The phenomenon of "stunned" myocardium: implications for coronary care nurses

In recent years, the use of thrombolytic therapy for the treatment of acute myocardial infarction has become the standard of care. A new phenomenon known as "stunned" myocardium has been described with the use of this treatment. Stunned myocardium refers to tissue that has been reperfused before of necrosis, but that remains dysfunctional. Stunned myocardium can regain its contractile function at any time from several hours to two weeks following reperfusion. It is important for nurses to understand this phenomenon and to incorporate this knowledge in the care of patients in the coronary care unit. Mechanisms that cause stunned myocardium are poorly understood. Some theories include: (a) reduction of ATP levels, (b) coronary artery microvascular spasm or plugging, (c) cytotoxic injury from oxygen-derived free radicals and (d) abnormalities of calcium flux. Nurses need to understand the response of stunned myocardium to various cardiac drugs when caring for post-myocardial infarction patients exhibiting heart failure. It is important to be aware that contractile function may not be optimal for up to two weeks after reperfusion.