Oxygenation-sensitive CMR for assessing vasodilator-induced changes of myocardial oxygenation

Background: As myocardial oxygenation may serve as a marker for ischemia and microvascular dysfunction, it could be clinically useful to have a non-invasive measure of changes in myocardial oxygenation. However, the impact of induced blood flow changes on oxygenation is not well understood. We used oxygenation-sensitive CMR to assess the relations between myocardial oxygenation and coronary sinus blood oxygen saturation (SvO(2)) and coronary blood flow in a dog model in which hyperemia was induced by intracoronary administration of vasodilators. Results: During administration of acetylcholine and adenosine, CMR signal intensity correlated linearly with simultaneously measured SvO(2) (r(2) = 0.74, P < 0.001). Both SvO(2) and CMR signal intensity were exponentially related to coronary blood flow, with SvO(2) approaching 87%. Conclusions: Myocardial oxygenation as assessed with oxygenation-sensitive CMR imaging is linearly related to SvO(2) and is exponentially related to vasodilator-induced increases of blood flow. Oxygenation-sensitive CMR may be useful to assess ischemia and microvascular function in patients. Its clinical utility should be evaluated.