Guidelines
SCCT expert consensus document on computed tomography imaging before transcatheter aortic valve implantation (TAVI)/transcatheter aortic valve replacement (TAVR)

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Abstract

Computed tomography (CT) plays an important role in the workup of patients who are candidates for implantation of a catheter-based aortic valve, a procedure referred to as transcatheter aortic valve implantation (TAVI) or transcatheter aortic valve replacement (TAVR). Contrast-enhanced CT imaging provides information on the suitability of the peripheral access vessels to accommodate the relatively large sheaths necessary to introduce the prosthesis. CT imaging also provides accurate dimensions of the ascending aorta, aortic root, and aortic annulus which are of importance for prosthesis sizing, and initial data indicate that compared with echocardiographic sizing, CT-based sizing of the prosthesis may lead to better results for postprocedural aortic valve regurgitation. Finally, CT permits one to predict appropriate fluoroscopic projections which are oriented orthogonal to the aortic valve plane. This consensus document provides recommendations about the use of CT imaging in patients scheduled for TAVR/TAVI, including data acquisition, interpretation, and reporting.

Section snippets

Aortic valve stenosis

Aortic valve stenosis is a common disease and frequently affects patients of older age. When symptoms are present, and in selected situations even for asymptomatic persons, aortic valve replacement is indicated.1, 2, 3 Although surgery for aortic valve replacement can usually be performed at relatively low risk, some conditions substantially increase the risk of conventional surgery. The conditions include, among others, frailty, prior radiation therapy that caused significant damage to the

Data acquisition protocols

CT imaging in the evaluation for TAVI/TAVR should include imaging of the aortic root, aorta, and iliac, as well as common femoral arteries. Hence, a large volume must be covered. To achieve the desired accuracy, imaging of the aortic root must be synchronized to the electrocardiogram (ECG) either by retrospective ECG gating or through the use of prospective ECG triggering. Spatial resolution must be high to provide adequate imaging, especially of the aortic root and of the iliofemoral arteries,

Assessment of the access route

The iliofemoral axis remains the most common route of access for TAVI/TAVR. Ongoing refinements have resulted in progressive reduction of the profile of the delivery systems for transfemoral TAVI/TAVR, and the required sheath sizes can be expected to decrease further in the future. Current delivery profiles, as well as the corresponding vendor recommendations for minimal vessel diameters, are listed in Table 3. Single-plane angiography, which is typically performed at the time of coronary

Assessment of the aorta

In addition to the iliac and femoral arteries, the entire aorta should be evaluated by CT angiography before a TAVI/TAVR procedure if a transfemoral approach is considered. Transverse axial images and multiplanar reconstructions are commonly used. Contraindications to a femoral access include massive elongation with kinking of the aorta, dissection, or large thrombi protruding into the lumen or other obstacles that may prevent advancing the valve through the aortic lumen. If a transaortic

Aortic annulus

Choosing the appropriate prosthesis size requires accurate measurement of the dimensions of the aortic annulus. If the prosthesis size is too small, embolization may occur, and paravalvular regurgitation is more frequent, with negative clinical outcome.24, 25, 26 If the prosthesis is too large relative to the aortic annulus, rupture may occur which is often fatal.

The aortic annulus is not a separate anatomic structure. Much rather, it is formed by the 3 lowest points of the aortic valve cusps

Other aortic root dimensions

Besides aortic annulus size, other anatomic measures of the aortic root have relevance for TAVI/TAVR planning. They include distance of the coronary ostia to the aortic valve plane, aortic cusp length, width of the aortic sinus, width of the sinotubular junction, and width of the ascending aorta. These measurements are important to avoid potentially catastrophic complications such as coronary occlusion and root injury.39 CT is well suited to provide these measures because of its multiplanar

Aortic annulus plane for fluoroscopy

During catheter-based implantation especially of the balloon-expandable prosthesis, it is important to use a fluoroscopic projection that provides an exact orthogonal view onto the aortic annular plane. Theoretically, an unlimited number of projections exist which will provide such a view, but most operators prefer a projection whereby the right coronary cusp is central and closest to the image intensifier, whereas the left and noncoronary cusps are positioned symmetrically to either side of

Aortic valve calcification

Calcific aortic valve stenosis is pathologically characterized by thickening of the aortic valve cusps with large calcific nodules that protrude on the aortic surface of the cusps. Unlike surgical aortic valve replacement, the diseased aortic cusps are not removed in TAVI/TAVR. The presence of valvular calcifications may be of importance to ensure prosthesis anchorage and avoid dislodgement.46 By contrast, excessive calcification may hamper the apposition of the prosthesis to the irregular

Data elements to be included in the report

The data elements included in the report are shown in Table 12.

Summary

CT imaging plays an important role in procedural planning for TAVI/TAVR and should be a fully integrated component of any TAVI/TAVR program. The use of CT in TAVI/TAVR is multifaceted and should include the assessment of vascular access of the aortic valve, annulus, and root and of the orientation of the annulus plane. Importantly, the person responsible for the interpretation of the CT examination should be integrated in the TAVI/TAVR team to ensure appropriate incorporation into the patient

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    Conflict of interest: S. Achenbach has received speaker honoraria from Siemens and Edwards Lifesciences, research grants from Siemens and Bayer Schering Pharma, and serves as a consultant to Servier and Guerbet. V. Delgado has received consulting fees from Medtronic and St. Jude Medical. J. Hausleiter has received speaker honoraria from Abbott Vascular and Siemens Medical Solutions. P. Schoenhagen has no conflict of interest. J.K. Min has received research support from and served on the medical advisory board of GE Healthcare. J.A. Leipsic has received speaker honoraria from Edwards Lifesciences.

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