Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science & Great Ormond Street Hospital for Children, London, UK.
Eur J Radiol. 2012 Dec;81(12):3912-7. doi: 10.1016/j.ejrad.2012.07.014. Epub 2012 Aug 11.
Transcatheter aortic valve replacement (TAVR) has been successfully used to treat patients with failing aortic bioprostheses. Computed tomography (CT) is the usual method of pre-procedural imaging for TAVR in the native position; however, the optimal modality for valve-in-valve procedures has not been established. CT can assess intracardiac anatomy and is superior to cardiovascular magnetic resonance (CMR) in the assessment of coronary artery disease. However, CMR can provide superior haemodynamic information, does not carry the risk of ionising radiation, and may be performed without contrast in patients with renal insufficiency. In this study, we compared CT and CMR for the evaluation of TAVR in a small cohort of patients with existing aortic bioprostheses.
21 patients with aortic bioprostheses were prospectively evaluated by CT and CMR, as pre-assessment for TAVR; agreement between measurements of aortic geometries was assessed.
16/21 patients had aortic bioprostheses constructed with a metal ring, and 5/21 patients had a metal strut construction. Patients with metal struts had significant metal-artefact on CMR, which compromised image quality in this region. There was good agreement between CT and CMR measurements of aortic geometry. The mean difference (d) in annulus area-derived diameter was 0.5mm (95% limits of agreement [L.A] 4.2mm). There was good agreement between modalities for the cross-sectional area of the sinuses of valsalva (d 0.5 cm(2), L.A 1.4 cm(2)), sinotubular junction (d 0.9 cm(2), L.A 1.5 cm(2)), and ascending aorta (d 0.6 cm(2), L.A 1.4 cm(2)). In patients without metal struts, the left coronary artery height d was 0.7 mm and L.A 2.8mm.
Our analysis shows that CMR and CT measurements of aortic geometry show good agreement, including measurement of annulus size and coronary artery location, and thus provide the necessary anatomical information for valve-in-valve TAVR planning. However, in patients with metal strut aortic valve constructions, CT should be performed due to the presence of limiting metal artefacts on CMR. CMR may be considered as an appropriate alternative to CT in patients in whom iodinated contrast agents are contraindicated or where additional haemodynamic assessment with phase-contrast CMR is required.
经导管主动脉瓣置换术（TAVR）已成功用于治疗主动脉生物瓣衰竭的患者。对于 TAVR 在原生位置的术前影像学，计算机断层扫描（CT）是常用的方法；然而，瓣中瓣手术的最佳方式尚未确定。CT 可以评估心内解剖结构，在冠状动脉疾病的评估方面优于心血管磁共振（CMR）。然而，CMR 可以提供更好的血液动力学信息，在肾功能不全的患者中，无需使用造影剂即可进行，且没有电离辐射的风险。在这项研究中，我们比较了 CT 和 CMR 在一小批有主动脉生物瓣的患者中的 TAVR 评估效果。
21 例主动脉生物瓣患者前瞻性地接受了 CT 和 CMR 评估，作为 TAVR 的术前评估；评估了主动脉几何结构测量值之间的一致性。
21 例患者中，16 例使用金属环构建主动脉生物瓣，5 例使用金属支柱构建。使用金属支柱的患者 CMR 上有明显的金属伪影，使该区域的图像质量受到影响。CT 和 CMR 测量的主动脉几何形状之间有很好的一致性。瓣环面积衍生直径的平均差异（d）为 0.5mm（95%一致性区间[L.A]为 4.2mm）。CMR 和 CT 对于窦部面积（d 0.5cm2，L.A 1.4cm2）、窦管交界（d 0.9cm2，L.A 1.5cm2）和升主动脉（d 0.6cm2，L.A 1.4cm2）的横截面积有很好的一致性。在没有金属支柱的患者中，左冠状动脉高度 d 为 0.7mm，L.A 为 2.8mm。
我们的分析表明，CMR 和 CT 测量的主动脉几何形状具有很好的一致性，包括瓣环大小和冠状动脉位置的测量，因此为瓣中瓣 TAVR 规划提供了必要的解剖信息。然而，在主动脉瓣有金属支柱结构的患者中，由于 CMR 上存在限制金属伪影，应进行 CT 检查。在对碘造影剂有禁忌或需要相位对比 CMR 进行额外血液动力学评估的患者中，CMR 可作为 CT 的适当替代。
