The Coronary Circulation in Acute Coronary Syndromes

Acute coronary syndromes constitute one of the most serious presentations of ischemic heart disease, accounting for a significant proportion of patients investigated and treated in the catheterization laboratory. When assessing both coronary stenoses and the microcirculation in the context of acute coronary syndromes (ACS), it is important to bear in mind that both ST elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTE-ACS) are associated with distinct modifications in coronary physiology and that therefore the principles applied to their assessment in chronic stable angina may not hold true. In this chapter we discuss the pathophysiology of the microvasculature during ACS followed by a review of the benefits and limitations of physiological assessment of both epicardial stenosis and the microvasculature during ACS.