This study was a prospective observational study that was conducted upon 25 patients presented to the cardiology department in Ain Shams University hospitals in the time interval from August 2016 to January 2017.
The study was approved by the Research Ethics Committee (Faculty of Medicine, Ain Shams University, FWA 00006444) and all patients signed an informed consent for participation in the study in accordance with the Declaration of Helsinki. We included patients presented with acute STEMI (any territory) within the first 12 h after onset of chest pain who were candidates for PPCI according to the most recent practice guidelines [6, 7]. There was no age or sex predilection.
Patients with delayed presentation (> 12 h), any previous history of ischemic heart diseases, hemodynamic instability, renal impairment (serum creatinine > 2 mg/dl), contraindications to MRI (claustrophobia, an implanted metallic device, pacemakers …), pregnant and lactating females were excluded from the study.
Eligible patients presented with acute STEMI were directly transferred with close monitoring to the catheterization laboratory after doing a rapid thorough clinical examination and signing an informed consent. Rapid evaluation with bedside echocardiography to exclude mechanical complications was done for all patients. All patients received an oral loading dose of Aspirin 300 mg and Clopidogrel 600 mg. Coronary angiography was done rapidly by operators highly experienced in PPCI using adequate orthogonal views to detect the culprit lesion. PPCI was done aiming at flow restoration in the culprit artery. Patients were then transferred to coronary care unit (CCU) under close monitoring and were kept on anti-ischemic measures.
All relevant characteristics of our patients were recorded including demographic characteristics, presence of major cardiovascular risk factors, myocardial territory affected, Killip class on presentation , procedural variables (thrombolysis in myocardial infarction [TIMI] flow before and after the procedure , use of thrombectomy device, method of revascularization [PTCA or stenting], type of stents, number of stents, myocardial blush grade [MBG]  after revascularization and presence of other major non-culprit artery stenosis) and postprocedural variables (peak cardiac enzymes, echocardiography variables and short-term complications related to MI or PCI procedure).
CMR was done 2–4 days after PPCI at the Radiodiagnosis Department, Ain Shams University using a 1.5 Tesla superconductive MR scanner (Philips Achieva-XR Medical Systems, Best, the Netherlands) with dedicated phased array Cardiac coil for enhanced resolution and increased signal-to-noise ratio.
The basic protocol included were single-shot black blood (axial, sagittal and coronal views), Cine short axial views, Cine 4 chamber views, Dynamic fast field echo (FFE) and Lock Locker.
The main sequences that were interpreted in this study were:
T2WI STIR (TR 2 beats, TE 80) (to detect the edematous changes in the form of bright signal intensity changes)
Post-contrast imaging: gadolinium was administered as bolus of 0.1 mmol/kg then delayed imaging from 10 to 30 min according to lock locker. (To detect the ischemic territorial affection, infarct size, percentage of microvascular occlusion).
In patients with microvascular obstruction (MO), the dark areas were included within infarct size analysis and the area of MO was evaluated separately.
Then the following parameters were calculated:
Area at risk = edema volume/volume of left ventricle (LV) mass.
Percentage of infarct size (infarction fraction) = infarction volume/volume LV mass.
Percentage of MO = volume MO/volume LV mass.
Myocardial salvage = area at risk - infarct size.
Myocardial salvage index (MSI) = area at risk - infarct size/area at risk.
The primary endpoint of the study was the occurrence of any major adverse cardiovascular events (MACE) defined as death or re-infarction or new-onset heart failure at 6 months follow-up after the index event.
Data were analyzed using MedCalc© version 15 (MedCalc© Software bvba, Ostend, Belgium) and version 23 (IBM© SPSS© Statistics IBM© Corp., Armonk, NY, USA) and normality of numerical data distribution was examined using the D’Agostino-Pearson test. Non-normally distributed numerical variables were presented as median and interquartile range and between-group differences were compared by the Mann-Whitney test. Categorical variables were presented as the percentage and number. P value was used to determine the statistical significance. A value of 0.05 is arbitrary a cut-off value; below it, the relationship between variables is considered statistically significant, and above it, the relation is considered statistically not significant.