Assessment of coronary vasomotor tone in humans

The assessment of endothelium-mediated modulation of coronary vasomotor tone in the intact human circulation under physiologic conditions requires very precise determination of both epicardial artery diameters, reflecting effects within the conduit vessels, as well as coronary blood flow, reflecting effects within the resistance vasculature during cardiac catherization. In the present report, the accuracy and limitations of quantitative approaches to assess arterial dimensions from coronary angiograms are discussed. Using state-of-the-art image-processing techniques and x-ray imaging, epicardial artery diameter changes within the range of 8–10% can be reliably detected by quantitative coronary angiography. In addition, advances in interventional techniques do provide a means to selectively assess intracoronary blood-flow velocities using intracoronary Doppler catheters. Combining epicardial artery diameter measurements and intracoronary blood-flow velocity parameters allows for a reasonably accurate instantaneous estimate of coronary arterial blood flow. The advantages and limitations of the intracoronary Doppler technique compared to other techniques are discussed.