The Peril of Reperfusion Injury

According to Mayo Clinic, myocardial ischemia a disease that takes place when blood flow to the heart muscle is decreased or blocked.¹ As a result, the patient may suffer from arrhythmia and heart attack. It is then plausible to guess that all the immediate dangers are over once the patient's body recuperates from ischemia by having the blood flow back to the myocardium following the ischemia. But, one can only wish that this is what happens because even the normal flow of blood after ischemia may not be as "normal" as we hope. It would not be too surprising though, if you had read my previous article on homeostasis and the consequences of breaking homeostasis since reperfusion is still a process that takes place after breaking the normal homeostasis of the body.

Understanding Reperfusion Injury

Reperfusion refers to the return of the blood flow to the tissue after undergoing ischemia. In heart, reperfusion can be beneficial in that a rapid reperfusion to the cardiocyte, or cardiac muscle cell, can reverse the damages that took place under ischemia. But, in some cases, this process of reperfusion may actually damage the cardiocytes and even lead to necrosis, which means the death of cells. Other damages of reperfusion injury include endothelial cell dysfunction, "which results in vasoconstriction, platelet and leukocyte activation, increased oxidant production, and increased fluid and protein extravasation."²

Dangers of Oxidative Stress

While there are various causes to reperfusion injury after ischemia, oxidative stress is worth discussing more than other factors. Increased blood flow to those tissues can create oxidative stress by changing the level of free oxygen radicals produced and modifying the metabolism of myocardium. Unlike regular oxygen, free oxygen radicals are very reactive and can cause damages to sarcolemma and enzymatic systems.² In terms of metabolisms, reperfusion injury prolongs the production of lactate, the product of anaerobic metabolism, which is problematic since our body is more effective at generating energy through aerobic metabolism.² The difference between anaerobic and aerobic basically explains why we can walk for miles while we usually burn out after several laps due to the limitation of anaerobic cellular respirations.

Attempts to Answer Reperfusion Injury

Because oxidative stress is a significant problem in reperfusion injury as stated earlier, antioxidants have been involved in clinical case studies to reduce the delayed time in converting from anaerobic to aerobic metabolism. Unfortunately, the results have not been definite and uncertain. Alternate angle of research that scientists and physicians are pursuing is now on pre-ischemic and pre-reperfusion to possibly look at preventing and limiting the degree of reperfusion injury.²

Positive Notes

A bright side about reperfusion injury is that because of the heavy involvement by oxygen, it gives a high level of incentives to researchers in both academic and pharmaceutical settings to explore the therapeutic solutions to it. This is very important because it is realistically not possible to hope for solutions to diseases that have low incentives to pharmaceutical companies. So, while there is not a direct solution currently, it is very possible that there will eventually be a solution to reperfusion injury because of the society's deep interest in heart diseases.

Works Cited

¹ Mayo Clinic Staff, "Myocardial Ischemia," http://www.mayoclinic.com/health/myocardial-ischemia/DS01179, Jan. 28, 2010.

² Verma S, Fedak PW, Weisel RD, Butany J, Rao V, Maitland A, Li RK, Dhillon B, Yau TM. 2002 May 21. "Fundamentals of Reperfusion Injury for the Clinical Cardiologist." Circulation. 105(20): 2322-6. This article is available for free on: http://circ.ahajournals.org/cgi/content/full/105/20/2332