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目的通过3个研究探讨增强指数(AIx)在动脉僵硬度评估方面的有效性。方法选取156名持续性非卧床腹膜透析(CAPD)患者为研究对象,根据是否患有糖尿病分为两组,测量患者的AIx;运用数学推理方法来验证AIx的有效性;运用临床数据来验证AIx公式的价值。结果糖尿病CAPD患者的AIx比非糖尿病患者低(P<0.05),这与预期结果完全相反。进一步研究显示AIx与外周脉压(PP)之间只存在弱相关性,研究也发现中心增强压力(AP)一般随着中心脉压(C-PP)的变化而变化。而在AIx的计算公式中,AP和C-PP分别作为其中的分子和分母,如果分母不确定,分子的增大并不能决定商必然增大。第2个研究通过数学推理的方法来验证AIx的有效性,数学推理显示,AIx是一个多因素决定的数值F=(ΔSBP-ΔDBP)×[心脏射血波峰(P1)-反射波波峰(P2)]+(ΔP2-ΔP1)×[SBP(收缩压)-DBP(舒张压)],提示其可能并非总是随着P2和AP的变化而变化,此结果在第3个研究中得到证实。结论AIx可能并非反映中心压力波形改变的敏感指标,而只是大动脉功能改变的一种表现,其局限性源于计算公式存在数学缺陷。
Objective To investigate the effectiveness of the augmentation index (AIx) in evaluating arterial stiffness through three studies. Methods A total of 156 patients with continuous ambulatory peritoneal dialysis (CAPD) were enrolled in this study. Patients were divided into two groups according to their diabetes mellitus. AIx was measured. Mathematical reasoning was used to verify the effectiveness of AIx. Clinical data were used to validate AIx The value of the formula. Results AIx in diabetic patients with CAPD was lower than in nondiabetic patients (P <0.05), contrary to the expected results. Further studies showed that there was only a weak correlation between AIx and peripheral pulse pressure (PP). Studies also found that the central augmentation pressure (AP) generally varies with changes in central pulse pressure (C-PP). In the calculation formula of AIx, AP and C-PP are respectively the numerator and denominator. If the denominator is not determined, the increase of the numerator does not determine that the quotient necessarily increases. The second study validated the validity of AIx through mathematical reasoning. Mathematical reasoning showed that AIx was a multivariate determinant F = (ΔSBP-ΔDBP) × [cardiac ejection peak (P1) -reflected wave peak (P2 )] + (ΔP2-ΔP1) × [SBP (systolic blood pressure) -DBP (diastolic blood pressure)], suggesting that this may not always change with changes in P2 and AP. This result was confirmed in the third study. Conclusions AIx may not be a sensitive index to reflect the change of central pressure waveform, but only a manifestation of the change of aortic function. The limitation of AIx is due to the mathematical defect in the formula.