Should everyone with an ejection fraction less than or equal to 30% receive an implantable cardioverter-defibrillator? Not everyone with an ejection fraction < or = 30% should receive an implantable cardioverter-defibrillator

Echocardiographic Longitudinal Strain Analysis in Heart Failure: Real Usefulness for Clinical Management Beyond Diagnostic Value and Prognostic Correlations? A Comprehensive Review

Heart failure (HF) is a highly prevalent clinical syndrome characterized by considerable phenotypic heterogeneity. The traditional classification based on left ventricular ejection fraction (LVEF) is widely accepted by the guidelines and represents the grounds for patient enrollment in clinical trials, even though it shows several limitations. Ejection fraction (EF) is affected by preload, afterload, and contractility, it being problematic to express LV function in several conditions, such as HF with preserved EF (HFpEF), valvular heart disease, and subclinical HF, and in athletes. Over the last two decades, developments in diagnostic techniques have provided useful tools to overcome EF limitations. Strain imaging analysis (particularly global longitudinal strain (GLS)) has emerged as a useful echocardiographic technique in patients with HF, as it is able to simultaneously supply information on both systolic and diastolic functions, depending on cardiac anatomy and physiology/pathophysiology. The use of GLS has proved helpful in terms of diagnostic performance and prognostic value in several HF studies. Universally accepted cutoff values and variability across vendors remain an area to be fully explored, hence limiting routine application of this technique in clinical practice. In the present review, the current role of GLS in the diagnosis and management of patients with HF will be discussed. We describe, by critical analysis of the pros and cons, various clinical settings in HF, and how the appropriate use and interpretation of GLS can provide important clues.

Implantable Cardioverter-Defibrillators in Trials of Drug Therapy for Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND Medical therapy for heart failure with reduced ejection fraction evolved since trials validated the use of implantable cardioverter-defibrillators (ICDs). We sought to evaluate the performance of ICDs in reducing mortality in the era of modern medical therapy by means of a systematic review and meta-analysis of contemporary randomized clinical trials of drug therapy for heart failure with reduced ejection fraction. METHODS AND RESULTS We systematically identified randomized clinical trials that evaluated drug therapy in patients with heart failure with reduced ejection fraction that reported mortality. Studies that enrolled <1000 patients, patients with left ventricular ejection fraction >40%, or patients in the acute phase of heart failure and study treatment with devices were excluded. We identified 8 randomized clinical trials, including 31 701 patients of whom 3631 (11.5%) had an ICD. ICDs were associated with a lower risk of all-cause mortality (relative risk [RR], 0.85; 95% CI, 0.78-0.94) and sudden cardiac death (RR, 0.49; 95% CI, 0.40-0.61). Results were consistent among studies published before and after 2010. In meta-regression analysis, the proportion of nonischemic etiology did not affect the associated benefit of ICD. CONCLUSIONS In our meta-analysis of contemporary randomized trials of drug therapy for heart failure with reduced ejection fraction, the rate of ICD use was low and associated with a decreased risk in both all-cause mortality and sudden cardiac death. This benefit was still present in trials with new medical therapy.

Impact of Left Ventricular Ejection Fraction on Recurrent Ventricular Tachyarrhythmias in Recipients of Implantable Cardioverter Defibrillators

OBJECTIVE

This study evaluates the impact of left ventricular ejection fraction (LVEF) on recurrences of ventricular tachyarrhythmias in recipients of implantable cardioverter defibrillator (ICD).

BACKGROUND

Data regarding recurrences of ventricular tachyarrhythmias in ICD recipients according to LVEF is limited.

METHODS

A large retrospective registry was used, including all consecutive ICD recipients with episodes of ventricular tachycardia (VT) or fibrillation (VF) from 2002 to 2016. Patients with LVEF <35% were compared to patients with LVEF ≥35%. The primary end point was first recurrences of ventricular tachyarrhythmias at 5 years. Secondary end points were ICD-related therapies, rehospitalization, and all-cause mortality at 5 years. Cox regression, Kaplan Meier, and propensity score matching analyses were applied.

RESULTS

A total of 528 consecutive ICD recipients were included (51% with LVEF ≥35% and 49% with LVEF <35%). LVEF <35% was associated with reduced freedom from recurrent ventricular tachyarrhythmias (40 vs. 49%, log rank p = 0.014; hazard ratio [HR] = 1.381; 95% confidence interval [CI] 1.066-1.788; p = 0.034), mainly attributed to recurrent sustained VT in primary preventive ICD recipients. Accordingly, LVEF <35% was associated with reduced freedom from first appropriate ICD therapies (28 vs. 41%, log rank p = 0.001; HR = 1.810; 95% CI 1.185-2.766; p = 0.001). Finally, LVEF <35% was associated with a higher rate of rehospitalization (23 vs. 34%; p = 0.005) and all-cause mortality at 5 years (13 vs. 29%; p = 0.001).

CONCLUSION

LVEF <35% was associated with reduced freedom from recurrent ventricular tachyarrhythmias, appropriate device therapies, rehospitalization and all-cause mortality secondary to index ventricular tachyarrhythmias.

Risk stratification for cardiac mortality using electrocardiographic markers based on 24-hour Holter recordings: the JANIES-SHD study

BACKGROUND

Recent guidelines have stated that left ventricular ejection fraction (LVEF) is the gold standard marker for identifying patients at risk for cardiac mortality. However, little information is present regarding electrocardiographic (ECG) markers. This study aimed to assess ECG markers for predicting mortality or serious arrhythmia in patients with structural heart disease (SHD).

METHODS

In total, 1829 patients were enrolled into the Japanese Multicenter Observational Prospective Study (JANIES study). In this study, we analyzed data of 719 patients (569 men, age 64 ± 13 years) with SHD including mainly ischemic heart disease (65.8%). As ECG markers based on 24-hour Holter recordings, nonsustained ventricular tachycardia (NSVT), ventricular late potentials, and heart rate turbulence (HRT) were assessed. The primary endpoint was all-cause mortality, and the secondary endpoint was fatal arrhythmic events.

RESULTS

During a mean follow-up of 21 ± 11 months, all-cause mortality was eventually observed in 39 patients (5.4%). Among those patients, 32 patients (82%) suffered from cardiac causes such as heart failure and arrhythmia. Multivariate Cox regression analysis showed that after adjustment for age and LVEF, documented NSVT [hazard ratio = 2.46, 95% confidence interval (CI): 1.16-5.18, p = 0.02] and abnormal HRT (hazard ratio = 2.40, 95% CI: 1.16-4.93, p = 0.02) were significantly associated with the primary endpoint. These two ECG markers also had significant predictive values with the secondary endpoint. The combined assessment of two ECG markers improved predictive accuracy.

CONCLUSION

This study demonstrated that combined assessment of documented NSVT and abnormal HRT based on 24-hour Holter ECG recordings are recommended for predicting future serious events in this population.

Systematic Review for the 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

BACKGROUND

Although large randomized clinical trials have found that primary prevention use of an implantable cardioverter-defibrillator (ICD) improves survival in patients with cardiomyopathy and heart failure symptoms, patients who receive ICDs in practice are often older and have more comorbidities than patients who were enrolled in the clinical trials. In addition, there is a debate among clinicians on the usefulness of electrophysiological study for risk stratification of asymptomatic patients with Brugada syndrome.

AIM

Our analysis has 2 objectives. First, to evaluate whether ventricular arrhythmias (VAs) induced with programmed electrostimulation in asymptomatic patients with Brugada syndrome identify a higher risk group that may require additional testing or therapies. Second, to evaluate whether implantation of an ICD is associated with a clinical benefit in older patients and patients with comorbidities who would otherwise benefit on the basis of left ventricular ejection fraction and heart failure symptoms.

METHODS

Traditional statistical approaches were used to address 1) whether programmed ventricular stimulation identifies a higher-risk group in asymptomatic patients with Brugada syndrome and 2) whether ICD implantation for primary prevention is associated with improved outcomes in older patients (>75 years of age) and patients with significant comorbidities who would otherwise meet criteria for ICD implantation on the basis of symptoms or left ventricular function.

RESULTS

Evidence from 6 studies of 1138 asymptomatic patients were identified. Brugada syndrome with inducible VA on electrophysiological study was identified in 390 (34.3%) patients. To minimize patient overlap, the primary analysis used 5 of the 6 studies and found an odds ratio of 2.3 (95% CI: 0.63-8.66; P=0.2) for major arrhythmic events (sustained VAs, sudden cardiac death, or appropriate ICD therapy) in asymptomatic patients with Brugada syndrome and inducible VA on electrophysiological study versus those without inducible VA. Ten studies were reviewed that evaluated ICD use in older patients and 4 studies that evaluated unique patient populations were identified. In our analysis, ICD implantation was associated with improved survival (overall hazard ratio: 0.75; 95% confidence interval: 0.67-0.83; P<0.001). Ten studies were identified that evaluated ICD use in patients with various comorbidities including renal disease, chronic obstructive pulmonary disease, atrial fibrillation, heart disease, and others. A random effects model demonstrated that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.72; 95% confidence interval: 0.65-0.79; P<0.0001), and a second "minimal overlap" analysis also found that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.61-0.82; P<0.0001). In 5 studies that included data on renal dysfunction, ICD implantation was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.60-0.85; P<0.001).

Systematic review for the 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

BACKGROUND

Although large randomized clinical trials have found that primary prevention use of an implantable cardioverter-defibrillator (ICD) improves survival in patients with cardiomyopathy and heart failure symptoms, patients who receive ICDs in practice are often older and have more comorbidities than patients who were enrolled in the clinical trials. In addition, there is a debate among clinicians on the usefulness of electrophysiological study for risk stratification of asymptomatic patients with Brugada syndrome.

AIM

Our analysis has 2 objectives. First, to evaluate whether ventricular arrhythmias (VAs) induced with programmed electrostimulation in asymptomatic patients with Brugada syndrome identify a higher risk group that may require additional testing or therapies. Second, to evaluate whether implantation of an ICD is associated with a clinical benefit in older patients and patients with comorbidities who would otherwise benefit on the basis of left ventricular ejection fraction and heart failure symptoms.

METHODS

Traditional statistical approaches were used to address 1) whether programmed ventricular stimulation identifies a higher-risk group in asymptomatic patients with Brugada syndrome and 2) whether ICD implantation for primary prevention is associated with improved outcomes in older patients (>75 years of age) and patients with significant comorbidities who would otherwise meet criteria for ICD implantation on the basis of symptoms or left ventricular function.

RESULTS

Evidence from 6 studies of 1138 asymptomatic patients were identified. Brugada syndrome with inducible VA on electrophysiological study was identified in 390 (34.3%) patients. To minimize patient overlap, the primary analysis used 5 of the 6 studies and found an odds ratio of 2.3 (95% CI: 0.63-8.66; p=0.2) for major arrhythmic events (sustained VAs, sudden cardiac death, or appropriate ICD therapy) in asymptomatic patients with Brugada syndrome and inducible VA on electrophysiological study versus those without inducible VA. Ten studies were reviewed that evaluated ICD use in older patients and 4 studies that evaluated unique patient populations were identified. In our analysis, ICD implantation was associated with improved survival (overall hazard ratio: 0.75; 95% confidence interval: 0.67-0.83; p<0.001). Ten studies were identified that evaluated ICD use in patients with various comorbidities including renal disease, chronic obstructive pulmonary disease, atrial fibrillation, heart disease, and others. A random effects model demonstrated that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.72; 95% confidence interval: 0.65-0.79; p<0.0001), and a second "minimal overlap" analysis also found that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.61-0.82; p<0.0001). In 5 studies that included data on renal dysfunction, ICD implantation was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.60-0.85; p<0.001).

Sudden cardiac death and pump failure death prediction in chronic heart failure by combining ECG and clinical markers in an integrated risk model

Background

Sudden cardiac death (SCD) and pump failure death (PFD) are common endpoints in chronic heart failure (CHF) patients, but prevention strategies are different. Currently used tools to specifically predict these endpoints are limited. We developed risk models to specifically assess SCD and PFD risk in CHF by combining ECG markers and clinical variables.

Methods

The relation of clinical and ECG markers with SCD and PFD risk was assessed in 597 patients enrolled in the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study. ECG indices included: turbulence slope (TS), reflecting autonomic dysfunction; T-wave alternans (TWA), reflecting ventricular repolarization instability; and T-peak-to-end restitution (Δα^Tpe) and T-wave morphology restitution (TMR), both reflecting changes in dispersion of repolarization due to heart rate changes. Standard clinical indices were also included.

Results

The indices with the greatest SCD prognostic impact were gender, New York Heart Association (NYHA) class, left ventricular ejection fraction, TWA, Δα^Tpe and TMR. For PFD, the indices were diabetes, NYHA class, Δα^Tpe and TS. Using a model with only clinical variables, the hazard ratios (HRs) for SCD and PFD for patients in the high-risk group (fifth quintile of risk score) with respect to patients in the low-risk group (first and second quintiles of risk score) were both greater than 4. HRs for SCD and PFD increased to 9 and 11 when using a model including only ECG markers, and to 14 and 13, when combining clinical and ECG markers.

Conclusion

The inclusion of ECG markers capturing complementary pro-arrhythmic and pump failure mechanisms into risk models based only on standard clinical variables substantially improves prediction of SCD and PFD in CHF patients.

Arrhythmia risk stratification of patients after myocardial infarction using personalized heart models

Sudden cardiac death (SCD) from arrhythmias is a leading cause of mortality. For patients at high SCD risk, prophylactic insertion of implantable cardioverter defibrillators (ICDs) reduces mortality. Current approaches to identify patients at risk for arrhythmia are, however, of low sensitivity and specificity, which results in a low rate of appropriate ICD therapy. Here, we develop a personalized approach to assess SCD risk in post-infarction patients based on cardiac imaging and computational modelling. We construct personalized three-dimensional computer models of post-infarction hearts from patients' clinical magnetic resonance imaging data and assess the propensity of each model to develop arrhythmia. In a proof-of-concept retrospective study, the virtual heart test significantly outperformed several existing clinical metrics in predicting future arrhythmic events. The robust and non-invasive personalized virtual heart risk assessment may have the potential to prevent SCD and avoid unnecessary ICD implantations.

Device therapy for acute systolic heart failure and atrial fibrillation

Patients with newly diagnosed cardiomyopathy require careful assessment of cause and initiation of treatment before the decision is made to implant an internal cardiac defibrillator. In patients with medicine-refractory atrial fibrillation and cardiomyopathy, atrioventricular node ablation and implantation of a biventricular pacemaker is the therapy of choice when tachycardia-induced cardiomyopathy is suspected and curative therapy is not possible.

The spectrum of epidemiology underlying sudden cardiac death

Sudden cardiac death (SCD) from cardiac arrest is a major international public health problem accounting for an estimated 15%-20% of all deaths. Although resuscitation rates are generally improving throughout the world, the majority of individuals who experience a sudden cardiac arrest will not survive. SCD most often develops in older adults with acquired structural heart disease, but it also rarely occurs in the young, where it is more commonly because of inherited disorders. Coronary heart disease is known to be the most common pathology underlying SCD, followed by cardiomyopathies, inherited arrhythmia syndromes, and valvular heart disease. During the past 3 decades, declines in SCD rates have not been as steep as for other causes of coronary heart disease deaths, and there is a growing fraction of SCDs not due to coronary heart disease and ventricular arrhythmias, particularly among certain subsets of the population. The growing heterogeneity of the pathologies and mechanisms underlying SCD present major challenges for SCD prevention, which are magnified further by a frequent lack of recognition of the underlying cardiac condition before death. Multifaceted preventative approaches, which address risk factors in seemingly low-risk and known high-risk populations, will be required to decrease the burden of SCD. In this Compendium, we review the wide-ranging spectrum of epidemiology underlying SCD within both the general population and in high-risk subsets with established cardiac disease placing an emphasis on recent global trends, remaining uncertainties, and potential targeted preventive strategies.

Clinical management and prevention of sudden cardiac death

Despite the revolutionary advancements in the past 3 decades in the treatment of ventricular tachyarrhythmias with device-based therapy, sudden cardiac death (SCD) remains an enormous public health burden. Survivors of SCD are generally at high risk for recurrent events. The clinical management of such patients requires a multidisciplinary approach from postresuscitative care to a thorough cardiovascular investigation in an attempt to identify the underlying substrate, with potential to eliminate or modify the triggers through catheter ablation and ultimately an implantable cardioverter-defibrillator (ICD) for prompt treatment of recurrences in those at risk. Early recognition of low left ventricular ejection fraction as a strong predictor of death and association of ventricular arrhythmias with sudden death led to significant investigation with antiarrhythmic drugs. The lack of efficacy and the proarrhythmic effects of drugs catalyzed the development and investigation of the ICD through several major clinical trials that proved the efficacy of ICD as a bedrock tool to detect and promptly treat life-threatening arrhythmias. The ICD therapy is routinely used for primary prevention of SCD in patients with cardiomyopathy and high risk inherited arrhythmic conditions and secondary prevention in survivors of sudden cardiac arrest. This compendium will review the clinical management of those surviving SCD and discuss landmark studies of antiarrhythmic drugs, ICD, and cardiac resynchronization therapy in the primary and secondary prevention of SCD.

Right ventricular dysfunction predisposes to inducible ventricular tachycardia at electrophysiology studies in patients with acute ST-segment-elevation myocardial infarction and reduced left ventricular ejection fraction

BACKGROUND

Inducible ventricular tachycardia (VT) is a strong predictor of spontaneous ventricular tachyarrhythmia following ST-segment-elevation myocardial infarction. Reduced left ventricular ejection fraction (EF) predisposes patients to inducible VT after ST-segment-elevation myocardial infarction. However, the role of right ventricular (RV) dysfunction in predisposing to inducible VT has not been described previously.

METHODS AND RESULTS

Consecutive patients with ST-segment-elevation myocardial infarction treated with primary percutaneous coronary intervention underwent predischarge radionuclide gated heart pool scan to assess ventricular EF. The study cohort included patients with reduced left ventricular EF (left ventricular EF ≤40%) who underwent electrophysiology study (n=220) in an attempt to induce VT. We defined RV dysfunction as RVEF ≤35%. The end point was sustained monomorphic VT (cycle length ≥200 ms). This was considered a positive study. No inducible arrhythmia, ventricular fibrillation, or flutter (cycle length <200 ms) was considered a negative study. Infarct region, infarct-related artery, male sex, and RVEF ≤35% were univariable predictors of positive test. After multivariable analysis, RVEF ≤35% had the strongest association as an independent predictor of inducible VT at electrophysiology study (P<0.001; odds ratio, 5.8; 95% confidence interval, 3.005-11.262).

CONCLUSIONS

RV dysfunction (RVEF ≤35%) predisposed to inducible VT at electrophysiology study in patients with impaired left ventricular EF (≤40%) after acute ST-segment-elevation myocardial infarction treated with primary percutaneous coronary intervention.

The utility of ADMIRE-HF risk score in predicting serious arrhythmic events in heart failure patients: incremental prognostic benefit of cardiac 123I-mIBG scintigraphy

BACKGROUND

A minority of heart failure (HF) patients who undergo implantable cardioverter defibrillator (ICD) implantation for primary prevention of sudden cardiac death (SCD) receive device therapy. Whether the addition of mIBG scintigraphy to conventional markers of arrhythmic risk can provide incremental risk stratification in HF patients has not been investigated.

METHODS

We identified 778 patients from the ADMIRE-HF study with LVEF < 35% and class II or III HF symptoms who did not have an ICD at the time of enrollment. Patients were followed up prospectively (median 5 17 months) for occurrence of arrhythmic events (ArE). Heart-to-mediastinum ratio (HMR) was determined as a measure of relative myocardial sympathetic nerve activity at baseline using 123I-mIBG. The primary endpoint was the first occurrence of ArE: a composite of SCD, appropriate ICD therapy, resuscitated cardiac arrest or sustained ventricular tachycardia. Multivariate regression was used to determine independent predictors of ArE and to derive a risk score for ArE prediction. The score was used to group patients according to their risk for ArE. Integrated discrimination improvement (IDI) was used to quantify improvement in risk assessment with addition of HMR.

RESULTS

ArE occurred in 54 patients (6.9%). ArE predictors were:HMR < 1.6 (HR 3.5, 95%CI [1.52-8], P 5 .02), LVEF < 25% (HR 2.0, 95% CI [1.28-3.05], P 5 .04) and SBP < 120 (HR 1.2,95%CI [1.03-1.39], P 5 .02). Event rates in the low-, intermediate-, and high risk groups were 2, 10 and 16%, respectively (P 5 .001). The score significantly improved risk prediction(IDI 5 45%, P 0.03).

CONCLUSION

123I-mIBG significantly provides incremental risk stratification for ArE in HF patients.

Risk stratification for sudden cardiac death: current approaches and predictive value

Sudden cardiac death (SCD) is a serious public health problem; the annual incidence of out-of-hospital cardiac arrest in North America is approximately 166,200. Identifying patients at risk is a difficult proposition. At the present time, left ventricular ejection fraction (LVEF) remains the single most important marker for risk stratification. According to current guidelines, most patients with LVEF <35% could benefit from prophylactic ICD implantation, particularly in the setting of symptomatic heart failure. Current risk stratification strategies fail to identify patients at risk of SCD in larger population groups encompassing a greater number of potential SCD victims. However, the best approach to identifying patients and the value of various risk stratification tools is not entirely clear. The goal of this review is to discuss the problem of SCD and the value of the different risk stratification markers and their potential clinical use either alone or in combination with other risk stratification markers.

Implantable cardioverter defibrillator therapy: a single center experience in saudi arabia

INTRODUCTION

Internal Cardioverter Defibrillators (ICD) has been shown to decrease mortality in patients such as those with structural heart disease or at high risk of sudden cardiac death. To date there is no data regarding the clinical features, and outcomes of ICD patients in Saudi Arabia. Accordingly, we explored the clinical features and outcomes of ICD therapy among Saudis.

METHODS

Patients who had ICD implantation in King Khalid University Hospital from November 2007 until January 2010 were enrolled.

RESULTS

One hundred and eight ICD were implanted between November 2007 and February 2010. The mean age was 58.6±13.2 years. The majority were male 94 (87%), the rate of Diabetes Mellitus (DM) was 58.3%, Hypertension (HTN) was 61.1%, and 63% were smokers. The mean ejection fraction (EF) was 24.5%. Of the 108 patient 90(83.3%) had ICD insertion for primary prevention and 18(16.7%) for secondary prevention. Of the 90 patients who ICD for primary prevention 62 (57.4%) had ischemic cardiomyopathy, 39(36.1%) had dilated cardiomyopathy and 7 (6.5%) had channelopathy. Over a mean follow-up of 18 months 4 (3.7%) died.

CONCLUSIONS

Our study describes for the first time patients characteristic and outcomes for ICD therapy in Saudi Arabia. Our patients are younger and have higher prevalence of risk factors that those in Western countries.

Right ventricular stimulation threshold at ICD implant predicts device therapy in primary prevention patients with ischaemic heart disease

AIMS

Myocardial excitability is known (amongst other reasons) to be related to the degree of ischaemia, contractile dysfunction and heart failure. It was hypothesized that the right ventricular (RV) stimulation threshold has prognostic value with respect to the occurrence of ventricular arrhythmias (VAs) and patient survival in recipients of an implantable cardioverter defibrillator (ICD).

METHODS AND RESULTS

Ischaemic heart disease patients receiving an ICD at Leiden University Medical Center as primary prevention for sudden cardiac death were included in this study. Right ventricular thresholds were determined at ICD implant. Data were collected on VAs triggering ICD therapy and on all-cause mortality. A total of 689 consecutive patients were included (87% male, age 63 ± 11 years, left ventricular ejection fraction (LVEF) 29 ± 11%) and followed for a median of 28 months. Post-implant RV-threshold was 0.7 ± 0.5 volt (V) at 0.5 ms pulse duration. Best dichotomous separation was reached at a cut-off of 1 V. During follow-up, 167 (24%) patients received appropriate ICD therapy, 88 (13%) had appropriate shocks and 134 (19%) died. Cumulative appropriate shock incidence for patients with RV threshold ≥ 1 V (n = 166) was 16% at 1 year, 24% at 3 years and 34% at 5 years compared with 4, 11 and 17% for patients with an RV-threshold < 1 V (n = 523). Adjusted hazard ratio of RV threshold ≥ 1 V was 2.0 (95% CI: 1.4-2.9) for appropriate therapy, 3.3 (95% CI: 2.0-5.4) for appropriate shocks and 1.6 (95% CI: 1.1-2.5) for mortality.

CONCLUSION

The RV stimulation threshold at ICD implant has a strong independent prognostic value for the occurrence of VAs triggering appropriate ICD therapy, appropriate shocks and mortality.

Update on primary prevention implantable cardioverter-defibrillator therapy

Although the death rate from cardiovascular disease has decreased, nearly 2400 Americans die from cardiovascular disease each day (an average of one person every 37 seconds). Sudden cardiac death (SCD) affects individuals in the prime of their lives, with resuscitation rates successful in only a minority of patients, in part due to absent defibrillation by lay responders. After the publication of positive trials, the Centers for Medicare & Medicaid Services approved the implantable cardioverter-defibrillator (ICD) for the primary prevention of SCD. More recently, ICD therapy also has been shown to be effective for the primary prevention of SCD in patients with systolic heart failure, sometimes with the addition of cardiac resynchronization therapy. This article reviews the current status of primary prevention ICD therapy.

[How to evaluate sudden cardiac death risk after myocardial infarction?]

Sudden cardiac death is the mode of death of more than half of coronary heart disease patients. Preventing sudden cardiac death involves prevention of ventricular arrhythmias occurrence as well as the treatment by an implantable cardioverter defibrillator. The evaluation of sudden cardiac death risk should consider the underlying cardiopathy, the associated coronary risk factors and all pharmacological treatment efficient to reduce ventricular remodeling and myocardial ischemia. Only significant low ejection fraction and positive ventricular testing in some cases are now considered are now considered by the current French recommendations for cardioverter defibrillator implantation in primary prevention. However, other noninvasive markers such as heart rate variability and T wave alternans are of interest in sudden cardiac death risk stratification after myocardial infarction.

Left ventricular ejection fraction as criterion for implantation of an implantable cardioverter-defibrillator in heart failure patients undergoing surgical left ventricular reconstruction

BACKGROUND

Besides implantation of an implantable cardioverter-defibrillator (ICD), a proportion of patients with left ventricular (LV) dysfunction due to ischemic cardiomyopathy are potential candidates for surgical LV reconstruction (Dor procedure), which changes LV ejection fraction (LVEF) considerably. In these patients, LVEF as selection criterium for ICD implantation may be difficult. This study aimed to determine the value of LVEF as criterium for ICD implantation in heart failure patients undergoing surgical LV reconstruction.

METHODS

Consecutive patients with end-stage heart failure who underwent ICD implantation and LV reconstruction were evaluated. During admission, two-dimensional (2D) echocardiography (LV volumes and LVEF) was performed before surgery and was repeated at 3 months after surgery. Over a median follow-up of 18 months, the incidence of ICD therapy was evaluated.

RESULTS

The study population consisted of 37 patients (59 +/- 11 years). At baseline, mean LVEF was 23 +/- 5%. Mean left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV) were 175 +/- 73 mL and 225 +/- 88 mL, respectively. At 3-month follow-up, mean LVEF was 41 +/- 9% (P < 0.0001 vs. baseline), and mean LVESV and LVEDV were 108 +/- 65 mL and 176 +/- 73 mL, respectively (P < 0.0001 vs. baseline). During 18-month follow-up, 12 (32%) patients had ventricular arrhythmias, resulting in appropriate ICD therapy. No significant relations existed between baseline LVEF (P = 0.77), LVEF at 3-month follow-up (P = 0.34), change in LVEF from baseline to 3-month follow-up (P = 0.28), and the occurrence of ICD therapy during 18-month follow-up.

CONCLUSION

LVEF before and after surgical LV reconstruction is of limited use as criterium for ICD implantation in patients with end-stage heart failure.

Risk stratification for sudden cardiac death: is there a clinical role for T wave alternans?

The proportion of cardiovascular deaths attributable to sudden cardiac death (SCD) is on the rise. Herein lies the rationale for developing risk stratification strategies to predict who will benefit from prophylactic implantable cardioverter-defibrillator (ICD) implantation. Current guidelines recommend prophylactic ICD therapy in patients with reduced left ventricular ejection fraction (LVEF). However, there are clear limitations in using LVEF alone to decide who should receive an ICD. There is mounting evidence that microvolt-level T-wave alternans (TWA) is an important marker of arrhythmic risk. TWA is appealing because it noninvasively probes the underlying electrophysiological substrate and has been linked to cellular mechanisms for arrhythmias. This review considers the clinical role of TWA for risk stratification of SCD.

Sudden cardiac arrest in patients with severe nonischemic heart failure: risk stratification with the heart failure survival score

The authors wanted to investigate whether the heart failure survival score (HFSS) is useful for sudden cardiac arrest (SCA) risk stratification and whether there is a difference with regard to congestive heart failure (CHF) etiology. Data of 712 severe CHF patients (New York Heart Association III/IV 58%/42%, mean age 62+/-8 years, mean left ventricular ejection fraction 26%+/-11%) during the period from 1993-2003 were analyzed. The HFSS was calculated using the Aaronson formula. SCA-free survival was calculated using Kaplan-Meier analysis according to the etiology of CHF: coronary artery disease (CAD) (n=317) vs no CAD (n=395). In regard to SCA risk, the authors found no significant overall difference between patients with or without CAD. Non-CAD HFSS high-risk patients had a significantly higher risk for SCA than all the other groups ( P<.001). The HFSS is useful for the detection of a subgroup of non-CAD severe CHF patients at very high risk for SCA.

Cost of preimplantation cardiac imaging in patients referred for a primary-prevention implantable cardioverter-defibrillator

Recent guidelines have focused on ejection fraction cut-off values to determine eligibility for primary-prevention implantable cardioverter-defibrillators (ICDs). Clinical trials that led to the guidelines used varying techniques for ejection fraction assessment, including echocardiography and multigated acquisition (MUGA) scan. A prospective cohort study to determine the economic attractiveness of repeated echocardiography and MUGA scanning during the evaluation process of patients referred for consideration of a primary-prevention ICD was undertaken. From January 2005 to December 2006, data were collected for patients aged >18 years with ejection fraction <30% referred for a primary-prevention ICD based on referral assessment of heart function in any form. Costs based on the 2006 Ontario Health Insurance Plan fee schedule were determined for clinical assessment, echocardiography, MUGA scanning, and ICD implantation in patients who remained eligible based on MUGA ejection fraction. The 100 patients (age 61.1 +/- 10.2 years; 78 men) assessed for primary-prevention ICD implantation had an ejection fraction of 28.9 +/- 12.3% using MUGA scan. Thirty-one of 100 patients (31%) had an ejection fraction >30% and were no longer eligible for an ICD. Although imaging increased preimplantation cost from dollars 130 to dollars 536 per patient, averted inappropriate ICDs decreased the overall per-patient cost from dollars 20,914 to dollars 14,877. Despite an additional testing cost of dollars 40,599, the overall cost savings was dollars 603,722 in the 100 patients, with a cost savings of dollars 6,037 per patient. In conclusion, verification of ejection fraction identified a significant proportion of patients who were not eligible for an ICD.

Non-sustained ventricular tachycardia as a predictor of sudden cardiac death in patients with left ventricular dysfunction: a meta-analysis

BACKGROUND

Identifying patients at risk of sudden cardiac death (SCD) remains a challenge.

AIM

To evaluate the performance of non-sustained ventricular tachycardia (NSVT) from 24 hour ambulatory electrocardiography as a predictor of SCD in patients with heart failure or non-ischaemic dilated cardiomyopathy with left ventricular systolic dysfunction (LVSD).

METHODS AND RESULTS

Study search and selection were performed by independent reviewers using a validated strategy. Eleven prognostic studies with >100 patients with good quality data and multivariate analysis of predictors of SCD were included. Publication bias was evaluated by funnel plot with Kendall's tau b test. A summary ROC (sROC) curve was built to evaluate predictive performance of NSVT. There was threshold effect (Spearman's correlation between sensitivity and specificity=-0.818, p<0.01) which indicates that combining sensitivity and specificity was not appropriate. The area of 0.68+/-0.02 under the sROC curve indicates a statistically significant contribution of NSVT in the prediction of SCD. The true negative rate varied from 89 to 97%. Multivariate analysis and meta-regression suggested that the contribution of NSVT to risk stratification is independent of ejection fraction.

CONCLUSIONS

Absence of NSVT indicated a low probability of SCD in patients with LVSD. A risk score including NSVT should be evaluated in prospective studies.

Baroreflex sensitivity: measurement and clinical implications

Alterations of the baroreceptor-heart rate reflex (baroreflex sensitivity, BRS) contribute to the reciprocal reduction of parasympathetic activity and increase of sympathetic activity that accompany the development and progression of cardiovascular diseases. Therefore, the measurement of the baroreflex is a source of valuable information in the clinical management of cardiac disease patients, particularly in risk stratification. This article briefly recalls the pathophysiological background of baroreflex control, and reviews the most relevant methods that have been developed so far for the measurement of BRS. They include three "classic" methods: (i) the use of vasoactive drugs, particularly the alpha-adrenoreceptor agonist phenylephrine, (ii) the Valsalva maneuver, which produces a natural challenge for the baroreceptors by voluntarily increasing intrathoracic and abdominal pressure through straining, and (iii) the neck chamber technique, which allows a selective activation/deactivation of carotid baroreceptors by application of a negative/positive pressure to the neck region. Two more recent methods based on the analysis of spontaneous oscillations of systolic arterial pressure and RR interval are also reviewed: (i) the sequence method, which analyzes the relationship between increasing/decreasing ramps of blood pressure and related increasing/decreasing changes in RR interval through linear regression, and (ii) spectral methods, which assess the relationship (in terms of gain) between specific oscillatory components of the two signals. The limitations of the coherence criterion for the computation of spectral BRS are discussed, and recent proposals for overcoming them are presented. Most relevant clinical applications of BRS measurement are finally reviewed with particular reference to patients with myocardial infarction and heart failure.

Sudden cardiac death: influence of diabetes

This article reviews current thinking on the problem of sudden cardiac death (SCD) within community settings, highlighting progress in understanding risks and mechanisms. Information available on the influence of diabetes as a risk factor for SCD and the question of whether this disease enhances susceptibility to ventricular arrhythmias is summarized as are central strategies in risk stratification and mortality prevention.

Implantable device therapy

Sudden cardiac death (SCD) accounts for two-thirds of fatal events related to heart disease. Coronary heart disease and non-ischemic cardiomyopathy are the most common causes of SCD. Data from major randomized trials have consistently shown that therapy with an implantable cardioverter defibrillator (ICD) results in a significant and meaningful effect on survival through a reduction in the risk of SCD in these population. These data have resulted in a marked increase in the application of implantable device therapy in the past 2 decades from secondary prevention with an implantable cardioverter/defibrillator (ICD) in survivors of a cardiac arrest to primary prevention of SCD in asymptomatic patients with ischemic and non-ischemic left ventricular dysfunction, and prevention of symptomatic heart failure progression and death with cardiac resynchronization therapy (CRT), and devices that combine CRT and ICD therapies (CRT-D). However, there are still areas of uncertainty regarding device therapy that include inconsistent benefit in risk-subgroups of patients with low ejection fraction; increased risk of heart failure after life-prolonging ICD therapy, and a considerable rate of device malfunction despite increasing sophistication. In the present review we focus on current data regarding the clinical indications as well as the safety and efficacy of implantable device therapy, including ICD, CRT, and CRT-D.

Prognostic value of T-wave alternans in patients with heart failure due to nonischemic cardiomyopathy: results of the ALPHA Study

OBJECTIVES

The aim of this study was to assess the prognostic value of T-wave alternans (TWA) in New York Heart Association (NYHA) functional class II/III patients with nonischemic cardiomyopathy and left ventricular ejection fraction (LVEF) < or =40%.

BACKGROUND

There is a strong need to identify reliable risk stratifiers among heart failure candidates for implantable cardioverter-defibrillator (ICD) prophylaxis. T-wave alternans may identify low-risk subjects among post-myocardial infarction patients with depressed LVEF, but its predictive role in nonischemic cardiomyopathy is unclear.

METHODS

Four hundred forty-six patients were enrolled and followed up for 18 to 24 months. The primary end point was the combination of cardiac death + life-threatening arrhythmias; secondary end points were total mortality and the combination of arrhythmic death + life-threatening arrhythmias.

RESULTS

Patients with abnormal TWA (65%) compared with normal TWA (35%) tests were older (60 +/- 13 years vs. 57 +/- 12 years), were more frequently in NYHA functional class III (22% vs. 19%), and had a modestly lower LVEF (29 +/- 7% vs. 31 +/- 7%). Primary end point rates in patients with abnormal and normal TWA tests were 6.5% (95% confidence interval [CI] 4.5% to 9.4%) and 1.6% (95% CI 0.6% to 4.4%), respectively. Unadjusted and adjusted hazard ratios were 4.0 (95% CI 1.4% to 11.4%; p = 0.002) and 3.2 (95% CI 1.1% to 9.2%; p = 0.013), respectively. Hazard ratios for total mortality and for arrhythmic death + life-threatening arrhythmias were 4.6 (p = 0.002) and 5.5 (p = 0.004), respectively; 18-month negative predictive values for the 3 end points ranged between 97.3% and 98.6%.

CONCLUSIONS

Among NYHA functional class II/III nonischemic cardiomyopathy patients, an abnormal TWA test is associated with a 4-fold higher risk of cardiac death and life-threatening arrhythmias. Patients with normal TWA tests have a very good prognosis and are likely to benefit little from ICD therapy.

End-of-life Decisions in ICD Patients with Malignant Tumors

BACKGROUND

The results of multiple implantable cardioverter-defibrillator (ICD) studies have demonstrated a survival benefit in specific high-risk populations, leading to the expansion of ICD implantation rates worldwide. Because the ICD reduces the incidence of sudden cardiac death, patients with these devices more often die of non-arrhythmic causes. For those with a malignancy, little is known about their preferences for disabling ICD therapy.

METHODS

The objective of the present study was to evaluate whether patients with an ICD and a malignant tumor desire deactivation of their ICD in order to have a death without ICD interventions, which are life-prolonging, bothersome, and prevent a peaceful death. All deceased patients having had an ICD implanted at our institution were retrospectively analyzed with respect to whether the option of disabling ICD therapy had been discussed and whether the ICD had been deactivated.

RESULTS

Two hundred and seventy-two patients received an ICD at our institution between January 1, 1994, and January 31, 2007. Thirty-six of the patients have died, and of these eight had a malignant tumor. In six of these eight patients (75%) the option of disabling their ICD therapy was discussed extensively; none wished to abandon the possibility of terminating a malignant arrhythmia by the ICD.

CONCLUSIONS

With the use of ICDs, patients with heart failure are more frequently protected from arrhythmic death, and consequently treating physicians are increasingly confronted with ICD patients presenting with a malignant tumor or other noncardiac terminal disease. In these situations, dialogue between the treating physician and the patient about the possibility of withdrawing ICD therapy is important to terminal care. The physician must be aware that the patient's attitude may contrast with his/her own, and that the patient may be resolute in maintaining ICD protection from arrhythmic death.

Sudden death prophylaxis in heart failure

Sudden cardiac death (SCD) is the leading cause of mortality in heart failure (HF). Today the implantable cardioverter-defibrillator (ICD) has become a commonplace therapy around the world for patients with both ischemic and non-ischemic cardiomyopathy and an ejection fraction (EF) < or = 35%. However, EF alone does not discriminate between the modes of death from HF (sudden arrhythmic death vs. non-sudden death). Other risk statifiers, such as electrophysiologic study and microvolt T-wave alternans testing, should therefore be used in the appropriate settings to minimize the number of unnecessary device implants. In addition, left ventricular mechanical dyssynchrony has now become recognized as an additional major marker of cardiac mortality. Its assessment should entail echocardiography rather than measurement of the QRS duration. This will allow us to better integrate the ability of cardiac resynchronization therapy (CRT) in enhancing cardiac function with the ability of an ICD in preventing SCD. This review aims to: 1) give a synthesis of the published evidence regarding the value of implantable ICDs and CRT in the primary prophylaxis of SCD in HF; 2) discuss controversial clinical issues in this area; and 3) recommend practical device-based management strategies.