The dependence of myocardial ischaemia on the blance between supply and demand (that is, sdequacy of blood flow for a certain rate of cardiac work) is a well established concept. However, the basic mechanisms of autoregula- tion and metabolic regulation on which the concept depends may be less familiar. Other measures such as coronary flow reserve and potency of coronary vasodila- tors also depend on the coronary flow control diagram illustrated in fig 1. It is obvious that coronary arterial occlusion impairs Supply but this is certainly not so obvious if there is coro- Nary artery stenosis, because of the presence of autoregula- Tion.
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