TRA has become the default（默认） access site for cardiac catheterization in many countries, and strategies to preserve the patency（开放） of the radial artery for future use are becoming an integral（必要的） part of the catheterization procedure.

冠脉领域，众多国家均以经桡优先，然而术后如何保证桡动脉依然通畅，变得尤为重要。

Our analysis represents the first systematic review of such radial protection strategies, synthesizing evidence from over 66 studies and 31 345 participants, to assess the incidence of and risk factors for RAO as well as to examine the effificacy of the measures used to prevent it. 

该研究聚焦于RAO的发生率、RAO的危险因素以及预防措施的有效性。通过回顾66篇研究和31345名患者，进行了首次系统分析。

Our analysis suggests that RAO is common, with incident rates of 7.7% for early RAO within 24 hours, declining to 5.5% at 1 month. Clinically, absence of radial pulse（桡动脉搏动） is often described as occluded artery; however, this can underestimate the true incidence of RAO. For example, in one study RAO incidence  defifined by absence of pulse was found to be 4.4%, whereas absence of radial artery flow（桡动脉血流） was found to be at 10.5%.

研究表明，RAO很常见。术后24小时内发生率为7.7%，1个月时下降到5.5%。临床上通常将桡动脉搏动消失描述为RAO，但是并非如此。有研究表明，同一批患者，桡动脉脉搏消失发生率为4.4%，而血流消失发生率为10.5%。

It is therefore recommended to use a more objective method of  assessment of RAO using radial flow as assessed by ultrasound(超声). In support of this, when studying the method of  assessment of RAO, we observed that the incidence of RAO  increased from 5.6% to 7.8% when ultrasound is used for detection of RAO. 

因此，超声才是RAO诊断的金标准。通过应用超声诊断，RAO的发生率从5.6%提高至7.8%。

Many baseline patient characteristics such as sex, age, body mass index, and procedural variables such as artery-to-sheath ratio, heparin use, and duration of compression have been reported to be associated with RAO, but there appears to be a lot of heterogeneity（异质性） in the literature. 

许多基线患者特征，如性别、年龄、体重指数和术中变量，如动脉-鞘比、肝素使用和压迫时间，已被报道与RAO相关，但在文献中似乎存在很多异质性。

The incidence of RAO varies according to the timing of assessment  of radial artery patency postprocedure. Acute RAO rates are higher acutely and decline with time. In the PROPHET study, the acute incidence of RAO (12%) was almost halved by the passage  of 28 days (7%). In accordance with these observations, our analysis also suggests a decreased incidence of RAO over a period of 28 days from 7.7% to 5.8%. 

不同时间评估桡动脉是否通畅，RAO的发生率就不同。RAO发生率随时间下降。在PROPHET研究中，RAO的急性发生率为12%，在28天的时间时几乎减半至7%。本研究也表明，在28天内，RAO的发生率从7.7%下降到5.8%。

This decline in the incidence of RAO with time can be explained by the spontaneous recanalization of the radial artery. Recanalization occurs  as the results of activation of primary fifibrinolysis（原发性纤维蛋白溶解）. The damaged  endothelium（内皮） facilitates this by releasing tissue plasminogen activator（组织纤溶酶原激活物） and urokinase, thus allowing fifibrinolysis to occur. 

RAO发生率随时间的下降可以用桡动脉的自发再通来解释。再通是原发性纤维蛋白溶解活化的结果。受损的内皮通过释放组织纤溶酶原激活物和尿激酶促进纤维蛋白溶解的发生。

TRA also negatively affects the structure and function of the radial artery, culminating in nonocclusive injury. Endothelial and vascular smooth muscle integrity play a central role in preserving the function of the arterial wall.  Damaged and dysfunctional endothelium has been strongly attributed to development of vascular disease and atherosclerosis.

TRA也会对桡动脉的结构和功能产生负面影响，最终导致非闭塞性损伤。内皮细胞和血管平滑肌的完整性在保护动脉壁功能中起着核心作用。血管内皮损伤和功能失调与血管疾病和动脉粥样硬化的发生密切相关。

More recently, changes in flow-mediated dilatation has been used as a surrogate（替代） of endothelial dysfunction. Flow-mediated dilatation is an in vivo bioassay（生物活性） of NO mediated endothelial function in which vascular endothelium releases NO as a vasodilatory（血管舒张） response according to the changes in the vascular blood flow. 

血流介导的扩张理论是内皮损伤理论的替代。血流的变化会促进NO释放，从而扩张血管。

Yan et al recently  demonstrated that average flow-mediated dilatation post 5-  Fr TRA reduced signifificantly from 11.5% to 4.1% immediately  after the procedure and dropped even further to 0.7% at  3 months.

Yan等人最近证实5- Fr TRA术后的平均血流介导的血管扩张，可使RAO发生率显著降低，从11.5%下降到4.1%，在术后3个月时进一步下降到0.7%。

This suggests that endothelial damage may  actually persist longer than perceived. Additionally, TRA also results in structural damage to the radial artery. Yonetsu et al  studied the structural changes in radial artery from acute  vascular trauma and found that 67% of radial arteries had intimal tears（内膜撕裂） and 36% had medial dissections（夹层） immediately  after transradial PCI.

这表明，内皮损伤实际上可能比想象的持续时间更长。此外，TRA还会导致桡动脉结构的破坏。Yonetsu等研究了急性血管创伤导致的桡动脉结构变化，发现经桡动脉PCI术后，67%的桡动脉出现了内膜撕裂，36%的桡动脉出现了内侧夹层。

The combination of these structural and functional changes in arterial wall lead to signifificant arterial remodeling, which may have important clinical implications. For instance, Sakai et al  studied patients  undergoing repeated transradial interventions in the same arm and found that the rate of successful radial access  decreases with successive procedures.  

动脉壁的这些结构和功能改变共同导致了动脉重塑。例如，Sakai等研究了在同一组接受重复经桡动脉介入治疗的患者，发现桡动脉入路的成功率随着连续手术的进行而降低。

Acute artery occlusion is thought to be a thrombotic（血栓形成）  phenomenon on a background of chronic occlusive changes.  Sheath insertion and instrumentation during TRA causes endothelial damage, exposing the thrombogenic connective tissue. In addition, blood stasis while achieving hemostasis provides the nidus（病灶） for thrombus formation. 

急性动脉闭塞被认为是慢性闭塞性改变背景下的血栓形成现象。TRA术中的置鞘和压迫会导致内皮损伤，暴露血栓形成的结缔组织。此外，止血时的血瘀为血栓形成提供了基础病灶。

Therefore, reducing  endothelial damage by minimizing compression time and using  small introducer sheath size along with patent hemostasis may help in reducing the occlusion rates. Saito et al studied the relationship between arterial blood flow and sheath size outer  diameter and found that incidence of blood flow reduction is  signifificantly low when radial artery inner diameter/cannulated  sheath outer diameter is ≥1.0 (artery/sheath diameter ratio >1).

因此，通过缩短压迫时间、使用较小尺寸的鞘管和有效止血来减少内皮损伤可能有助于降低闭塞率。Saito等研究了动脉血流与鞘管外径的关系，发现当桡动脉内径/鞘管外径≥1.0时，血流减少的发生率明显较低。