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Published on: February 16, 2016
Myocardial edema after ischemia/reperfusion is not stable and follows a bimodal pattern: imaging and histological
Rodrigo Fernández-Jiménez1, Javier Sánchez-González2, Jaume Agüero3
1Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain; Hospital Universitario Clínico San Carlos, Madrid, Spain.
Insights
Myocardial edema after ischemia/reperfusion exhibits a bimodal pattern, with an initial wave resolving within 24 hours and a second wave peaking around day 7. This challenges the long-held view of persistent edema.
Area of Science:
- Cardiovascular Research
- Medical Imaging
- Histopathology
Background:
- Myocardial edema is traditionally thought to persist for at least one week post-ischemia/reperfusion.
- Previous studies lacked longitudinal data from very early to late reperfusion stages.
Purpose of the Study:
- To longitudinally characterize the edematous response after experimental myocardial ischemia/reperfusion using imaging and histology.
- To investigate the temporal pattern of myocardial edema in the first week post-reperfusion.
Main Methods:
- 25 Large-White pigs underwent 40-minute ischemia/reperfusion.
- Cardiac magnetic resonance (CMR) imaging (T2-weighted, T2-mapping) and histological water content analysis were performed at 120 minutes, 24 hours, 4 days, and 7 days post-reperfusion.
- Control group (n=5) underwent baseline CMR only.
Main Results:
- Reperfusion induced increased T2 relaxation times in the ischemic region.
- Myocardial edema showed a bimodal pattern: high at reperfusion, decreased by 24 hours, and increased again by day 7.
- CMR T2 times mirrored water content, returning to normal at 24 hours and rising by day 7.
Conclusions:
- Myocardial edema follows a bimodal pattern in the first week after ischemia/reperfusion, contrary to previous assumptions.
- An initial edema wave resolves within 24 hours.
- A secondary, progressive wave of edema emerges days after reperfusion, peaking around day 7.
Background:
It is widely accepted that edema occurs early in the ischemic zone and persists in stable form for at least 1 week after myocardial ischemia/reperfusion. However, there are no longitudinal studies covering from very early (minutes) to late (1 week) reperfusion stages confirming this phenomenon.
Objectives:
This study sought to perform a comprehensive longitudinal imaging and histological characterization of the edematous reaction after experimental myocardial ischemia/reperfusion.
Methods:
The study population consisted of 25 instrumented Large-White pigs (30 kg to 40 kg). Closed-chest 40-min ischemia/reperfusion was performed in 20 pigs, which were sacrificed at 120 min (n = 5), 24 h (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 and T2-mapping sequences were performed at every 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-h CMR, ischemic myocardium T2 times returned to normal values (similar to those seen pre-infarction). 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: 2 high water content peaks at reperfusion and at day 7, and a significant decrease at 24 h.
Conclusions:
Contrary to the accepted view, myocardial edema during the first week after ischemia/reperfusion follows a bimodal pattern. The initial wave appears abruptly upon reperfusion and dissipates at 24 h. Conversely, the deferred wave of edema appears progressively days after ischemia/reperfusion and is maximal around day 7 after reperfusion.
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