目的 :观察X综合征患者一氧化氮 (NO)及血管内皮依赖性舒张功能的变化。方法 :采用高分辨率超声检测 2 5例X综合征患者血管内皮依赖性舒张功能 ,并测定其血浆NO含量 ,与 2 0例正常人进行对照。结果 :①X综合征组患者反应性充血引起的肱动脉内径变化较对照组明显减弱 [(6 .1± 2 .0 ) %∶(15 .6± 3.2 ) % ,P <0 .0 1],而两组患者对硝酸甘油的反应差异无统计学意义 [(15 .5± 1.5 ) %∶(15 .1± 2 .1) % ,P >0 .0 5 ]。②X综合征组患者在胸痛前、胸痛发作时及胸痛后 2h血浆NO含量分别为 (4 0 .6 7± 8.0 3)、(2 9.2 5± 9.87)、(39.5 4± 6 .0 7)μmol/L ,与正常对照组 (5 7.6 7± 10 .89) μmol/L比较均 P <0 .0 1;心绞痛发作时NO含量明显低于发作前及发作后。③血管内皮依赖性舒张功能的变化与血浆NO含量呈正相关 (r =0 .832 8,P <0 .0 1)。结论 :X综合征患者与明显的血管内皮依赖性舒张功能障碍、心绞痛发作和NO水平降低有关 ,提示内皮功能异常在X综合征患者的发病过程中起重要作用 Objective: To observe the changes of nitric oxide (NO) and endothelium-dependent vasodilatation in patients with syndrome X.Methods: Methods: The endothelium-dependent vasodilation of 25 patients with syndrome X was detected by high-resolution ultrasound. The plasma NO level was measured and compared with 20 healthy controls. Results: ① The changes of the brachial artery diameter caused by reactive hyperemia in patients with syndrome X were significantly weaker than those in the control group [(6.1 ± 2.0)%: (15.6 ± 3.2)%, P <0.01] There was no significant difference in response to nitroglycerin between the two groups [(15.5 ± 1.5)%: (15.1 ± 2.1)%, P> 0.05). ② The levels of plasma NO in patients with syndrome X before chest pain, at onset of chest pain, and at 2 hours after chest pain were (40.76 ± 8.03), (29.5 ± 9.87), (39.5 4 ± 6.07) μmol / L, compared with the normal control group (5 7.67 ± 10.89) μmol / L, P <0.01; the content of NO in angina pectoris was significantly lower than before and after the onset of seizures. ③ The changes of endothelium-dependent diastolic function was positively correlated with plasma NO level (r = 0.832 8, P <0.01). Conclusions: Patients with syndrome X are associated with marked endothelium-dependent dysthymia, angina pectoris and decreased NO levels, suggesting that endothelial dysfunction plays an important role in the pathogenesis of syndrome X