Interaction between Gregg's phenomenon and coronary flow control: a model study

Coronary perfusion pressure, Pp, affects coronary arterial resistance, Ra, (autoregulation) as well as myocardial oxygen consumption, MVo(2) (Gregg's phenomenon). The interaction between the effects of Pp and MVo(2) on corona ry flow control was investigated using a coronary flow control model. Model analysis predicts that response of the pressure-flow ratio, p/q(t), follow ing a change in Pp depends on the sensitivity of Ra to a change in tissue o xygen concentration (tone sensitivity) and on the sensitivity of MVo(2) to a change in capillary pressure (Gregg's sensitivity). At high tone sensitiv ity Gregg's effect is small, whereas at high Gregg's sensitivity autoregula tion is attenuated. In experiments glibenclamide decelerated the p/q(t) in response to a pressure step by a factor of four. However, the proposed mode l demonstrates that this is compatible with a reduction in rate of change o f Ra by a factor of ten. This is due to the interaction of negative and pos itive feedback gains in the model. Model analysis demonstrates that autoreg ulation and Gregg's phenomenon compete with each other in controlling coron ary flow.