Sudden cardiac death in non-ischemic dilated cardiomyopathy: a critical appraisal of existing and potential risk stratification tools.

Non ischemic dilated cardiomyopathy poses a significant risk of malignant ventricular arrhythmias and subsequent sudden cardiac death. The pathologic and electrophysiological substrate implicated to arrhythmogenesis has been quite adequately defined over the last decades and multiple forms of myocardial fibrosis - diffuse, patchy or gross scarring - are being studied regarding their arrhythmogenic potential. Moreover, the recent demonstration and continuous expansion of knowledge regarding causative genes in dilated cardiomyopathy open a new chapter in the field of diagnosis and prognosis of these patients. Numerous noninvasive and invasive methods have been used to stratify patients according to sudden cardiac death level of risk. Severely reduced left ventricular systolic myocardial function, expressed mostly by left ventricular ejection function, NYHA functional class, syncope and invasive electrophysiological study with programmed electrical stimulation have been incorporated into international guidelines, though leaving significant proportions of primary prevention patients out of stratification schemes. Electrocardiographic markers, signal-averaged ECG, heart rate variability, heart rate turbulence, baroreflex sensitivity, heart rate recovery and T-wave alternans have given conflicting results in non ischemic dilated cardiomyopathy. During the last decade, cardiac magnetic resonance, especially with gadolinium enhancement, has made a step forward in defining the fibrotic substrate of such patients. Prospective studies have given promising results, demonstrating correlation between late gadolinium enhancement and ventricular arrhythmogenesis. Identification of patients with genetically caused dilated cardiomyopathy prone to sudden cardiac death and large prospective trials investigating cardiac magnetic resonance and its prognostic potential may be able to establish a new era in stratification schemes.