LAUSR

Article history: Received 17 April 2018 Accepted 18 April 2018 due to the fact that the infarct-related artery supplied (e.g. via collaterals) also the myocardium previously supplied by the CTO coronary artery. Thus, the myocardium at risk may be larger in such patients. The results of the study should prompt clinicians to assess viability and ischemia with CMR in patients with STEMI andmultivessel disease, especially in thosewith a CTO. Thismay enable identification of patients Up to 25% of patients with obstructive epicardial coronary artery disease have a chronic total occlusion (CTO) of an epicardial coronary artery [1]. Such patients represent a heterogeneous group as theymay have preservedor impaired left ventricular function, viable or scarredmyocardium and most importantly, they may be symptomatic or asymptomatic. Due to recent technical advances in interventional cardiology CTOpercutaneous coronary intervention (PCI) is now feasible in many cases [2], yet until now no randomized controlled trial has shown whether or not CTO-PCI has a prognostic impact. Factors such as coronary anatomy (e.g. vessel size, take-off and presence of collaterals), viability and myocardial ischemia are likely to influence CTO-PCI success and prognosis. Although previous data have shown that the presence of a CTO in patients with acute coronary syndrome (ACS) is associated with worse outcome compared to patients with ACSwithout a CTO [3], data on the underlying reasons for the observed outcome is lacking. In this issue of the journal, a study by Saad et al. [4] fills this gap and provides explanations for these previous clinical observations using cardiac magnetic resonance imaging (CMR). The authors assessed a large cohort of patients with ST-segment myocardial infarction (STEMI) undergoing primary PCI and performed CMR for viability, left ventricular ejection fraction (LVEF) and myocardial salvage indexwithin the first 10 days after the index event. Patients were divided into those with single vessel disease, multivessel disease with CTO and multivessel disease without concomitant CTO. The authors showed that patients with STEMI, multivessel disease and concomitant CTO in a non-infarct related artery had larger infarcts, lower myocardial salvage index and worse LVEF compared to the other patient groups. Moreover, the authors were able to demonstrate that the former group of patients had significantly more endpoint events over a follow-up period of 12month using death, re-infarction and re-admission for heart failure as the primary endpoint. In addition, multivessel disease with concomitant CTO was a significant independent predictor of clinical outcome. The authors should be congratulated for having performed this study. The results of the study are conceivable as LVEF alone has previously been shown to be an independent predictor of outcome in ACS patients [5]. The