Department of Radiology, Mayo Clinic, Rochester, MN 55905-0002, USA.
Radiographics. 2012 Sep-Oct;32(5):1399-420. doi: 10.1148/rg.325115727.
Valvular disease is estimated to account for as many as 20% of cardiac surgical procedures performed in the United States. It may be congenital in origin or secondary to another disease process. One congenital anomaly, bicuspid aortic valve, is associated with increased incidence of stenosis, regurgitation, endocarditis, and aneurysmal dilatation of the aorta. A bicuspid valve has two cusps instead of the normal three; resultant fusion or poor excursion of the valve leaflets may lead to aortic stenosis, the presence of which is signaled by dephasing jets on magnetic resonance (MR) images. Surgery is generally recommended for patients with severe stenosis who are symptomatic or who have significant ventricular dysfunction; transcatheter aortic valve implantation (TAVI) is an emerging therapeutic option for patients who are not eligible for surgical treatment. Computed tomography (CT) is an essential component of preoperative planning for TAVI; it is used to determine the aortic root dimensions, severity of peripheral vascular disease, and status of the coronary arteries. Aortic regurgitation, which is caused by incompetent closure of the aortic valve, likewise leads to the appearance of jets on MR images. The severity of regurgitation is graded on the basis of valvular morphologic parameters; qualitative assessment of dephasing jets at Doppler ultrasonography; or measurements of the regurgitant fraction, volume, and orifice area. Mild regurgitation is managed conservatively, whereas severe or symptomatic regurgitation usually leads to valve replacement surgery, especially in the presence of substantial left ventricular enlargement or dysfunction. Bacterial endocarditis, although less common than aortic stenosis and regurgitation, is associated with substantial morbidity and mortality. Electrocardiographically gated CT reliably demonstrates infectious vegetations and benign excrescences of 1 cm or more on the valve surface, allowing the assessment of any embolic complications.
瓣膜疾病在美国施行的心脏手术中约占 20%。它可能是先天性的，也可能继发于其他疾病过程。一种先天性异常，即二叶式主动脉瓣，与狭窄、反流、心内膜炎和主动脉瘤样扩张的发生率增加有关。二叶瓣有两个瓣叶而不是正常的三个；瓣叶融合或活动不良可能导致主动脉瓣狭窄，磁共振（MR）图像上相位失准喷射提示存在这种狭窄。对于有症状或有明显心室功能障碍的严重狭窄患者，一般建议手术治疗；对于不符合手术治疗条件的患者，经导管主动脉瓣植入术（TAVI）是一种新兴的治疗选择。CT 是 TAVI 术前规划的重要组成部分；它用于确定主动脉根部尺寸、外周血管疾病严重程度和冠状动脉状况。主动脉瓣关闭不全引起的主动脉瓣反流同样会导致 MR 图像上出现喷射。反流的严重程度基于瓣叶形态学参数分级；多普勒超声心动图上相位失准喷射的定性评估；或反流分数、容量和瓣口面积的测量。轻度反流保守治疗，而重度或有症状的反流通常导致瓣膜置换手术，特别是在存在大量左心室扩大或功能障碍的情况下。细菌性心内膜炎虽然比主动脉瓣狭窄和反流少见，但与较高的发病率和死亡率相关。心电图门控 CT 可靠地显示感染性赘生物和瓣膜表面 1 厘米或以上的良性赘生物，允许评估任何栓塞并发症。
