Coronary microvascular functional reserve: Quantification of long-term changes with electron-beam CT - Preliminary results in a porcine model

PURPOSE: To evaluate the ability of electron-beam computed tomography (CT) to help quantify long-term changes in coronary microvascular functional reserve in a porcine model. MATERIALS AND METHODS: Electron-beam CT-based intramyocardial blood volume and perfusion and Doppler ultrasonography (US)-based intracoronary blood flow were obtained in 13 pigs at baseline and again 3 months later. Measurements were obtained at rest and after the administration of adenosine. The short-term variation during 30 minutes of electron-beam CT measurements was assessed in nine additional pigs. RESULTS: Short-term variation of blood volume and perfusion averaged 8% and 9%, respectively, and was similar for both weight groups at rest and after adenosine administration. At rest, intracoronary blood flow, blood volume, and perfusion remained unchanged from baseline to follow-up. Long-term increases (percentage change with adenosine relative to that at rest) in blood volume and perfusion reserves were consistent with increasing intracoronary blood flow reserves. Despite these long-term changes in intracoronary blood flow, blood volume, and perfusion, the blood volume-to-perfusion relationship suggests a similar blood volume distribution among different microvascular functional components in normal porcine myocardium at both weight groups. CONCLUSION: Electron-beam CT may be of value for quantifying long-term changes in intramyocardial microvascular function.