Isolated Defect of Adenosine-Mediated Coronary Vasodilation: Functional Evidence for New Microangiopathic Entity

Objectives. The present study describes an isolated defect of the coronary vasodilation in response to adenosine in five patients examined for clinically suspected coronary microangiopathy. Background. Coronary microangiopathies can be defined functionally as dysregulation of the microcirculatory vasomotion. Methods. The five patients were compared with 24 control subjects. Coronary flow velocity was measured with an intracoronary Doppler guide wire (0.018 in. [0.046 cm], 12 MHz) at rest and during intracoronary administration of adenosine (80 μg/min and 160 μg/min over 3 min each), papaverine (10-mg bolus) and acetylcholine (30 μg/min over 5 min). Diameters of the epicardial coronary arteries were measured by quantitative coronary angiography. Results. All subjects (patients and control) exhibited angiographically normal epicardial coronary arteries and normal and comparable endothelium-independent and -dependent vasomotion, as assessed with papaverine (mean [± SD] relative coronary flow reserve 2.62 ± 0.66 vs. 2.97 ± 0.88, p = 0.32) and acetylcholine (volumetric coronary flow reserve 2.61 ± 0.27 vs. 2.91 ± 0.67, p = 0.58), respectively. Affected patients were identified by an isolated complete defect of the adenosine-mediated vasodilation compared with control subjects (relative coronary flow reserve in response to 80 μg/min of adenosine 1.08 ± 0.17 vs. 2.45 ± 0.74 [p < 0.001] and 160 μg/min of adenosine 1.03 ± 0.15 vs. 2.89 ± 0.65 [p < 0.001]). Conclusions. These findings are consistent with functional evidence for new entity of coronary microangiopathy affecting subtype of the endothelium-independent vasomotion.