TT-CMR provided prognostic information soon after STEMI. However, it did not substantially improve risk reclassification beyond traditional CMR indexes.

We aimed to characterize the organization of collagen within a fibrotic scar in swine and human samples from patients with chronic infarctions. Swine were subjected to occlusion of the left anterior descending artery followed by reperfusion 1 week (acute myocardial infarction group) or 1 month (chronic myocardial infarction group) after infarction. The organization of the collagen fibers (Fast Fourier Transform of samples after picrosirius staining; higher values indicate more disorganization) was studied in 100 swine and 95 human samples. No differences in collagen organization were found between the acute and chronic groups in the core area of the scar in the experimental model. In the chronic group, the endocardium [0.90 (0.84-0.94); median (interquartile range)], epicardium [0.84 (0.79-0.91)] and peripheral area [0.73 (0.63-0.83)] displayed a much more disorganized pattern than the core area of the fibrotic scar [0.56 (0.45-0.64)]. Similarly, in human samples, the collagen fibers were more disorganized in all of the outer areas than in the core of the fibrotic scar (P < 0.0001). Both in a highly controlled experimental model and in patient samples, collagen fibers exhibited an organized pattern in the core of the infarction, whereas the outer areas displayed a high level of inhomogeneity. This finding contributes pathophysiological information regarding the healing process and may lead to a clearer understanding of the genesis and invasive treatment of arrhythmias after acute myocardial infarction.

This study aimed to assess the time course of circulating neutrophil and lymphocyte counts and their ratio (NLR) in ST-segment elevation myocardial infarction (STEMI) and coronavirus disease (COVID)-19 and explore their associations with clinical events and structural damage. Circulating neutrophil, lymphocyte and NLR were sequentially measured in 659 patients admitted for STEMI and in 103 COVID-19 patients. The dynamics detected in STEMI (within a few hours) were replicated in COVID-19 (within a few days). In both entities patients with events and with severe structural damage displayed higher neutrophil and lower lymphocyte counts. In both scenarios, higher maximum neutrophil and lower minimum lymphocyte counts were associated with more events and more severe organ damage. NLR was higher in STEMI and COVID-19 patients with the worst clinical and structural outcomes. A canonical deregulation of the immune response occurs in STEMI and COVID-19 patients. Boosted circulating innate (neutrophilia) and depressed circulating adaptive immunity (lymphopenia) is associated with more events and severe organ damage. A greater understanding of these critical illnesses is pivotal to explore novel alternative therapies.

No abstract

In extensive nonreperfused myocardial infarction (MI), remote fibrosis has been documented. Early reperfusion by primary angioplasty represents the gold standard method to minimize the extension of the infarction. We aimed to ascertain whether fibrosis also affects remote regions in reperfused MI in swine and patients. Swine were subjected to a transient occlusion of the left anterior descending artery followed by 1-week or 1-month reperfusion. Collagen content in the remote area macroscopically, microscopically, by magnetic resonance microimaging, and at the molecular level was similar to controls. In patients with previous MI, samples from autopsies displayed a significant increase in collagen content only in the infarct region. In patients with previous MI submitted to cardiac magnetic resonance-T1 mapping, the extracellular volume fraction in remote segments was similar to that for controls. In all scenarios, the remote region did not show a significant increase of collagen content in comparison with controls.

Delayed enhancement cardiovascular magnetic resonance (MR) is the gold-standard for non-invasive assessment after myocardial infarction (MI). MR microscopy (MRM) provides a level of detail comparable to the macro objective of light microscopy. We used MRM and correlative histopathology to identify infarct and remote tissue in contrast agent-free multi-sequence MRM in swine MI hearts. One control group (n = 3 swine) and two experimental MI groups were formed: 90 min of ischemia followed by 1 week (acute MI = 6 swine) or 1 month (chronic MI = 5 swine) reperfusion. Representative samples of each heart were analysed by contrast agent-free multi-sequence (T1-weighting, T2-weighting, T2*-weighting, T2-mapping, and T2*-mapping). MRM was performed in a 14-Tesla vertical axis imager (Bruker-AVANCE 600 system). Images from MRM and the corresponding histopathological stained samples revealed differences in signal intensities between infarct and remote areas in both MI groups (p-value < 0.001). The multivariable models allowed us to precisely classify regions of interest (acute MI: specificity 92% and sensitivity 80%; chronic MI: specificity 100% and sensitivity 98%). Probabilistic maps based on MRM images clearly delineated the infarcted regions. As a proof of concept, these results illustrate the potential of MRM with correlative histopathology as a platform for exploring novel contrast agent-free MR biomarkers after MI.

No abstract

Background Following myocardial infarction (MI), we aimed to characterize morphometric and genetic changes in extracellular matrix (ECM) components from ischemia onset until late phases after coronary reperfusion in necrotic and salvaged myocardium. Results Swine were divided into one control ( n = 5) and three MI groups: 90-min of ischemia without reperfusion, or followed by 1-week or 1-month reperfusion ( n = 5 per group). In samples from the necrotic and salvaged areas, ECM components were morphometrically quantified and mRNA levels of factors involved in ECM remodeling were evaluated. After 90-min of ischemia, fibronectin, laminin, and elastic fibers content as well as upregulated mRNA expression of tissue inhibitors of metalloproteinases (TIMP)1, TIMP2, TIMP3 and connective tissue growth factor increased in the necrotic and salvaged myocardium. In both reperfused MI groups, collagen-I, collagen-III, elastic fibers, glycosaminoglycans, laminin, and fibronectin levels heightened in the necrotic but not the salvaged myocardium. Moreover, mRNA expression of TIMP1, TIMP2 and TIMP3, as well as metalloproteinase-2 and metalloproteinase-9 heightened in the necrotic but not in the salvaged myocardium. Conclusions Matrix remodeling starts after ischemia onset in both necrotic and salvaged myocardium. Even if ECM composition from the salvaged myocardium was altered after severe ischemia, ECM makes a full recovery to normal composition after reperfusion. Therefore, rapid coronary reperfusion is essential not only to save cardiomyocytes but also to preserve matrix, thus avoiding impaired left ventricular remodeling.