The novel role of Micro T-Wave alternans in arrhythmic risk stratification of patients with left ventricular dysfunction

According to the recent class I recommendation of ACC/AHA guidelines, all patients with an ischemic and non-ischemic cardiomyopathy, New York Heart Association (NYHA) functional class II­III and left ventricular ejection fraction (LVEF) ≤ 30% could benefit from implantable cardioverter defibrillator (ICD) therapy for primary prevention of sudden cardiac death (SCD). Nevertheless, trials have highlighted a small absolute reduction in annual mortality from ICD therapy in this population. Moreover, costs of these devices would be excessive for medical care. For these reasons, it is nowadays mandatory to further identify in this big population a low arrhythmic risk subgroup of patients who is unlikely to benefit from ICD placement. On the other hand, by focusing only on LVEF ≤ 30% as risk predictor for SCD, there is the danger of missing a significant number of patients with LVEF beyond this value that might benefit from ICD therapy. In the last few years, several clinical studies have demonstrated that micro T-wave alternans (MTWA), a new stratifier for arrhythmic risk, is an effective tool to identify patients with LVEF ≤ 30% who are at low risk of SCD, and who are unlikely to require ICD therapy. Moreover, recent data have confirmed that MTWA is a promising stratifier for malignant arrhythmias in patients with LVEF ranging from 30 to 40%, so that this new non-invasive test could be useful also in this “borderline” population to identify high risk patients not meeting ICD eligibility criteria of current guidelines.