A 65-year-old Caucasian male presents to the ER with sudden onset of right-sided calf and foot pain. His past medical history is significant for hypertension, type II diabetes mellitus, atrial fibrillation and stable angina. Physical examination reveals paleness of the right leg and diminished right popliteal pulse. Immediate angiography is ordered that reveals an obstructive thrombus in the right common femoral artery. The thrombus extraction is followed by a rapid surge of serum creatine kinase level, which is best explained by:

Question

A 65-year-old Caucasian male presents to the ER with sudden onset of right-sided calf and foot pain.  His past medical history is significant for hypertension, type II diabetes mellitus, atrial fibrillation and stable angina.  Physical examination reveals paleness of the right leg and diminished right popliteal pulse.  Immediate angiography is ordered that reveals an obstructive thrombus in the right common femoral artery.  The thrombus extraction is followed by a rapid surge of serum creatine kinase level, which is best explained by:

Quizplus · Accepted Answer

Ischemia is characterized by the reduction of blood flow, usually as a result of mechanical obstruction within the arterial system (eg, thrombus). If the flow of blood to the ischemic tissue is restored in a timely manner, those cells that were reversibly injured will typically recover. Sometimes, however, the cells within the damaged tissue will paradoxically die at an accelerated pace through apoptosis or necrosis after resumption of blood flow. This process is termed reperfusion injury, and is thought to occur secondary to one or more of the following mechanisms: 1) oxygen free radical generation by parenchymal cells, endothelial cells, and leukocytes; 2) severe, irreversible mitochondrial damage described as "mitochondrial permeability transition"; 3) inflammation, which attracts circulating neutrophils that cause additional injury; and 4) activation of the complement pathway, causing cell injury and further inflammation. When the cells within heart, brain, or skeletal muscle are injured, the enzyme creatine kinase leaks across the damaged cell membrane and into circulation (as seen in this patient). (Choice A) Cellular swelling arises secondary to changes in ion concentration and the influx of water. This state is considered a hallmark of reversible injury, and is not directly associated with the leakage of intracellular proteins such as creatine kinase. (Choice C) Glutathione peroxidase actually reduces cellular injury by catalyzing free radical breakdown. The presence of this enzyme is not responsible for the release of creatine kinase. (Choice D) Mitochondrial vacuolization reduces the cellular capacity for ATP generation and is associated with irreversible injury. Creatine kinase release is not directly associated with this mitochondrial change, however. (Choice E) Nuclear shrinkage (pyknosis), fragmentation, and dissolution characterize irreversible injury of the cell. Creatine kinase release is not directly associated with such nuclear changes, however. Educational Objective: Reperfusion injury is thought to occur secondary to oxygen free radical generation, mitochondrial damage, and inflammation.

A 65-Year-Old Caucasian Male Presents to the ER with Sudden