Background information concerning the topics of the First Symposium of the IIfTC

"The Ischemic myocardium. Definitions, Measurements and Pathophysiology"

The opening symposium of this institute was devoted to the theme: "The ischemic myocardium: definitions, measurements, and pathophysiology". The emphasis of this meeting was an analysis of the assumed conceptual framework within which the reported observations were interpreted.

Questions arose early as to the very definition of ischemia. Some researchers felt that a state of ischemia occurs as soon as blood flow becomes insufficient to sustain normal contractile function. Other researchers advocated a different definition of ischemia that accounts for the phenomenon of "down-regulation". Down-regulation is a reduction in myocardial function caused by partial restriction of coronary blood flow, such that the reduction in function is sufficient to prevent any "damage" to the myocardium as a result of the reduced flow. Thus, the alternate definition considers ischemia to be a state in which blood supply is insufficient to meet the oxygen requirements of the myocardium at its reduced level of contractile function. In this sense, the down-regulated myocardium is not ischemic. Accordingly, an obviously ischemic myocardium by the former definition may not be ischemic at all by the latter definition.

Is it at all necessary to have a unifying definition of ischemia, or is it enough to have several working definitions that would satisfy the temporary needs of scientists doing their experimental research? Some of the participants felt that mutually exclusive working definitions of the same concept were unproblematic, so long as everyone was aware of the explicit definition in use. From an epistemological point of view, then, crucially important questions were: (1) how the definitions interrelate, (2) how appropriately they classify the experimental phenomena being studied, and (3) how fruitful the definitions are for pointing up future studies.