CT support of cardiac structural interventions

Abstract

Due to its high temporal and isotropic spatial resolution, CT has become firmly established for pre-procedural imaging in the context of structural heart disease interventions. CT allows to very exactly measure dimensions of the target structure, CT can provide information regarding the access route and, as a very valuable addition, volumetric CT data sets can be used to identify fluoroscopic projection angulations to optimally visualize the target structure and place devices. This review provides an overview of current methods and applications of pre-interventional CT to support adult cardiac interventions including transcatheter aortic valve implantation, percutaneous mitral valve intervention, left atrial appendage occlusion and paravalvular leak closure.

Figure 1.

Determination of aortic annulus dimensions in CT. (A,B) Creation of a double-oblique plane of the aortic annulus (white bold line) containing the lowest insertion points of the right, left, and noncoronary aortic valve cusps (C, arrows). Ao, aorta; LV, left ventricle. Three different approaches to determine aortic annulus size have been suggested: (D) From the long and short diameters, the mean diameter can be calculated. (E) From the annulus area, the diameter can be deducted under the assumption that this area changes to a circle when a valve is implanted. (F) From the circumference, the diameter can be derived assuming that the circumference will stay constant during the implantation and that the annulus will achieve a perfectly circular shape after prosthesis implantation.

Figure 2.

Assessment of native valve leaflet length and coronary ostium height. (A) Routinely, the length of the native valve leaflet and the height of the left and right coronary ostia are measured to predict possible ostial occlusion during prosthesis implantation. LM, left main coronary artery; RCA, right coronary artery. (B) Aortic root of a 82-year-old female patient showing a shallow left sinus of Valsalva, a native left leaflet length of 13 mm and an annulus-ostium distance of 12 mm, portending a moderate risk of ostial occlusion. (C) Subtotal stenosis of the left main coronary artery ostium after transcatheter implantation of an aortic valve prosthesis (arrow). (D) Left main coronary artery ostium after implantation of a stent (arrow).

Figure 3.

Determination of a suitable fluoroscopic angulation. (A) Double-oblique plane at the level of the aortic valve commissures. The white line corresponds to the angulation of an image plane that is orthogonal both to the aortic annulus plane and to the commissural line between the left and noncoronary aortic valve. R, right coronary cusp; N, noncoronary cusp; L, left coronary cusp. (B) The predicted angulation (LAO 2°/caudal 7°) was used during the TAVI procedure as C-arm angulation for the first aortogram. (C) Final angiogram with the implanted TAVI prosthesis.

Figure 4.

Caseous Mitral Annular Calcification. Caseous mitral annular calcification (arrows). (A) Density within the liquefied core is typically similar to contrast enhanced blood. (B) Hence, an additional non-enhanced acquisition is highly useful to identify this condition.

Figure 5.

Detection of left atrial appendage thrombus by CT angiography. (A) First pass CT angiogram demonstrating a filling defect (white arrow) in the left atrial appendage suggestive of a thrombus. (B) Delayed phase CT angiogram acquired 60 sec after contrast application confirms the presence of a thrombus (white arrow).

Figure 6.

Measurement of left atrial appendage ostium. (A) The plane of the LAA orifice is formed by the pulmonary vein ridge superiorly to the inferior junction of the left atrium and the LAA at the level of the circumflex artery. In a transaxial plane, the left circumflex coronary artery is identified (white arrow). Perpendicular to the left circumflex (white line), an oblique section is created which produces a vertical long-axis view of the heart (B) with the left circumflex coronary artery (white arrow) displayed in cross-section below the left atrial appendage (LAA) ostium. (C) Depending on the applied device system, the landing zone of the occluder varies. For a WATCHMAN^TM occluder, the plane of implantation is identified approximately 10–20 mm (*, here 15 mm) from the ostium (dashed lined) and measured between the left circumflex coronary artery and the edge of the landing zone (blue line). (D) Short axis of the plane of implantation for measurement of minimum (20 mm) and maximum (25 mm) diameter predicting a 27 mm WATCHMAN^TM occluder. (E) Imaging of the implanted 27 mm WATCHMAN^TM occluder.

Figure 7.

(A) Paravalvular leak (arrow) in a patient with a prosthetic aortic valve. Windowing is set to window 1500 HU and center 400 HU to minimize beam hardening effects. (B-H) A 53-year-old male patient with a paravalvular leak 8 months after bioprosthetic aortic valve replacement. (B,C,D) Pre-procedural CT angiography shows the presence of a paravalvular leak (white arrow) between the aortic valve prosthesis (Edwards CE Perimount 23 mm) and the noncoronary cusp. (E) CT-derived measurement in a double oblique plane revealed a 0.48 × 0.73 cm leak. The purple line corresponds to the desired plane in (F) which is orthogonal to the prosthetic valve plane (RAO 14°/caudal 6°) and was used during the implantation procedure for C-arm angulation (G). (G) Invasive angiogram of the implanted 7 mm occluder (Ductus arteriosus occluder Hyperion PDA-I 07) (white arrow) in RAO 14° and caudal 6° angulation. (H) Device enhancement imaging of the implanted occluder (white arrow).