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Myocardial Edema After Ischemia/Reperfusion Is Not Stable and Follows a Bimodal Pattern: Imaging and Histological Tissue Characterization | Journal Scan
Study Questions:
What are the temporal patterns of myocardial edema in the very early (minutes) to late (1 week) stages after post-ischemic myocardial reperfusion?
Methods:
In a study population of 25 instrumented large-white pigs (30-40 kg), 20 pigs underwent 40 minutes of closed-chest ischemia/reperfusion. Pigs were subsequently sacrificed at 120 minutes (n = 5), 24 hours (n = 5), 4 days (n = 5), and 7 days (n = 5) after reperfusion, and processed for histological quantification of myocardial water content. Cardiac magnetic resonance (CMR) scans with T2-weighted short-tau inversion recovery (T2W-STIR) and T2-mapping sequences were performed at each follow-up stage until sacrifice. Five additional pigs sacrificed after baseline CMR served as controls.
Results:
In all pigs, reperfusion was associated with a significant increase in T2 relaxation times in the ischemic region. On 24-hour CMR, ischemic myocardium T2 times returned to normal (similar to pre-infarction) values. Thereafter, ischemic myocardium-T2 times in CMR performed on days 4 and 7 after reperfusion progressively and systematically increased. On day 7, CMR T2 relaxation times were as high as those observed at reperfusion. Myocardial water content analysis in the ischemic region showed a parallel bimodal pattern: two high water content peaks at reperfusion and at day 7, and a significant decrease at 24 hours.
Conclusions:
Contrary to the accepted view, myocardial edema during the first week after ischemia/reperfusion follows a bimodal pattern. Edema initially appears abruptly upon reperfusion and dissipates at 24 hours; delayed edema appears progressively days after ischemia/reperfusion, and is maximal around day 7 after reperfusion.
Perspective:
An intense edematous reaction is known to occur after ischemia/reperfusion. This study, using both CMR and histological analysis in a large-animal model, suggests that there is a temporally bimodal edema response, with rapid appearance of edema early after reperfusion, subsequent dissipation within the next 24 hours, and later gradual representation of edema that peaks at approximately 7 days. This challenges the accepted view of a stable and persistent edematous reaction after ischemia/reperfusion, and could have translational implications in the assumption that myocardial edema is a marker of ischemic ‘memory.’
Keywords: Myocardial Reperfusion, Myocardium, Edema, Reperfusion, Infarction, Magnetic Resonance Imaging, Ischemia, Models, Animal
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