Primary Prevention of Sudden Arrhythmic Death in Dilated Cardiomyopathy: Current Guidelines and Risk Stratification

Double Gain: The Radio Frequency Catheter Ablation of Ventricular Aneurysm Related Recurrent Ventricular Tachycardia on a Tremendous Cardiac Outpouching

Dilated cardiomyopathy (DCM) is a classic type of non-ischemic cardiomyopathy. Of these, idiopathic cardiomyopathy (IDCM) is a rare type of non-genetic dilated cardiomyopathy. More specifically, the patient had suspected IDCM combined with sustained polymorphic ventricular tachycardia (PMVT) of left ventricular basal segmental origin, cardiac systolic dysfunction and an ejection fraction (EF) of 29%. He had an abnormally large ventricular aneurysm (VA) in the posterior wall of the left ventricle with left ventricular end diastolic dimension (LVDd) of 90 mm. We performed an endocardial radiofrequency catheter ablation (RFCA) of the patient’s recurrent ventricular tachycardia (VT) on the basis of an implantable cardioverter (ICD). Although minimally invasive RFCA also carries a high risk, it is currently a two-pronged option to improve the patient’s quality of life and to prevent the recurrence of VT. Postoperatively, the patient was routinely given optimal anti-arrhythmic and heart failure (HF) treatments to improve cardiac function as well as being followed up for 9 months. The patient’s EF ascended to 36% without any recurrence of VT. In summary, RFCA of suspected IDCM combined with VA and VT of basal area origin would be an effective treatment.

Longitudinal arrhythmic risk assessment based on ejection fraction in patients with recent-onset non-ischemic dilated cardiomyopathy

BACKGROUND

Practice guidelines suggest the use of implantable cardioverter-defibrillators in patients with left ventricular ejection fractions (LVEF) ≤ 35% despite 3 to 6 months of guideline-directed medical therapy (GDMT). It remains unclear whether this strategy is appropriate for patients with dilated cardiomyopathy (DCM), who can experience reverse ventricular remodeling for up to 24 months after the initiation of GDMT. The aim of this study was to assess the longitudinal dynamic relationship between LVEF ≤ 35% and arrhythmic risk in patients with recent-onset nonischemic DCM on GDMT.

METHODS

A retrospective analysis was conducted among patients with recent-onset DCM (≤6 months) and recent initiation of GDMT (≤3 months) consecutively enrolled in a longitudinal registry. Risk for major ventricular arrhythmic events or sudden cardiac death was assessed in relationship to LVEF ≤ 35% at enrollment and 6 and 24 months after initiation of GDMT.

RESULTS

Five hundred forty-four patients met the inclusion criteria. LVEF ≤ 35% identified patients with increased risk for major ventricular arrhythmic events or sudden cardiac death starting from 24 months after initiation of GDMT (hazard ratio, 2.126; 95% CI, 1.065-4.245; P = .03). However, LVEF ≤ 35% at presentation or 6 months after enrollment did not have prognostic significance. Sixty-seven percent of 131 patients with LVEF ≤ 35% at 6 months after initiation of GDMT had improved LVEFs (to >35%) by 24 months. This late LVEF improvement correlated with lower arrhythmic risk (P = .012) and was preceded by a reduction of LV dimensions in the first 6 months of GDMT.

CONCLUSIONS

In patients with DCM, the present findings suggest that risk stratification for major ventricular arrhythmic events or sudden cardiac death on the basis of LVEF ≤ 35% is effective after 2 years of GDMT, but not after 6 months. In selected patients with DCM, it would be appropriate to wait 24 months before primary prevention ICD implantation.

Beyond Ejection Fraction: Novel Clinical Approaches Towards Sudden Cardiac Death Risk Stratification in Patients with Dilated Cardiomyopathy

Implantable Cardioverter-Defibrillator (ICD) therapy is indicated for patients at risk for sudden cardiac death due to ventricular tachyarrhythmia. The most commonly used risk stratification algorithms use Left Ventricular Ejection Fraction (LVEF) to determine which patients qualify for ICD therapy, even though LVEF is a better marker of total mortality than ventricular tachyarrhythmias mortality. This review evaluates imaging tools and novel biomarkers proposed for better risk stratifying arrhythmic substrate, thereby identifying optimal ICD therapy candidates.

Echocardiographic Advances in Dilated Cardiomyopathy

Although the overall survival of patients with dilated cardiomyopathy (DCM) has improved significantly in the last decades, a non-negligible proportion of DCM patients still shows an unfavorable prognosis. DCM patients not only need imaging techniques that are effective in diagnosis, but also suitable for long-term follow-up with frequent re-evaluations. The exponential growth of echocardiography’s technology and performance in recent years has resulted in improved diagnostic accuracy, stratification, management and follow-up of patients with DCM. This review summarizes some new developments in echocardiography and their promising applications in DCM. Although nowadays cardiac magnetic resonance (CMR) remains the gold standard technique in DCM, the echocardiographic advances and novelties proposed in the manuscript, if properly integrated into clinical practice, could bring echocardiography closer to CMR in terms of accuracy and may certify ultrasound as the technique of choice in the follow-up of DCM patients. The application in DCM patients of novel echocardiographic techniques represents an interesting emergent research area for scholars in the near future.

The Necessity of an ICD-Therapy in Patients with Indications for Primary Prevention of Sudden Cardiac Death. One Center Experience

Aim      Analysis of responses of cardioverter-defibrillators implanted in patients with cardiomyopathies (CMPs) of various origins and a high risk of sudden cardiac death (SCD) to assess the effectiveness of a modern strategy for primary prevention of SCD.Material and methods  In the Federal Center for High Medical Technologies in Kaliningrad from 2014 through 2018, implantable cardioverter-defibrillators (ICD) and cardiac resynchronization therapy defibrillators (CRT-D) were installed in 165 patients. Major indications for device implantation in these patients included left ventricular (LV) systolic dysfunction with ejection fraction (EF) ≤35 %; chronic heart failure (CHF) consistent with the New York Heart Association (NYHA) functional class (FC) II-III (IV for CRT-D) without previous episodes of life-threatening ventricular arrhythmias, circulatory arrest and resuscitation, which was consistent with the current international strategy for primary prevention of SCD. The study patients were divided into two groups based on the CMP origin; group 1 included 101 (61.2 %) patients with CMP of ischemic origin (ICMP) and group 2 consisted of 64 (38.8 %) patients with CMP of non-ischemic origin (NCMP). Information about arrhythmic episodes and device activation was retrieved from the device electronic memory during visits of patients to the clinic and was also transmitted to the clinic by a remote monitoring system. This information was studied and evaluated for the validity and effectiveness of the device triggering. If necessary, the parameters of detection and treatment were adjusted taking into account the obtained information. Information was analyzed and statistically processed with the SPSS Statistics 20.0 software.Results The patients were followed up for 28.3 ± 15.6 months, during which the devices delivered therapy to 55 (33.3%) patients of the entire group. In the ICMP group, the devices were activated in 44 (26.7 %) patients and in the NCMP group, the devices were activated in 11 (6.7 %) patients. In group 1 (ICMP), appropriate triggering was observed in 33 (20.0%) patients and inappropriate triggering was observed in 11 (6.7%) patients. In group 2 (NCMP), appropriate triggering was observed in 2 (1.2 %) patients and inappropriate triggering was observed in 9 (5.5 %) patients. The main cause of inappropriate triggering was atrial fibrillation (AF). 17 (10.3 %) patients with ICMP had sustained ventricular tachycardia (VT), which did not reach the detection frequency for ICD therapy; these VTs were only detected by devices and terminated spontaneously. Intragroup differences in the number of patients who received an appropriate treatment were statistically significant: 33 (32.6 %) in the ICMP group vs. 2 (3.1 %) in the NCMP group (р<0.006). Differences in the number of patients who received an inappropriate treatment were not statistically significant although their number was greater in the NCMP group than in the ICMP group (9 (14.1 %) vs. 11 (10.9 %), р>0.05).Conclusion      A higher requirement for the ICD treatment was revealed in patients with ICMP compared to patients with NCMP. The low demand for the ICD treatment in patients with NCMP and the more frequent inappropriate actuation of the devices in this patient group due to AF allow a conclusion that the criteria for primary prevention of SCD with ICD (LV EF ≤35% and clinically significant CHF) are not equally effective indications for ICD implantation in patients with ICMP and NCMP. It can be assumed that life-threatening ventricular arrhythmias are evident in patients with NCMP before the development of hemodynamically significant LV dysfunction and CHF, which warrants further research in this direction.

Assessment of Myocardial Fibrosis Using Two-Dimensional and Three-Dimensional Speckle Tracking Echocardiography in Dilated Cardiomyopathy With Advanced Heart Failure

BACKGROUND

This study aimed to depict strain parameters derived from 2-dimensional (2D)- and 3-dimensional (3D) speckle tracking echocardiography and to explore which may best reflect myocardial fibrosis (MF) in dilated cardiomyopathy with advanced heart failure by comparing with histologic fibrosis.

METHODS AND RESULTS

We analyzed 75 patients with dilated cardiomyopathy with advanced heart failure who underwent echocardiographic examination before heart transplantation. Strain parameters derived from 2D- and 3D speckle tracking echocardiography were as follows: left ventricular global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS) and tangential strain (TS). The degree of MF was quantified using Masson's staining in left ventricular myocardial samples obtained from all patients. Seventy-five patients were divided into 3 groups according to the tertiles of histologic MF (mild, moderate, and severe MF groups). Patients with severe MF had lower 3DGLS, 3DGRS, 3DTS, and 2DGLS than those with mild and moderate MF. MF strongly correlated with 3DGLS (r = 0.72, P < .001), weakly with 3DGRS (r = -0.39, P = .001), 3DGCS (r = 0.30, P = .009), 3DTS (r = 0.47, P < .001), and 2DGLS (r = 0.44, P < .001), but did not correlate with 2DGCS and 2DGRS. Receiver operating characteristic analysis revealed that the area under the curve of 3DGLS for detecting severe MF was significantly larger than that of other strain parameters (0.86 vs 0.59-0.70, P < .05 for all). The multivariate linear regression models using 3DGLS (R² = 0.76; Akaike information criterion = 331) was found to be a more accurate indicator to predict MF than that with 3DTS (R² = 0.65, Akaike information criterion = 354) and 2DGLS (R² = 0.66, Akaike information criterion = 352).

CONCLUSIONS

Three-dimensional GLS may be an optimal surrogate marker for reflecting MF in patients with dilated cardiomyopathy with advanced heart failure.

Prognostic value of late gadolinium enhancement in cardiac MRI of non-ischemic dilated cardiomyopathy patients

Background

The role of late gadolinium enhancement (LGE) in cardiac MRI (CMR) as prognostic marker in non-ischemic dilated cardiomyopathy (NIDCM) is evolving.

Objective

To study the effect of LGE in the prognosis of NIDCM patients.

Methods

112 consecutive NIDCM patients, who underwent CMR, were prospectively followed up for 745 ± 320 days. Primary end point was occurrence of MACE {composite of all-cause mortality, resuscitated cardiac arrest, sustained ventricular tachycardia (VT)/appropriate ICD shock, heart failure (HF) hospitalization}.

Results

LGE was present in 44 out of 112 patients (39%). The primary end point (MACE) was significantly higher in LGE + ve group compared to the LGE –ve group (72.7% vs. 29.4%; p < 0.0001). Similarly, cardiac mortality (9.1% vs 2.9%; p < 0.049), VT (13.6% vs. 2.9%; p < 0.031), HF hospitalization (63.6% vs. 30.9%; p < 0.001) were significantly more in LGE + ve group. In univariate model, LGE demonstrated the strongest association with MACE (Hazard ratio [HR] = 2.96 [95% CI 1.685 to 5.201; p < 0.0001). LGE extent of >14% of LV predicted MACE with 90.6% sensitivity and 86% specificity. HR of LGE extent >14% of LV for MACE is 6.12; p < 0.01. LGE was associated with MACE irrespective of its location, pattern or distribution. Multivariate model showed LGE and its extent >14% of LV volume were strongest predictor of MACE.

Conclusion

LGE and its extent >14% predicts adverse cardiac events in NIDCM irrespective of LVEF and LGE location, pattern or distribution. This study emphasises the role of CMR in risk stratification of NIDCM patients and guiding therapy.

Risk Stratification for Sudden Cardiac Death in Non-Ischaemic Dilated Cardiomyopathy

Purpose of Review

Non-ischaemic dilated cardiomyopathy (DCM) occurs in 1 in 2500 individuals in the general population and is associated with considerable morbidity and mortality. Studies involving large numbers of unselected DCM patients have led to consensus guidelines recommending implantable cardioverter-defibrillator (ICD) implantation for protection against sudden cardiac death (SCD) in those with LVEF ≤35%. The purpose of this article is to review the literature for other potential markers including serological, electrocardiographic, echocardiographic, cardiac magnetic resonance, ambulatory ECG and genetic data, to highlight other potential markers that may optimise risk stratification for SCD in this cohort and thereby allow a more personalized approach to ICD-implantation.

Recent Findings

Recent studies including the Danish study to assess the efficacy of ICDs in patients with non-ischemic systolic heart failure on mortality (DANISH) trial have questioned the benefits of ICD implantation in this group of patients with no changes in all-cause mortality. Recent pooled cohorts of patients with genetic DCM and in particular in those with Lamin A/C (LMNA) mutations have identified patients at increased risk of SCD and allowed the creation of algorithms to prognosticate SCD risk in mutation carriers. Furthermore, genetic testing has identified other DCM-causing genes including filamin C (FLNC) and RBM20 which may be associated with higher rates of ventricular arrhythmia.

Summary

To date, risk-stratification for SCD has been hampered by the utilisation of heterogenous subsets of idiopathic DCM patients and by use of static risk models where predictions are based on a single time point with a lack of consideration of disease progression. The current focus of personalised risk-stratification for SCD is shifting towards better characterisation of underlying DCM aetiology and the development of multi-parametric risk-stratification models that incorporate time-dependent disease characteristics and novel biomarkers.

Modes of death and prognostic outliers in chronic heart failure

BACKGROUND

The impact of incident sudden cardiac death (SCD) on the predictive accuracy of prognostic risk scores for patients with chronic heart failure (HF) has rarely been examined. We assessed the relationship between estimated probability of death and modes of death in this population, as well as the predictors of death and survival in prognostic outliers.

METHODS AND RESULTS

The MAGGIC 3-year probability of death was estimated in 6,859 participants of the GISSI-HF trial (mean age 67±11 years, 78% men, 91% with ejection fraction <40%, mean follow-up 3.5±1.3 years, observed mortality 28.4%). The incidence of SCD progressively decreased with increased probability of death, and occurred in 52.5% of patients estimated at low-risk (N = 61 with probability <14%) vs. in 23.5% of the high-risk ones (N = 375 with probability >56%, P < .0001). On the contrary, death from worsening HF was significantly more frequent in the latter group (19.7% vs. 46.1%, P < .0001). The overall predictive accuracy of the MAGGIC model improved after excluding deaths from SCD (AUC from 0.731 to 0.760, P = .0034). Among patients estimated at low-risk (N = 61 dead, 743 alive), independent predictors of death were older age, longer history of HF, higher serum uric acid and chronic obstructive pulmonary disease. The only predictor of survival in patients estimated at high-risk (N = 210 alive, 375 dead) was higher systolic blood pressure.

CONCLUSIONS

The MAGGIC risk score demonstrated its scarce ability to capture SCD, particularly in chronic HF patients estimated at low risk of death. Newer and better prognostic tools in the evolving horizon of HF are needed.

Implantable Cardioverter-Defibrillators are the Main Link in the Modern Concept of Sudden Cardiac Death Prevention. Problems and Prospects of the Development of the Method

The article covers the development of the problem of sudden cardiac death prevention with the implantable cardioverter-defibrillators from the moment of creation of these devices to our days. The current concept of primary prevention of sudden cardiac death, based on the severity of manifestation of heart failure and left ventricular dysfunction, is not effective enough. Its practical application is difficult because it requires mass application of implantable defibrillators, with low predictive accuracy of these criteria in terms of development of life-threatening arrhythmias. The development of methods for visualizing the myocardium, allowing to assess the severity of myocardial fibrosis, as well as the possibilities of medical genetics, at the present stage, allows us to clarify indications for implantation of cardioverter-defibrillators and thereby significantly improve the concept of preventing sudden cardiac death with these instruments.

Outcome in Dilated Cardiomyopathy Related to the Extent, Location, and Pattern of Late Gadolinium Enhancement

OBJECTIVES

This study sought to investigate the association between the extent, location, and pattern of late gadolinium enhancement (LGE) and outcome in a large dilated cardiomyopathy (DCM) cohort.

BACKGROUND

The relationship between LGE and prognosis in DCM is incompletely understood.

METHODS

The authors examined the association between LGE and all-cause mortality and a sudden cardiac death (SCD) composite based on the extent, location, and pattern of LGE in DCM.

RESULTS

Of 874 patients (588 men, median age 52 years) followed for a median of 4.9 years, 300 (34.3%) had nonischemic LGE. Estimated adjusted hazard ratios for patients with an LGE extent of 0 to 2.55%, 2.55% to 5.10%, and >5.10%, respectively, were 1.59 (95% confidence interval [CI]: 0.99 to 2.55), 1.56 (95% CI: 0.96 to 2.54), and 2.31 (95% CI: 1.50 to 3.55) for all-cause mortality, and 2.79 (95% CI: 1.42 to 5.49), 3.86 (95% CI: 2.09 to 7.13), and 4.87 (95% CI: 2.78 to 8.53) for the SCD endpoint. There was a marked nonlinear relationship between LGE extent and outcome such that even small amounts of LGE predicted a substantial increase in risk. The presence of septal LGE was associated with increased mortality, but SCD was most associated with the combined presence of septal and free-wall LGE. Predictive models using LGE presence and location were superior to models based on LGE extent or pattern.

CONCLUSIONS

In DCM, the presence of septal LGE is associated with a large increase in the risk of death and SCD events, even when the extent is small. SCD risk is greatest with concomitant septal and free-wall LGE. The incremental value of LGE extent beyond small amounts and LGE pattern is limited.

Usefulness of Addition of Magnetic Resonance Imaging to Echocardiographic Imaging to Predict Left Ventricular Reverse Remodeling in Patients With Nonischemic Cardiomyopathy

Defining short-term prognosis in nonischemic cardiomyopathy (NICM) is challenging in clinical practice. Although left ventricular reverse remodeling (LVRR) is a key prognostic marker in NICM there are few parameters able to predict it. We investigated whether a complete structural and functional cardiac magnetic resonance imaging (cMRI) evaluation was incremental to the classic clinical-echocardiographic approach in predicting LVRR in a large cohort of NICM patients receiving evidence-based treatment. Patients with a recent diagnosis of NICM (<3 months) who underwent complete clinical, echocardiographic and cMRI assessment were consecutively enrolled from 2008 to 2016. LVRR was defined as an increase in ≥10 points or normalization of left ventricular ejection fraction, associated with a ≥10% reduction or normalization of left ventricular end-diastolic diameter at midterm (median time 20 months) echocardiographic follow-up. Among 80 NICM patients included in the study, LVRR was observed in 43 (54%). At multivariate analysis, the clinical-echocardiographic evaluation failed to identify independent predictors of LVRR. However, absence of late gadolinium enhancement (odds ratio [OR] 9.07; confidence interval [CI] 2.7 to 13.1; p value 0.0003), left ventricular mass (OR 1.018; CI 1.001 to 1.036; p value 0.045) and peak circumferential strain (OR 1.213; CI 1.011 to 1.470; p value 0.049) assessed by cMRI were independently associated with LVRR. A model for LVRR prediction based on cMRI and clinical-echocardiographic parameters performed significantly better than the clinical-echocardiographic model alone (area under curve 0.84 vs 0.72; p value 0.023). In conclusion, an integrated imaging approach with the addition of a structural and functional cMRI study to the standard-of-care evaluation improves the prediction of LVRR in a large cohort of patients with recently diagnosed NICM receiving evidence-based treatment.

Sudden Cardiac Death in Genetic Cardiomyopathies

Sudden cardiac death (SCD) caused by ventricular arrhythmias is common in patients with genetic cardiomyopathies (CMs) including dilated CM, hypertrophic CM, and arrhythmogenic right ventricular CM (ARVC). Phenotypic features can identify individuals at high enough risk to warrant placement of an implantable cardioverter-defibrillator, although risk stratification schemes remain imperfect. Genetic testing is valuable for family cascade screening but with few exceptions (eg, LMNA mutations) do not identify higher risk for SCD. Although randomized trials are lacking, observational data suggest that ICDs can be beneficial. Vigorous exercise can exacerbate ARVC disease progression and increase likelihood of ventricular arrhythmias.

Prediction and Prevention of Sudden Cardiac Death

Sudden death is a major problem, with significant impact on public health. Many conditions predispose to sudden cardiac death and sudden cardiac arrest (SCA), foremost among them coronary artery disease, and an effective therapy exists in the form of the implantable cardioverter defibrillator. Risk stratification for SCA remains imperfect, especially for patients with nonischemic cardiomyopathy. Ongoing trials may make it easier to identify those at high risk, and potentially those at very low risk, in the future.

Phenotype and Clinical Outcomes of Titin Cardiomyopathy

BACKGROUND

Improved understanding of dilated cardiomyopathy (DCM) due to titin truncation (TTNtv) may help guide patient stratification.

OBJECTIVES

The purpose of this study was to establish relationships among TTNtv genotype, cardiac phenotype, and outcomes in DCM.

METHODS

In this prospective, observational cohort study, DCM patients underwent clinical evaluation, late gadolinium enhancement cardiovascular magnetic resonance, TTN sequencing, and adjudicated follow-up blinded to genotype for the primary composite endpoint of cardiovascular death, and major arrhythmic and major heart failure events.

RESULTS

Of 716 subjects recruited (mean age 53.5 ± 14.3 years; 469 men [65.5%]; 577 [80.6%] New York Heart Association function class I/II), 83 (11.6%) had TTNtv. Patients with TTNtv were younger at enrollment (49.0 years vs. 54.1 years; p = 0.002) and had lower indexed left ventricular mass (5.1 g/m² reduction; p_adjusted = 0.03) compared with patients without TTNtv. There was no difference in biventricular ejection fraction between TTNtv^+/- groups. Overall, 78 of 604 patients (12.9%) met the primary endpoint (median follow-up 3.9 years; interquartile range: 2.0 to 5.8 years), including 9 of 71 patients with TTNtv (12.7%) and 69 of 533 (12.9%) without. There was no difference in the composite primary outcome of cardiovascular death, heart failure, or arrhythmic events, for patients with or without TTNtv (hazard ratio adjusted for primary endpoint: 0.92 [95% confidence interval: 0.45 to 1.87]; p = 0.82).

CONCLUSIONS

In this large, prospective, genotype-phenotype study of ambulatory DCM patients, we show that prognostic factors for all-cause DCM also predict outcome in TTNtv DCM, and that TTNtv DCM does not appear to be associated with worse medium-term prognosis.

Cardiac magnetic resonance imaging: Which information is useful for the arrhythmologist?

Cardiac magnetic resonance (CMR) is a non-invasive, non-ionizing, diagnostic technique that uses magnetic fields, radio waves and field gradients to generate images with high spatial and temporal resolution. After administration of contrast media (e.g., gadolinium chelate), it is also possible to acquire late images, which make possible the identification and quantification of myocardial areas with scar/fibrosis (late gadolinium enhancement, LGE). CMR is currently a useful instrument in clinical cardiovascular practice for the assessment of several pathological conditions, including ischemic and non-ischemic cardiomyopathies and congenital heart disease. In recent years, its field of application has also extended to arrhythmology, both in diagnostic and prognostic evaluation of arrhythmic risk and in therapeutic decision-making. In this review, we discuss the possible useful applications of CMR for the arrhythmologist. It is possible to identify three main fields of application of CMR in this context: (1) arrhythmic and sudden cardiac death risk stratification in different heart diseases; (2) decision-making in cardiac resynchronization therapy device implantation, presence and extent of myocardial fibrosis for left ventricular lead placement and cardiac venous anatomy; and (3) substrate identification for guiding ablation of complex arrhythmias (atrial fibrillation and ventricular tachycardias).

Personalizing Risk Stratification for Sudden Death in Dilated Cardiomyopathy: The Past, Present, and Future

Results from the DANISH Study (Danish Study to Assess the Efficacy of ICDs in Patients With Non-Ischemic Systolic Heat Failure on Mortality) suggest that for many patients with dilated cardiomyopathy (DCM), implantable cardioverter-defibrillators do not increase longevity. Accurate identification of patients who are more likely to die of an arrhythmia and less likely to die of other causes is required to ensure improvement in outcomes and wise use of resources. Until now, left ventricular ejection fraction has been used as a key criterion for selecting patients with DCM for an implantable cardioverter-defibrillator for primary prevention purposes. However, registry data suggest that many patients with DCM and an out-of-hospital cardiac arrest do not have a markedly reduced left ventricular ejection fraction. In addition, many patients with reduced left ventricular ejection fraction die of nonsudden causes of death. Methods to predict a higher or lower risk of sudden death include the detection of myocardial fibrosis (a substrate for ventricular arrhythmia), microvolt T-wave alternans (a marker of electrophysiological vulnerability), and genetic testing. Midwall fibrosis is identified by late gadolinium enhancement cardiovascular magnetic resonance imaging in ≈30% of patients and provides incremental value in addition to left ventricular ejection fraction for the prediction of sudden cardiac death events. Microvolt T-wave alternans represents another promising predictor, supported by large meta-analyses that have highlighted the negative predictive value of this test. However, neither of these strategies have been routinely adopted for risk stratification in clinical practice. More convincing data from randomized trials are required to inform the management of patients with these features. Understanding of the genetics of DCM and how specific mutations affect arrhythmic risk is also rapidly increasing. The finding of a mutation in lamin A/C, the cause of ≈6% of idiopathic DCM, commonly underpins more aggressive management because of the malignant nature of the associated phenotype. With the expansion of genetic sequencing, the identification of further high-risk mutations appears likely, leading to better-informed clinical decision making and providing insight into disease mechanisms. Over the next 5 to 10 years, we expect these techniques to be integrated into the existing algorithm to form a more sensitive, specific, and cost-effective approach to the selection of patients with DCM for implantable cardioverter-defibrillator implantation.

Sudden death risk stratification in non-ischemic dilated cardiomyopathy using old and new tools: a clinical challenge

INTRODUCTION

Risk stratification for sudden cardiac death in non-ischemic dilated cardiomyopathy (NIDCM) remains a clinical challenge. Areas covered: Currently, left ventricular ejection fraction (LVEF), severity of heart failure symptoms according to NYHA classification, and morphology and duration of the QRS complex guide device management in these patients with implantation of a cardioverter defibrillator (ICD) and/or cardiac resynchronization therapy (CRT) devices. Recently, the results of a randomized trial stirred some controversy regarding the utility of ICD in NIDCM patients, however, a subsequent meta-analysis confirmed prior findings of the survival-prolonging benefit of device therapy. Newer risk markers, like late gadolinium enhancement in cardiac magnetic resonance imaging (CMR) detecting myocardial fibrosis, are encouraging in improving risk stratification in these patients. Furthermore, resurgence of an old tool, the electrophysiology study (EPS), and technical advances in genetics in identifying high-risk familial NIDCM, appear promising in this direction. Expert commentary: Based on old and new tools, a more individualized approach may be applied in NIDCM patients, whereby CMR, EPS and genetics may provide further guidance, particularly in patients with LVEF>35%. These issues are herein reviewed and a practical algorithm is proposed for risk stratification and device implantation in NIDCM patients with LVEF below and above 35%.