The role of cardiac magnetic resonance non-contrast T1 mapping in differentiation between injured and salvaged myocardium in acute and chronic myocardial infarction

Introduction

Cardiac magnetic resonance (CMR) has grown over the past several years as a widely used modality in the evaluation of myocardial injury, which is mostly based on the late enhancement (LE) technique [1–3]. The recently developed CMR mapping imaging is a promising tool in myocardial evaluation, which relies on changes in T1 and T2 relaxation times and extracellular volume (ECV) [1–3]. Contrary to LE, the native T1 and T2 mapping technique is a quantitative evaluation, does not require administration of gadolinium contrast, and may be helpful in the evaluation of patients in whom contrast is contraindicated, such as those with severe renal failure.
T1 mapping relaxation values reveal prolongation in edema and necrosis with their relative shortening in fibrosis and hemorrhage [1]. Thus, T1 mapping is a promising technique in the detailed evaluation of acute and chronic myocardial injury [2]. In acute myocardial infarction, edema and necrosis are observed due to destruction of cell membranes and can be detected using the T1 mapping technique as an increase in its value [4]. Microvascular obstruction (MVO) in the infarct core (no-reflow phenomenon) can also be evaluated in native T1 mapping, where pseudo-normalization of T1 values are seen due to the accumulation of methemoglobin (T1 shortening effect). In a chronic infarct, necrotic tissue is replaced by fibrosis or lipids, which is revealed by a decrease in native T1 mapping value when compared to the acute stage However, there is a paucity of data concerning the relationship between T1 mapping values of the peri-infarct area and remote myocardium in acute and chronic stages of the infarct.

Aim

Therefore, the aim of our study was to perform comparative quantitative evaluation of the T1 mapping values of the infarcted and salvaged myocardium in acute and chronic stages of the infarct.

Material and methods

Cardiac magnetic resonance examinations were performed in patients with acute STEMI and in the 6-month follow-up on a 3T Magnetom Skyra scanner (Siemens, Erlangen, Germany). Images were obtained in consecutive short-axis slices covering the left ventricle (LV) and three long-axis (2-, 3-, and 4-chamber) slices. T1 mapping was performed using the Modified Look-Locker Inversion-Recovery (MOLLI) sequence. Consecutive short-axis LE images covering the LV were obtained approximately 10–15 min after administration of a gadolinium-based contrast agent (0.1...


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