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Pathophysiology Underlying the Bimodal Edema Phenomenon After Myocardial Ischemia/Reperfusion
Rodrigo Fernández-Jiménez1, Jaime García-Prieto2, Javier Sánchez-González3
1Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain; Hospital Universitario Clínico San Carlos, Madrid, Spain.
Insights
The two waves of myocardial edema after ischemia/reperfusion (I/R) are distinct. The initial edema is caused by reperfusion, while the delayed edema is linked to the heart’s tissue healing processes.
Area of Science:
- Cardiovascular Research
- Pathophysiology
- Myocardial Infarction
Background:
- Post-ischemia/reperfusion (I/R) myocardial edema exhibits a bimodal pattern: an initial wave upon reperfusion and a deferred wave days later.
- Understanding the mechanisms behind this bimodal edema is crucial for managing myocardial infarction outcomes.
Purpose of the Study:
- To investigate the underlying pathophysiology of the bimodal edematous reaction following myocardial ischemia/reperfusion.
- To differentiate the causes of the early and delayed edema waves.
Main Methods:
- Utilized 40 instrumented pigs subjected to various myocardial infarction protocols.
- Assessed edema via water content quantification, serial cardiac magnetic resonance T2-mapping, and histology/immunohistochemistry.
- Compared reperfused versus non-reperfused ischemia models and evaluated the impact of steroid therapy.
Main Results:
- Maximal interstitial edema occurred early post-reperfusion, with peak neutrophil, macrophage, and collagen content at 24 hours, day 4, and day 7, respectively.
- Reperfused pigs showed significantly higher myocardial water content and T2 relaxation times.
- Permanent occlusion or steroid therapy reduced day 7 edema, altering T2 relaxation dynamics.
Conclusions:
- The two edema waves post-I/R have different pathophysiological origins.
- The initial edema wave is a direct consequence of reperfusion.
- The deferred edema wave is primarily driven by tissue healing processes.
Background:
Post-ischemia/reperfusion (I/R) myocardial edema was recently shown to follow a consistent bimodal pattern: an initial wave of edema appears on reperfusion and dissipates at 24 h, followed by a deferred wave that initiates days after infarction, peaking at 1 week.
Objectives:
This study examined the pathophysiology underlying this post-I/R bimodal edematous reaction.
Methods:
Forty instrumented pigs were assigned to different myocardial infarction protocols. Edematous reaction was evaluated by water content quantification, serial cardiac magnetic resonance T2-mapping, and histology/immunohistochemistry. The association of reperfusion with the initial wave of edema was evaluated in pigs undergoing 40-min/80-min I/R and compared with pigs undergoing 120-min ischemia with no reperfusion. The role of tissue healing in the deferred wave of edema was evaluated by comparing pigs undergoing standard 40-min/7-day I/R with animals subjected to infarction without reperfusion (chronic 7-day coronary occlusion) or receiving post-I/R high-dose steroid therapy.
Results:
Characterization of post-I/R tissue changes revealed maximal interstitial edema early on reperfusion in the ischemic myocardium, with maximal content of neutrophils, macrophages, and collagen at 24 h, day 4, and day 7 post-I/R, respectively. Reperfused pigs had significantly higher myocardial water content at 120 min and T2 relaxation times on 120 min cardiac magnetic resonance than nonreperfused animals. Permanent coronary occlusion or high-dose steroid therapy significantly reduced myocardial water content on day 7 post-infarction. The dynamics of T2 relaxation times during the first post-infarction week were altered significantly in nonreperfused pigs compared with pigs undergoing regular I/R.
Conclusions:
The 2 waves of the post-I/R edematous reaction are related to different pathophysiological phenomena. Although the first wave is secondary to reperfusion, the second wave occurs mainly because of tissue healing processes.
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