Vascular endothelial dysfunction is associated with reversible myocardial perfusion defects in the absence of obstructive coronary artery disease

Background. The purpose of this study was to investigate whether endothelial dysfunction contributes to abnormal myocardial perfusion imaging (MPI) observed in patients without obstructive coronary artery disease (CAD). It is unclear whether reversible MPI defects detected in the absence of obstructive CAD represent underlying vascular pathology or are false-positive MPI results. Recent evidence suggests that coronary endothelial dysfunction might play a role in the pathogenesis of these defects. Methods and Results. We prospectively recruited 36 patients with chest discomfort, reversible abnormalities on NIPI, and nonobstructive or absent CAD (stenosis < 50% on coronary angiography). The control group (n = 55) consisted of patients with chest discomfort and similar cardiac risk factors but with normal MFI findings. Vascular endothelial function was assessed in the brachial artery by ultrasound as the response to hyperemia and reported as percent flow-mediated dilation (FMD). Response to sublingual nitroglycerin was used as an indicator of endothebum-independent vasodilation. The patients with abnormal NIPI findings and nonobstructive CAD had a significantly lower FMD (9.0% +/- 7.2%), indicating endothelial dysfunction, compared with those with similar risk factors and normal NIPI findings (12% +/- 5.2%) (P = .03). Baseline brachial artery size and endothelium-independent dilation were similar between groups. On multivariate analysis, only endothelial dysfunction was predictive of reversible MPI defects. Conclusions. Patients with chest pain and reversible MPI defects but without obstructive CAD have lower FMD indicative of endothelial dysfunction, as compared with similar patients with normal MPI findings. The possibility of a causal link between reversible MPI defects and endothelial dysfunction needs further exploration.