Prognosis of coronary flow reserve: a new therapeutic target?

Coronary circulation, as in other vascular territories, is able to maintain its constant flow even with changes in the myocardial perfusion pressure. This physiological adaptation mechanism is defined as autoregulation. The concept of coronary flow reserve (CFR) is related to the ratio between the coronary blood flow after maximum vasodilatation, and the coronary blood flow at rest.1 The highest CFR is in the subepicardial layer of the myocardium. The CFR is lower in the subendocardial layer, so in relation to a decrease in myocardial flow, the subendocardial CFR is exhausted first. It is well known that in the absence of macroscopic coronary artery disease, the decrease of the CFR can be attributed to alterations in the microvascular circulation.2 CFR can be measured by magnetic resonance imaging, positron emission tomography, coronariography, and transthoracic echocadiography. The last technique is especially useful because of its disposability, low costs, and the absence of radiation exposure. The lower limit of CFR proposed by Dimitrow et al .3 using different methods in control groups is 3.0. A reduction in CFR can be found in some diseases associated with coronary microvascular dysfunction such as hypertrophic cardiomyopathy (CFR 2.21±0.2), dilated cardiomyopathy (DCM) (CFR 1.9±0.2), and Syndrome X (CFR 2.27±0.3).4 The assessment of CFR … *Corresponding author. Tel: +34 91 3303290; Fax: +34 91 3303292. E-mail address : jlzamorano{at}vodafone.es