Baciground Impaired coronary flow reserve (CFR) in patients with hypertension may be caused by epicardial coronary stenosis or microvascular dysfunction.Antihypertensive treatment has been shown to improve coronary microvascular dysfunction.The aim of this study was to evaluate the impact of uncontrolled blood pressure (BP) on diagnostic accuracy of CFR for detecting significant coronary stenosis.Methods A total of 98 hypertensive patients scheduled for coronary angiography (CAG) due to chest pain were studied.Of them,45 patients had uncontrolled BP (defined as the office BP ＞140/90 mmHg (1 mmHg=0.133 kPa) in general hypertensive patients,or ＞130/80 mmHg in hypertensive individuals with diabetes mellitus),and the remaining 53 patients had well-controlled BP.CFR was measured in the left anterior descending coronary artery (LAD) during adenosine triphosphate-induced hyperemia by non-invasive transthoracic Doppler echocardiography (TTDE) within 48 hours prior to CAG.Significant LAD stenosis was defined as ＞70％ luminal narrowing.Diagnostic accuracy of CFR for detecting significant coronary stenosis was analyzed with a receiver operating characteristic analysis.Results CFR was significantly lower in patients with uncontrolled BP than in those with well-controlled BP (2.1±0.6 vs.2.6±0.9,P ＜0.01).Multivariate linear regression analysis of the study showed that the value of CFR was independently associated with the angiographically determined degree of LAD stenosis (β=-0.445,P ＜0.0001) and the presence of uncontrolled BP (β=-0.272,P=0.014).With a receiver operating characteristic analysis,CFR ＜2.2 was the optimal cut-off value for detecting LAD stenosis in all hypertensive patients (AUC 0.83,95％C/0.75-0.91) with a sensitivity of 75％,a specificity of 78％,and an accuracy of 77％.A significant reduction of diagnostic specificity was observed in patients with uncontrolled BP compared with those with well-controlled BP (67％ vs.93％,P=0.031).Conclusions CFR measurement by TTDE is valuable in the diagnosis of significant coronary stenosis in hypertensive patients.However,the diagnostic specificity is reduced in patients with uncontrolled BP.