Evaluation of Sudden Cardiac Death Risk Using Cardiac Magnetic Resonance

Abstract

Sudden cardiac death (SCD) is not uncommon event worldwide. In a report from the Unites States, age-adjusted nationwide incidence of SCD was estimated at 60 per 100000 residents, and the public health burden of SCD is greater than individual cancer [1]. Moreover, the survival to discharge in out-of-hospital cardiac arrest is only 6.4% in patients who required emergency medical services [2]. To prevent this devastating consequence and improve survival, implantable cardioverter-defibrillator (ICD) is considered as the treatment of choice for patients who survive SCD or have a high risk of SCD. However, the decision whether to implant ICD is not straightforward. In a series of major trials, only 20−35% of patients experienced appropriate shock delivery in 1 to 3 years after ICD implantation [3]. Simultaneously, the cumulative incidence of inappropriate shock during 5 years of follow-up was 18%, which is associated with the increased risk of all-cause mortality [4]. In addition, in the pooled analysis of randomized clinical trials, 9.1% of patients experienced complications associated with ICD over 16 months [5]. Given the expense and risks of ICDs, accurately differentiating patients at higher risk of SCD is important.Based on current guidelines, ICD for primary prevention is recommended in symptomatic patients with left ventricular ejection fraction (LVEF) <35% who did not respond to medical treatment (Table 1) [6][7][8]. Therefore, to date, transthoracic echocardiography (TTE) has played a major role for identifying patients with severe left ventricular (LV) dysfunction and higher risk of SCD. However, the issue on the selection of patients for ICD implantation based on LVEF using TTE has been raised constantly [8,9]. First, although two-dimensional (2D) TTE remains the most commonly used technique for the measurement of LVEF, it is based on geometric assumptions and is often limited by the sonic window. Second, use of LVEF alone showed a lack of sensitivity and specificity for the prediction of SCD. Although patients with severe LV dysfunction were shown to be at higher risk, they constitute less than one third of SCD cases [10,11]. In many instances, SCDs occur as the first manifestation of heart disease or in patients with a heart disease but with no or mild LV systolic dysfunction [12]. In a community-based prospective study entitled Oregon Sudden Unexpected Death Study, only 20% of patients who experienced SCD were eligible for ICD implantation based on the current guidelines that included LVEF and symptoms [13].Recently, great technical advances and diminished scan times have been achieved in the field of cardiac magnetic resocc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Sudden cardiac death (SCD) is a significant problem worldwide and the risk strati...