Myocardial protection: an expanding or contracting discipline?

For the past thirty years cardiac surgeons have had a unique opportunity to study the consequences of myocardial ischemia and reperfusion. With the advent of an ability to intervene in acute myocardial syndromes, cardiologists have vigorously joined that effort as have fundamental scientists. Exogenous myocardial protective strategies have emerged as have novel strategies that take advantage of endogenous mechanisms of myocardial protection. As a consequence of improved myocardial protection, operative mortality and morbidity, in particular the low output syndrome, have diminished. However, despite important increases in the knowledge base referable to myocardial ischemia and reperfusion, major advances in myocardial protection have slowed in the past several years. This article explores potential untapped options for augmenting myocardial protection and focuses on the potential adverse interactions between cardiopulmonary bypass and myocardial protection as a prime target for future investigations leading to improved myocardial management during heart operations. Perfusion (2003) 18, 139i/143. It has been about 30 years since myocardial protection was identified as an important area for study by cardiac surgeons. I have had the opportunity to poll several audiences within the past few years regarding the management of two illustrative cases. One of these cases is a patient with complex coronary artery disease and the second is that of a patient with combined coronary and valvular heart disease. In each instance, I provided several options for the use of cardioplegia. These included the temperature and composition of the cardioplegia, the mode (antegrade and/or retrograde) delivery, the frequency of administration and the use of terminal warm cardioplegia. The point of most common agreement was that cardioplegia should be used and generally surgeons employ blood cardioplegia. Very few surgeons responded that they use complex buffering, metabolic fortification or normothermia. Most surgeons employ a selective use of retrograde cardioplegia and administer cardioplegia every 15 i/30 minutes. Remarkably, there was a great disparity among respondents if you consider the total cardioplegic strategy. I remain impressed at this fact, which may reflect the disagreement over the efficacy of the many advantages that complex cardioplegia compositions offer, a general satisfaction with the techniques individually employed or a dissociation between practical application and the science of myocardial protection. Surveys are useful to determine how effectively a body of evidence that may be derived from the literature is applied to daily practice. In this instance, the results are slightly surprising to the extent that one might have predicted a greater degree of uniformity of responses after 30 years of investigation in this field. Some of the reasons for these disparities are explored in this paper. When considering protection for the heart during cardiac operations, it is useful to consider the interaction between four elements common to most procedures. These are ischemia, reperfusion, cardiopulmonary bypass (CPB) and the operation performed. Each of these components of the surgery has the potential to induce injury. In any instance of injury, the inciting factor may be primarily the consequence of any one of these four causes, but the other three will always intensify the extent of injury. In recent years, the evolution of off-pump techniques for coronary bypass grafting has elimi