The Ten Minute TAVR CT- A Guide to Effi cient and Effective Interpretation Of Pre-Procedure CTA Using Automated Software

Christopher Coleman, MD; Pragnesh Parikh, MD; Patricia Mergo, MD; Brian Shapiro, MDDepartment of Radiology, Mayo Clinic, Jacksonville, FL

© 2013 Mayo Foundation for Medical Education and Research

Measurements• Multiplanar reconstructions and software-assisted center line

drawing provides a cross sectional view of the desired portion of the aortoiliac system [Fig. 2].

• Iliac arteries evaluated for tortuosity and dense calcifi cations.

• Narrowest luminal diameter of each iliac/common femoral artery identifi ed [Fig. 3].

- Dictate the size of the sheath that can be introduced into the vessel and whether a transapical approach is required.

- Newer generation systems can be placed through an 18 French sheath, for which the suggested minimum vessel lumen diameter ranges from 6.0-6.5 mm.

- Oversized sheaths can result in serious vascular injury.

• Cross sectional measurements derived from software center line reconstruction

- Aortic sinus [Fig. 4]

- Sinotubular junction [Fig. 5]

- Maximum dimension of the ascending and descending aorta [Fig. 6].[6]

• The software attempts to assess the aortic annulus plane but manual manipulation is often required.

- Annulus is in plane formed by the inferior most insertion point of each of the three coronary cusps [Fig. 7].

- Oval approximation is created, and the short and long axis diameter, circumference and cross sectional area are calculated.

- Not necessarily be orthogonal to the left ventricular outfl ow tract.

- Then distance from the coronary ostia to the annulus plane can be assessed [Fig. 8].

- Qualitative burden of valve calcifi cation evaluated to minimize risk of occluding coronary ostia with compressed valve calcifi cations, as the valve implant displaces the native valve and its calcifi cations, rather than replace them.

Major Teaching Points: 1. Pre-procedure planning is vital to the success of TAVR.

2. CTA is critical to evaluate the entire aortofemoroiliac arterial system, which is often tortuous in the target population. CTA also appears to more accurately measure the aortic annulus.

3. Computer software can simplify and expedite the CTA planning for TAVR by using vessel centerlines to ensure orthogonal measurements. However, some manual manipulation is often required, during the aortic annulus measurement, as it is often not orthogonal to the left ventricular outfl ow tract.

4. Automated vessel measurements can underestimate luminal diameter in heavily calcifi ed arteries, as vessel lumen estimates tend to completely exclude large wall calcifi cations. Refi nements in software algorithms would be helpful to improve this shortcoming

Figure 2Center line illustration and the reconstructed CT generated automatically. From here, cross-sectional measurements from the LVOT through the femoral arteries can be recorded.

Figure 3

Computer-generated short and long axis diameter and cross sectional areas of the iliofemoral trees based on center line reformatting. Note the outline excludes areas of large calcifi cations. The true luminal cross-sectional area is probably more closely approximated by an outline which bisects these areas of calcifi ed plaque.

Figure 4Sinus of Valsalva. This plane is orthogonal to the left ventricular outfl ow tract, and can be measured automatically after center-line formation.

Figure 5Sinotubular junction measurements can also be obtained from software analysis.

Figure 6Descending aorta cross sectional area and minimum transverse dimensions

Figure 7

Aortic annulus with manual measurements of short and long axis and cross sectional area. The annulus plane is determined by fi nding the lowest insertion point of the valve cusp and performing manual reconstruction until all three cusp insertions are in a single plane.

Figure 8After the annulus plane is identifi ed, distance from the coronary cusps to the ostia of the left main

and right coronary arteries can be measured. These measurements still must be made by hand.

References1. Leon MB, Smith CR, Mack M, et al. Transcatheter aortic-valve

implantation for aortic stenosis in patients who cannot undergo surgery. N Engl J Med 2010;363:1597– 607.

2. Messika-Zeitoun D, Serfaty JM, Brochet E, et al. Multimodal assessment of the aortic annulus diameter: implications for transcatheter aortic valve implantation. J Am Coll Cardiol 2010;55:186 –94.

3. Webb JG, Pasupati S, Humphries K, et al. Percutaneous transarterial aortic valve replacement in selected high-risk patients with aortic stenosis. Circulation 2007;116:755– 63.

4. Achenbach S, Delgado V, et al. SCCT Expert Consensus Document on Computed Tomography Imaging Before Transcatheter Aortic Valve Implantation (TAVI)/transcatheter aortic valve replacement (TAVR). J Cardiovascular Computed Tomography 2012;6;366-380.

5. Willson AB, Webb JG, LaBounty TM, Achenbach S, Moss R, Wheeler M, Thompson C, Min JK, Gurvitch R, Norgard BL, Hague C, Toggweiler S, Binder RK, Freeman M, Poulson S, Wood DA, Leipsic J: 3-dimensional aortic annular assessment by multidetector computed tomography predicts moderate or severe paravalvular regurgitation after transcatheter aortic valve replacement: implications for sizing of transcatheter heart valves. J Am Coll Cardiol. 2012;59:1287–94.

6. Masson JB, Kovac J, Schuler G, Ye J, Cheung A, Kapadia S, Tuzcu ME, Kodali S, Leon MB, Webb JG: Transcatheter aortic valve implantation: review of the nature, management, and avoidance of procedural complications. JACC Cardiovasc Interv. 2009;2:811–920.

Dictation TemplateSpecifi c measurements for assessment for TAVI placement are as follows (measured at the narrowest point of the lumen of the measured segment):

Distance of left main to annulus: [] mmDistance of RCA to annulus: [] mmAortic diameter at the annulus: [] mmAnnulus circumference: [] mmAnnulus area: [] cm2Aortic diameter at level of sinus of valsalva: [] mmAortic diameter at the sinotubular junction: [] mmAortic diameter proximal ascending aorta: [] mmAortic diameter mid ascending aorta: [] mmAortic diameter distal ascending aorta: [] mmAortic diameter mid arch level: [] mmAortic diameter proximal descending aorta: [] mmAortic diameter distal abdominal aorta: [] mm

Right common iliac artery: [] mmLeft common iliac artery: [] mmRight external iliac artery: [] mmLeft external iliac artery: [] mmRight common femoral artery: [] mmLeft common femoral artery: [] mmAortic lumen: [atherosclerotic change]

Nonvascular fi ndings:Chest: []Abdomen: []Pelvis: []

Technique: The patient was given [] mL IV []. 0.75 mm sections with contrast enhancement and maximum intensity projections are reconstructed. The heart rate during the scan was [] beats per minute and the scan was reconstructed at [] % of the R-to-R interval. Additionally, a CTA of the chest/abdomen/pelvis was performed.

ProtocolCT imaging should include the aortic root through the common femoral arteries. Maximum slice thickness is 1mm, and imaging is obtained with breath holding. ECG gating should be performed when imaging the aortic root, either retrospectively or by ECG triggering during image acquisition.[4] Imaging should be performed during systole since this is when the annulus is largest.[5] Additionally, the annulus adopts a more rounded confi guration during systole, as opposed to more oval during diastole.

PurposeTranscatheter Aortic Valve Replacement (TAVR) is a new, minimally invasive alternative to open aortic valve replacement which has recently been approved in selected patients by the FDA. It has been shown to improve outcomes compared with medical therapy in patients who are unsuitable for surgical replacement.[1] Appropriate patient selection and correct prosthesis sizing are crucial to minimize complication-related morbidity such as aortic annulus rupture and signifi cant paravalvular regurgitation. Transesophageal echocardiography is the “gold standard” for aortic measurements and annulus sizing. However, Messika-Zeitoun et al. showed in 2010 that TEE signifi cantly underestimated the size of the aortic annulus.[2] CTA has been shown to more accurately assess aortic annulus size, especially in patients with more ovoid annulus morphologies. Appropriate prosthesis sizing is important in avoiding the major complications of TAVR, including aortic regurgitation and embolization.[3] Manual measurement using multiplanar reconstruction is possible and suggested, but remains time-consuming. We demonstrate the use of software, TeraRecon Aquarius Intuition version 4.4.8.36.843 (Foster City, CA) to facilitate effi cient, accurate measurements for pre-procedure planning.

There is a wealth of information critical to surgical planning that can be gained from pre-procedure CT. The patient must be shown to have an annulus diameter >18mm. Valve calcifi cations can be identifi ed. The peripheral access route can be evaluated.[4] Additionally, non-cardiothoracic abnormalities should be evaluated. At Mayo, we use the Edwards SAPIEN valve prosthesis [Fig. 1]

Figure 1Edwards SAPIEN Transcatheter Heart Valve shown alone and mounted on the deployment balloon.

Coned down intraoperative radiograph after successful deployment.