Myocardial Microvascular Function

The functional significance of an epicardial stenosis is affected by numerous variables including lesion severity, microvascular function and the extent of collateral recruitment. I mpaired microvascular flow has been shown to be associated with adverse outcomes. Thus, the epicardial vessels of the coronary circulation cannot be considered in isolation but need to be considered together with the myocardial microvasculature. However, concurrent examination of epicardial and microvasculature resistances has been limited in the past by the requirement for simultaneous use of pressure and flow wires.

Using the pressure-sensor tipped guidewire (described above), a recently validated method of thermodilution to estimate flow has facilitated examination of integrated coronary physiology with a single wire allowing simultaneous assessment of both these resistances ( Figure 3 ). However, these parameters have not been examined in patients with acute coronary syndromes in whom microvascular dysfunction would be anticipated as a result of endothelial dysfunction and microembolisation.