Myocardial Protection During Reperfusion

Abstract

After prolonged periods of energy depletion, myocardial cells may rapidly deteriorate during the early stage of reperfusion. It has now been clearly demonstrated that this kind of acute lethal reperfusion injury is due to specific processes elicited by cellular re-energization. The most prominent single cause of acute harm to the reoxygenated myocardial cells is myofibrillar hypercontraction. Hypercontraction is caused by a resupply of energy of the myofibrils at excessive cytosolic Ca²⁺ concentrations. Additionally, the ability of the cytoskeleton to withstand large mechanical forces seems to be weakened after a prolonged period of energy depletion. Intracellular acidosis during the early stage of reperfusion represents a natural mechanism of protection against acute reperfusion injury. The reperfused myocardial cell may also suffer from uncontrolled water uptake and increased sarcolemmal fragility, favoring osmotic damage of cell membranes. As yet therapeutical interventions trying to specifically interfere with these pathomechanisms of reperfusion injury have only been tested experimentally. It seems promising to evaluate their utility for myocardial protection in cardio-surgical operations.

Key words

Reperfusion injury - Oxygen paradox - Myocardial protection - Calcium - Hypercontracture - Acidosis - Na⁺/H⁺exchange