Ventricular arrhythmias and sudden cardiac death: new research insights with clinical implications

Ventricular arrhythmias are major causes of death and limiting symptoms in virtually all forms of heart disease. Seminal work of several research groups in the last few decades has greatly increased our knowledge of pathophysiology, mechanism, and treatment options.1,2 From these insights, a variety of options exist for management of patients with ventricular arrhythmias with the ultimate goal remaining the prevention of the catastrophic event of sudden cardiac death (SCD). These options include implantation of cardioverter-defibrillators, catheter ablation, and pharmacologic treatment.3 Despite the remarkable achievements in the field, many challenges remain both in the risk stratification for SCD4 and in the application and outcome of interventional procedures.5 This Focused Issue of EP Europace is dedicated to manuscripts presenting research findings concerning these important topics. The limitations of relying solely on left ventricular ejection fraction for risk stratification after myocardial infarction have been repeatedly demonstrated.4 Katritsis et al.6 review the role of electrophysiology testing and the potential role of the programmed ventricular stimulation, an old tool, as risk stratifier. In another article in this issue,7 Ng et al. review new findings from the LifeMap, a novel tool for risk stratification that assimilates the utility of two markers, the regional restitution instability index, and the peak electrocardiogram restitution slope. The introduction of a novel risk calculator for patients with hypertrophic cardiomyopathy has significantly informed the decision making process guiding defibrillator implantation for primary prevention of SCD.8 Despite its practicality, the calculator has limitations with one of these being the uncertainty of its utility in specific settings. Liebregts et al.9 examined the predictive ability of the model in a large series of patients undergoing alcohol septal ablation and confirmed the predictive ability of the model in this setting. Although most patients at risk for SCD suffer from ischaemic, dilated non-ischaemic, or hypertrophic cardiomyopathy, other uncommon diseases are also associated with an elevated risk. Such an example is the Fabry disease. Baig et al.10 report the findings of a systematic review on risk factors for ventricular arrhythmias and SCD in this disease. The value of the defibrillators for prevention of SCD in patients with reduced ejection fraction has been proven in large randomized trials and is recommended by the guidelines. Recently, the DANISH trial has questioned the value of defibrillator implantation for primary prevention of SCD in patients with non-ischaemic cardiomyopathy11 and has attracted great interest.12 To shed more light on this important, clinically relevant issue, Romero et al.13 performed a systematic review and meta-analysis of trials evaluating the defibrillator for primary prevention of SCD in non-ischaemic cardiomyopathy, including the DANISH trial. Despite the effectiveness of the implanted defibrillator for terminating arrhythmias and preventing sudden death pharmacologic treatment remains essential to reduce arrhythmia recurrences. Beta-blockers have been shown to reduce the number of arrhythmic episodes and the number of therapies delivered by the defibrillator. Ruwald et al.14 studied the effect of the beta-blocker dose on ventricular arrhythmias and major clinical endpoints in patients who received a defibrillator for primary prevention and observed a decreased risk of adverse endpoints with increasing dosage of beta-blockers. Mapping and ablation of ventricular arrhythmias can be particularly challenging and the issue contains several papers describing useful technical and procedural aspects. Magnetic resonance imaging can provide valuable information to define the VT substrate and has great potential to transform the approach to targeting scar-related VT wth ablation.15 Hennig et al.16 report data on the usefulness of high-resolution late gadolinium-enhanced magnetic resonance for identification of the underlying substrate of ventricular arrhythmias. In another study, Wang et al.17 investigated the feasibility of non-invasive electrocardiographic imaging for mapping of scar substrate and re-entry circuits that may be particularly useful for characterizing short-lived ventricular tachycardia circuits. Pace-mapping is a widely applied technique in ablation of ventricular tachycardia but has limitations. Li et al.18 examined the feasibility of a software navigation algorithm based on pace-mapping for identification of target areas for ventricular arrhythmia ablation in patients with and without structural heart disease. Important insight into current clinical practice and in particular into the implementation of current guidelines in clinical practice across Europe is provided in a respective survey of the European Heart Rhythm Association that fortunately suggests a reasonably high adherence to guidelines in daily clinical practice.19 Finally, the issue contains further papers reporting novel findings in the field of ventricular arrhythmias and SCD.20–25 We sincerely hope that you enjoy reading this Focused Issue, and that these insights will be helpful to you for the management of patients with ventricular arrhythmias. The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.