<0.001 for all). Multivariable analysis showed that Black patients with NICM experienced a higher risk of all types of arrhythmia or ICD therapy (VTA ≥170 bpm, hazard ratio [HR] 1.71; VTA ≥200 bpm, HR 1.58; ATA, HR 1.87; appropriate therapy, HR 1.62; inappropriate therapy, HR 1.86; P≤0.01 for all), higher burden of tachyarrhythmias or therapies (VTA, HR 1.84; appropriate therapy, HR 1.84; P<0.001 for both), and a higher risk of death (HR 1.92; P=0.014). In contrast, in ischemic cardiomyopathy, the risk of all types of tachyarrhythmia, ICD therapy, or death was similar between Black patients and White patients. Both Black patients and White patients derived a significant and similar benefit from ICD implantation.

CONCLUSIONS

Among patients with NICM with an ICD for primary prevention, Black patients compared with White patients had a high risk and burden of VTA, ATA, and ICD therapies with a lower survival rate. Nevertheless, the overall benefit of the ICD was maintained and was similar to that of White patients.

Multidisciplinary Critical Care Management of Electrical Storm: JACC State-of-the-Art Review

Electrical storm (ES) reflects life-threatening cardiac electrical instability with 3 or more ventricular arrhythmia episodes within 24 hours. Identification of underlying arrhythmogenic cardiac substrate and reversible triggers is essential, as is interrogation and programming of an implantable cardioverter-defibrillator, if present. Medical management includes antiarrhythmic drugs, beta-adrenergic blockade, sedation, and hemodynamic support. The initial intensity of these interventions should be matched to the severity of ES using a stepped-care algorithm involving escalating treatments for higher-risk presentations or recurrent ventricular arrhythmias. Many patients with ES are considered for catheter ablation, which may require the use of temporary mechanical circulatory support. Outcomes after ES are poor, including frequent ES recurrences and deaths caused by progressive heart failure and other cardiac causes. A multidisciplinary collaborative approach to the management of ES is crucial, and evaluation for heart transplantation or palliative care is often appropriate, even for patients who survive the initial episode.

Overview of Cardiac Arrhythmias and Treatment Strategies

Maintenance of normal cardiac rhythm requires coordinated activity of ion channels and transporters that allow well-ordered propagation of electrical impulses across the myocardium. Disruptions in this orderly process provoke cardiac arrhythmias that may be lethal in some patients. Risk of common acquired arrhythmias is increased markedly when structural heart disease caused by myocardial infarction (due to fibrotic scar formation) or left ventricular dysfunction is present. Genetic polymorphisms influence structure or excitability of the myocardial substrate, which increases vulnerability or risk of arrhythmias in patients. Similarly, genetic polymorphisms of drug-metabolizing enzymes give rise to distinct subgroups within the population that affect specific drug biotransformation reactions. Nonetheless, identification of triggers involved in initiation or maintenance of cardiac arrhythmias remains a major challenge. Herein, we provide an overview of knowledge regarding physiopathology of inherited and acquired cardiac arrhythmias along with a summary of treatments (pharmacologic or non-pharmacologic) used to limit their effect on morbidity and potential mortality. Improved understanding of molecular and cellular aspects of arrhythmogenesis and more epidemiologic studies (for a more accurate portrait of incidence and prevalence) are crucial for development of novel treatments and for management of cardiac arrhythmias and their consequences in patients, as their incidence is increasing worldwide.

Arrhythmia and Survival Outcomes among Black and White Patients with a Primary Prevention Defibrillator

Background

Black Americans have a higher risk of non-ischemic cardiomyopathy (NICM) than White Americans. We aimed to evaluate racial disparities in the risk of tachyarrhythmias among patients with an implantable cardioverter defibrillator (ICD).

Methods

The study population comprised 3,895 ICD recipients enrolled in the U.S. in primary prevention ICD trials. Outcome measures included first and recurrent ventricular tachy-arrhythmia (VTA) and atrial tachyarrhythmia (ATA), derived from adjudicated device data, and death. Outcomes were compared between self-reported Black vs. White patients with a cardiomyopathy (ischemic [ICM] and NICM).

Results

Black patients were more likely to be female (35% vs 22%) and younger (57±12 vs 62±12) with a higher frequency of comorbidities. Blacks patients with NICM compared with Whites patients had a higher rate of first VTA, fast VTA, ATA, appropriate-, and inappropriate-ICD-therapy (VTA≥170bpm: 32% vs. 20%; VTA≥200bpm: 22% vs. 14%; ATA: 25% vs. 12%; appropriate 30% vs 20%; and inappropriate: 25% vs. 11%; p<0.001 for all). Multivariable analysis showed that Black patients with NICM experienced a higher risk of all types of arrhythmia/ICD-therapy (VTA≥170bpm: HR=1.69; VTA≥200bpm: HR=1.58; ATA: HR=1.87; appropriate: HR=1.62; and inappropriate: HR=1.86; p≤0.01 for all), higher burden of VTA, ATA, ICD therapies, and a higher risk of death (HR=1.86; p=0.014). In contrast, in ICM, the risk of all types of tachyarrhythmia, ICD therapy, or death was similar between Black and White patients.

Conclusions

Among NICM patients with an ICD for primary prevention, Black compared with White patients had a high risk and burden of VTA, ATA, and ICD therapies.

Clinical Perspective

What Is New?: Black patients have a higher risk of developing non-ischemic cardiomyopathy (NICM) but are under-represented in clinical trials of implantable cardioverter defibrillators (ICD). Therefore, data on disparities in the presentation and outcomes in this population are limited.This analysis represents the largest group of self-identified Black patients implanted in the U.S. with an ICD for primary prevention with adjudication of all arrhythmic events.What Are the Clinical Implications?: In patients with a NICM, self-identified Black compared to White patients experienced an increased incidence and burden of ventricular tachyarrhythmia, atrial tachyarrhythmia, and ICD therapies. These differenced were not observed in Black vs White patients with ischemic cardiomyopathy (ICM).Although Black patients with NICM were implanted at a significantly younger age (57±12 vs 62±12 years), they experienced a 2-fold higher rate of all-cause mortality during a mean follow up of 3 years compared with White patients.These findings highlight the need for early intervention with an ICD, careful monitoring, and intensification of heart failure and antiarrhythmic therapies among Black patients with NICM.

Electrical storm management in structural heart disease

Electrical storm (ES) is a life-threatening condition characterized by at least three separate episodes of ventricular arrhythmias (VAs) over 24 h, each requiring therapeutic intervention, including implantable cardioverter defibrillator (ICD) therapies. Patients with ICDs in secondary prevention are at higher risk of ES and the most common presentation is that of scar-related monomorphic VAs. Electrical storm represents a major unfavourable prognostic marker in the history of patients with structural heart disease, with an associated two- to five-fold increase in mortality, heart transplant, and heart failure hospitalization. Early recognition and prompt treatment are crucial to improve the outcome. Yet, ES management is complex and requires a multidisciplinary approach and well-defined protocols and networks to guarantee a proper patient care. Acute phase stabilization should include a comprehensive clinical assessment, resuscitation and sedation management skills, ICD reprogramming, and acute sympathetic modulation, while the sub-acute/chronic phase requires a comprehensive heart team evaluation to define the better treatment option according to the haemodynamic and overall patient's condition and the type of VAs. Advanced anti-arrhythmic strategies, not mutually exclusive, include invasive ablation, cardiac sympathetic denervation, and, for very selected cases, stereotactic ablation. Each of these aspects, as well as the new European Society of Cardiology guidelines recommendations, will be discussed in the present review.

Age and the Risk of Ventricular Tachyarrhythmia in Patients With an Implantable Cardioverter-Defibrillator

BACKGROUND

The benefit of implantable cardioverter-defibrillators (ICDs) in elderly patients is controversial.

OBJECTIVES

The aims of this study were to evaluate the risk for ventricular tachyarrhythmia (VTA) and ICD shocks by age groups and to assess the competing risk for VTA and death without prior VTA.

METHODS

The study included 5,170 primary prevention ICD recipients enrolled in 5 landmark ICD trials (MADIT [Multicenter Automatic Defibrillator Implantation Trial] II, MADIT-Risk, MADIT-CRT [MADIT Cardiac Resynchronization Therapy], MADIT-RIT [MADIT Reduce Inappropriate Therapy], and RAID [Ranolazine in High-Risk Patients With Implanted Cardioverter-Defibrillator]). Fine and Gray regression analysis was used to evaluate the risk for fast VTA (ventricular tachycardia ≥200 beats/min or ventricular fibrillation) vs death without prior fast VTA in 3 prespecified age groups: <65, 65 to <75, and ≥75 years.

RESULTS

The cumulative incidence of fast VTA at 3 years was similar for patients <65 years of age and those 65 to <75 years of age (17% vs 15%) and was lowest among patients ≥75 years of age (10%) (P < 0.001). Multivariate Fine and Gray analysis showed a 40% lower risk for fast VTA in patients ≥75 years of age (HR: 0.60; 95% CI: 0.46-0.78; P < 0.001) compared with patients <65 years of age. In patients ≥75 years of age, a risk reversal was observed whereby the risk for death without prior fast VTA exceeded the risk for developing fast VTA. A history of nonsustained ventricular tachycardia, male sex, and the presence of nonischemic cardiomyopathy were identified as predictors of fast VTA in patients ≥75 years of age.

CONCLUSIONS

Patients ≥75 years of age have a significantly lower risk for VTA and ICD shocks compared with younger patients. Aging is associated with a higher risk for death compared with the risk for fast VTA, the reverse of what is seen in younger patients.

Usefulness of the MADIT-ICD Benefit Score in a Large Mixed Patient Cohort of Primary Prevention of Sudden Cardiac Death

Background: Decision-making in primary prevention is not always trivial and many clinical scenarios are not reflected in current guidelines. To help evaluate a patient’s individual risk, a new score to predict the benefit of an implantable defibrillator (ICD) for primary prevention, the MADIT-ICD benefit score, has recently been proposed. The score tries to predict occurrence of ventricular arrhythmias and non-arrhythmic death based on data from four previous MADIT trials. We aimed at examining its usefulness in a large single-center register of S-ICD patients with various underlying cardiomyopathies. Methods and results: All S-ICD patients with a primary preventive indication for ICD implantation from our large single-center database were included in the analysis (n = 173). During a follow-up of 1227 ± 978 days, 27 patients developed sustained ventricular arrhythmias, while 6 patients died for non-arrhythmic reasons. There was a significant correlation for patients with ischemic cardiomyopathy (ICM) (n = 29, p = 0.04) to the occurrence of ventricular arrhythmia. However, the occurrence of ventricular arrhythmias could not sufficiently be predicted by the MADIT-ICD VT/VF score (p = 0.3) in patients with (n = 142, p = 0.19) as well as patients without structural heart disease (n = 31, p = 0.88) and patients with LV-EF < 35%. Of the risk factors included in the risk score calculation, only non-sustained ventricular tachycardias were significantly associated with sustained ventricular arrhythmias (p = 0.02). Of note, non-arrhythmic death could effectively be predicted by the proposed non-arrhythmic mortality score as part of the benefit score (p = 0.001, r = 0.3) also mainly driven by ICM patients. Age, diabetes mellitus, and a BMI < 23 kg/m2 were key predictors of non-arrhythmic death implemented in the score. Conclusion: The MADIT-ICD benefit score adds a new option to evaluate expected benefit of ICD implantation for primary prevention. In a large S-ICD cohort of primary prevention, the value of the score was limited to patients with ischemic cardiomyopathy. Future research should evaluate the performance of the score in different subgroups and compare it to other risk scores to assess its value for daily clinical practice.

Aging-associated susceptibility to stress-induced ventricular arrhythmogenesis is attenuated by tetrodotoxin

Aging is associated with increased prevalence of life-threatening ventricular arrhythmias, but mechanisms underlying higher susceptibility to arrhythmogenesis and means to prevent such arrhythmias under stress are not fully defined. We aimed to define differences in aging-associated susceptibility to ventricular fibrillation (VF) induction between young and aged hearts. VF induction was attempted in isolated perfused hearts of young (6-month) and aged (24-month-old) male Fischer-344 rats by rapid pacing before and following isoproterenol (1 μM) or global ischemia and reperfusion (I/R) injury with or without pretreatment with low-dose tetrodotoxin, a late sodium current blocker. At baseline, VF could not be induced; however, the susceptibility to inducible VF after isoproterenol and spontaneous VF following I/R was 6-fold and 3-fold higher, respectively, in old hearts (P < 0.05). Old animals had longer epicardial monophasic action potential at 90% repolarization (APD₉₀; P < 0.05) and displayed a loss of isoproterenol-induced shortening of APD₉₀ present in the young. In isolated ventricular cardiomyocytes from older but not younger animals, 4-aminopyridine prolonged APD and induced early afterdepolarizations (EADs) and triggered activity with isoproterenol. Low-dose tetrodotoxin (0.5 μM) significantly shortened APD without altering action potential upstroke and prevented 4-aminopyridine-mediated APD prolongation, EADs, and triggered activity. Tetrodotoxin pretreatment prevented VF induction by pacing in isoproterenol-challenged hearts. Vulnerability to VF following I/R or catecholamine challenge is significantly increased in old hearts that display reduced repolarization reserve and increased propensity to EADs, triggered activity, and ventricular arrhythmogenesis that can be suppressed by low-dose tetrodotoxin, suggesting a role of slow sodium current in promoting arrhythmogenesis with aging.

Pharmacologic Management for Ventricular Arrhythmias: Overview of Anti-Arrhythmic Drugs

Ventricular arrhythmias (Vas) are a life-threatening condition and preventable cause of sudden cardiac death (SCD). With the increased utilization of implantable cardiac defibrillators (ICD), the focus of VA management has shifted toward reduction of morbidity from VAs and ICD therapies. Anti-arrhythmic drugs (AADs) can be an important adjunct therapy in the treatment of recurrent VAs. In the treatment of VAs secondary to structural heart disease, amiodarone remains the most well studied and current guideline-directed pharmacologic therapy. Beta blockers also serve as an important adjunct and are a largely underutilized medication with strong evidentiary support. In patients with defined syndromes in structurally normal hearts, AADs can offer tailored therapies in prevention of SCD and improvement in quality of life. Further clinical trials are warranted to investigate the role of newer therapeutic options and for the direct comparison of established AADs.

Reduction in Ventricular Tachyarrhythmia Burden in Patients Enrolled in the RAID Trial

BACKGROUND

The RAID (Ranolazine Implantable Cardioverter-Defibrillator) randomized placebo-controlled trial showed that ranolazine treatment was associated with reduction in recurrent ventricular tachycardia (VT) requiring appropriate implantable cardioverter-defibrillator (ICD) therapy.

OBJECTIVES

This study aimed to identify groups of patients in whom ranolazine treatment would result in the highest reduction of ventricular tachyarrhythmia (VTA) burden.

METHODS

Andersen-Gill analyses were performed to identify variables associated with risk for VTA burden among 1,012 patients enrolled in RAID. The primary endpoint was VTA burden defined as VTA episodes requiring appropriate treatment.

RESULTS

Multivariate analysis identified 7 factors associated with increased VTA burden: history of VTA, age ≥65 years, New York Heart Association functional class ≥III, QRS complex (≥130 ms), low ejection fraction (<30%), atrial fibrillation (AF), and concomitant antiarrhythmic drug (AAD) therapy. The effect of ranolazine on VTA burden was seen among patients without concomitant AAD therapy (HR [HR]: 0.68; 95% CI: 0.55-0.84; P < 0.001), whereas no effect was seen among those who are concomitantly treated with other AADs (HR: 1.33; 95% CI: 0.90-1.96; P = 0.16); P = 0.003 for interaction. In patients with cardiac resynchronization therapy (CRT) ICDs, ranolazine treatment was associated with a 36% risk reduction for VTA recurrence (HR: 0.64; 95% CI: 0.47-0.86; P < 0.001), whereas among patients with ICDs without CRT no significant effect was noted (HR: 0.94; 95% CI: 0.74-1.18; P = 0.57); P = 0.047 for interaction.

CONCLUSIONS

In patients with high risk for VTA, ranolazine is effective in reducing VTA burden, with significantly greater effect in CRT-treated patients, those without AF, and those not treated with concomitant AADs. In patients already on AADs or those with AF, the addition of ranolazine did not affect VTA burden. (Ranolazine Implantable Cardioverter-Defibrillator Trial [RAID]; NCT01215253).

The MADIT-ICD benefit score helps to select implantable cardioverter-defibrillator candidates in cardiac resynchronization therapy

AIMS

The aim of this study is to evaluate whether the MADIT-ICD benefit score can predict who benefits most from the addition of implantable cardioverter-defibrillator (ICD) to cardiac resynchronization therapy (CRT) in real-world patients with heart failure with reduced ejection fraction (HFrEF) and to compare this with selection according to a multidisciplinary expert centre approach.

METHODS AND RESULTS

Consecutive HFrEF patients who received a CRT for a guideline indication at a tertiary care hospital (Ziekenhuis Oost-Limburg, Genk, Belgium) between October 2008 and September 2016, were retrospectively evaluated. The MADIT-ICD benefit groups (low, intermediate, and high) were compared with the current multidisciplinary expert centre approach. Endpoints were (i) sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and (ii) non-arrhythmic mortality. Of the 475 included patients, 165 (34.7%) were in the lowest, 220 (46.3%) in the intermediate, and 90 (19.0%) in the highest benefit group. After a median follow-up of 34 months, VT/VF occurred in 3 (1.8%) patients in the lowest, 9 (4.1%) in the intermediate, and 13 (14.4%) in the highest benefit group (P < 0.001). Vice versa, non-arrhythmic death occurred in 32 (19.4%) in the lowest, 32 (14.6%) in the intermediate, and 3 (3.3%) in the highest benefit group (P = 0.002). The predictive power for ICD benefit was comparable between expert multidisciplinary judgement and the MADIT-ICD benefit score: Uno's C-statistic 0.69 vs. 0.69 (P = 0.936) for VT/VF and 0.62 vs. 0.60 (P = 0.790) for non-arrhythmic mortality.

CONCLUSION

The MADIT-ICD benefit score can identify who benefits most from CRT-D and is comparable with multidisciplinary judgement in a CRT expert centre.

Arrhythmic and Mortality Outcomes Among Ischemic Versus Nonischemic Cardiomyopathy Patients Receiving Primary ICD Therapy

OBJECTIVES

This study sought to determine the association of cardiomyopathy etiology with the likelihood of ventricular arrhythmias, appropriate implantable cardioverter-defibrillator (ICD) therapy, and mortality.

BACKGROUND

There are conflicting data on the benefit of primary prevention ICD therapy in patients with ischemic versus nonischemic cardiomyopathy (ICM/NICM).

METHODS

The study population comprised 4803 patients with ICM (n = 3,106) or NICM (n = 1,697) with a primary prevention ICD enrolled in 5 randomized trials conducted between 1997 and 2017. The primary end point was sustained ventricular tachycardia (VT) ≥200 beats/min or ventricular fibrillation (VF). Secondary end points included appropriate ICD therapy and all-cause mortality. Differences in cause-specific mortality, including noncardiac, sudden cardiac, and non-sudden cardiac death, were also examined.

RESULTS

Patients with ICM were significantly older and had more comorbid conditions, whereas those with NICM had a more advanced heart failure class at enrollment and were more often prescribed medical or cardiac resynchronization therapy for heart failure. Multivariate analysis showed that ICM versus NICM had a similar risk of VT/VF events (HR: 0.98 [95% CI: 0.79-1.20]) and appropriate ICD therapy (HR: 1.03 [95% CI: 0.87-1.22]), whereas the risk of all-cause mortality was 1.8-fold higher among ICM versus NICM patients (HR: 1.84 [95% CI: 1.42-2.38]), dominated by non-sudden cardiac mortality.

CONCLUSIONS

Combined data from 5 landmark ICD clinical trials show that ICM patients experience a similar risk of life-threatening ventricular arrhythmic events but have an increased risk of all-cause mortality, dominated by non-sudden cardiac death, compared with NICM patients.

Ranolazine: An Old Drug with Emerging Potential; Lessons from Pre-Clinical and Clinical Investigations for Possible Repositioning

Ischemic heart disease is a significant public health problem with high mortality and morbidity. Extensive scientific investigations from basic sciences to clinics revealed multilevel alterations from metabolic imbalance, altered electrophysiology, and defective Ca²⁺/Na⁺ homeostasis leading to lethal arrhythmias. Despite the recent identification of numerous molecular targets with potential therapeutic interest, a pragmatic observation on the current pharmacological R&D output confirms the lack of new therapeutic offers to patients. By contrast, from recent trials, molecules initially developed for other fields of application have shown cardiovascular benefits, as illustrated with some anti-diabetic agents, regardless of the presence or absence of diabetes, emphasizing the clear advantage of “old” drug repositioning. Ranolazine is approved as an antianginal agent and has a favorable overall safety profile. This drug, developed initially as a metabolic modulator, was also identified as an inhibitor of the cardiac late Na⁺ current, although it also blocks other ionic currents, including the hERG/Ikr K⁺ current. The latter actions have been involved in this drug’s antiarrhythmic effects, both on supraventricular and ventricular arrhythmias (VA). However, despite initial enthusiasm and promising development in the cardiovascular field, ranolazine is only authorized as a second-line treatment in patients with chronic angina pectoris, notwithstanding its antiarrhythmic properties. A plausible reason for this is the apparent difficulty in linking the clinical benefits to the multiple molecular actions of this drug. Here, we review ranolazine’s experimental and clinical knowledge on cardiac metabolism and arrhythmias. We also highlight advances in understanding novel effects on neurons, the vascular system, skeletal muscles, blood sugar control, and cancer, which may open the way to reposition this “old” drug alone or in combination with other medications.

Modulation of the effects of class Ib antiarrhythmics on cardiac NaV1.5-encoded channels by accessory NaVβ subunits

Native myocardial voltage-gated sodium (Na_V) channels function in macromolecular complexes comprising a pore-forming (α) subunit and multiple accessory proteins. Here, we investigated the impact of accessory Na_Vβ1 and Na_Vβ3 subunits on the functional effects of 2 well-known class Ib antiarrhythmics, lidocaine and ranolazine, on the predominant Na_V channel α subunit, Na_V1.5, expressed in the mammalian heart. We showed that both drugs stabilized the activated conformation of the voltage sensor of domain-III (DIII-VSD) in Na_V1.5. In the presence of Na_Vβ1, the effect of lidocaine on the DIII-VSD was enhanced, whereas the effect of ranolazine was abolished. Mutating the main class Ib drug-binding site, F1760, affected but did not abolish the modulation of drug block by Na_Vβ1/β3. Recordings from adult mouse ventricular myocytes demonstrated that loss of Scn1b (Na_Vβ1) differentially affected the potencies of lidocaine and ranolazine. In vivo experiments revealed distinct ECG responses to i.p. injection of ranolazine or lidocaine in WT and Scn1b-null animals, suggesting that Na_Vβ1 modulated drug responses at the whole-heart level. In the human heart, we found that SCN1B transcript expression was 3 times higher in the atria than ventricles, differences that could, in combination with inherited or acquired cardiovascular disease, dramatically affect patient response to class Ib antiarrhythmic therapies.

Effect of ranolazine on Tp-e interval, Tp-e/QTc, and P-wave dispersion in patients with stable coronary artery disease

INTRODUCTION

Ranolazine is an antianginal drug and also exhibits antiarrhythmic effect by affecting action potential time, refractory period, and repolarization reserve. We evaluated the effect of ranolazine therapy on myocardial repolarization parameters (Tp-e, QT, QTc intervals, Tp-e/QT, and Tp-e/QTc ratios), index of cardiac electrophysiological balance (iCEB) (QT/QRS, QTc/QRS) and P-wave dispersion (PWD) in patients with stable coronary artery disease (CAD).

METHODS

This study included 175 patients, aged between 35 and 90 years who were followed with stable CAD for at least 3 months. Ninety patients had been receiving ranolazine for at least 1 month, and 85 patients had never received ranolazine. All patients' basic demographic data, risk factors, medications, and echocardiographic parameters recorded. Myocardial repolarization parameters, P-wave times, and PWD were analyzed from 12 lead electrodes.

RESULTS

There was no variation between the groups in terms of basic demographic parameters and CAD risk factors. Tp-e interval (87.3 ± 14.4 vs. 90.8 ± 12.4 msn, P < .001), Tp-e/QT (0.22 ± 0.04 vs. 0.23 ± 0.03; P = .03), Tp-e/QTc (0.21 ± 0.04 vs. 0.22 ± 0.04 P = .001), and PWD (39.2 ± 13.7 vs. 43.5 ± 12.9 P = .028) were significantly lower in the ranolazine group. But iCEB was similar in both groups. In multivariate analysis after adjusted confounding factors such as age and BMI, Tp-e/QTc ratio, QTc, Pmax, and PWD were found significantly in ranolazine group again.

CONCLUSION

Tp-e/QTc ratio, QTc, Pmax, and PWD were significantly lower in stable CAD patients under ranolazine therapy. In stable CAD patients, the prognostic significance of ranolazine for arrhythmic events requires further evaluation of these parameters through long-term follow-up and large-scale prospective studies.

Implantable cardioverter defibrillator shocks from ventricular tachyarrhythmias in patients with ischemic heart disease: Preventative measures, shortcomings, cost-effectiveness, and global practice perspectives

Implantable cardioverter defibrillators (ICDs) have proven to be life-saving devices in patients with ischemic cardiomyopathy (ICM) who are prone to develop ventricular tachycardia (VT) and fibrillation (VF). Antiarrhythmic drugs (AADs) are commonly prescribed in many such patients with ICDs to treat and prevent different forms of arrhythmias in clinical practice. When these patients experience recurrent monomorphic VT despite chronic AADs therapy, or when AAD therapy is contraindicated or not tolerated, and VT storm is refractory to AAD therapy, catheter ablation constitute guideline-based class I indication of treatment. However, what should be the most appropriate strategy to prevent first ICD shock or subsequent multiple shocks from VT/VF in patients with ICM who undergo ICD implantation without prior incidence of cardiac arrest, remains debatable. The purpose of this review is to discuss preventative aspects of ICD shocks for VT and the shortcomings of these measures along with the cost-effectiveness and global perspectives based on the current knowledge of the topic.

Arrhythmogenic and antiarrhythmic actions of late sustained sodium current in the adult human heart

Late sodium current (late INa) inhibition has been proposed to suppress the incidence of arrhythmias generated by pathological states or induced by drugs. However, the role of late INa in the human heart is still poorly understood. We therefore investigated the role of this conductance in arrhythmias using adult primary cardiomyocytes and tissues from donor hearts. Potentiation of late INa with ATX-II (anemonia sulcata toxin II) and E-4031 (selective blocker of the hERG channel) slowed the kinetics of action potential repolarization, impaired Ca2+ homeostasis, increased contractility, and increased the manifestation of arrhythmia markers. These effects could be reversed by late INa inhibitors, ranolazine and GS-967. We also report that atrial tissues from donor hearts affected by atrial fibrillation exhibit arrhythmia markers in the absence of drug treatment and inhibition of late INa with GS-967 leads to a significant reduction in arrhythmic behaviour. These findings reveal a critical role for the late INa in cardiac arrhythmias and suggest that inhibition of this conductance could provide an effective therapeutic strategy. Finally, this study highlights the utility of human ex-vivo heart models for advancing cardiac translational sciences.

CaMKII in Regulation of Cell Death During Myocardial Reperfusion Injury

Cardiovascular disease is the leading cause of death worldwide. In spite of the mature managements of myocardial infarction (MI), post-MI reperfusion (I/R) injury results in high morbidity and mortality. Cardiomyocyte Ca²⁺ overload is a major factor of I/R injury, initiating a cascade of events contributing to cardiomyocyte death and myocardial dysfunction. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a critical role in cardiomyocyte death response to I/R injury, whose activation is a key feature of myocardial I/R in causing intracellular mitochondrial swelling, endoplasmic reticulum (ER) Ca²⁺ leakage, abnormal myofilament contraction, and other adverse reactions. CaMKII is a multifunctional serine/threonine protein kinase, and CaMKIIδ, the dominant subtype in heart, has been widely studied in the activation, location, and related pathways of cardiomyocytes death, which has been considered as a potential targets for pharmacological inhibition. In this review, we summarize a brief overview of CaMKII with various posttranslational modifications and its properties in myocardial I/R injury. We focus on the molecular mechanism of CaMKII involved in regulation of cell death induced by myocardial I/R including necroptosis and pyroptosis of cardiomyocyte. Finally, we highlight that targeting CaMKII modifications and cell death involved pathways may provide new insights to understand the conversion of cardiomyocyte fate in the setting of myocardial I/R injury.

Predicted benefit of an implantable cardioverter-defibrillator: the MADIT-ICD benefit score

AIMS

The benefit of prophylactic implantable cardioverter-defibrillator (ICD) is not uniform due to differences in the risk of life-threatening ventricular tachycardia (VT)/ventricular fibrillation (VF) and non-arrhythmic mortality. We aimed to develop an ICD benefit prediction score that integrates the competing risks.

METHODS AND RESULTS

The study population comprised all 4531 patients enrolled in the MADIT trials. Best-subsets Fine and Gray regression analysis was used to develop prognostic models for VT (≥200 b.p.m.)/VF vs. non-arrhythmic mortality (defined as death without prior sustained VT/VF). Eight predictors of VT/VF (male, age < 75 years, prior non-sustained VT, heart rate > 75 b.p.m., systolic blood pressure < 140 mmHg, ejection fraction ≤ 25%, myocardial infarction, and atrialarrhythmia) and 7 predictors of non-arrhythmic mortality (age ≥ 75 years, diabetes mellitus, body mass index < 23 kg/m2, ejection fraction ≤ 25%, New York Heart Association ≥II, ICD vs. cardiac resynchronization therapy with defibrillator, and atrial arrhythmia) were identified. The two scores were combined to create three MADIT-ICD benefit groups. In the highest benefit group, the 3-year predicted risk of VT/VF was three-fold higher than the risk of non-arrhythmic mortality (20% vs. 7%, P < 0.001). In the intermediate benefit group, the difference in the corresponding predicted risks was attenuated (15% vs. 9%, P < 0.01). In the lowest benefit group, the 3-year predicted risk of VT/VF was similar to the risk of non-arrhythmic mortality (11% vs. 12%, P = 0.41). A personalized ICD benefit score was developed based on the distribution of the two competing risks scores in the study population (https://is.gd/madit). Internal and external validation confirmed model stability.

CONCLUSIONS

We propose the novel MADIT-ICD benefit score that predicts the likelihood of prophylactic ICD benefit through personalized assessment of the risk of VT/VF weighed against the risk of non-arrhythmic mortality.

Survival After Implantable Cardioverter-Defibrillator Shocks

BACKGROUND

There are conflicting data on the impact of implantable cardioverter-defibrillator (ICD) shocks on subsequent mortality.

OBJECTIVES

The aim of this study was to determine whether the arrhythmic substrate leading to ICD therapy or the therapy itself increases mortality.

METHODS

The study cohort included 5,516 ICD recipients who were enrolled in 5 landmark ICD trials (MADIT-II, MADIT-RISK, MADIT-CRT, MADIT-RIT, RAID). The authors evaluated the association of device therapy with subsequent mortality in 4 separate time-dependent models: model I, type of ICD therapy; model II, type of arrhythmia for which ICD therapy was delivered; model III, combined assessment of all arrhythmia and therapy types during follow-up; and model IV, incremental risk associated with repeated ICD shocks.

RESULTS

When analyzed by the type of ICD therapy (model I), a first appropriate ICD shock was associated with increased risk of subsequent mortality with or without concomitant occurrence of inappropriate shock during follow-up (hazard ratio [HR]: 2.78 and 2.31; p < 0.001 and p = 0.12), whereas inappropriate shock alone was not associated with mortality risk (HR: 1.23; p = 0.42). Similarly, ICD therapy for ventricular tachycardia (VT) ≥200 beats/min or ventricular fibrillation (VF) (model II) was associated with increased risk of death with or without concomitant therapy for VT <200 beats/min (HRs: 2.25 and 2.62; both p < 0.001), whereas appropriate therapy for VT <200 beats/min or inappropriate therapy (regardless of etiology) did not reach statistical significance (all p > 0.10). Combined assessment of all therapy and arrhythmia types during follow-up (model III) showed that appropriate ICD shocks for VF, shocks for fast VT (≥200 beats/min) without prior antitachycardia pacing (ATP), as well as shocks for fast VT delivered after failed ATP, were associated with the highest risk of subsequent death (HR: all >2.8; p < 0.001). Finally, 2 or more ICD appropriate shocks were not associated with incremental risk to the first appropriate ICD shock (model IV).

CONCLUSION

The combined data from 5 landmark ICD trials suggest that the underlying arrhythmic substrate rather than the ICD therapy is the more important determinant of mortality in ICD recipients.

Hospitalization for Heart Failure and Subsequent Ventricular Tachyarrhythmias in Patients With Left Ventricular Dysfunction

OBJECTIVES

This study aimed to evaluate the risk of sustained life-threatening ventricular tachyarrhythmias (VTAs) after hospitalization for heart failure (HHF).

BACKGROUND

HHF is common among patients with an implantable cardioverter-defibrillator (ICD).

METHODS

We analyzed all 5,511 ICD patients enrolled in the landmark MADIT and RAID trials. Multivariate Cox regression was used to evaluate the association of in-trial HHF occurrence with the risk of subsequent VTA and the composite end point of VTA or cardiac death.

RESULTS

Mean age was 64 ± 11 years, 23% were women, 62% were ischemic, and 40% had cardiac resynchronization therapy with defibrillators. The 3-year cumulative rate of VTA subsequent to HHF was significantly higher than the corresponding rate without HHF (44% vs. 24%, respectively; p < 0.001). After multivariable adjustment, time-dependent HHF was shown to be associated with a 79% increased risk for VTA and a 2.9-fold increased risk for VTA/cardiac death (p < 0.001 for both). In-trial development of atrial tachyarrhythmia (ATA) was also identified as an independent risk factor for the VTA and VTA/cardiac death end points (hazard ratios [HRs]: 1.59 and 1.43, respectively; p ≤ 0.001 for both) but did not affect the association of HHF with VTA. Subgroup analysis demonstrated that the association of HHF with the risk of subsequent VTA was maintained among risk subsets categorized by age, sex, history of ATA, and implantation indication, but was significantly more pronounced among patients with nonischemic versus ischemic cardiomyopathy (HRs: 2.54 and 1.43, respectively; p value for interaction: 0.017).

CONCLUSIONS

HHF is a powerful risk factor for subsequent VTA in patients implanted with an ICD. These data may be used for improved risk stratification in this population.

Mitochondrial Ca2+, redox environment and ROS emission in heart failure: Two sides of the same coin?

Heart failure (HF) is a progressive, debilitating condition characterized, in part, by altered ionic equilibria, increased ROS production and impaired cellular energy metabolism, contributing to variable profiles of systolic and diastolic dysfunction with significant functional limitations and risk of premature death. We summarize current knowledge concerning changes of intracellular Na+ and Ca2+ control mechanisms during the disease progression and their consequences on mitochondrial Ca2+ homeostasis and the shift in redox balance. Absent existing biological data, our computational modeling studies advance a new 'in silico' analysis to reconcile existing opposing views, based on different experimental HF models, regarding variations in mitochondrial Ca2+ concentration that participate in triggering and perpetuating oxidative stress in the failing heart and their impact on cardiac energetics. In agreement with our hypothesis and the literature, model simulations demonstrate the possibility that the heart's redox status together with cytoplasmic Na+ concentrations act as regulators of mitochondrial Ca2+ levels in HF and of the bioenergetics response that will ultimately drive ATP supply and oxidative stress. The resulting model predictions propose future directions to study the evolution of HF as well as other types of heart disease, and to develop novel testable mechanistic hypotheses that may lead to improved therapeutics.

Late Sodium Current Inhibitors as Potential Antiarrhythmic Agents

Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials.

Challenges and Opportunities for Therapeutic Targeting of Calmodulin Kinase II in Heart

Heart failure remains a major health burden around the world. Despite great progress in delineation of molecular mechanisms underlying development of disease, standard therapy has not advanced at the same pace. The multifunctional signaling molecule Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has received considerable attention over recent years for its central role in maladaptive remodeling and arrhythmias in the setting of chronic disease. However, these basic science discoveries have yet to translate into new therapies for human patients. This review addresses both the promise and barriers to developing translational therapies that target CaMKII signaling to abrogate pathologic remodeling in the setting of chronic disease. Efforts in small molecule design are discussed, as well as alternative targeting approaches that exploit novel avenues for compound delivery and/or genetic approaches to affect cardiac CaMKII signaling. These alternative strategies provide hope for overcoming some of the challenges that have limited the development of new therapies.

Handling of Ventricular Fibrillation in the Emergency Setting

Ventricular fibrillation (VF) and sudden cardiac death (SCD) are predominantly caused by channelopathies and cardiomyopathies in youngsters and coronary heart disease in the elderly. Temporary factors, e.g., electrolyte imbalance, drug interactions, and substance abuses may play an additive role in arrhythmogenesis. Ectopic automaticity, triggered activity, and reentry mechanisms are known as important electrophysiological substrates for VF determining the antiarrhythmic therapies at the same time. Emergency need for electrical cardioversion is supported by the fact that every minute without defibrillation decreases survival rates by approximately 7%–10%. Thus, early defibrillation is an essential part of antiarrhythmic emergency management. Drug therapy has its relevance rather in the prevention of sudden cardiac death, where early recognition and treatment of the underlying disease has significant importance. Cardioprotective and antiarrhythmic effects of beta blockers in patients predisposed to sudden cardiac death were highlighted in numerous studies, hence nowadays these drugs are considered to be the cornerstones of the prevention and treatment of life-threatening ventricular arrhythmias. Nevertheless, other medical therapies have not been proven to be useful in the prevention of VF. Although amiodarone has shown positive results occasionally, this was not demonstrated to be consistent. Furthermore, the potential proarrhythmic effects of drugs may also limit their applicability. Based on these unfavorable observations we highlight the importance of arrhythmia prevention, where echocardiography, electrocardiography and laboratory testing play a significant role even in the emergency setting. In the following we provide a summary on the latest developments on cardiopulmonary resuscitation, and the evaluation and preventive treatment possibilities of patients with increased susceptibility to VF and SCD.

Ventricular Arrhythmias

Ventricular tachycardia is commonly seen in medical practice. It may be completely benign or portend high risk for sudden cardiac death. Therefore, it is important that clinicians be familiar with and able to promptly recognize and manage ventricular tachycardia when confronted with it clinically. In many cases, curative therapy for a given ventricular arrhythmia may be provided after a thorough understanding of the underlying substrate and mechanism. In this article, the authors broadly review the current classification of the different ventricular arrhythmias encountered in medical practice, provide brief background regarding the different mechanisms, and discuss practical diagnosis and management scenarios.

Dose-Dependent Effects of Ranolazine on Reentrant Ventricular Arrhythmias Induced After Subacute Myocardial Infarction in Rabbits

Ranolazine has been found to prevent ventricular arrhythmias (VAs) during acute myocardial infarction (AMI). This study aimed to investigate its efficacy on VAs induced several days post-MI. For this purpose, 13 anesthetized rabbits underwent coronary artery ligation. Ten of these animals that survived AMI were reanesthetized 3 to 7 days later for electrophysiologic testing. An endocardial monophasic action potential combination catheter was placed in the right ventricle for simultaneous pacing and recording. Monophasic action potential duration, ventricular effective refractory period (VERP), and VAs induced by programmed stimulation were assessed. Measurements were performed during control pacing, and following an intravenous infusion of either a low-dose ranolazine (2.4 mg/kg, R1) or a higher dose ranolazine (4.8 mg/kg cumulative dose, R2). During control stimulation, 2 animals developed primary ventricular fibrillation (VF), 6 sustained ventricular tachycardia (sVT), and 2 nonsustained VT (nsVT). R1 did not prevent the appearance of VAs in any of the experiments; in contrast, it aggravated nsVT into sVT and complicated sVT termination in 2 of 6 animals. Sustained ventricular tachycardia cycle length and VERP were only slightly decreased after R1 (112 ± 5 vs 110 ± 6 ms and 101 ± 11 vs 98 ± 10 ms, respectively). R2 suppressed inducibility of control nsVT, VF, and sVT in 2 animals. In 4 animals with still inducible sVT, R2 significantly prolonged VT cycle length by 150 ± 23 ms (P < .01), and VERP by 120 ± 7 ms (P < .001) versus control. In conclusion, R2 exerted antiarrhythmic efficacy against subacute-MI VAs, whereas R1 rather aggravated than prevented these arrhythmias. Ventricular effective refractory period prolongation could partially explain the antiarrhythmic action of R2 in this rabbit model.

Strategies to Reduce Recurrent Shocks Due to Ventricular Arrhythmias in Patients with an Implanted Cardioverter-Defibrillator

Ventricular arrhythmias are a therapeutic challenge, owing to their relatively unpredictable and deadly nature. Many patients are treated with an implantable cardioverter-defibrillator for either primary or secondary prevention of ventricular arrhythmias, meaning those who are at high risk of versus those who have experienced ventricular arrhythmias or sudden cardiac arrest, respectively. Despite the life-saving benefit, ICD comes with the risk of recurrent shocks for both appropriate and inappropriate rhythms. Patients with recurrent shocks have a poor quality of life and increased mortality rates. In this article, we review data for optimal device settings, medical management and radiofrequency ablation strategies to minimise the frequency of ICD shock, with a focus on treatment of ventricular arrhythmias, to reduce patient morbidity and mortality, and to maximise wellbeing and quality of life.

Prevention of Recurrent Ventricular Tachycardia in Patients With Implantable Cardioverter Defibrillators-A Network Meta-analysis

BACKGROUND

The optimal management for the prevention of recurrent ventricular tachycardia in patients with implantable cardioverter-defibrillators (ICDs) offers a challenge with no set guidelines regarding which therapy offers a best safety and efficacy profile.

STUDY QUESTION

Which therapeutic strategy, among antiarrhythmic drugs and catheter ablation (CA), offers the most effective and safe approach in patients with ICDs?

DATA SOURCES

Randomized controlled trials (RCTs) comparing the efficacy and safety of antiarrhythmic drugs or CA against a placebo group. RCTs were identified from a comprehensive search in PubMed, Embase, and Cochrane library.

STUDY DESIGN

Our outcomes of interest were reductions in appropriate ICD shocks, inappropriate ICD shocks, and overall mortality. We used the event rates in both groups, and then using a frequentist approach employing a graph theory methodology, we constructed a network meta-analysis model.

RESULTS

Fourteen RCTs with 3815 participants and 6 different interventions treatments were included in our network meta-analysis. The most effective treatment for the prevention of recurrent ventricular tachycardia after ICD is amiodarone followed by CA. Amiodarone is most effective in the reduction of appropriate and inappropriate ICD shocks with an odds ratio (OR) of 0.29 [95% confidence interval (CI), 0.11-0.74] and 0.15 (95% CI, 0.04-0.60), respectively. CA was effective in the reduction of appropriate ICD shocks (OR, 0.41; 95% CI, 0.20-0.87), whereas sotalol was effective in the reduction of inappropriate ICD shocks (OR, 0.46; 95% CI, 0.22-0.95). There was no significant reduction in the overall mortality from any therapy. There was a trend of increased mortality associated with amiodarone therapy (OR, 2.40; 95% CI, 0.92-6.26).

CONCLUSIONS

Amiodarone remains the most efficacious therapy for the reduction of appropriate and inappropriate shocks in patients with ICD. No therapy resulted in mortality reduction, but amiodarone showed a trend toward increased mortality.

Anti-arrhythmic drug therapy in implantable cardioverter-defibrillator recipients

Implantable cardioverter-defibrillators (ICDs) have revolutionized the primary and secondary prevention of patients with ventricular arrhythmias. However, the adverse effects of appropriate or inappropriate shocks may require the adjunctive use of anti-arrhythmic drugs (AADs). Beta blockers are the cornerstone of pharmacological primary and secondary prevention of ventricular arrhythmias. In addition to their established efficacy at reducing the incidence of ventricular arrhythmias, beta-blockers are safe with few side effects. Amiodarone is superior to beta blockers and sotalol for the prevention of ventricular arrhythmia recurrence. However, long-term amiodarone use is associated with significant side effects that limit its utility. Sotalol and mexiletine are the main alternatives to amiodarone with a better side effect profile though they are less efficacious at preventing ventricular arrhythmia recurrence. Dofetilide, azimilide and ranolazine are emerging as therapeutic options for secondary prevention; more studies are needed to assess efficacy and safety in comparison to currently used agents. Beta blockers and amiodarone are the mainstay of therapy in patients experiencing electrical storm; their use reduces the frequency of ventricular arrhythmias and ICD intervention as well as affording time until catheter ablation can be considered.