脉压对颈动脉壁重构的影响——探讨Laplace定律对大血管重构的作用

Effect of Pulse Pressure on Carotid Remodeling——Application of Laplace Law

目的:血管壁的增厚和功能指数正越来越多的被用作评价心血管疾病的重要指标。然而大血管的结构、功能、压力的相互关系在活体上还没有很好的确定。我们研究组对一组正常和高血压病人进行了大血管的结构-功能-压力的相互关系的交叉研究。方法:307例正常和高血压的人群被选择到此研究,其中男110例,女197例。年龄49～75岁。颈动脉内膜和中层厚度(Intima-media wall thickness,IMT)和内腔直径(Lumen diameter,LD)用Diasonic(DRF400)高分辨率超声来确定。血管壁环状压(Circumferential stress,Cs)是依据LAPLACE定律(δ=P×r/h)计算。其中压力(Pressure,P)用平均压和脉压两种方法计算。此动脉的结构和功能指数用年龄、身高和心率来校正。颈动脉压用无创压力感受器测定。结果:共有70例高血压(BP>140/90)患者。用年龄、身高和心率校正后的内中膜厚度和内腔直径在高血压组显著增加。而且IMT随着脉压的增大而增大(r=0.39,P<0.001)。内腔半径与内中膜厚度比值(R/IMT,R=LD/2)和环状压在高血压组明显增加。但是不管高血压或正常人群的R/IMT比值与脉压呈负相关关系(r=0.38,P<0.001),而与平均压无关。结论:在高血压状态下颈动脉壁重构是服从LAPLACE定律的,但颈动脉壁重构不足以抵销高血压状态下的血管壁环状压的增加。

Objectives: Parameters of carotid wall thickness and function are increasingly being used as surrogate makers of cardiovascular diseases, but in vivo structure - function - pressure relationships have not been well defined. This study examined the relationships between carotid blood pressure, arterial geometry and wall stress. Methods: We studied 307 normotensive and hypertensive subjects (110males, 197 females), aged 49 - 75 years. Central pulse pressure (PPcen) was derived from carotid artery measured by appla-nation tonometry. A Diasonic DRF400 high resolution B - mode ultrasound machine was used to determine carotid intima - media thickness (IMT) and lumen diameter (LD) . Mean and pulsatile circumferential stress (Cs) was calculated according to the Laplace (δ= P×r/h) relationship. Indices of arterial geometry and function were adjusted for age, height and heart rate. Results: Hypertension (screening BP > 140/ 90) was present in 70 subjects. Hypertension individually singificantly increased adjusted IMT and LD. R/ IMT (where R = LD/2) and Cs were increased in hypertensives. R/IMT was inversely correlated with PPcen (r = -0.38; P < 0.001), but not with mean blood pressure (MAP) . Conclusion: In an older population carotid artery wall remodelling appears to follow Laplace law but is insufficient to prevent an increase in circumferential stress in subjects with higher blood pressure. The critical blood pressure parameter in Laplace law is associated with pulse pressure but not mean blood pressure in vivo.