Quantitative and qualitative assessment of acute myocardial injury by CMR at multiple time points after acute myocardial infarction.

BACKGROUND: Recent experimental studies have shown a dynamic time course of myocardial edema with an initial wave of edematous reaction within hours after reperfusion which almost resolved at 24 h. However, this dynamic pattern appears to be absent in clinical cohort studies. Thus far, no studies have combined a quantitative and qualitative assessment of acute myocardial injury in a large clinical cohort to explain these divergent findings. METHODS: A cohort of 225 patients (59 ±â€¯11 years, 83% men) with successfully reperfused STEMI within 12 h of symptom onset were included. Quantitative measurements of myocardial damage such as T1 mapping and T2 triple short-tau inversion recovery (STIR), contrast-to-noise ratio (CNR) and their impact on area-at-risk (AAR), infarct size (IS), and myocardial salvage index (MSI) were assessed at different time points. One-way analysis of variance (ANOVA) and linear regression analysis was used to compare myocardial damage at the different time points. RESULTS: A small fraction of patients underwent CMR within 24 h of reperfusion (17/225, 7.6%). No significant variations in AAR, IS, MSI, T2 STIR CNR, or native T1 maps were observed between the different time points after reperfusion. Time of CMR was not a significant predictor of AAR (P = 0.90), IS (P = 0.27), MSI (P = 0.23) or T2 STIR CNR (P = 0.23). CONCLUSIONS: The majority of CMR exams in STEMI patients are performed outside the dynamic time window of early post-MI edema. The stable pattern of markers of acute myocardial damage at different time points suggests these markers are reliable for the prognostication of patients after STEMI.

Cardiovascular magnetic resonance myocardial feature tracking using a non-rigid, elastic image registration algorithm: assessment of variability in a real-life clinical setting.

BACKGROUND: Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a promising technique for quantification of myocardial strain from steady-state free precession (SSFP) cine images. We sought to determine the variability of CMR-FT using a non-rigid elastic registration algorithm recently available in a commercial software package (Segment, Medviso) in a real-life clinical setting. METHODS: Firstly, we studied the variability in a healthy volunteer who underwent 10 CMR studies over five consecutive days. Secondly, 10 patients were selected from our CMR database yielding normal findings (normal group). Finally, we prospectively studied 10 patients with known or suspected myocardial pathology referred for further investigation to CMR (patient group). In the patient group a second study was performed respecting an interval of 30 min between studies. All studies were manually segmented at the end-diastolic phase by three observers. In all subjects left ventricular (LV) circumferential and radial strain were calculated in the short-axis direction (EccSAX and ErrSAX, respectively) and longitudinal strain in the long-axis direction (EllLAX). The level of CMR experience of the observers was 2 weeks, 6 months and >20 years. RESULTS: Mean contouring time was 7 ± 1 min, mean FT calculation time 13 ± 2 min. Intra- and inter-observer variability was good to excellent with an coefficient of reproducibility (CR) ranging 1.6% to 11.5%, and 1.7% to 16.0%, respectively and an intraclass correlation coefficient (ICC) ranging 0.89 to 1.00 and 0.74 to 0.99, respectively. Variability considerably increased in the test-retest setting with a CR ranging 4.2% to 29.1% and an ICC ranging 0.66 to 0.95 in the patient group. Variability was not influenced by level of expertise of the observers. Neither did the presence of myocardial pathology at CMR negatively impact variability. However, compared to global myocardial strain, segmental myocardial strain variability increased with a factor 2-3, in particular for the basal and apical short-axis slices. CONCLUSIONS: CMR-FT using non-rigid, elastic registration is a reproducible approach for strain analysis in patients routinely scheduled for CMR, and is not influenced by the level of training. However, further improvement is needed to reliably depict small variations in segmental myocardial strain.