Title:Microvascular Function/Dysfunction Downstream a Coronary Stenosis
Volume: 19
Issue: 13
Author(s): Giacinta Guarini, Paola Giuseppina Capozza, Alda Huqi, Doralisa Morrone, William M. Chilian and Mario Marzilli
Affiliation:
Keywords:
Coronary microcirculation, coronary stenosis, myocardial ischemia, endothelial dysfunction, atherosclerosis, cardiovascular disease, blood supply, myocardium, transient, coronary revascularization
Abstract: For decades coronary macrovascular atherosclerosis has been considered the principal manifestation of coronary heart disease,
with most of our effort dedicated to identifying and removal of coronary stenosis. However, growing body of literature indicates that
coronary microcirculation also contributes substantially to the pathophysiology of cardiovascular disease. An understanding of mechanisms
regulating microvascular function is of critical importance in understanding its role in disease, especially because these regulatory
mechanisms vary substantially across species, vascular bed and due to comorbidities.
Indeed, the most obvious consequence of coronary stenosis is that it may limit blood supply to the dependent myocardium to the point of
causing ischaemia during exercise or even at rest. However, this flow limiting effect is not only due to the passive hydraulic effect of a
narrowed conduit, but also to active responses in the coronary microcirculation triggered by the presence of an epicardial stenosis. To understand
this problem it is important to review the inter-related mechanisms that regulate flow to the left ventricular wall and modulate
transmural distribution of flow. These regulatory mechanisms operate hierarchically and are heterogeneously distributed along the coronary
vascular tree. It is also important to discuss the effect of myocardial performance in modulating both blood flow demands and coronary
resistance. Some of the interactions between coronary stenosis and microcirculation are transient, like those documented in acute
coronary syndromes or during percutaneous interventions. However, microcirculatory remodeling may be triggered by a chronic coronary
stenosis, leading to a sustained impairment of blood supply even after successful removal of the epicardial stenosis. A deeper understanding
of these phenomena may explain paradoxical findings in patients undergoing coronary revascularization, particularly when functional
tests are used in their assessment. These aspects are discussed in detail in this review.
