Author`s reply.

To the Editor,

We would like to thank authors for her comments and interest in our study “No association between scar size and characteristics on T-wave alternans in postmyocardial infarction patients with relatively preserved ventricular function presented with non-sustained ventricular tachycardia”, published in Anatolian J Cardiol 2014; 14: 442-447 (1). In our study, we used a relatively small post-MI patient group with nonsustained ventricular tachycardia and mild systolic dysfunction and compared two noninvasive arrhythmic risk methods that are accurate in this population (2, 3). We found no relationship between scar parameters and presence of T wave alternans. A study by Kraaier et al. (4), published at a similar time as our study, investigated the relationship between T-Wave alternans (TWA) and scar, assessed with CMR, in patients with depressed left ventricular functions. In this small study, neither in patients with ICM or DCM a relation was found between the occurrence of TWA and the presence, transmurality, or extent of myocardial scar. Their study shows that, our results may be conclusive in patients with depressed LV functions.

Current guidelines recommend insertion of ICDs for patients with reduced left ventricular ejection fraction (LVEF), but the majority of sudden deaths occurs in patients with only moderately reduced or preserved LVEF (5). Identification of patients who are at high risk of dying suddenly is an unresolved clinical challenge.

LVEF, as a classical risk factor, is an indirect measurement of scar size. Many factors may affect LVEF, in addition to scar size, such as preload, afterload, autonomic factors medications, and post-infarction remodeling (6). For this reason, measurement of the scar size by CMR may give additional prognostic information beyond LVEF. Klem et al. (7) tested whether an assessment of myocardial scarring by cardiac MRI would improve risk stratification in patients evaluated for ICD implantation. In patients with LVEF >30%, significant scarring (>5% LV) identifies a high-risk cohort with similar risk as in those with LVEF ≤30%. Conversely, in patients with LVEF ≤30%, minimal or no scarring identifies a low-risk cohort similar to those with LVEF >30% (7). We therefore found that a larger peri-infarction zone, seen by CMR, is associated with ventricular tachycardia inducibility in post-MI patients with preserved LVEF. In our study, LVEF was similar among patients with and without VT inducibility (8).

Risk assessment of sudden death in patients with relatively preserved LVEF is still an unsolved issue. Based on the hypothesis, also supported by our study (8), Kadish et al. (9) designed the Defibrillators to Reduce Risk by Magnetic Resonance Imaging Evaluation (DETERMINE) Trial. The goal of this study was to test the hypothesis that patients with an infarct size of >10%, randomized to ICD and medical therapy, will have improved survival as compared to those randomized to medical therapy alone. CMR would have been performed in patients with CAD and LVEF of >35% and less than 50% (or patients with an LVEF of 30%-35% and New York Heart Association class I heart failure without a history of ventricular arrhythmias). Death from any cause was selected as the endpoint for the trial. Unfortunately, to reach the target randomization, approximately 10,000 patients would never have been screened with CMR. Due to slow enrollment, this study recently halted. We believe that randomized trials with follow-up with CMR will identify patients who need an ICD after myocardial infarction better than standard techniques in the near future.