Primary prevention of sudden cardiac death in heart failure: will the solution be shocking?

Molecular and Functional Remodeling of Superior and Inferior SAN in a Rat Model of HCM

BACKGROUND

Recently, our laboratory presented functional and molecular evidence for the presence of 2 competing sinoatrial node (SAN) pacemakers in healthy human and rat hearts. Anatomically localized near the superior vena cava and inferior vena cava, the superior and inferior SANs (sSAN and iSAN, respectively) preferentially control fast and slow normal heart rates. However, only 1 dominant pacemaker, primarily the sSAN, was functional in the failing rat heart with hypertrophic cardiomyopathy.

OBJECTIVES

This study aimed to determine the transcriptional basis of functional silencing of 1 of 2 dominant pacemakers in failing rat hearts.

METHODS

Ascending aortic constriction was performed on 1-week-old male Sprague-Dawley rat pups to induce left ventricular hypertrophy and heart failure. The dominant pacemaker was anatomically mapped in adult (10-12 weeks old) healthy and failing rat hearts using optical mapping in isolated right atrial tissue preparations. RNA sequencing was used to identify regional sSAN/iSAN gene expression differences between healthy and failing rat hearts.

RESULTS

In all failing rat hearts optically mapped in this study (n = 4), only the sSAN pacemaker was functional, while the iSAN was silent. Compared to healthy rat hearts, a total of 3,640 genes were downregulated, and 4,518 genes were upregulated in failing rat hearts. The functional quiescence of the iSAN in these failing rat hearts may be explained by their downregulation of sodium, potassium, and calcium ion channels as well as their downregulation of specific structural genes, including ankyrin, titin, and myosin heavy chain. Moreover, the iSAN showed predominant downregulation of several key transcription factors such as Tbx5, Tbx3, Shox2, and Smad9.

CONCLUSIONS

Pressure-overload-induced heart failure resulted in significant downregulation of critical transcription factors, ion channels, and structural transcripts of the iSAN, which could explain the functional silencing of the iSAN in failing rat hearts.

Multimodality Imaging of Sudden Cardiac Death and Acute Complications in Acute Coronary Syndrome

Sudden cardiac death (SCD) is a potentially fatal event usually caused by a cardiac arrhythmia, which is often the result of coronary artery disease (CAD). Up to 80% of patients suffering from SCD have concomitant CAD. Arrhythmic complications may occur in patients with acute coronary syndrome (ACS) before admission, during revascularization procedures, and in hospital intensive care monitoring. In addition, about 20% of patients who survive cardiac arrest develop a transmural myocardial infarction (MI). Prevention of ACS can be evaluated in selected patients using cardiac computed tomography angiography (CCTA), while diagnosis can be depicted using electrocardiography (ECG), and complications can be evaluated with cardiac magnetic resonance (CMR) and echocardiography. CCTA can evaluate plaque, burden of disease, stenosis, and adverse plaque characteristics, in patients with chest pain. ECG and echocardiography are the first-line tests for ACS and are affordable and useful for diagnosis. CMR can evaluate function and the presence of complications after ACS, such as development of ventricular thrombus and presence of myocardial tissue characterization abnormalities that can be the substrate of ventricular arrhythmias.

Heart failure in mice induces a dysfunction of the sinus node associated with reduced CaMKII signaling

Dysfunction of the sinoatrial node (SAN), the natural heart pacemaker, is common in heart failure (HF) patients. SAN spontaneous activity relies on various ion currents in the plasma membrane (voltage clock), but intracellular Ca2+ ([Ca2+]i) release via ryanodine receptor 2 (RYR2; Ca2+ clock) plays an important synergetic role. Whereas remodeling of voltage-clock components has been revealed in HF, less is known about possible alterations to the Ca2+ clock. Here, we analyzed [Ca2+]i handling in SAN from a mouse HF model after transverse aortic constriction (TAC) and compared it with sham-operated animals. ECG data from awake animals showed slower heart rate in HF mice upon autonomic nervous system blockade, indicating intrinsic sinus node dysfunction. Confocal microscopy analyses of SAN cells within whole tissue showed slower and less frequent [Ca2+]i transients in HF. This correlated with fewer and smaller spontaneous Ca2+ sparks in HF SAN cells, which associated with lower RYR2 protein expression level and reduced phosphorylation at the CaMKII site. Moreover, PLB phosphorylation at the CaMKII site was also decreased in HF, which could lead to reduced sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) function and lower sarcoplasmic reticulum Ca2+ content, further depressing the Ca2+ clock. The inhibition of CaMKII with KN93 slowed [Ca2+]i transient rate in both groups, but this effect was smaller in HF SAN, consistent with less CaMKII activation. In conclusion, our data uncover that the mechanism of intrinsic pacemaker dysfunction in HF involves reduced CaMKII activation.

Role of Implantable Cardioverter Defibrillator in Heart Failure With Contemporary Medical Therapy

Implantable cardioverter defibrillator therapy is indicated in a subset of patients with heart failure with reduced ejection as primary prevention for sudden cardiac death. The advent of novel medical therapies including mineralocorticoid receptor antagonists, angiotensin receptor blocker/neprilysin inhibitors, and sodium-glucose transporter 2 inhibitor in the past 2 decades has revolutionized heart failure with reduced ejection management. Current guideline-directed medical therapy has reduced all-cause mortality and sudden cardiac death and confers a considerable improvement in left ventricular ejection fraction over a short period of time. However, there is limited evidence at present to suggest whether implantable cardioverter defibrillator therapy continues to have the same benefit in sudden cardiac death prevention at current left ventricular ejection fraction cutoff indications for patients on contemporary guideline-directed medical therapy for heart failure with reduced ejection. In this review, the authors propose in lieu of current evidence that it is reasonable to reevaluate indications for implantable cardioverter defibrillator therapy in patients on contemporary guideline-directed medical therapy for heart failure with reduced ejection.

RyR2 and Calcium Release in Heart Failure

Heart Failure (HF) is defined as the inability of the heart to efficiently pump out enough blood to maintain the body's needs, first at exercise and then also at rest. Alterations in Ca2+ handling contributes to the diminished contraction and relaxation of the failing heart. While most Ca2+ handling protein expression and/or function has been shown to be altered in many models of experimental HF, in this review, we focus in the sarcoplasmic reticulum (SR) Ca2+ release channel, the type 2 ryanodine receptor (RyR2). Various modifications of this channel inducing alterations in its function have been reported. The first was the fact that RyR2 is less responsive to activation by Ca2+ entry through the L-Type calcium channel, which is the functional result of an ultrastructural remodeling of the ventricular cardiomyocyte, with fewer and disorganized transverse (T) tubules. HF is associated with an elevated sympathetic tone and in an oxidant environment. In this line, enhanced RyR2 phosphorylation and oxidation have been shown in human and experimental HF. After several controversies, it is now generally accepted that phosphorylation of RyR2 at the Calmodulin Kinase II site (S2814) is involved in both the depressed contractile function and the enhanced arrhythmic susceptibility of the failing heart. Diminished expression of the FK506 binding protein, FKBP12.6, may also contribute. While these alterations have been mostly studied in the left ventricle of HF with reduced ejection fraction, recent studies are looking at HF with preserved ejection fraction. Moreover, alterations in the RyR2 in HF may also contribute to supraventricular defects associated with HF such as sinus node dysfunction and atrial fibrillation.

Altered microRNA and mRNA profiles during heart failure in the human sinoatrial node

Heart failure (HF) is frequently accompanied with the sinoatrial node (SAN) dysfunction, which causes tachy-brady arrhythmias and increased mortality. MicroRNA (miR) alterations are associated with HF progression. However, the transcriptome of HF human SAN, and its role in HF-associated remodeling of ion channels, transporters, and receptors responsible for SAN automaticity and conduction impairments is unknown. We conducted comprehensive high-throughput transcriptomic analysis of pure human SAN primary pacemaker tissue and neighboring right atrial tissue from human transplanted HF hearts (n = 10) and non-failing (nHF) donor hearts (n = 9), using next-generation sequencing. Overall, 47 miRs and 832 mRNAs related to multiple signaling pathways, including cardiac diseases, tachy-brady arrhythmias and fibrosis, were significantly altered in HF SAN. Of the altered miRs, 27 are predicted to regulate mRNAs of major ion channels and neurotransmitter receptors which are involved in SAN automaticity (e.g. HCN1, HCN4, SLC8A1) and intranodal conduction (e.g. SCN5A, SCN8A) or both (e.g. KCNJ3, KCNJ5). Luciferase reporter assays were used to validate interactions of miRs with predicted mRNA targets. In conclusion, our study provides a profile of altered miRs in HF human SAN, and a novel transcriptome blueprint to identify molecular targets for SAN dysfunction and arrhythmia treatments in HF.

The in- and out-of-hospital management of HF patients: results from a nationwide Belgian survey

BACKGROUND

We conducted a nationwide survey to describe the in-and out-of-hospital flow (diagnosis, treatment and follow-up) of patients with heart failure with reduced ejection fraction (HFrEF).

METHOD

A survey was developed with five dedicated HF cardiologists. The data are all self-reported by cardiologists.

RESULTS

The response rate was 84%. Presence of a dedicated HF cardiologist or HF nurse was indicated by 49% and 46% of the hospitals respectively. Devices (p < .05), angiotensin receptor neprilysin inhibitors, and rehabilitation are considered more standard of care therapy by dedicated compared to non-dedicated HF cardiologists. Most cardiologists indicated that target dosages of HF drugs can be reached in 25‒75% of patients. Achieving >75% of the target dose seems easier for angiotensin converting enzyme inhibitor/angiotensin receptor blockers (ACEI/ARB) (22%) and mineralocorticoid receptor antagonists (25%), compared to β-blockers (10%) and angiotensin receptor neprilysin inhibitors (7%). 62%, 49% and 4% of the cardiologists indicated to use subtypes of angiotensin converting enzyme inhibitors, angiotensin receptor blockers and β-blockers respectively not validated in the HF population. In the acute setting, dedicated HF cardiologists (23%) are less influenced by blood parameters for decongestion compared to non-dedicated HF cardiologists (39%). They tend to change patients more to guideline-recommended drugs (60% vs 47%). Six minutes walk test and ergospirometry are significantly more used by dedicated compared to non-dedicated HF cardiologists for HF drug change (17% and 29% vs 2% and 4%).

CONCLUSION

This survey showed that a minority of hospitals have HF care. Those that do, report a higher implementation of guideline-recommended diagnosis, treatment and follow-up of HF patients. Competent authorities could use this survey as a tool to improve HF care.

Prognostic value of prealbumin, N-terminal pro-B-type natriuretic peptide, heart type fatty acid binding protein, and cardiac troponin I in elderly patients for heart failure and poor outcomes

Objectives

This study aimed to investigate the prognostic value of serum prealbumin, N-terminal pro-B-type natriuretic peptide (NT-proBNP), heart type fatty acid binding protein (hFABP), and cardiac troponin I (cTnI) for heart failure and cardiac death in elderly patients.

Methods

We studied 426 consecutive patients with New York Heart Association classes I to IV who were recruited between February 2014 and 2018. Cardiac mortality was the primary end point. Receiver operator characteristic curves were created to analyze predictive values.

Results

When prealbumin, NT-proBNP, hFABP, and cTnI were combined, the areas under the receiver operator characteristic curve reached 0.930 and 0.903 for heart failure and cardiac death, respectively. Prealbumin, NT-proBNP, hFABP, and cTnI levels changed differently during therapy in patients in different prognosis groups. These parameters improved in patients who did not develop major adverse cardiovascular events (MACEs), but were unchanged or deteriorated in patients with MACEs. Multivariate Cox regression analysis showed that these parameters were significant independent risk factors for MACEs and cardiac death.

Conclusions

Our study shows that serum prealbumin, NT-proBNP, hFABP, and cTnI levels are significant prognostic factors for elderly patients with poor cardiac function. These parameters are more accurate for prognosis when used together.

Clinical and Hospital Factors Affecting Treatment with Primary Prevention Implantable Cardioverter-Defibrillators in Ischemic Cardiomyopathy Patients

PURPOSE

Implantable cardioverter defibrillators (ICD) are the standard of care for primary prevention (PP) in patients with ischemic cardiomyopathy (ICM). However, PP ICD implantation is underused in Asian countries. This study investigated ICD implantation rates and factors associated with appropriate PP ICD implants for ICM.

MATERIALS AND METHODS

In this prospective multicenter observational registry (ADVANCE-ICM registry), ICM patients who were eligible for PP ICD were screened and enrolled. Factors associated with appropriate ICD implantation, including hospital and clinical factors, were investigated.

RESULTS

Of the 1453 ICM patients eligible for PP ICD [1111 male; median age, 71.0 (61.0-78.0) years], only 76 (5.2%) patients underwent ICD implantation. Among hospital factors, a non-monetary incentive for referral (72.4% vs. 52.9%, p=0.001) and total hospital system score (6.0 vs. 5.0, p=0.013) were higher in the ICD than in the no-ICD group. In multivariate analysis, total hospital system score [odds ratio (OR), 1.28; 95% confidence interval (CI), 1.10-1.50] was an independent factor for predicting ICD implantation, along with clinical factors, including high New York Heart Association class (≥III: OR, 7.29; 95% CI, 2.97-17.87) and younger age (<70 years: OR, 2.14; 95% CI, 1.30-3.53).

CONCLUSION

PP ICD implantation for ICM patients is underused in Korea. Hospital factors were important for improving PP ICD implantation rate, suggesting that new screening and referral systems for ICM patients would improve the PP ICD implantation rate (Clinical trial registration No. NCT03590925).

Galactin-3 and soluble ST2 as complementary tools to cardiac MRI for sudden cardiac death risk stratification in heart failure: A review

Heart failure (HF) is recognized as one of the leading causes of morbidity and mortality worldwide. Every year about 500,000 new cases of HF are diagnosed in the United States. The predominant etiology of death in HF patients include sudden cardiac death (SCD) and pump failure. Prediction of mode of death may help in devising management decisions. In patients with HF, the presence of myocardial fibrosis has been a known risk factor for SCD and thus it could be used as a criterion in risk stratification for SCD. However, the underlying pathophysiology of SCD is uncertain and controversial, which makes it necessary to develop newer tools to enhance SCD risk stratification. The newer tools should be innovative enough either to complement or to replace the currently available tools. In this scoping review, we highlighted the utilization of novel biomarkers galectin-3 (gal-3) and soluble ST2 (sST2) and discussed that how they might complement currently available tools such as, cardiac MRI (CMR) for SCD risk stratification in HF patients.

The rationale for repurposing funny current inhibition for management of ventricular arrhythmia

Management of ventricular arrhythmia in structural heart disease is complicated by the toxicity of the limited antiarrhythmic options available. In others, proarrhythmia and deleterious hemodynamic and noncardiac effects prevent practical use. This necessitates new thinking in therapeutic agents for ventricular arrhythmia in structural heart disease. Ivabradine, a funny current (I_f) inhibitor, has proven safety in heart failure, angina, and inappropriate sinus tachycardia. Although it is commonly known that funny channels are primarily expressed in the sinoatrial node, atrioventricular node, and conducting system of the ventricle, ivabradine is known to exert effects on metabolism, ion homeostasis, and membrane electrophysiology of remodeled ventricular myocardium. This review considers novel concepts and evidence from clinical and experimental studies regarding this paradigm, with a potential role of ivabradine in ventricular arrhythmia.

Gut microbiota, endotoxemia, inflammation, and oxidative stress in patients with heart failure, left ventricular assist device, and transplant

BACKGROUND

Gut microbial imbalance may contribute to endotoxemia, inflammation, and oxidative stress in heart failure (HF). Changes occurring in the intestinal microbiota and inflammatory/oxidative milieu during HF progression and following left ventricular assist device (LVAD) or heart transplantation (HT) are unknown. We aimed to investigate variation in gut microbiota and circulating biomarkers of endotoxemia, inflammation, and oxidative stress in patients with HF (New York Heart Association, Class I-IV), LVAD, and HT.

METHODS

We enrolled 452 patients. Biomarkers of endotoxemia (lipopolysaccharide and soluble [sCD14]), inflammation (C-reactive protein, interleukin-6, tumor necrosis factor-α, and endothelin-1 adiponectin), and oxidative stress (isoprostane) were measured in 644 blood samples. A total of 304 stool samples were analyzed using 16S rRNA sequencing.

RESULTS

Gut microbial community measures of alpha diversity were progressively lower across worsening HF class and were similarly reduced in patients with LVAD and HT (p < 0.05). Inflammation and oxidative stress were elevated in patients with Class IV HF vs all other groups (all p < 0.05). Lipopolysaccharide was elevated in patients with Class IV HF (vs Class I-III) as well as in patients with LVAD and HT (p < 0.05). sCD14 was elevated in patients with Class IV HF and LVAD (vs Class I-III, p < 0.05) but not in patients with HT.

CONCLUSIONS

Reduced gut microbial diversity and increased endotoxemia, inflammation, and oxidative stress are present in patients with Class IV HF. Inflammation and oxidative stress are lower among patients with LVAD and HT relative to patients with Class IV HF, whereas reduced gut diversity and endotoxemia persist in LVAD and HT.

Innate immune response in the pathogenesis of heart failure in survivors of myocardial infarction

Among the different cardiovascular disease complications, atherosclerosis-induced myocardial infarction (MI) is the major contributor of heart failure (HF) and loss of life. This review presents short- and long-term features of post-MI in human hearts and animal models. It is known that the heart does not regenerate, and thus loss of cardiac cells after an MI event is permanent. In survivors of a heart attack, multiple neurohumoral adjustments as well as simultaneous remodeling in both infarcted and noninfarcted regions of the heart help sustain pump function post-MI. In the early phase, migration of inflammatory cells to the infarcted area helps repair and remove the cell debris, while apoptosis results in the elimination of damaged cardiomyocytes, and there is an increase in the antioxidant response to protect the survived myocardium against oxidative stress (OS) injury. However, in the late phase, it appears that there is a relative increase in OS and activation of the innate inflammatory response in cardiomyocytes without any obvious inflammatory cells. In this late stage in survivors of MI, a progressive slow activation of these processes leads to apoptosis, fibrosis, cardiac dysfunction, and HF. Thus, this second phase of an increase in OS, innate inflammatory response, and apoptosis results in wall thinning, dilatation, and consequently HF. It is important to note that this inflammatory response appears to be innate to cardiomyocytes. Blunting of this innate immune cardiomyocyte response may offer new hope for the management of HF.

Risk Stratification of Sudden Cardiac Death in Patients with Heart Failure: An update

Heart failure (HF) is a complex clinical syndrome in which structural/functional myocardial abnormalities result in symptoms and signs of hypoperfusion and/or pulmonary or systemic congestion at rest or during exercise. More than 80% of deaths in patients with HF recognize a cardiovascular cause, with most being either sudden cardiac death (SCD) or death caused by progressive pump failure. Risk stratification of SCD in patients with HF and preserved (HFpEF) or reduced ejection fraction (HFrEF) represents a clinical challenge. This review will give an update of current strategies for SCD risk stratification in both HFrEF and HFpEF.

Cardiac Fibrosis and Arrhythmogenesis

Myocardial injury, mechanical stress, neurohormonal activation, inflammation, and/or aging all lead to cardiac remodeling, which is responsible for cardiac dysfunction and arrhythmogenesis. Of the key histological components of cardiac remodeling, fibrosis either in the form of interstitial, patchy, or dense scars, constitutes a key histological substrate of arrhythmias. Here we discuss current research findings focusing on the role of fibrosis, in arrhythmogenesis. Numerous studies have convincingly shown that patchy or interstitial fibrosis interferes with myocardial electrophysiology by slowing down action potential propagation, initiating reentry, promoting after-depolarizations, and increasing ectopic automaticity. Meanwhile, there has been increasing appreciation of direct involvement of myofibroblasts, the activated form of fibroblasts, in arrhythmogenesis. Myofibroblasts undergo phenotypic changes with expression of gap-junctions and ion channels thereby forming direct electrical coupling with cardiomyocytes, which potentially results in profound disturbances of electrophysiology. There is strong evidence that systemic and regional inflammatory processes contribute to fibrogenesis (i.e., structural remodeling) and dysfunction of ion channels and Ca2+ homeostasis (i.e., electrical remodeling). Recognizing the pivotal role of fibrosis in the arrhythmogenesis has promoted clinical research on characterizing fibrosis by means of cardiac imaging or fibrosis biomarkers for clinical stratification of patients at higher risk of lethal arrhythmia, as well as preclinical research on the development of antifibrotic therapies. At the end of this review, we discuss remaining key questions in this area and propose new research approaches. © 2017 American Physiological Society. Compr Physiol 7:1009-1049, 2017.

Implantable cardioverter/defibrillators for primary prevention in dilated cardiomyopathy post-DANISH: an updated meta-analysis and systematic review of randomized controlled trials

BACKGROUND

Sudden cardiac death (SCD) is frequent in patients with heart failure due to dilated cardiomyopathy (DCM). Implantable cardioverter/defibrillator (ICD) device therapy is currently used for primary prevention. However, publication of the DANISH trial has recently given reason for doubt, showing no significant improvement in all-cause mortality in comparison to contemporary medical therapy.

METHODS

We performed a meta-analysis of all randomized controlled trials comparing ICD therapy to medical therapy (MT) for primary prevention in DCM. The primary outcome was all-cause mortality; secondary analyses were performed on sudden cardiac death, cardiovascular death and non-cardiac death.

RESULTS

Five trials including a total of 2992 patients were included in the pooled analysis. Compared to contemporary medical treatment there was a significant mortality reduction with ICD device therapy [odds ratio (OR) 0.77, 95% confidence interval (CI) 0.64-0.93; p = 0.006]. SCD was decreased significantly (OR 0.43, CI 0.27-0.69; p = 0.0004), while cardiovascular death and non-cardiac death showed no differences. Sensitivity analyses showed no influence of amiodarone therapy on overall results. Analysis of MT details revealed the DANISH population to adhere the most to current guideline recommendations. In addition, it was the only study including a substantial amount of CRT devices (58%).

CONCLUSIONS

Our meta-analysis of all available randomized evidence shows a survival benefit of ICD therapy for primary prevention in DCM. DANISH results suggest an attenuation of this ICD advantage when compared to contemporary medical and cardiac resynchronization therapy. Until larger trials have confirmed this finding, ICD therapy should remain the recommendation for primary prevention of SCD in DCM.

Ventricular Arrhythmia after Acute Myocardial Infarction: 'The Perfect Storm'

Ventricular tachyarrhythmias (VAs) commonly occur early in ischaemia, and remain a common cause of sudden death in acute MI. The thrombolysis and primary percutaneous coronary intervention era has resulted in the modification of the natural history of an infarct and subsequent VA. Presence of VA could independently influence mortality in patients recovering from MI. Appropriate risk assessment and subsequent treatment is warranted in these patients. The prevention and treatment of haemodynamically significant VA in the post-infarct period and of sudden cardiac death remote from the event remain areas of ongoing study.

Timing and Location of Medical Emergency Team Activation Is Associated with Seriousness of Outcome: An Observational Study in a Tertiary Care Hospital

Purpose

The medical emergency team (MET) can be activated anytime and anywhere in a hospital. We hypothesized the timing and location of MET activation are associated with seriousness of outcome.

Materials and Methods

We tested for an association of clinical outcomes with timing and location using a university hospital cohort in Japan (n = 328). The primary outcome was short-term serious outcome (unplanned ICU admission after MET activation or death at scene).

Results

Patients for whom the MET was activated in the evening or night-time had significantly higher rates of short-term serious outcome than those for whom it was activated during the daytime (vs. evening: adjusted OR = 2. 53, 95% CI = 1.24–5.13, P = 0.010; night-time: adjusted OR = 2.45, 95% CI = 1.09–5.50, P = 0.030). Patients for whom the MET was activated in public space had decreased short-term serious outcome compared to medical spaces (public space: adjusted OR = 0.19, 95% CI = 0.07–0.54, P = 0.0017). Night-time (vs. daytime) and medical space (vs. public space) were significantly associated with higher risks of unexpected cardiac arrest and 28-day mortality.

Conclusions

Patients for whom the MET was activated in the evening/night-time, or in medical space, had a higher rate of short-term serious outcomes. Taking measures against these risk factors may improve MET performance.

Radionuclide Imaging Applications in Cardiomyopathies and Heart Failure

Multiple epidemiological factors including population aging and improved survival after acute coronary syndromes have contributed to a heart failure (HF) prevalence in the USA in epidemic proportions. In the absence of transplantation, HF remains a progressive disease with poor prognosis. The structural and functional abnormalities of the myocardium in HF can be assessed by various radionuclide imaging techniques. Radionuclide imaging may be uniquely suited to address several important clinical questions in HF such as identifying etiology and guiding the selection of patients for coronary revascularization. Newer approaches such as autonomic innervation imaging, phase analysis for synchrony assessment, and other molecular imaging techniques continue to expand the applications of radionuclide imaging in HF. In this manuscript, we review established and evolving applications of radionuclide imaging for the diagnosis, risk stratification, and management of HF.

The impacts of age and frailty on heart rate and sinoatrial node function

KEY POINTS

Sinoatrial node (SAN) function declines with age; however, not all individuals age at the same rate and health status can vary from fit to frail. Frailty was quantified in young and aged mice using a non-invasive frailty index so that the impacts of age and frailty on heart rate and SAN function could be assessed. SAN function was impaired in aged mice due to alterations in electrical conduction, changes in SAN action potential morphology and fibrosis in the SAN. Changes in SAN function, electrical conduction, action potential morphology and fibrosis were correlated with, and graded by, frailty. This study shows that mice of the same chronological age have quantifiable differences in health status that impact heart rate and SAN function and that these differences in health status can be identified using our frailty index.

ABSTRACT

Sinoatrial node (SAN) dysfunction increases with age, although not all older adults are affected in the same way. This is because people age at different rates and individuals of the same chronological age vary in health status from very fit to very frail. Our objective was to determine the impacts of age and frailty on heart rate (HR) and SAN function using a new model of frailty in ageing mice. Frailty, which was quantified in young and aged mice using a frailty index (FI), was greater in aged vs. young mice. Intracardiac electrophysiology demonstrated that HR was reduced whereas SAN recovery time (SNRT) was prolonged in aged mice; however, both parameters showed heteroscedasticity suggesting differences in health status among mice of similar chronological age. Consistent with this, HR and corrected SNRT were correlated with, and graded by, FI score. Optical mapping of the SAN demonstrated that conduction velocity (CV) was reduced in aged hearts in association with reductions in diastolic depolarization (DD) slope and action potential (AP) duration. In agreement with in vivo results, SAN CV, DD slope and AP durations all correlated with FI score. Finally, SAN dysfunction in aged mice was associated with increased interstitial fibrosis and alterations in expression of matrix metalloproteinases, which also correlated with frailty. These findings demonstrate that age-related SAN dysfunction occurs in association with electrical and structural remodelling and that frailty is a critical determinant of health status of similarly aged animals that correlates with changes in HR and SAN function.

Desmosomal junctions are necessary for adult sinus node function

AIMS

Current mechanisms driving cardiac pacemaker function have focused on ion channel and gap junction channel function, which are essential for action potential generation and propagation between pacemaker cells. However, pacemaker cells also harbour desmosomes that structurally anchor pacemaker cells to each other in tissue, but their role in pacemaker function remains unknown.

METHODS AND RESULTS

To determine the role of desmosomes in pacemaker function, we generated a novel mouse model harbouring cardiac conduction-specific ablation (csKO) of the central desmosomal protein, desmoplakin (DSP) using the Hcn4-Cre-ERT2 mouse line. Hcn4-Cre targets cells of the adult mouse sinoatrial node (SAN) and can ablate DSP expression in the adult DSP csKO SAN resulting in specific loss of desmosomal proteins and structures. Dysregulation of DSP via loss-of-function (adult DSP csKO mice) and mutation (clinical case of a patient harbouring a pathogenic DSP variant) in mice and man, respectively, revealed that desmosomal dysregulation is associated with a primary phenotype of increased sinus pauses/dysfunction in the absence of cardiomyopathy. Underlying defects in beat-to-beat regulation were also observed in DSP csKO mice in vivo and intact atria ex vivo. DSP csKO SAN exhibited migrating lead pacemaker sites associated with connexin 45 loss. In vitro studies exploiting ventricular cardiomyocytes that harbour DSP loss and concurrent early connexin loss phenocopied the loss of beat-to-beat regulation observed in DSP csKO mice and atria, extending the importance of DSP-associated mechanisms in driving beat-to-beat regulation of working cardiomyocytes.

CONCLUSION

We provide evidence of a mechanism that implicates an essential role for desmosomes in cardiac pacemaker function, which has broad implications in better understanding mechanisms underlying beat-to-beat regulation as well as sinus node disease and dysfunction.

Most Heart Failure Patients Die from Pump Failure: Implications for Therapy

Careful review of the literature of the last 20 years since the appearance of the first positive trials in heart failure indicates an evolution in the mode of death moving from sudden death to a predominance of pump failure death (i.e., death due to progression of heart failure). Pump failure is becoming a leading cause of mortality in a range of patient profiles, including patients with newly diagnosed or severe heart failure, patients with devices, and patients with heart failure associated with Chagas' disease. Indeed, the evidence suggests that modern management strategies, such as beta-blockers and devices, are successful in preventing sudden death. However, this means that optimally treated patients are at greater risk for the consequences of pump failure (death, hospitalization, and reduced quality of life). This highlights a new important unmet need in heart failure, and a priority for current research should be therapies that reduce pump failure death and hospitalization for more cost-effective management of the disease. Insofar as one-third of heart failure patients do not survive more than 3 years after diagnosis, properly addressing pump failure is an essential target in heart failure.

Importance of Implantable Cardioverter-Defibrillator Back-Up in Cardiac Resynchronization Therapy Recipients: A Systematic Review and Meta-Analysis

BACKGROUND

It remains to be determined whether patients receiving cardiac resynchronization therapy (CRT) benefit from the addition of an implantable cardioverter-defibrillator (ICD).

METHODS AND RESULTS

We performed a literature search looking for studies of patients implanted with CRTs. Comparisons were performed between patients receiving CRT-defibrillator (CRT-D) versus CRT-pacemaker (CRT-P). The primary outcome was all-cause mortality. Data were pooled using a random-effects model. The relative risk (RR) and hazard ratio (HR, when available) were used as measurements of treatment effect. Nineteen entries were entitled for inclusion, comprising 12 378 patients (7030 receiving CRT-D and 5348 receiving CRT-P) and 29 799 patient-years of follow-up. Those receiving CRT-D were younger, were more often males, had lower NYHA class, lower prevalence of atrial fibrillation, higher prevalence of ischemic heart disease, and were more often on beta-blockers. Ten studies showed significantly lower mortality rates with the CRT-D device, while the remaining 9 were neutral. The pooled data of studies revealed that CRT-D patients had significantly lower mortality rates compared with CRT-P patients (mortality rates: CRT-D 16.6% versus CRT-P 27.1%; RR=0.69, 95% CI 0.62-0.76; P<0.00001). The number needed to treat to prevent one death was 10. The observed I(2) values showed moderate heterogeneity among studies (I(2)=48%). The benefit of CRT-D was more pronounced in ischemic cardiomyopathy (HR=0.70, 95% CI 0.59-0.83, P<0.001, I(2)=0%), but a trend for benefit, albeit of lower magnitude, could also be seen in non-ischemic dilated cardiomyopathy (HR=0.79, 95% CI 0.61-1.02, P=0.07, I(2)=36%).

CONCLUSIONS

The addition of the ICD associates with a reduction in the risk of all-cause mortality in CRT patients. This seems to be more pronounced in patients with ischemic cardiomyopathy.

Cardiac sympathetic innervation assessed with (123)I-MIBG retains prognostic utility in diabetic patients with severe left ventricular dysfunction evaluated for primary prevention implantable cardioverter-defibrillator

BACKGROUND

Scintigraphy with iodine-123-metaiodobenzylguanidine ((123)I-MIBG) is a non-invasive tool for the assessment of cardiac sympathetic innervation (CSI) that has proven to be an independent predictor of survival. Recent studies have shown that diabetic patients with heart failure (HF) have a higher deterioration in CSI. It is unknown if (123)I-MIBG has the same predictive value for diabetic and non-diabetic patients with advanced HF. An analysis is performed to determine whether CSI with (123)I-MIBG retains prognostic utility in diabetic patients with HF, evaluated for a primary prevention implantable cardioverter-defibrillator (ICD).

MATERIAL AND METHODS

Seventy-eight consecutive HF patients (48 diabetic) evaluated for primary prevention ICD implantation were prospectively enrolled and underwent (123)I-MIBG to assess CSI (heart-to-mediastinum ratio - HMR). A Cox proportional hazards multivariate analysis was used to determine the influence of (123)I-MIBG images for prediction of cardiac events in both diabetic and non-diabetic patients. The primary end-point was a composite of arrhythmic event, cardiac death, or admission due to HF.

RESULTS

During a mean follow-up of 19.5 [9.3-29.3] months, the primary end-point occurred in 24 (31%) patients. Late HMR was significantly lower in diabetic patients (1.30 vs. 1.41, p=0.014). Late HMR≤1.30 was an independent predictor of cardiac events in diabetic (hazard ratio 4.53; p=0.012) and non-diabetic patients (hazard ratio 12.31; p=0.023).

CONCLUSIONS

Diabetic patients with HF evaluated for primary prevention ICD show a higher deterioration in CSI than non-diabetics; nevertheless (123)I-MIBG imaging retained prognostic utility for both diabetic and non-diabetic patients.

Effect on mode of death of heart failure treatment started with bisoprolol followed by Enalapril, compared to the opposite order: results of the randomized CIBIS III trial

BACKGROUND

Mode of death in chronic heart failure (CHF) may be of relevance to choice of therapy for this condition. Sudden death is particularly common in patients with early and/or mild/moderate CHF. β-Blockade may provide better protection against sudden death than ACE inhibition (ACEI) in this setting.

METHODS

We randomized 1010 patients with mild or moderate, stable CHF and left ventricular ejection fraction ≤35%, without ACEI, β-blocker or angiotensin-receptor-blocker therapy, to either bisoprolol (n = 505) or enalapril (n = 505) for 6 months, followed by their combination for 6-24 months. The two strategies were blindly compared regarding adjudicated mode of death, including sudden death and progressive pump failure death.

RESULTS

During the monotherapy phase, 8 of 23 deaths in the bisoprolol-first group were sudden, compared to 16 of 32 in the enalapril-first group: hazard ratio (HR) for sudden death 0.50; 95% confidence interval (CI) 0.21-1.16; P= 0.107. At 1 year, 16 of 42 versus 29 of 60 deaths were sudden: HR 0.54; 95% CI 0.29-1.00; P= 0.049. At study end, 29 of 65 versus 34 of 73 deaths were sudden: HR 0.84; 95% CI 0.51-1.38; P= 0.487. Comparable figures for pump failure death were: monotherapy, 7 of 23 deaths versus 2 of 32: HR 3.43; 95% CI 0.71-16.53; P= 0.124, at 1 year, 13 of 42 versus 5 of 60: HR 2.57; 95% CI 0.92-7.20; P= 0.073, at study end, 17 of 65 versus 7 of 73: HR 2.39; 95% CI 0.99-5.75; P= 0.053. There were no significant between-group differences in any other fatal events.

CONCLUSION

Initiating therapy with bisoprolol compared to enalapril decreased the risk of sudden death during the first year in this mild systolic CHF cohort. This was somewhat offset by an increase in pump failure deaths in the bisoprolol-first cohort.

Anticoagulation in heart failure: current status and future direction

Despite therapeutic advances, patients with worsening heart failure (HF) requiring hospitalization have unacceptably high post-discharge mortality and re-admission rates soon after discharge. Evidence suggests a hypercoagulable state is present in patients with HF. Although thromboembolism as a direct consequence of HF is not frequently clinically recognized, it may contribute to mortality and morbidity. Additionally, many patients with HF have concomitant disorders conferring additional thrombotic risk, including atrial fibrillation (AF) and coronary artery disease (CAD). Acute coronary syndrome (ACS), a known consequence of coronary thrombosis, is a common precipitating factor for worsening HF. Coronary thrombosis may also cause sudden death in patients with HF and CAD. Because data are largely derived from observational studies or trials of modest size, guideline recommendations on anticoagulation for HF vary between organizations. The recently presented Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction trial of HF patients in sinus rhythm suggested anticoagulation reduces the risk of stroke, although rates of the combined primary endpoint (death, ischemic stroke, or intracerebral hemorrhage) were similar for acetylsalicylic acid and warfarin. Newer oral anticoagulants dabigatran, apixaban, and rivaroxaban have successfully completed trials for the prevention of stroke in patients with AF and have shown benefits in the subpopulation of patients with concomitant HF. Positive results of the Anti-Xa Therapy to Lower Cardiovascular Events in Addition to Standard Therapy in Subjects with Acute Coronary Syndrome-Thrombolysis in Myocardial Infarction 51 (ATLAS ACS 2-TIMI 51) trial of rivaroxaban in ACS are also encouraging. These data suggest there is a need to assess the potential role for these newer agents in the management of patients hospitalized for HF who continue to have a high post-discharge event rate despite available therapies.

Cardiac resynchronisation therapy: pacemaker versus internal cardioverter-defibrillator in patients with impaired left ventricular function

OBJECTIVE

Studies have shown beneficial effects of cardiac resynchronisation therapy (CRT) on mortality among patients with heart failure. However the incremental benefits in survival from CRT with a defibrillator (CRT-D) are unclear. The choice of appropriate device remains unanswered.

METHOD

This is a single-centre observational study in a tertiary cardiac centre. Patients (n=500) implanted with a CRT device with pacing alone (CRT-P) (n=354) and CRT-D (n=146) were followed for at least 2 years (mean 29 months, SD 14 months). The primary end point was all-cause mortality.

RESULTS

A total of 116 deaths (23.2%) were recorded: 88 (24.8%) and 28 (19.2%), in the CRT-P and CRT-D groups, respectively. At 1 year there was a trend favouring CRT-D (HR 0.54, 95% CI 0.27 to 1.07, p=0.08) but this was attenuated by the 2nd year and became insignificant at the end of follow-up (HR 0.76, 95% CI 0.50 to 1.170, p=0.21). There was no survival benefit from having an internal cardioverter-defibrillator if patients were deemed non-responders to CRT. 27% of the CRT-P patients with ischaemic cardiomyopathy met indications for potential internal cardioverter-defibrillator implantation for primary prevention. These were older patients with poorer baseline function in comparison with CRT-D patients with devices for primary prevention. Once these differences were adjusted for, there was no difference in outcome between the groups.

CONCLUSIONS

CRT-D did not offer additional survival advantage over CRT-P at longer-term follow-up, as the clinical benefit of a defibrillator attenuated with time. Further work is needed to define which subset of patients benefit from CRT-D.

A plea for the wider use of CRT-P in candidates for cardiac resynchronisation therapy

Spectacular developments have taken place, in the last 10 years, in the device-based management of heart failure (HF). Patients presenting with chronic HF may benefit from a device implanted with a view to: (1) resynchronise the pump function of a discoordinated failing heart or (2) prevent sudden arrhythmic death by automatic cardioversion or defibrillation. This "point-of-view" article reviews the large amount of information gathered in the past 10 years on the use of cardiac resynchronisation therapy (CRT), with or without cardioverter defibrillator (ICD), and puts in perspective the advisability of using one, the other or both treatments in distinct patient subsets. There is currently no strong scientific evidence supporting the systematic implantation of CRT-ICD (CRT-D) instead of CRT pacemakers (CRT-P). Plain common sense should limit the prescription of these costly and complicated devices to patients in need of secondary prevention of ventricular arrhythmias or, for primary prevention, in younger patients without major concomitant illnesses. The preferential choice of CRT-P for the remainder of ambulatory patients in New York Heart Association (NYHA) functional class III or IV is currently acceptable. Because of insufficient data regarding the performance of CRT-P in patients presenting in NYHA functional class I or II, CRT-D is currently the device of choice for this sub-population.

An open-label dose escalation study to evaluate the safety of administration of nonviral stromal cell-derived factor-1 plasmid to treat symptomatic ischemic heart failure

RATIONALE

Preclinical studies indicate that adult stem cells induce tissue repair by activating endogenous stem cells through the stromal cell-derived factor-1:chemokine receptor type 4 axis. JVS-100 is a DNA plasmid encoding human stromal cell-derived factor-1.

OBJECTIVE

We tested in a phase 1, open-label, dose-escalation study with 12 months of follow-up in subjects with ischemic cardiomyopathy to see if JVS-100 improves clinical parameters.

METHODS AND RESULTS

Seventeen subjects with ischemic cardiomyopathy, New York Heart Association class III heart failure, with an ejection fraction ≤40% on stable medical therapy, were enrolled to receive 5, 15, or 30 mg of JVS-100 via endomyocardial injection. The primary end points for safety and efficacy were at 1 and 4 months, respectively. The primary safety end point was a major adverse cardiac event. Efficacy end points were change in quality of life, New York Heart Association class, 6-minute walk distance, single photon emission computed tomography, N-terminal pro-brain natruretic peptide, and echocardiography at 4 and 12 months. The primary safety end point was met. At 4 months, all of the cohorts demonstrated improvements in 6-minute walk distance, quality of life, and New York Heart Association class. Subjects in the 15- and 30-mg dose groups exhibited improvements in 6-minute walk distance (15 mg: median [range]: 41 minutes [3-61 minutes]; 30 mg: 31 minutes [22-74 minutes]) and quality of life (15 mg: -16 points [+1 to -32 points]; 30 mg: -24 points [+17 to -38 points]) over baseline. At 12 months, improvements in symptoms were maintained.

CONCLUSIONS

These data highlight the importance of defining the molecular mechanisms of stem cell-based tissue repair and suggest that overexpression of stromal cell-derived factor-1 via gene therapy is a strategy for improving heart failure symptoms in patients with ischemic cardiomyopathy.

Implantable cardioverter defibrillator therapy activation for high risk patients with relatively well preserved left ventricular ejection fraction. Does it really work?

BACKGROUND

Current guidelines for the primary prevention of sudden cardiac death have used a left ventricular ejection fraction (LVEF) ≤ 35% as a critical point to justify implantable cardioverter defibrillator (ICD) implantation in post myocardial infarction patients and in those with nonischemic dilated cardiomyopathy. We compared mortality and ICD activation rates among different ICD group recipients using a cut-off value for LVEF ≤ 35%.

METHODS

We followed up for a mean period of 41.1 months 495 ICD recipients (442 males, 65.6 years old, 68.9% post myocardial infarction patients, 422 with LVEF ≤ 35%). Prevention was considered primary in patients who fulfilled guidelines criteria or had inducible ventricular arrhythmia during programmed ventricular stimulation for patients with LVEF >35%.

RESULTS

Over the course of the trial, 84 of 495 patients died; 69 experienced cardiac death (6 sudden) and 15 non cardiac death. ICD recipients with LVEF ≤ 35% compared to those with preserved LVEF (mean LVEF=43%) had a greater incidence of total mortality (18% vs. 11%, log rank p=0.028) and cardiac death (15.4% vs. 5.5%, log rank p=0.005). There was no difference in the incidence for appropriate device therapy between patients with LVEF ≤ 35% and those with LVEF >35% (56.9% vs. 65.8%, log rank p=0.93). In the multivariate analysis the presence of advanced New York Heart Association stage predicted both total mortality (HR=2.69, 95% CI 1.771-4.086) and cardiac death (HR=3.437, 95% CI 2.163-5.463).

CONCLUSIONS

ICD therapy may protect heart failure patients at early stages from arrhythmic morbidity and mortality, based on an electrophysiology-guided risk stratification approach.

Oxidized CaMKII causes cardiac sinus node dysfunction in mice

Sinus node dysfunction (SND) is a major public health problem that is associated with sudden cardiac death and requires surgical implantation of artificial pacemakers. However, little is known about the molecular and cellular mechanisms that cause SND. Most SND occurs in the setting of heart failure and hypertension, conditions that are marked by elevated circulating angiotensin II (Ang II) and increased oxidant stress. Here, we show that oxidized calmodulin kinase II (ox-CaMKII) is a biomarker for SND in patients and dogs and a disease determinant in mice. In wild-type mice, Ang II infusion caused sinoatrial nodal (SAN) cell oxidation by activating NADPH oxidase, leading to increased ox-CaMKII, SAN cell apoptosis, and SND. p47-/- mice lacking functional NADPH oxidase and mice with myocardial or SAN-targeted CaMKII inhibition were highly resistant to SAN apoptosis and SND, suggesting that ox-CaMKII-triggered SAN cell death contributed to SND. We developed a computational model of the sinoatrial node that showed that a loss of SAN cells below a critical threshold caused SND by preventing normal impulse formation and propagation. These data provide novel molecular and mechanistic information to understand SND and suggest that targeted CaMKII inhibition may be useful for preventing SND in high-risk patients.

Changes in Ion Channel Gene Expression Underlying Heart Failure-Induced Sinoatrial Node Dysfunction

Background—

Heart failure (HF) causes a decline in the function of the pacemaker of the heart—the sinoatrial node (SAN). The aim of the study was to investigate HF-induced changes in the expression of the ion channels and related proteins underlying the pacemaker activity of the SAN.

Methods and Results—

HF was induced in rats by the ligation of the proximal left coronary artery. HF animals showed an increase in the left ventricular (LV) diastolic pressure (317%) and a decrease in the LV systolic pressure (19%) compared with sham-operated animals. They also showed SAN dysfunction wherein the intrinsic heart rate was reduced (16%) and the corrected SAN recovery time was increased (56%). Quantitative polymerase chain reaction was used to measure gene expression. Of the 91 genes studied during HF, 58% changed in the SAN, although only 1% changed in the atrial muscle. For example, there was an increase in the expression of ERG, K v LQT1, K ir 2.4, TASK1, TWIK1, TWIK2, calsequestrin 2, and the A1 adenosine receptor in the SAN that could explain the slowing of the intrinsic heart rate. In addition, there was an increase in Na + -H + exchanger, and this could be the stimulus for the remodeling of the SAN.

Conclusions—

SAN dysfunction is associated with HF and is the result of an extensive remodeling of ion channels; gap junction channels; Ca 2+ -, Na + -, and H + -handling proteins; and receptors in the SAN.

The anatomy and physiology of the sinoatrial node--a contemporary review

The sinoatrial node is the primary pacemaker of the heart. Nodal dysfunction with aging, heart failure, atrial fibrillation, and even endurance athletic training can lead to a wide variety of pathological clinical syndromes. Recent work utilizing molecular markers to map the extent of the node, along with the delineation of a novel paranodal area intermediate in characteristics between the node and the surrounding atrial muscle, has shown that pacemaker tissue is more widely spread in the right atrium than previously appreciated. This can explain the phenomenon of a "wandering pacemaker" and concomitant changes in the P-wave morphology. Extensive knowledge now exists regarding the molecular architecture of the node (in particular, the expression of ion channels) and how this relates to pacemaking. This review is an up-to-date summary of the current state of our appreciation of the above topics.

Soluble ST2 for predicting sudden cardiac death in patients with chronic heart failure and left ventricular systolic dysfunction

OBJECTIVES

We studied whether the measurement of the soluble form of ST2 (sST2), an interleukin-1 receptor family member, could identify heart failure (HF) patients at risk of sudden cardiac death (SCD).

BACKGROUND

The prediction of SCD remains an important challenge in patients with mild-to-moderate chronic HF. Concentrations of sST2 have been found increased and related to worse long-term outcomes in patients with acute HF. Whether sST2 has a prognostic role in SCD is unknown.

METHODS

A nested case-control study was performed on 36 cases of SCD and 63 control patients (matched for age, sex, and left ventricular ejection fraction) obtained from the MUSIC (MUerte Súbita en Insuficiencia Cardíaca) registry, a 3-year multicenter registry of ambulatory HF patients (New York Heart Association functional class II to III, left ventricular ejection fraction < or =45%). Demographic, clinical, echocardiographic, electrical, and biochemical data were collected at enrollment.

RESULTS

Concentrations of sST2 were greater among decedents (0.23 ng/ml [interquartile range 0.16 to 0.43 ng/ml] vs. 0.12 ng/ml [interquartile range 0.06 to 0.23 ng/ml], p = 0.001) and were predictive of experiencing SCD (+0.1 ng/ml, odds ratio: 1.39, 95% confidence interval: 1.09 to 1.78, p = 0.006). On the basis of a combined biomarker status, only 4% of patients experienced SCD for neither sST2 nor N-terminal pro-B-type natriuretic peptide (NT-proBNP) above receiver-operator characteristic-derived cut-off points (0.15 ng/ml and 2,000 ng/l, respectively), 34% for either biomarker above, and 71% for both biomarkers above (p < 0.001 for trend). This combined variable added incremental prognostic value to the multivariable regression model (p < 0.001).

CONCLUSIONS

Elevated sST2 concentrations are predictive of SCD in patients with chronic HF and provide complementary information to NT-proBNP levels. A combined biomarker approach may have an impact on clinical decision-making.

Current status of implantable cardioverter-defibrillator therapy in heart failure

Sudden cardiac arrest is one of the leading causes of death in patients with heart failure (HF). The implantable cardioverter-defibrillator (ICD) is the only evidence-based treatment strategy for patients who have survived a life-threatening ventricular arrhythmic event. Randomized clinical trials have shown that specific subsets of HF patients with ischemic and nonischemic dilated cardiomyopathy benefit from ICD therapy for primary prevention of sudden cardiac arrest. Cardiac resynchronization therapy has become the device-based therapy of choice for improving symptoms and survival in severe HF patients with evidence of ventricular dyssynchrony. This review summarizes the current status of ICD therapy in treating HF patients based on randomized clinical trials and current practice guidelines.

Rates and predictors of appropriate implantable cardioverter-defibrillator therapy delivery: results from the EVADEF cohort study

BACKGROUND

The implantable cardioverter defibrillator (ICD) is the therapy of choice in patients at risk for sudden cardiac death in both primary and secondary prevention indication. There are no recent data concerning the delivery rate and etiology of appropriate ICD therapies in routine medical care.

METHODS

The EVADEF study was a French multicenter, prospective, observational cohort study of ICD patients with a 2-year follow-up. Every 6 months we recorded patients' survival status and evaluated appropriate ICD therapies-antitachycardia pacing or shocks. Causes of ICD activation were also recorded from among ventricular tachycardia (VT), fast VT and ventricular fibrillation (VF).

RESULTS

From 2001 to 2003, 2296 unselected patients were implanted and followed until 2005. During a mean follow-up of 20.5 months, 274 deaths occurred. In 2009 patients with cardiopathy, 22 patients per 100 person-years had at least one appropriate therapy. Twenty-four and 11 patients per 100 person-years had at least one therapy in secondary and primary prevention, respectively. Age >65 years, left ventricular ejection fraction <30% and secondary prevention were independently associated with appropriate therapy. Besides, 5 patients per 100 person-years had at least 1 episode of life-threatening arrhythmia (fast VT or VF). Left ventricular ejection fraction <30% and secondary prevention were independently associated with life-threatening arrhythmia. In 287 patients without cardiopathy, the rate of appropriate therapy was twice as less, whereas the rate of life-threatening arrhythmia was similar.

CONCLUSION

Over a 24-month follow-up, the rate of appropriate therapy was substantial while few patients had life-threatening arrhythmia. Appropriate therapies and life-threatening arrhythmia were more frequent in patients with secondary prevention indication.

Heart failure

Despite advances in management of heart failure, the condition remains a major public-health issue, with high prevalence, poor clinical outcomes, and large health-care costs. Risk factors are well known and, thus, preventive strategies should have a positive effect on disease burden. Treatment of established systolic chronic heart failure includes use of agents that block the renin-angiotensin-aldosterone and sympathetic nervous systems to prevent adverse remodelling, to reduce symptoms and prolong survival. Diuretics are used to achieve and maintain euvolaemia. Devices have a key role in management of advanced heart failure and include cardiac resynchronisation in patients with evidence of cardiac dyssynchrony and implantation of a cardioverter defibrillator in individuals with low ejection fraction. Approaches for treatment of acute heart failure and heart failure with preserved ejection fraction are supported by little clinical evidence. Emerging strategies for heart failure management include individualisation of treatment, novel approaches to diagnosis and tracking of therapeutic response, pharmacological agents aimed at new targets, and cell-based and gene-based methods for cardiac regeneration.

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.