Gated Computed Tomography Evaluation of the Aortic Root for Treatment Planning of Patients With Aortic Stenosis

Abstract

Computed tomography image analysis for transcatheter aortic valve replacement requires a comprehensive analysis of aortic root anatomy. There is no absolute threshold for any measurement that can determine treatment choice. Rather, image interpretation is a qualitative exercise, and decisions are based on accumulated experience from computed tomography anatomical review and treatment outcomes that help to refine future case selection. This review addresses potentially challenging scenarios for transcatheter aortic valve replacement and describes the imaging findings that should be considered in deciding a treatment approach. Common challenges are discussed with images to illustrate typical findings.

Keywords: aortic valve; computed tomography; surgical aortic valve replacement; transcatheter aortic valve replacement.

Figure 1

Representative images of mild (A), moderate (B), and severe (C) calcification. Mild calcification: (A) A short-axis view of the aortic annulus showing 1 nodule of calcification extending <5.0 mm and covering <10% of the perimeter; the nodule is located between the right coronary cusp and noncoronary cusp (NCC). (D) Semiautomated volume calcium detection at the level of the region of interest of mild calcification. (G) Volume-rendered image showing mild calcification. Moderate calcification: (B) Two nodules at the level of the aortic annulus covering <20%. One nodule extending >5.0 and <10.0 mm. (E) Semiautomated volume calcium detection at the level of the region of interest of moderate calcification. (H) Volume-rendered image showing moderate calcification. Severe calcification: (C) Layered calcification covering >20% of the perimeter and 1 nodule below the NCC extending >10.0 mm in depth and >5.0 mm in diameter. (F) Semiautomated volume calcium detection at the level of the region of interest of severe calcification. (I) Volume-rendered image showing severe left ventricular outflow tract calcification.

Figure 2

Representative images of calcium deposits by location along the circumference of the annulus. (A) Two calcium nodules are present, with a small nodule under the noncoronary cusp and a larger nodule in the aortic mitral curtain. (B) Calcium arc adjacent to the membranous septum and right ventricle and right atrium. (C) Two calcium nodules are present, 1 in the left ventricular myocardium under the right coronary cusp and the second under the left coronary cusp in the left ventricular free wall.

Figure 3

Approaches to annular measurement where there is focal vs extensive left ventricular outflow tract calcification. (A) Annular measurement outside (including) the calcification obtains an area measurement of 608.0 mm², which overestimates the actual treatable annular area. (B) Annular measurement inside (excluding) the calcification shows an area measurement of 545.0 mm². (C) Annular measurement through a focal calcium nodule obtains an area measurement of 396.0 mm², which most accurately estimates the treatable annulus.

Figure 4

Representative images of high and low calcium load in noncontrast and contrast scans. (A) Noncontrast image of a patient with an aortic valve calcium score of 2736 AU and (B) contrast image in the same patient showing calcification volume of 992.0 mm². (C) Noncontrast image of the aortic valve with a calcium score of 1828 AU and (D) contrast image showing calcification volume of 460.0 mm².

Figure 5

An illustrative case of treatment of a sinotubular junction (STJ) with extensive calcification using a short-frame balloon-expandable valve. (A) Cross-sectional image showing measurement of the STJ diameter and presence of significant calcification. (B) Volume-rendered image of the aortic root showing the distance from aortic annulus to STJ calcification. (C) Visualizing of planned valve implantation and expected interaction STJ calcification at the planned implantation depth. (D) Post-TAVR volume-rendered image showing adequate distance from STJ calcification. TAVR, transcatheter aortic valve replacement.

Figure 6

Illustrative examples of bicuspid valves. (A) Raphe calcification with contralateral leaflet calcification and (B) raphe calcification without contralateral leaflet calcification.

Figure 7

Illustrative cases of bicuspid valves with flared and tapered aortic root anatomy. The flared aortic root (A) has adequate space for valve implantation as seen by the interaction between the aortic root and the planned valve (B). The tapered aortic root (C) does not have adequate space for valve implantation based on the interaction between the aortic root and planned transcatheter aortic valve replacement prosthesis (D).

Figure 8

Two contrasting cases of low left main. The first case shows a left main coronary height of 11.2 mm (A), heavy calcification of the left coronary leaflet tip and relatively narrow sinus of Valsalva width (B), and increased risk of left main obstruction with valve implantation on the volume-rendered image (C). The second case presents a left main coronary height of 9.0 mm (D), low burden of calcification of the left coronary leaflet tip and relatively wide sinus of Valsalva width (E), and low risk of left main obstruction with valve implantation on the volume-rendered image (F).

Figure 9

Illustrative case of a small annulus treated with a self-expandingACURATEneo2 valve. (A) Aortic annular measurement of 325.6 mm², perimeter of 64.5 mm, and nodular calcification, (B) left ventricular outflow tract measurement of 321.5 mm² and nodular calcificaition, (C) longitudinal images of the aortic root, and (D) fluoroscopic image of the ACURATE neo2 (Boston Scientific) small valve size deployed.

Central Illustration

Components for CT evaluation of aortic root including LVOT calcification, leaflet and STJ calcification, assessment of bicuspid valves, left main closure risk, and procedural planning for large or small annuli.