Current Status of CT Imaging Before Common Transcatheter Interventions for Structural Heart Disease

Figures

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  Figure 1. The different embryological origins of PFO and ASD are reflected in their morphological appearance. A PFO is the result of failed fusion between the interatrial groove (IAG) and the septum primum (arrow), resulting in an intermittent interatrial communication with an oblique trajectory between the atrial septal rims (dashed line in (a)). Conversely, an ASD is a permanent connection between the left and right atrium with a trajectory perpendicular to the axis of the interatrial septum and without overlapping septal rims. (dashed line in (b)). LA: left atrium; RA: right atrium; ASD: atrial septal defect; PFO: patent foramen ovale.

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  Figure 2. Ostium secundum ASD (asterisk in (a,b)) with inadequate septal rim, making this patient ineligible for transcatheter closure. Note the dilatation of the right ventricle due to chronic volume overload (c). RA; right atrium; LA: left atrium.

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  Figure 3. An 82-year-old man with severe symptomatic aortic stenosis. Double-oblique cross-sectional images through the aortic sinus in the systolic (a) and diastolic (b) phase. Note the thickened and heavily calcified leaflets in this tricuspid valve and the stenotic luminal area in systole (a).

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  Figure 4. Volume-rendered image of the aortic sinus illustrating the aortic annulus. The annulus is a virtual structure, formed by connecting the nadirs of the insertion points of the aortic leaflets (dotted line). The left and non-coronary sinus of Valsalva are indicated in red and purple.LAD: left anterior descendens artery; RCA: right coronary artery; LCX Left circumflex artery.

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  Figure 5. Recommended measurements at the level of the aortic annulus. Annular planimetry must be performed at the aortic annulus. Using double-oblique reformatted images, the correct plane lies just distally in the direction of the LVOT from the image where the leaflets can just barely be seen (asterisk in (a)). In most cases, the aortic annulus will have in cross-sectional images an oval shape, with short and long axes (red lines in (b)). Additional measurements are the annular perimeter (c) and annular area (d), marked in red.

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  Figure 6. Besides the aortic annulus, a number of other measurements (marked with red lines) are considered of importance to determine patient eligibility and optimal matching of the patient’s anatomy to a specific device size. These include the cross-sectional dimensions of the aortic sinus (a), the distances from the annular plane to the ostium of the left main coronary artery (b) and the right coronary artery (c), the dimensions of the sinotubular junction (d) and the maximum double-oblique diameter of the ascending aorta (e).

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  Figure 7. Prominent subvalvular calcification reaching over the anterior mitral valve leaflet (arrow). Subvalvular calcification can be encountered with varying degrees of severity and can lead to less stable device deployment. As such, its presence and amount must always be commented on.

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  Figure 8. Assessing the patency route for the transfemoral delivery of an aortic THV. Initially, a comprehensive view of the thoraco-abdominal aorta is presented, utilising both maximum intensity projection (MIP) (a) and volume rendering (VR) techniques (b). This enables a global evaluation of the calcification load and distribution, most effectively visualised in the MIP image (a), while vascular tortuosity is better illustrated on the VR images (b). Furthermore, a curved multiplanar reformation (cMPR) of each iliac axis is acquired (only the right side is depicted here) for optimal visualisation of the lumen (c). Cross-sectional images (d–f) taken perpendicularly to this centreline provide an accurate evaluation of the true luminal diameter (red lines), which is essential for transporting the THV. In every segment of the arterial access route, identifying the narrowest luminal diameter is crucial, as localised narrowing can hinder device passage and increase procedural complexity and complication rates. In this instance, the right external iliac artery and the common iliac artery have focal minimal luminal diameters of 4–5 mm, rendering them less suitable for device transport compared to…

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  Figure 9. One of the possible access routes for both balloon- and self-expandable THVs is the transaortic approach. This approach, however, requires a clear landing zone in the anterior wall of the ascending aorta at about 6 cm above the annular plane (a). Panel (b) shows extensive wall calcification in an 86-year-old man with unavailable femoral access due to severely stenotic iliac arteries. In this patient, the transaortic approach is also precluded by the aforementioned very extensive calcifications in the aortic wall (arrow). The investigation of any possible obstruction along the possible access routes is paramount for procedural success, not only for the evaluation of route patency but also for determining patient eligibility to receive the device.

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  Figure 10. Useful pre-planning measurements to obtain before pre-transcatheter mitral valve repair in an 80-year-old female with a heavily calcified mitral annulus. The first step (A) is to create a short-axis view by cutting through the apex of the left ventricle and then identifying the left fibrous trigone (B) on the short axis. From there, the cross-hair is aligned along the right fibrous trigone (C) on the long axis to finally obtain the mitral annulus plane (D), from which the following measurements are taken: trigone–trigone diameter (yellow line), septo-lateral distance (blue line), inter-commissural distance (purple line) and area of the annulus (red circle). Finally, to identify the neo-LVOT, the shortest distance on the LVOT view between the septal leaflet of the mitral valve and the LVOT is determined (E), against the plane from which the aortomitral angle can be measured (yellow lines). Perpendicular to this level, the neo-LVOT area will be contoured in the short-axis view (red circle). Here, the angle was 44°, which indicates a low risk of neo-LVOT obstruction (risk increases when the angle approaches or exceeds 90°). The area was <190 mm2, indicating a high risk of neo-LVOT…

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  Figure 11. Useful pre-planning measurements to provide before pre-transcatheter mitral valve repair after prior mitral valve repair: valve in ring (yellow contours, upper line) and valve in valve (blue contours, bottom line). The steps to determine the neo-LVOT are similar: First, (A) obtain a short-axis view of the valve plane by cutting through the apex of the left ventricle on the long axis. From the centre of the valve plane, rotate the cross-hair through the LVOT on the short axis to obtain a long-axis LVOT view (B). To easily identify the most inferior point of the septal mitral valve leaflet, we suggest increasing slab thickness (C), and from there, position the centre of the cross-hair at this point and rotate the cross-hair to cut through the LVOT to obtain the neo-LVOT on the short axis (D). For the long-axis LVOT (back to thin slice), provide the annulus-to-septum distance (red line) and the neo-LVOT area (red circle). An annulus-to-septum distance of <18 mm indicates a higher risk of neo-LVOT obstruction.

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  Figure 12. Benefit of an additional delayed-phase image acquisition to distinguish between slow flow and a true thrombus in the LAA. The initial acquisition in the arterial phase shows the incomplete opacification of the LAA (asterisk in (a)). However, an additional delayed-phase acquisition shows homogeneous opacification, excluding the presence of a thrombus (asterisk in (b)). This is important, as an LAA thrombus is a contraindication for LAA closure and represents an increased risk for thromboembolic stroke. LAA: left atrial appendage.