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部分性肺静脉异位连接是指四支肺静脉中的一条或数条(但非全部)肺静脉的引流异常直接或间接与右心房连接。
疾病病因
(一)发病原因心脏胚胎发育的关键时期是在妊娠的第2～8周，先天性心血管畸形也主要发生于此阶段。先天性心脏病的发生有多方面的原因，大致分为内在的和外部的2类，其中以后者多见。内在因素主要与遗传有关，特别是染色体易位和畸变，例如21-三体综合征、13-三体综合征、14-三体综合征、15-三体综合征和18-三体综合征等，常合并先天性心血管畸形;此外，先天性心脏病患者子女的心血管畸形的发生率比预计发病率明显的多。外部因素中较重要的有宫内感染，尤其是病毒感染，如风疹、腮腺炎、流行性感冒及柯萨奇病毒等;其他如妊娠期接触大剂量射线、使用某些药物、患代谢性疾病或慢性病、缺氧、母亲高龄(接近更年期)等，均有造成先天性心脏病的危险。
(二)发病机制
1.病理解剖 部分性肺静脉连接异常可单独存在，或合并其他心脏畸形，最常见的是静脉窦型房间隔缺损，少见的有二尖瓣狭窄、右室双出口、室间隔缺损、法洛四联症、肺动脉狭窄、主动脉缩窄、动脉导管未闭、右位心等。本病类型很多，如右上肺静脉直接引流入右上腔静脉、右肺静脉与右心房连接、右肺静脉与下腔静脉连接、左肺静脉与左无名静脉连接，以右肺静脉与右上腔静脉连接最常见，右肺静脉异常较左肺静脉常见。同侧肺静脉汇入同侧的心房可见于心脾综合征及共同心房时。
(1)右肺静脉与右上腔静脉或右心房连接：最常见，约占3/4。右肺上叶和中叶的肺静脉分别与上腔静脉相连在奇静脉入口与右心房、上腔静脉连接处之间，而右下肺叶肺静脉正常回流入左心房。常伴静脉窦型房间隔缺损，偶尔上腔静脉骑跨在缺损上。
(2)右肺静脉与下腔静脉相连：所有右肺静脉(偶可为右肺中、下叶的肺静脉)形成共干汇入下腔静脉(图3)，此类型不多见。共干与下腔静脉的连接在胸片上右下肺野呈特征性新月形阴影，故又可称为“弯刀综合征”(scimitar syndrome)，尚伴有心脏异位、右肺发育不良、主动脉异常血管供应右肺等畸形。
2.病理生理 本病目前尚未发现肺静脉梗阻，故血流动力学特征仅为部分连接异常的肺静脉左向右分流。单支肺静脉连接异常其血流量仅占所有肺静脉血流的20%，因而无明显的临床表现。
在伴有房间隔缺损时，血流动力学变化包括心房水平、肺静脉水平的左向右分流。肺动脉高压较少发生。但弯刀综合征患儿，若伴有肺实变、肺动脉肌层增厚，肺血管阻力增加，可出现肺动脉高压。
症状体征 单支肺静脉异位连接者无临床症状;一侧肺静脉异位引流，其症状与无梗阻型完全性肺静脉异位连接相类似，青紫不常见，心力衰竭也大都罕见。伴有房间隔缺损者，体检以房缺体征为主。房隔完整者，可闻及第2心音分裂，分裂音宽但不固定，随呼吸而变化。肺动脉瓣可及收缩期杂音。 根据临床表现和辅助检查可明确诊断。
检查化
1.胸部X线 中等量的左向右分流，X线表现与中型房间隔缺损相似，即肺血多、右心室扩大，有时可见异位连接的静脉。肺静脉异位连接于左无名静脉时，可出现“雪人征”。
2.心电图 与房间隔缺损相似。表现为V1导联rsr’或rsR’。但房间隔完整且肺静脉开口处只有小的左向右分流患者，心电图常正常。
3.超声心动图 心脏超声对于诊断本病的四个肺静脉开口较难，有时即使肺静脉完全正常时，也显示不清。当无房间隔缺损而出现右心室容量负荷增加时，须考虑有部分性肺静脉异位连接。当有静脉窦型房间隔缺损，在剑突下平面可看到右肺静脉异位开口于右心房;在稍后一切面，可显示在冠状窦内的肺静脉异位开口;怀疑弯刀综合征患儿，以剑突下长、短轴切面，可见下腔静脉及下腔与右房交汇处，进而得以显示异位连接的肺静脉;垂直静脉可从胸骨上短轴切面显示。有时心脏超声可十分正确的诊断本病。但即使没有捕捉到异位开口的肺静脉，也不能排除此病。
4.心导管 本病大多无须用心导管术检查，它只用于诊断病因不明的病例及了解弯刀综合征患者肺动脉走向、肺实变情况(图4)。选择性肺动脉造影，观察肺静脉回流情况，以显示肺静脉的异位连接;若导管可插入肺静脉，选择性肺静脉造影，可以清晰显示肺静脉解剖位置;在弯刀综合征中，主动脉的选择性造影也很必要。
5.其他无创性显像 CT和MRI均可用于该病的诊断。在无创性检查中，这可能是最准确的，除外还能同时发现肺实变等伴发畸形。
鉴别诊断
注意与房间隔缺损鉴别，主要依据影像学检查鉴别。
并发症
重症病例可反复出现肺部感染，晚期出现梗阻型肺动脉高压。
预防保健
先心病的发生是多种因素的综合结果，为预防先心病的发生，应开展科普知识的宣传和教育，对适龄人群进行重点监测，充分发挥医务人员和孕妇及其家属的作用。
1.戒除不良生活习惯，包括孕妇本人及其配偶，如嗜烟、酗酒等。
2.孕前积极治疗影响胎儿发育的疾病，如糖尿病、红斑狼疮、贫血等。
3.积极做好产前检查工作，预防感冒，应尽量避免使用已经证实有致畸胎作用的药物，避免接触有毒、有害物质。
4.对高龄产妇、有先心病家族史、夫妇一方有严重疾病或缺陷者，应重点监测。
治疗用药
(一)治疗在无充血性表现的病例中，无须药物治疗。若肺循环∶体循环大于2∶1，则需手术纠正。右肺静脉异位连接者，在腔静脉或右心房内通过一人造隧道直接将肺静脉与左心房相连，亦可将右肺静脉与左房直接吻合。弯刀综合征合并大的主-肺动脉连接者，可出现心力衰竭及肺高压，手术以前先行心导管术，在主-肺动脉连接处以弹簧圈填塞，从而改善心力衰竭症状，降低肺动脉压。极少数患儿，必要时可切除部分肺叶。
(二)愈后大多数患儿的愈后与左向右分流的房间隔缺损相同，很少出现肺血管疾病。术后长期随访证实，尚无肺静脉梗阻及肺高压，但仍需定期对小儿进行监控。右上肺静脉异位引流伴静脉窦型房缺患儿，术后30%～40%可发生病态窦房结综合征。在其他类型的小儿中，心律失常则较少出现。
Discussion(讨论): Partial anomalous pulmonary venous connection (PAPVC) is present when one or more, but not all, of the pulmonary veins connect to a systemic vein, the right atrium, or the coronary sinus. The veins of the right lung have two to ten times the number of anomalous connections as those from the left lung. When an anomalous vein exists, it usually connects to the nearest adjacent systemic vein. The left lung veins connect to the left innominate vein, the coronary sinus, the hemiazygous vein, or to an anomalous vertical vein that drains into the innominate vein. In the right lung, the right superior pulmonary vein may connect to the right superior vena cava or azygous vein. The right inferior vein may connect with either the inferior or superior vena cava, or hepatic vein, or the azygous vein. The right pulmonary veins may also connect directly to the right atrium. Less common variations include absence of the coronary sinus with pulmonary veins from either side connecting to multiple systemic sites or to the left atrium. Rarely, an anomalous pulmonary vein will connect to the portal vein. Many variations exist in the number, size, and connections of the four pulmonary veins. If an atrial septal defect is present, about 10% of patients will have a pulmonary venous abnormality. The chest radiograph is usually normal because the pulmonary-to-systemic flow ratio is generally less than two to one.UqJ
When an entire lung is drained by an anomalous connection, the main pulmonary arteries are slightly enlarged. One type of anomalous pulmonary vein is easily identified on the chest film. The"scimitar sign" consists of a linear opacity, usually but not always at the base of the right lung, which widens as it courses inferiorly and ends in the inferior vena cava.UqJ
The hypogenetic lung syndrome is a rare congenital anomaly that consists of anomalous pulmonary venous drainage to the inferior vena cava, hypoplastic or aplastic pulmonary artery segments, and hypoplastic or absent bronchi. The hypoplasia of the right lung secondarily may rotate the heart toward the right hemithorax and cause a mild dextrocardia.UqJ
Pulmonary venous anomalies may be identified with cross-sectional imaging and obviate the need for further studies. Because of the relatively high prevalence of PAPVC, a number of cases will be discovered incidentally during CT scans for other reasons. CT will demonstrate the course and termination of the anomalous vein, the bronchial distribution, abnormal lobation, and mediastinal shift and confirm the distinction from other venous structures, such as a left superior vena cava, pulmonary varices, and pulmonary arteriovenous fistulas. Since the majority of patients with PAPVC are asymptomatic, further evaluation after positive identification with CT is usually unwarranted. Complications of PAPVC result from pulmonary infection, atrial septal defect or dilation of the right atrial septal defect, or dilation of the right atrium and ventricle. Other imaging modalities may be required in these circumstances.UqJ
Pulmonary angiography remains the standard examination for locating all the pulmonary veins. Selective injection into the right and left pulmonary arteries will visualize all pulmonary veins during a prolonged filming sequence. Alternative methods of locating pulmonary veins at catheterization include exploring the right atrium and adjacent systemic veins and documenting the anomaly by the entrance of the catheter into the vein or by a small hand injection of contrast material.UqJ
References(参考文献):
Taveras & Ferrucci, Radiology, Volume 2, Chapter 83, Pathoangiography,
Physiology, and Chest Film in Atrial Septal Defect, by Larry P. Elliott.
Brody H: Drainage of the pulmonary veins into the right side of the heart.
Arch Pathol 33:221, 1942.
Kalke BR, Carlson RG, Ferlic RM et al: Partial anomalous pulmonary
venous connections. Am J Cardiol 20:91, 1967.
Roehm JOF Jr, Jue KL, Amplatz K: Radiographic features of the scimitar
syndrome. Radiology 85:856, 1966.
Mathey J, Galey JJ, Logears Y, et al: Anomalous pulmonary venous return
into inferior vena cava and associated bronchovascular anomalies
(the scimitar syndrome). Thorax 23:398, 1968.
Greene R, Miller SW: Cross-sectional imaging of silent pulmonary venous
anomalies. Radiology 159:279, 1986.
Goodwin JD, Tarver RD: Scimitar syndrome: Four new cases examined
with CT. Radiology 159: 15, 1986.
Pennes DR, Ellis JH: Anomalous pulmonary venous drainage of the left
upper lobe shown by CT scans. Radiology 159:22, 1986.
Olson MA, Becket GJ: The scimitar syndrome: CT findings in partial anomalous
pulmonary venous return. Radiology 159:25, 1986.
Schatz SL, Ryviker MJ. Deutsch AM, Cohen HR: Partial anomalous pulmonary
venous drainage of the right lower lobe shown by CT scans. Radiology 159:21, 1986.
文章来自：影像园
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