Norris H Cameron, Mangum Tyler S, Kern Julia P, Elliott Jonathan E, Beasley Kara M, Goodman Randy D, Mladinov Suzana, Barak Otto F, Bakovic Darija, Dujic Zeljko, Lovering Andrew T
Department of Human Physiology, University of Oregon, Eugene, OR, UK.
Oregon Heart and Vascular Institute, Springfield, OR, UK.
Exp Physiol. 2016 Aug 1;101(8):1128-42. doi: 10.1113/EP085811.
What is the central question of this study? Do individuals with chronic obstructive pulmonary disease have blood flow through intrapulmonary arteriovenous anastomoses at rest or during exercise? What is the main finding and its importance? Individuals with chronic obstructive pulmonary disease have a greater prevalence of blood flow through intrapulmonary arteriovenous anastomoses at rest than age-matched control subjects. Given that the intrapulmonary arteriovenous anastomoses are large enough to permit venous emboli to pass into the arterial circulation, patients with chronic obstructive pulmonary disease and an elevated risk of thrombus formation may be at risk of intrapulmonary arteriovenous anastomosis-facilitated embolic injury (e.g. stroke or transient ischaemic attack). The pulmonary capillaries prevent stroke by filtering venous emboli from the circulation. Intrapulmonary arteriovenous anastomoses are large-diameter (≥50 μm) vascular connections in the lung that may compromise the integrity of the pulmonary capillary filter and have recently been linked to cryptogenic stroke and transient ischaemic attack. Prothrombotic populations, such as individuals with chronic obstructive pulmonary disease (COPD), may be at increased risk of stroke and transient ischaemic attack facilitated by intrapulmonary arteriovenous anastomoses, but the prevalence and degree of blood flow through intrapulmonary arteriovenous anastomoses in this population has not been fully examined and compared with age-matched healthy control subjects. We used saline contrast echocardiography to assess blood flow through intrapulmonary arteriovenous anastomoses at rest (n = 29 COPD and 19 control subjects) and during exercise (n = 10 COPD and 10 control subjects) in subjects with COPD and age-matched healthy control subjects. Blood flow through intrapulmonary arteriovenous anastomoses was detected in 23% of subjects with COPD at rest and was significantly higher compared with age-matched healthy control subjects. Blood flow through intrapulmonary arteriovenous anastomoses at rest was reduced or eliminated in subjects with COPD after breathing hyperoxic gas. Sixty per cent of subjects with COPD who did not have blood flow through the intrapulmonary arteriovenous anastomoses at rest had blood flow through them during exercise. The combination of blood flow through intrapulmonary arteriovenous anastomoses and potential for thrombus formation in individuals with COPD may permit venous emboli to pass into the arterial circulation and cause stroke and transient ischaemic attack. Breathing supplemental oxygen may reduce this risk in COPD. The link between blood flow through intrapulmonary arteriovenous anastomoses, stroke and transient ischaemic attack is worthy of future investigation in COPD and other populations.
本研究的核心问题是什么？患有慢性阻塞性肺疾病的个体在静息状态或运动期间是否存在肺内动静脉吻合支的血流？主要发现及其重要性是什么？与年龄匹配的对照受试者相比，患有慢性阻塞性肺疾病的个体在静息状态下通过肺内动静脉吻合支的血流发生率更高。鉴于肺内动静脉吻合支足够大，能够使静脉栓子进入动脉循环，患有慢性阻塞性肺疾病且血栓形成风险升高的患者可能存在肺内动静脉吻合支促进的栓塞性损伤风险（如中风或短暂性脑缺血发作）。肺毛细血管通过从循环中滤过静脉栓子来预防中风。肺内动静脉吻合支是肺内直径较大（≥50μm）的血管连接，可能会损害肺毛细血管滤器的完整性，并且最近已与不明原因的中风和短暂性脑缺血发作相关联。促血栓形成人群，如患有慢性阻塞性肺疾病（COPD）的个体，可能因肺内动静脉吻合支而增加中风和短暂性脑缺血发作的风险，但该人群中通过肺内动静脉吻合支的血流发生率和程度尚未得到充分研究并与年龄匹配的健康对照受试者进行比较。我们使用生理盐水对比超声心动图评估患有COPD的受试者和年龄匹配的健康对照受试者在静息状态（COPD组29例，对照组19例）和运动期间（COPD组10例，对照组10例）通过肺内动静脉吻合支的血流。23%的COPD受试者在静息状态下检测到通过肺内动静脉吻合支的血流，与年龄匹配的健康对照受试者相比显著更高。COPD受试者在吸入高氧气体后，静息状态下通过肺内动静脉吻合支的血流减少或消失。60%在静息状态下没有通过肺内动静脉吻合支血流的COPD受试者在运动期间有血流通过。COPD个体中通过肺内动静脉吻合支的血流与血栓形成可能性的结合可能使静脉栓子进入动脉循环并导致中风和短暂性脑缺血发作。吸入补充氧气可能会降低COPD中的这种风险。通过肺内动静脉吻合支的血流、中风和短暂性脑缺血发作之间的联系值得在COPD和其他人群中进行进一步研究。
