Abstract
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.
Highlights
Delayed enhancement cardiovascular magnetic resonance (MR) is the gold-standard for noninvasive assessment after myocardial infarction (MI)
One control group (n = 3 swine) and two experimental MI groups were formed: 90 min of ischemia were followed by 1 week or 1 month reperfusion
The images obtained from the histology were compared with those derived from MR microscopy (MRM) in order to identify the remote and infarct areas in the MRM images (Fig. 1)
Summary
Delayed enhancement cardiovascular magnetic resonance (MR) is the gold-standard for noninvasive assessment after myocardial infarction (MI). We used MRM and correlative histopathology to identify infarct and remote tissue in contrast agent-free multi-sequence MRM in swine MI hearts. Delayed enhancement cardiovascular magnetic resonance (MR) is the most used imaging technique for comprehensive non-invasive assessment of the structural consequences of myocardial infarction (MI) in patients[1]. Novel sequences recently incorporated into the clinical armamentarium are designed to indirectly evaluate fibrotic tissue (T1-post contrast and extracellular volume fraction), the presence of oedema during the acute post-MI phase (T1-mapping5,6), and the extent of haemorrhage in the infarcted area (T2*-mapping[2]). Left panel showing acute MI images (A): Histopathological stain with haematoxylin-eosin (a,e), T1-weighted imaging (b,f), T2-weighted imaging (c,g) and T2*-weighted image (d,h) for remote and infarcted tissues respectively. High tissue contrast makes it the method of choice to measure infarct size and determine the transmural extent of infarction[7,8]
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