computed tomography imaging in the context of ... · 2.2. ecg-synchronized cta of the aortic root...

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GUIDELINES

Computed Tomography Imaging in theContext of Transcatheter Aortic ValveImplantation (TAVI)/TranscatheterAortic Valve Replacement (TAVR)
An Expert Consensus Document of theSociety of Cardiovascular Computed Tomography
Philipp Blanke, MD,a Jonathan R. Weir-McCall, MBCHB, PHD,b Stephan Achenbach, MD,c Victoria Delgado, MD, PHD,d

Jörg Hausleiter, MD,e Hasan Jilaihawi, MD,f Mohamed Marwan, MD,c Bjarne L. Nørgaard, MD, PHD,g

Niccolo Piazza, MD, PHD,h Paul Schoenhagen, MD, PHD,i Jonathon A. Leipsic, MDa

1. PREAMBLE/INTRODUCTION

Since the publication of the first expert consensusdocument on computed tomography imaging beforetranscatheter aortic valve implantation (TAVI)/trans-catheter aortic valve replacement (TAVR) by the So-ciety of Cardiovascular Computed Tomography(SCCT) in 2012 (1), there has been tremendousadvancement in the field. Significant technologicaladvancements and a wealth of trial data have led todeep integration of TAVI/TAVR and CT Imaging intoclinical practice. The indications for TAVI/TAVR as thetreatment strategy for patients with symptomatic se-vere aortic stenosis (AS) has expanded from those who

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From the aDepartment of Radiology, St Paul’s Hospital & University of BritibDepartment of Radiology, University of Cambridge, Addenbrooke’s Hosp

Cardiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen,

Center, Leiden University Medical Center, Leiden, the Netherlands; eM

Maximilians-Universität München, Munich, Germany; fNew York UnigDepartment of Cardiology, Aarhus University Hospital, Aarhus, Denmark

Canada; and the iImaging Institute and Heart&Vascular Institute, Cleveland

This paper will be copublished in the Journal of the Cardiovascular Compute

Dr. Blanke is a consultant for Edwards Lifesciences and Circle Cardiovascu

Edwards Lifesciences, Medtronic, Neovasc, and Tendyne Holdings, for whi

receives speaker fees from Abbott Vascular; and has received departme

Biotronik, Edwards Lifesciences, GE Healthcare, and Boston Scientific. D

Abbott Vascular and Edwards LifeSciences. Dr. Jilaihawi has acted as a

research grants from Medtronic and Abbott Vascular. Dr. Marwan has receiv

Edwards Lifesciences. Dr. Norgaard has received unrestricted institutional r

and HeartFlow. Dr. Piazza is a clinical proctor and consultant for, has receiv

board and steering committee for Medtronic. Dr. Leipsic serves as a consul

Cardiovascular Imaging; and receives speaking fees from GE Healthcare.

relationships relevant to the contents of this paper to disclose.

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are ineligible for surgery or high risk surgical candi-dates to also now include those at intermediate riskfor conventional surgical valve replacement (2–6).

Advances in non-invasive imaging have supportedgrowth and maturation of the field. Clinical outcomeshave improved based on the thoughtful integration ofadvanced non-invasive imaging into patient selec-tion, treatment planning, device selection, and de-vice positioning. While computed tomography (CT)was initially used primarily for the assessment ofperipheral access, the role of CT has grown substan-tially and CT is now the gold standard tool for annularsizing, determination of risk of annular injury andcoronary occlusion, and to provide co-planar

https://doi.org/10.1016/j.jcmg.2018.12.003

sh Columbia, Vancouver, British Columbia, Canada;

ital, Cambridge, United Kingdom; cDepartment of

Germany; dDepartment of Cardiology, Heart Lung

edizinische Klinik und Poliklinik I der Ludwig-

versity Medical Center, New York, New York;

; hMcGill University Health Centre, Montreal, QC,

Clinic Lerner College of Medicine, Cleveland, Ohio.

d Tomography.

lar Imaging; and provides CT core lab services for

ch he receives no direct compensation. Dr. Delgado

ntal unrestricted research grants from Medtronic,

r. Hausleiter has received speaker honoraria from

consultant for Edwards Lifesciences; and received

ed speaker honoraria from Siemens Healthcare and

esearch grants from Edwards Lifesciences, Siemens,

ed research grants from, and serves on an advisory

tant and has stock options in HeartFlow and Circle

All other authors have reported that they have no

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https://doi.org/10.1016/j.jcmg.2018.12.003

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Blanke et al. J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 1 2 , N O . 1 , 2 0 1 9

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fluoroscopic angle prediction in advance of the pro-cedure. Further benefits of cardiac CT have alsobeen demonstrated in the follow-up of TAVI/TAVRfor assessment of post-procedural complicationsincluding identification of leaflet thickening (7,8).

Since the last SCCT consensus statement, there hasbeen a substantial volume of new data publisheddescribing the use of CTA in TAVI/TAVR planning andpost-procedural assessment. This updated consensusstatement has been written to better reflect the datanow available. The content and recommendations ofthis document reflect an expert consensus taking intoconsideration all published literature, but is not initself a systematic review. For recommendations,level of consensus was graded as strong ($9 inagreement out of the 11 members of the writinggroup), moderate (7 to 8) and weak (6). Any recom-mendations with less than 6 of the author group insupport of the statement were not adopted into thisexpert consensus document.

2. CT DATA ACQUISITION AND

RECONSTRUCTION

Data acquisition strategies and scanning protocolsvary depending on scanner manufacturer, system,and institutional preferences (9). This documentprovides recommendations for reliable CT imageacquisition for TAVI/TAVR planning. The keycomponent of all approaches is an ECG-synchronizedcomputed tomographic angiography (CTA) data setthat covers at least the aortic root in order to provideartifact free anatomical information of the aortic root,followed by a commonly non-ECG synchronized CTAdata acquisition of the aorto/ilio/femoral vasculaturefor assessment of the access vasculature. Ideally, bothacquisitions are combined in a comprehensive scan-ning protocol with a single contrast administration.The sequence of patient preparation and the relevantprinciples of CT data acquisition will be explained inbrief below.

2.1. SCAN STRATEGY AND SCAN COVERAGE. Ingeneral, two different approaches are used tocombine the ECG-synchronized data set of the aorticroot structures and the non-ECG-synchronizedcomputed tomography angiography (CTA) of theaorto/ilio/femoral vasculature into one comprehen-sive acquisition protocol:

1) Cardiac ECG-synchronized data set of the aorticroot and heart followed by a non-ECG-synchronized CTA of the thorax, abdomen, andpelvis. Although this approach can result in repeatdata acquisition of the aortic root and cardiacstructures, the time-intensive ECG-synchronized

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data acquisition is kept to a minimum, allowing fora reduction of the overall contrast dose. Further-more, limiting the ECG-synchronized data acqui-sition decreases the radiation dose-intensiveportion of the examination, despite parts of thescan range possibly being covered twice. The ECG-synchronized data set should at least cover theaortic root, but can include the entire heart.

2) ECG-synchronized data acquisition of the thoraxfollowed by a non-ECG-synchronized CTA of theabdomen and pelvis. A disadvantage of thisapproach is the higher radiation dose, and therelatively long acquisition time required for theentire thorax with potential need for largercontrast dose and risk of breathing artifacts.

The scanner hardware employed may furtherdictate which of these approaches is employed.

2.2. ECG-SYNCHRONIZED CTA OF THE AORTIC ROOT

AND HEART: ACQUISITION TECHNIQUE. The selectedacquisition mode as well as exposure settings shouldaccount for dynamic changes of aortic root geometryand dimensions throughout the cardiac cycle. Giventhat aortic root dimensions are commonly larger insystole (10,11), and that most sizing algorithms fortranscatheter heart valves are based on systolic di-mensions, systolic scan coverage is recommended.However, diastolic information may be valuable forevaluation of aortic valve morphology and rarely, thelargest dimensions of the annulus may occur indiastole in the setting of inversed dynamism in septalhypertrophy (11–13). For that reason, image acquisi-tion covering the entire cardiac cycle should beconsidered. This wider phase of acquisition offeringsystolic and diastolic data may be particularly usefulif systolic reconstructions are degraded by artifact.Scan coverage should at least include the aortic rootbut coverage of the entire heart is beneficial.

For CT systems with limited detector coverage, i.e.,systems that cannot cover the entire aortic rootwithin one rotation, retrospective ECG-gating allowscoverage of the entire cardiac cycle, while offeringmost flexibility regarding data salvage by means ofECG-editing. Dose-modulation may be used to miti-gate the high radiation exposure, with peak tubecurrent applied during at least systole. However, tubecurrent outside of the peak acquisition windowshould be maintained to such a level as to allow forcharacterization of the aortic annulus and valve.Prospective ECG-triggering may constitute an alter-native. However, this technique is more susceptibleto step-artifacts in the setting of increased heart ratevariability (e.g. premature contractions, atrial fibril-lation) with the risk of rendering images inadequate

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TABLE 1 Preferred Mode of Acquisition for ECG-Synchronized CTA of the Aortic Root Stratified by Scanner System

Manufacturer Scanner Geometry Preferred Acquisition Mode

GE 64-row family Spiral/helical acquisition with retrospectively ECG-gated image reconstruction

Revolution (256 row) Prospectively ECGgated, axial one beat acquisition

Philips All scanners Spiral/helical acquisition with retrospectively ECG-gated image reconstruction

Siemens All scanners Spiral/helical acquisition with retrospectively ECG-gated image reconstruction

Toshiba 64/80-row family Spiral/helical acquisition with retrospectively ECG-gated image reconstruction

Aquilion One (320/640 row) Prospectively ECGgated, axial one beat acquisition

J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 1 2 , N O . 1 , 2 0 1 9 Blanke et al.J A N U A R Y 2 0 1 9 : 1 – 2 4 Guidelines

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for quantitative analysis, and does not allow for im-age salvage by means of ECG-editing. If employed,the acquisition window should be kept wide to coverat least systole.

For systems with whole-heart coverage (i.e., 16-cmdetector coverage), an ECG-gated one beat acquisi-tion should be employed. Peak tube current should beapplied at least during systole, with consideration forcoverage of the entire cardiac cycle. Recommendedacquisition mode for employed scanner systems arelisted in Table 1.

Other acquisition settings, in particular tubevoltage and tube current settings should followinstitutional policies and preferences but shouldallow for acquisition of image data with sufficientlylow image noise to ensure fully diagnostic imagequality in thin-slice reconstructions. Guidance onacquisition settings is outlined in the ‘Radiation pa-rameters’ section below (9). In centers with multiplescanners, matching the most complex patients (suchas those with arrhythmias, cardiac failure, or chronickidney disease) to higher specification scanners (suchas those with whole heart coverage, or dual sources)should be considered (14).

2.3. NON-ECG SYNCHRONIZED CTA OF THE AORTO/ILIO/

FEMORAL VASCULATURE: ACQUISITION TECHNIQUE.

The CTA of the aorto/ilio/femoral vasculature shouldextend from the upper thoracic aperture to the lessertrochanter to include the thoracic and abdominalaorta, the iliac arteries and common femoral arteries,the latter constituting the most common vascularaccess site. For a more comprehensive evaluation thescan range can be extended cephalad to fully includethe subclavian arteries for assessment of this alter-native access route (15). Most commonly, this CTA isperformed employing a helical, non-ECG synchro-nized data acquisition immediately following theECG-synchronized data set of the aortic root. Otheracquisition settings, in particular tube voltage andtube current settings should follow institutional pol-icies and preferences, but should allow for acquisitionof image data with sufficiently low image noise toensure fully diagnostic image quality in thin-slice

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reconstructions. Most scanner systems require abrief intermission between the ECG-synchronizedand non-synchronized data acquisition to repositionthe table and adjust scan settings. This needs to beaccounted for by the contrast administration protocolin order to allow for sufficient contrast attenuation ofthe aorto/ilio/femoral vasculature.

2.4. RADIATION PARAMETERS AND CONSIDERATIONS.

Acquisition parameters should employ the ‘As low asreasonably achievable’ (ALARA) principle (9). Ac-cording to recommendations on radiation protectionin cardiovascular CT by the Society of CardiovascularComputed Tomography (SCCT), a tube potential of 100kV should be considered for patients weighing #90 kgor with a body mass index (BMI) #30 kg/m2; whereas atube potential of 120 kV is usually indicated for pa-tients weighing >90 kg and with a BMI> 30 kg/m2 (9).Tube current should be adjusted, based on individualpatient’s size, to the lowest setting that guaranteesacceptable image noise (9). Expected increase in im-age noise with lower tube current can be mitigatedwith the use of iterative image reconstruction. Themajority of commercially available scanner systemsprovide software algorithms to automatically adjustexposure parameters to the patient’s body habituswithin defined boundaries.

To date, patients being treated with TAVI/TAVRhave predominantly been septuagenarians and octo-genarians with the mean age of patients receivingTAVI/TAVR being 79.8 to 83.6 years in high and in-termediate risk trials, 79.1 years in the all comerNOTION trial and 80.1 years in the low risk OBSER-VANT registry with mean age not expected to dropbelow 75 years of age in low risk cohorts (4–6,16,17).As a result the primary concern for the imaging pro-tocol should be to ensure diagnostic quality images,and to minimize the need for repeat CTA and repeatcontrast administration. In case of younger patients,the most effective mode for reducing radiation dose isto minimize the scan volume performed using ECG-synchronization as well as limiting the peak dosecoverage when using dose modulation. Prospectivelytriggered acquisitions focusing on systole can be

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TABLE 2 Recommendations for IV Contrast Administration

Parameter Recommendation

Iodine concentration Iodinated contrast agent as per institutional standards

Flow rate 4–6 ml/s

Volume As per institutional standard for routine coronary cardiac CT, commonly50–100 cc

IV-access Antecubital vein

Timing Bolus tracking to allow for peak contrast in the ascending aorta (mayvary with scanning system used)

TABLE 3 Summary o

Recommendation

The imaging volume sh

Imaging of the aortic r

Imaging of the aorta a

Choice of acquisition m

CT acquisitions should

Thin slice collimation a

In patients with an eGF

In patients with eGFR <

Routine use of beta blo

Beta blocker use may b

Use of nitroglycerin is

*Based on level of consens

ALARA ¼ as low as reasotranscatheter aortic valve



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considered a reasonable alternative particularly inpatients with lower and regular heart rates.

2.5. CONTRAST ADMINISTRATION. Intravenous contrastadministration is required for assessment of theaortic root anatomy and peripheral vasculature. Inparticular accurate identification of the annular planeand contour, as well as accurate evaluation of theaccess route requires sufficient contrast enhance-ment. Optimal images require high intra-arterialopacification, and attenuation values should exceed250 Hounsfield units (9).

Use of dual head injector and antecubital IV accessis recommended. Timing of contrast administrationand the start of the ECG-synchronized data acquisi-tion should be achieved using bolus tracking with aregion of interest in the ascending aorta, althoughvariation occurs with the specific scanner systememployed. Flow rates of 4 to 6 ml/s commonly resultin sufficient contrast attenuation, but should beadjusted to both, body habitus and iodine concen-tration of the contrast agent employed (Table 2). Totalcontrast volume commonly varies between 50 and100 cc, with higher volumes needed in larger patientsand in older CT scanners with lower Z-axis coverage.In general, optimization of the comprehensive

f Recommendations for CT Acquisition Prior to TAVI/TAVR

ould include the aortic root, aortic arch and ilio-femoral access

oot should be performed using ECG-synchronized acquisition

nd iliofemoral vessels can be performed without ECG synchronization

ode should be tailored according to available scanner technology

focus on optimization of image quality while in accordance with ALARA princi

nd reconstructed slice thickness #1 mm for the root and #1.5 mm for the per

R $30 ml/min/1.73 m2 no pre hydration is required

30 ml/min/1.73 m2 reduction of iodinated contrast volume and prehydration

ckade is not recommended.

e considered in selected cases and should be used cautiously with careful clin

contra-indicated

us.

nably achievable; ECG ¼ electrocardiogram; eGFR ¼ estimated glomerular filtration rate; Creplacement.


scanning protocol for the scanning system employedallows for lower overall contrast volumes (seeTable 3).

In patients with impaired kidney function totalamount of contrast should be reduced to a minimumwhile still ensuring sufficient contrast attenuation.This can be achieved using lower flow rates as low as 3ml/s, low tube potential (down to 80kVp), multi-phasic contrast injection protocols and diligent opti-mization of the scanning protocol and timing (18,19).Prospective high pitch imaging is an alternative use-ful adjunct to low contrast dose whilst maintainingimage quality (20).

2.6. PATIENT PREPARATION. Patients should beinstructed to maintain an adequate fluid intake priorto the examination. In patients with eGFR $30 ml/min/1.73 m2, even in the presence of concomitant riskfactors, a regime of no prophylaxis has been shown tobe non-inferior to IV hydration for the prevention ofacute kidney injury (21). In cases with severe renalimpairment, cautious pre-scan intravenous hydrationmay be beneficial and should be considered accordingto institutional protocols (22).

For administration of iodinated contrast, at least a20-gauge intravenous access should be placed, pref-erably in an antecubital vein. Although elevated heartrates may negatively affect image quality, in partic-ular when using single-source systems, it is not rec-ommended to perform routine heart rate control withbeta blockade, given the risk of potential side effectsin patients with severe aortic stenosis. Administra-tion of sublingual nitrates in patients with significantAS is contraindicated.

2.7. NON-CONTRAST CARDIAC CT. Non-contrast eval-uation of the aortic root is not an essential componentof the TAVI/TAVR work-up, but may have utility in

Grade ofRecommendation*

Strong

Strong

Strong

Strong

ples Strong

ipheral vasculature should be obtained and used. Strong

Weak

may be considered Strong

Strong

ical oversight Strong

Strong

T ¼ computed tomography; TAVI ¼ transcatheter aortic valve implantation; TAVR ¼



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the setting of uncertain AS severity where the aorticvalve calcium score is known to correlate well withaortic stenosis severity (23). This is of most use insuspected low-flow low-gradient AS in those witheither a preserved or reduced ejection fraction withno flow reserve on dobutamine stress echocardiog-raphy (24). In this situation, the calcium score of thevalve can be used to adjudicate the presence orabsence of severe aortic stenosis (25). CT acquisitionfor the assessment of aortic valve calcification shouldbe performed using the same acquisition parametersused for assessment of the coronary artery calciumscore although further studies are underway todetermine thresholds for post-contrast CT scans(26,27). The valvular calcification is then contouredutilizing standard coronary artery calcium scoringsoftware, with contours applied around the valvularcalcification, ensuring the exclusion of aortic wall,left ventricular outflow tract (LVOT) or coronarycalcification. Sex-specific thresholds are utilized,with an Agatston score of $3,000 in men and $1,600in women making severe aortic stenosis very likely,while an Agatston score of <1,600 in men and <800 inwomen makes it highly unlikely (24). Non-contrastcardiac CT should not be used for annular sizing dueto the inability to identify the cusp hinge points andthus the inability to accurately and reproduciblydefine the annular plane.2.8. RECONSTRUCTION TECHNIQUE. ECG-synchro-nized CT data should be reconstructed as an axial,thin-sliced multiphasic data set, also referred to as‘cine’, ‘functional’ or ‘4D-CT’. Multiphasic data setsshould be reconstructed with <1mm slice thicknessusing a small reconstruction field of view encom-passing only the cardiac structures and a 512 � 512matrix in order to optimize spatial resolution. Prior toimage reconstruction, the ECG-tracing should bemanually reviewed to ensure correct R-peak identi-fication by the scanning system, with manualcorrection if required. When using retrospective ECG-gating, ECG-editing should be considered to reduceartifacts in the setting of increased heart rate vari-ability, e.g., in premature contractions or atrialfibrillation. For relative image reconstruction, recon-struction interval should be spaced at #10% intervalsacross the acquired portion of the cardiac cycle.Alternatively, if available on the employed scanningsystem, multiphasic data sets can be reconstructedusing absolute image reconstruction at 50msec in-crements, which result in superior image quality inpatients with increased heart rate variability such asin atrial fibrillation (28,29).

The non-ECG synchronized CTA of the aorto/ilio/femoral vasculature should be reconstructed as an


axial data set with #1.5 mm slice thickness in acontiguous or overlapping fashion, using a large fieldof view and either filtered back projection or iterativereconstruction.

3. AORTIC ROOT: ANATOMICAL DEFINITIONS

AND ASSESSMENT

Precise understanding and assessment of the anat-omy of the aortic valvular complex is crucial to ach-ieve optimal sizing of transcatheter heart valves(THV) as well as to identify patients at increasedanatomical risk for adverse events such as coronaryartery occlusion. The aortic root is an extension ofthe left ventricular outflow tract, extending from thebasal attachment of the aortic valve cusps within theLVOT to their peripheral attachment at the level ofthe sinotubular junction. Its components are the si-nuses of Valsalva, the fibrous interleaflet trianglesand the valvular cusps themselves (30,31).

3.1. AORTIC ANNULUS: DEFINITIONS AND MEASUREMENT

TECHNIQUES. For the purpose of anatomical sizing inthe context of TAVI/TAVR, the aortic annulus isdefined as the luminal contour within a virtual planealigned with the most basal attachment points of thethree aortic valve cusps (sometimes referred to asthe ‘basal hinge points’). Quantitative assessmentrequires the accurate identification of each of thesethree points in turn to create a plane that transectsall three.

Identification and positioning of the annular planecan be performed:

1. Manually, using standard multiplanar reformats,the technique for which is shown in Figure 1.

2. Using a software-based facilitating workflow withmanual identification of the basal hinge points byplacing marker points with subsequent positioningof the plane by the software.

3. Semi-automatically, by means of automatedsoftware-based anatomical segmentation, withverification by a trained observer and manualcorrection where required.

While facilitated or semi-automated workflowsmay be used, the interpreter analyzing the imagingmust confirm the accuracy of the generated annularplane and perform manual corrections if required. Fora summary of recommendations please see Table 5.

For quantification of annular dimensions, variousmeasurement tools are available across softwareplatforms (Fig. 2):

1. Cubic spline interpolation: Manually placed seg-mentation points which are automatically con-nected by a cubic spline interpolation.


FIGURE 1 Identifying the Annular Plane in Aortic Valves With Tricuspid Morphology



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FIGURE 2 Contouring Tools for Annular Segmentation


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2. Polygon: Manually placed segmentation points whichare automatically connected by straight lines.

3. Attenuation/Hounsfield unit based contourdetection.

4. Freehand contour: The annular contour is tracedmanually with the cursor.

All techniques commonly provide the annular areain either [mm2] or [cm2]. Cubic spline interpolationcommonly provide also the annular perimeter in[mm]. Polygon tools may underestimate the annularperimeter when compared to cubic spline interpola-tion, given the straight line connection of the seg-mentation points. Attenuation/Hounsfield unit basedcontour detection as well as freehand contour tech-niques may, depending on the software platform,result in jagged contours, artificially increasing thereported perimeter. For this reason, smoothing algo-rithms may be used to create a rather spline-likecontour. Perimeter values should only be reportedwhen using these measurement tools, if the contouris smoothened.

Most contouring tools provide short and long axisdimensions in [mm] which are automatically derivedby software algorithms, although methodology differ


between platforms (e.g., perpendicular versus non-perpendicular orientation; intersection centricversus eccentric). Alternative, manual caliper mea-surements can be performed. Overall, short and longaxis dimensions inform on the eccentricity of theannular cross-sectional dimensions. Importantly,manual caliper measurements should not be used toassess overall annular dimensions instead of con-touring tools.

Independent of the measurement technique used,the annular contour should be drawn along the blood-pool tissue interface, carefully avoiding presence ofany tissue within the contour and avoiding anycontrast outside of the contour. In case of annularcalcification, irrespective of crescent or protrudingdistribution, the contour should be drawn in a har-monic fashion as if no calcium is present, as this aidsin measurement standardization.

3.2. ANNULAR DYNAMISM & PHASE SELECTION.

During systole, conformational changes withdecrease in ellipticity as well as stretch of the annularcontour commonly result in a larger annular area andperimeter as compared to diastole (Fig. 3) (10,32). Thisannular dynamism has significant implications for


FIGURE 3 Dynamic Changes of the Aortic Annulus Throughout the Cardiac Cycle

Example with common anatomy and regular dynamism (upper row), demonstrating larger dimensions in systole than diastole, in parts due to bulging of the aortomitral

continuity (dashed yellow line) towards the left atrium in systole and flattening in diastole. The lower row shows an example of septal hypertrophy with smaller

annular dimensions in systole than diastole, in part due bulging of the basal septum (dashed blue line) into the annulus during systole.

TABLE 4 Grading Sc

Grade

Good (diagnostic)

Fair (diagnostic)

Poor (non-diagnostic)



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sizing with the potential for unintended undersizingif sizing is based on diastolic assessment (12,33).

Annular measurements should be performed usingthe ECG-synchronized, ideally multiphasic dataset.Identifying the reconstruction phase with largestannular dimensions is important given the implica-tions for device sizing. The annular anatomy shouldbe reviewed throughout the available portion of thecardiac cycle and the phase yielding the largest di-mensions with adequate image quality should bevisually identified. Importantly, changes in theorientation of the annular plane throughout the car-diac cycle may require adjustment of the imagingplane. Care should be taken to identify a reconstruc-tion phase with adequate image quality, ie. sharpdepiction of the annular contour. Reconstructionphases with inadequate depiction of the annularcontour, i.e., blur or double contours, should beavoided.

ale for Image Quality for Assessment of the Aortic Root

Definition

� Sharp depiction of the annular contour with sufficient contrastattenuation in the absence of artifacts

� Low contrast attenuation� Increased image noise� Mild motion artifacts, double contours or stair-step artifacts

� Too low contrast attenuation� Excessive image noise� Excessive motion artifacts or double contours� Pronounced stair-step artifact transecting the annular contour


3.3. IMAGE QUALITY. Reliable quantification ofaortic annular and aortic root dimensions requiresadequate image quality defined by sharp depiction ofthe annular contour given sufficient contrast attenu-ation, noise preposition as well as absence of motionartifacts, double contours, or stair step artifacts.Image quality can be rated using a subjective, quali-tative grading scale as good, fair and poor (non-diagnostic) (Table 4).

3.4. LANDING ZONE CALCIUM. The device landingzone comprises the valve cusps, aortic annulus andLVOT (34,35). It has been demonstrated that thepresence of severe calcification of the LVOT andaortic valve is associated with increased risk of par-avalvular regurgitation particularly when calciumprotrudes into the LVOT (36–40). In clinical practice,the description of annular (within annular plane) andsub-annular (upper 4 to 5 mm of the LVOT wheredevice gets into contact) calcification is almostexclusively performed in a subjective, qualitativefashion graded as none, mild, moderate, severe basedon the circumferential extent, the depth of extensioninferiorly into the LVOT and the thickness of thecalcification projecting radially into the LVOT (Fig. 4).Annular and sub-annular calcification should bedescribed as crescent/flat/adherent or protruding aswell as its relation to the aortic cusps. The location ofcalcification within the LVOT varies significantlyacross severe aortic stenosis patients. The region


TABLE 5 Summary of Recommendations for the Sizing and Reporting of the Aortic Valve, Annulus and Outflow Tract

RecommendationGrade of

Recommendation*

Annulus assessment and planning

While facilitated or semi-automated workflows may be used, the interpreter analyzing the imaging must be able to confirm theaccuracy of the generated annular plane and perform manual corrections if required.

Strong

Systolic measurements are preferred for measurement and calculation of device sizing Strong

Area and perimeter measurements are preferred for sizing of the aortic annulus over isolated 2 dimensional measurements andshould be provided in the report

Strong

Landing zone calcification

Annular and subannular calcification should be qualitatively described regarding morphology and extent as well as relation tothe aortic valve cusps.

Strong

Valve morphology

Number of cusps should be stated, and if a bicuspid valve is present, its morphology should be classified. Strong

The presence of a median raphe and the absence/presence of calcification of this should be mentioned Strong

The aortic annulus size should be measured and reported in bicuspid aortic valves as for tricuspid aortic valves. Strong

Aortic root measurement

Pre-TAVI/TAVR CT assessment should include coronary height, mean SOV diameter, and STJ height and diameter Strong

Coronary ostial distance from aortic annulus should be measured in a perpendicular fashion from the established annular plane Strong

*Based on level of consensus.

CT ¼ computed tomography; SOV ¼ sinus of valsalva; STJ ¼ sinotubular junction; TAVI ¼ transcatheter aortic valve implantation; TAVR ¼ transcatheter aortic valvereplacement.


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below the non-coronary and the left coronary cusps,including the intervalvular fibrosa, is most frequentlyaffected. Large protruding nodules of calcificationmay increase the risk of annular rupture particularlywith balloon expandable valves and should thus bespecifically mentioned in the report (34). Finally, thedevice landing zone is in close spatial relationshipwith the conduction system which may be com-pressed and damaged, causing atrioventricular blockand need for pacemaker implantation especially inthe context of severe calcification of the subannulardevice landing zone, with this effect amplified in thepresence of pre-existent right bundle branch block(41,42). Unusual findings with regard to these vari-ables should be included in the report.

3.5. VALVE MORPHOLOGY: DEFINITION AND

MEASUREMENT TECHNIQUES. Bicuspid aortic valves(BAV) are found in up to 6% of patients presenting forTAVI/TAVR, and are associated with lower devicesuccess rates and higher rates of paravalvular regur-gitation, but similar outcomes (43,44). Numerousclassifications of BAV morphology exist includingthat of Sievers and Schmidtke (45) (which essentiallyfocuses on the number of raphes (0, 1 or 2 for therespective types). More recently, a TAVI/TAVR-directed simplified BAV classification has been pro-posed. It distinguishes BAV morphology regarding (a)number of commissures (two vs. three) and (b) pres-ence or absence of a raphe, yielding 3 broad mor-phologies: 1) tricommissural, in clinical routine oftenreferred to as ‘functional’ or ‘acquired’ BAV (not partof Sievers classification); 2) bicommissural raphe-type


(equivalent to Sievers Type 1); and 3) bicommissuralnon raphe-type (equivalent to Sievers Type 0) (Fig. 5)(47). Ascending aortic dilation and aneurysms are lesscommon in ‘tricommissural’ BAV than ‘bicommissu-ral’ BAV. Within ‘bicommissural’ BAV, the non-raphetype BAV typically exhibits larger sinus diametersdespite smaller annuli. For bicommissural raphe-typeBAV, raphe characteristics may also be describedqualitatively and quantitatively including raphelength and raphe calcium (47).

Valve morphology should be systematically char-acterized and reported in all pre-TAVI/TAVR CT re-ports. Further, the degree of raphe calcificationshould be reported, e.g. using a qualitative scale(mild, moderate, severe), as severe raphe calcificationmay relate to higher likelihood of paravalvularregurgitation (44).

Defining the annulus may be a challenge in BAV,particularly in Sievers Type 0 BAVs where there areonly two hinge points to define the annular plane.The technique used for tricuspid aortic valves there-fore frequently needs to be adjusted as detailed inFigure 6. The annulus size should be measured andreported in the same fashion for BAV as for tricuspidaortic valves. The ascending aorta should also beexamined in BAV due to the association between BAVand aortopathy (46).

3.6. CORONARY OSTIAL HEIGHT AND SINUS OF

VALSALVA ASSESSMENT. Coronary occlusion is afeared complication of TAVI/TAVR which, whilerelatively rare with an incidence of 0.66%, is associ-ated with a poor clinical outcome with a reported 30


FIGURE 4 Qualitative Grading of Annular/Sub-Annular and Left Ventricular Outflow Tract Calcification



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day mortality of up to 40.9% (48,49). CT is wellestablished as the pre-procedural imaging gold stan-dard for the determination of the risk of coronaryocclusion. Low coronary ostial height (<12 mm) fromthe annulus and sinus of Valsalva mean diameter <30mm connote an increased risk of coronary occlusion.However, it should be noted that there is no absolutethreshold at which the procedure should be consid-ered contra-indicated, given the relatively low spec-ificity of these measurements (48), and thus coronaryostial height should not be considered as an isolatedmeasure of risk of occlusion. Rather, the derivedvalues for coronary height and sinus of Valsalvawidth should be interpreted in the context of annulardimensions, overall root dimensions and the antici-pated THV size.

To ensure reproducibility the coronary ostialheight should be measured in a perpendicular fashionto the annular plane using an electronic caliper tool


from the annular plane to the lower edge of the cor-onary artery ostium, yielding a value in [mm] (Fig. 7).Sinus of valsalva diameter should be measured cuspto commissure in parallel to the annular plane usingthree caliper measurements in [mm]. For symmetricsinus of Valsalva anatomies, the three values can beaveraged (Fig. 7). There is no recommendation as towhether these measurements are to be performed insystole or diastole. The SOV diameter and coronaryartery heights should be included in the report.3.7. SINOTUBULAR JUNCTION. Sinotubular (STJ)diameter and height are relevant to identify anato-mies in which the anticipated THV may potentiallyget into contact with the STJ. In particular when usingballoon-expandable devices in low STJ height anato-mies, STJ diameter should be compared to the antic-ipated THV size in order to identify anatomies withsmaller STJ diameter than THV diameter, whichwould be indicative of increased risk for STJ injury.


FIGURE 5 The Heterogeneous Spectrum of Bicuspid Aortic Valve Morphology


11

The STJ height should be measured in a perpen-dicular fashion to the annular plane using an elec-tronic caliper tool from the annular plane to the lowestedge of the STJ, yielding a value in [mm] (Fig. 7). STJdiameter should be measured using a caliper tool onan imaging plane aligned with the STJ (Fig. 7).

3.8. ASCENDING AORTA. The ascending aorta shouldbe assessed for the presence of aortopathy. Ascending


aortic dimensions should be assessed on double-oblique multiplanar reformats in [mm] (Fig. 7).

3.9. OPTIMAL PROJECTION CURVE. Ideally, TAVI/TVAR is performed with fluoroscopic angulationsproviding a coplanar view of the aortic annuluswithout parallax. CT can be used to identify thesepatient-specific ‘optimal’ C-arm angulations (50,51).Use of these CT-derived angulations allows


FIGURE 6 Identifying the Annular Plane in Bicuspid Aortic Valves With Sievers Type 0 Morphology



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FIGURE 7 Schematic for Assessment of Aortic Root Dimensions


13


TABLE 6 Summary of Recommendations for the Reporting of Fluoroscopic Angulation

Recommendation Grade of Recommendation*

Fluoroscopic planning

Provision of optimal fluoroscopic projection angulations based on CT for each individual patient should be considered. Strong

If the patient is not positioned supine for the CT examination, this should be noted in the report and proposed fluoroscopicangles should not be provided

Strong


CT ¼ computed tomography; TAVR ¼ transcatheter aortic valve replacement.



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optimization of initial pre-deployment fluoroscopicangulation, reducing the need for repeat pre-deployment root shots thereby reducing radiationexposure, contrast usage and procedural time (52,53).Optimal C-arm angulations should be reported asdegrees [�] LAO or RAO with the corresponding valuesfor cranial or caudal angulation. Dependent on insti-tutional preferences, typically views are eithercentered on the right coronary cusp, or use pre-defined LAO angulation (e.g., LAO 10�), or are opti-mized for visualization of the left main stem. Whenidentified projections result in cranial or caudalangulation >25�, alternate angulations should beprovided, given the physical restraints of the C-arms.However, it is essential to recognize that CT predictedangulations are only valid if the patient’s chest ispositioned in a similar fashion on the CT table asduring the procedure. Please refer to Table 6 for asummary of recommendations.

3.10. SIZING CONSIDERATIONS. CT is the non-invasive imaging gold standard for annular sizingand THV selection (1). In clinical practice, balloonexpandable devices are largely sized on the basis ofannular area, with self-expandable devices relying onperimeter. The reasons for this are partly historical butalso reflect different risk profiles of these devices andthe geometric implications of sizing with the differentvariables. Sizing based on manually assessed shortand long axis diameters have been shown to be lessreproducible (54), and can be considered obsolete.3.10.1. Oversizing. The term ‘oversizing’ has beenintroduced over the last 6 years to help describe whena THV is deployed that is larger than the nativeannulus. The term ‘oversizing’ is a generic term asoversizing can be calculated based on any measure-ment of the annulus. In routine, oversizing is calcu-lated as a percentage [%], as follows:Oversizing [%] ¼ (THV nominal measurement/

annular measurement � 1) � 100It is important to recognize, that the percentage

oversizing calculated is strongly dependent on theannular measurement used, with very differentimplication of oversizing area than oversizing perim-eter or perimeter derived diameter (55). Given the


formula of a circle where area ¼ p*radius2 andcircumference ¼ p*diameter, the area in-creases exponentially while perimeter increases pro-portionally with increasing diameter. The percentagearea oversizing is approximately 2-fold greater thanthe percentage perimeter when dealing with a perfectcircle but the implications are even greater than ex-pected owing to the non-circular geometry of theannulus. Both annular area and perimeter are clini-cally acceptable, but it is imperative that the imagerand implanting physician appreciate the differencesand are aware of the parameter being used for devicesizing of specific devices. Further, the optimalthreshold for oversizing is also device specific (56,57).Thus routine reporting of oversizing is not required,however familiarity of the concept is beneficial forsubsequent discussion in Heart Team meetings.3.10.2. Modification of sizing based on root calcification.CT not only provides information regarding annularsize, but also provides important ancillary informationthat is helpful in guiding sizing and THV selection.Annular and sub-annular calcification, particularlywhen protruding into the lumen, can result inincreased risk of both annular rupture and para-valvular regurgitation. Protruding landing zone calci-fication below the non-coronary cusp has been shownto bemost closely-associatedwith annular injury, withthis effect amplified when combined with aggressiveannular oversizing (58). Presence, location and char-acteristics of subannular calcification should thus beintegrated into all pre-TAVI/TAVR CT scan reports asdescribed in the ‘landing zone calcium’ section.

3.10.3. Annular rupture. Annular rupture is an infre-quent adverse event but is associated with a highmortality if it occurs (58,59). Patient and procedurerelated factors increasing risk of annular ruptureinclude female sex, use of balloon-expandable valves,significant prosthesis oversizing, and prior radiationtherapy. In addition, the presence of moderate/severesub-annular calcification, particularly below the non-coronary cusp on pre-procedural CTA, is associatedwith a significantly increased risk for annular rupture(34). In addition, the depth of calcification within theLVOT is also important, as calcification immediately


TABLE 7 Summary of Recommendations for the Reporting of Vascular Access, Coronary Artery, and Non-Cardiac, Non-Vascular Findings


Recommendation*

Vascular access

While facilitated or semi-automated work-flows may be used, the interpreter analyzing the imaging must be able to confirm the accuracy of thegenerated vessel centerline and perform manual corrections if required.

Strong

The minimal luminal diameter along both the right and left iliofemoral system should be provided including the anatomical location to the level of theexpected puncture site

Strong

All areas of >270� calcification in the iliofemoral arteries should be reported Strong

Calcification located anteriorly at the site of probable puncture should be reported. Strong

The report should include a clear description of all vascular pathologies including aneurysms, dissection, and occlusions. Strong

Coronary arteries

Reporting of the coronary arteries for severity of coronary artery disease can be considered in appropriately selected patients, if image quality is ofdiagnostic quality

Strong

The presence and course of anomalous coronary arteries should be reported. Strong

Non-cardiac, non-vascular

CT images should be reviewed for incidental findings Strong

Extracardiac findings should be reviewed and reported in the context of the healthcare environment and health status of the patient Strong

Significant findings should be included in the dictated report and when appropriate verbally communicated to the Heart team. Strong


CT ¼ computed tomography; SOV ¼ sinus of valsalva; STJ ¼ sinotubular junction; TAVI ¼ transcatheter aortic valve implantation; TAVR ¼ transcatheter aortic valve replacement.


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below the annular plane connotes a higher risk thancalcification lower within the LVOT. Protruding nod-ules of calcification are considered to connote higherrisk than flat or mural calcification. The risk of aorticannulus rupture increases with the degree of over-sizing of the prosthesis (particularly with >20%oversizing) and with the extent of calcification of theupper part of the LVOT (within 2 mm below theannulus plane) particularly when immediately belowthe non-coronary cusp (34,58).3.10.4. Atrio-ventricular conduction block. An increaseddepth of implantation is the most frequently identi-fied predictor of LBBB with both balloon- and self-expandable prostheses (60–65). Reduced implantdepth during TAVI/TAVR has been shown to signifi-cantly decrease mortality and permanent pacemakerinsertion rate (66). In addition, shorter length of thesemi-membranous septum has been reported to beassociated with higher risk of conduction disturbancepost TAVI/TAVR, with a length of less than approx.8mm predictive of high-degree AV-block, particularlywhen combined with a deep implant depth, or thepresence of pre-existent right bundle branch block(41,42,67). The length of the semi-membranousseptum can be measured in the coronal plane, at thelongest point between the annular level and themuscular septum (67). However, routine assessmentof semi-membranous septum length has not seenwidespread adoption into clinical routine.

4. VASCULAR ACCESS

4.1. OVERVIEW. Vascular complications are inde-pendently associated with increased morbidity and


mortality after TAVI/TAVR, however the rates ofcomplications have fallen with improved pre-procedural screening with major vascular complica-tions currently occurring in 4.5% of procedures(68,69). Access sheath sizes have reduced in size,however this simply shifts the threshold at whichtrans-femoral access can be achieved, rather thannegating the importance of identification and quan-tification of vascular disease and dimensions (70).Given the continuous evolution of delivery systems,no reference is made to current devices and vesseldiameter requirements. Please refer to Table 7 for asummary of recommendations.

Analysis of iliofemoral vessel size, calcification,and tortuosity is required to determine if trans-femoral access can be achieved or whether an alter-native access route is required (71,72). Due to itsability to accurately quantify all these aspects, CTprovides greater predictive value for vascular com-plications than invasive angiography (73).

Risk factors for vascular complications are anexternal sheath diameter that exceeds the minimalartery diameter, moderate or severe calcification,and vessel tortuosity (75–77). While early reportsdescribed an increased risk at a sheath:diameterratio $1.05, more recent work on modern accessdevices which are typically smaller with anincreasing prevalence of expanding sheath designs,suggests a more liberal threshold of $1.12 can besafely used (73).

4.2. QUANTIFICATION OF LUMINAL DIMENSIONS.

The minimal diameter of the vasculature between theaortic valve and the right and left common femoral




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artery should be reported. This can be performedeither manually on multiplanar reformats using adouble-oblique technique, or using semi-automaticpost-processing using centerline placement andcurved multiplanar reformats. When the latter isused, manual verification of the center line should beperformed to ensure accurate vessel tracking, andappropriate intra-luminal location of the centerline.When using either technique, attention should bepaid to the potential for calcium blooming artifact,and appropriate windowing used to correct for thiswhere necessary. It should also be ensured that allmeasurements are performed perpendicular to thelong axis of the vessel at the location of the maximumstenosis. Transverse source images allow no morethan a preliminary assessment of vessel size.

4.3. CALCIFICATION. Extend and distribution ofcalcifications of the iliofemoral vasculature should beassessed and reported. To describe the severity, asubjective, semi-quantitative grading scale can beused: none, mild (spotty), moderate (coalescing), se-vere (bulky, protruding, horse-shoe, circumferential).Care should be taken to identify circumferential ornear-circumferential (horse-shoe) calcificationparticularly in areas of tortuosity or bifurcations, asthese prevent vessel expansion when the sheath andvalve passes through.

4.4. TORTUOSITY. Tortuosity of vascular structurescan be assessed on transverse source images, butevaluation is facilitated using a volume rendereddisplay frommultiple viewing angles, such as anterior-posterior and RAO or LAO projections. In the absenceof calcification, Iliofemoral arterial tortuosity is notnecessarily a contraindication for femoral access, astortuous vessel segments usually straightened withsheath insertion. However, when calcified, tortuoussegments carry a substantial risk of access failure andthe operator should be advised about this situation.

4.5. ACCESS SITE. Careful interrogation of the com-mon femoral artery puncture site is important toensure that that there is no focal stenosis nor calcifi-cations anteriorly that may interfere with the arterialpuncture or deployment of arterial closure devices(74). Also, the anatomy should be reviewed for thepresence of a high femoral artery bifurcation. Rele-vant findings should be reported, ideally withdetailed location in relation to fluoroscopically iden-tifiable anatomical landmarks, such as the level of thefemoral head (e.g., lower third).

4.6. AORTA. For transfemoral access, the thoracicand abdominal aorta should be assessed for thepresences of relevant pathologies. In particular, thepresence of ascending aortic aneurysm and the


degree of ascending aortic calcification should benoted—the latter relevant for potential cross-clamping. Further relevant pathologies includeabnormal elongation and kinking, dissections, aneu-rysms, and exophytic plaque.

4.7. ALTERNATE ACCESS. If transfemoral access isnot feasible, depending on local practice, subclavianand/or carotid arteries can be reported using the sametechniques and reporting parameters of the iliofe-moral vessels (78,79). Due to more favorable angula-tion, an left-sided approach is preferred forsubclavian access. Finally, if a transcaval approach isto be considered, the presence, size and level ofcalcification free windows of the aortic wall adjacentto the inferior vena cava should be reported (80).Additionally the report should also include a cleardescription of all vascular pathologies including an-eurysms, dissection, and occlusions.

5. CORONARY ARTERIES

In the setting of good image quality, modest motionartifact in particular, coronary CTA can rule out sig-nificant coronary stenosis with high negative predic-tive value (81–85). However confident assessment ofcoronary stenosis severity on TAVI/TAVR scans ischallenging, particularly due to a high prevalence ofcoronary calcification and higher heart rates resultingin motion artifact (86). Beta-blockade must be usedwith caution and nitroglycerin is contra-indicated,with the absence of these associated with reduceddiagnostic accuracy (9). Independent from theassessment for CAD, the presence and course ofanomalous coronary arteries, easily interpreted,should be reported.

6. INCIDENTAL NON-CARDIAC

NON-VASCULAR FINDINGS

With growing evidence and increasing clinical adop-tion, TAVI/TAVR is increasingly being performed inyounger patients with lower risk profiles. This in-creases the relevance of incidental findings on CT asthe life expectancy of patients undergoing TAVI/TAVR will be longer than in the past. All imagingobtained should be reviewed carefully for incidentalfindings. This is best performed by trained radiolo-gists, either as a combined or separate report ac-cording to local practices. The clinicalrecommendations and downstream management ofincidental findings on pre-TAVI/TAVR CT will varyaccording to the risk profile and life expectancy of thepatients as well as local clinical practice. Please referto Table 7 for a summary of recommendations.


FIGURE 8 MPR Alignment and Semi-Quantitative Grading of

Hypo-Attenuated Leaflet Thickening

The dashed yellow line indicates the orientation of the long

axis views in the lower row, aligned with the center of the

cusps. The extent of leaflet thickening can be graded on a

subjective 4-tier grading scale along the curvilinear orientation

of the leaflet. Typically, hypo-attenuated leaflet thickening

appears meniscal-shaped on long axis reformats, with greater

thickness at the base than towards the center of the leaflet.


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7. POST-TAVI/TAVR CT

Echocardiography is the test for evaluation of trans-catheter heart valve function and durability (87,88).CT enables post-implant imaging of transcatheterheart valves (geometry, position, leaflets) (89–98),There is however, no consensus regarding the clinicalneed to perform routine cardiac CT in TAVI/TAVR re-cipients. Cardiac CT is an important adjunctive mo-dality to echocardiography in patients where there isconcern for valve thrombosis, infective endocarditis,or structural degeneration (24,99). Hypoattenuatedleaflet thickening (HALT) (Figs. 8 and 9) and restrictedleaflet motion (also referred to as HAM [hypoattenu-ation affecting motion]) determined by CT oftenindicate leaflet thrombus formation (7,8,100–102).When echocardiography is indeterminate, CTA can beuseful for adjudication of leaflet thrombus. Whenimaging in the post TAVI/TAVR setting for theassessment of HALT, full cardiac cycle imaging isrecommended to maximize image quality and topermit assessment of leaflet motion. IV contrastadministration and timing should be performed as perthe routine TAVI/TAVR workup, although a smallercontrast dose is required due to the lack of need for


peripheral vasculature imaging. Leaflet thickeningshould be described based on location, extent inlength and overall thickness. Importantly, HALT takesa meniscal shape when viewed on a long-axis MPR atthe center of the cusp (Figs. 8 and 9). In regard toextent of HALT along the curvilinear leaflet, as sub-jective grading scale can be employed as outlined inFigure 8.

Restricted motion should be reported as present orabsent. Restricted valve motion without thickeningon CTA is rare and should be reported with greatcaution, to avoid the risk of unnecessary treatment(100,102,103).

8. VALVE-IN-VALVE IMPLANTATION

8.1. OVERVIEW. Valve in valve (VIV) implantation ofTHVs into failing bioprosthetic valves has evolved asa treatment alternative with high technical successrates and promising patient outcomes (104). Broadly,bioprosthetic valves can be categorized as stentedsurgical (rigid scaffold), stentless surgical (no rigidscaffold), and transcatheter heart valves.

The Valve-in-Valve International Data (VIVID)Registry has shown that coronary occlusion is morecommon in VIV than TAVI/TAVR in native aorticstenosis, with occlusion reported in 2.3% of VIVcompared with 0.66% in native valve TAVI/TAVR(48,105). Factors related to the observed higher fre-quency are canted position of the stented surgicalbioprosthesis within the aortic root and small rootdimensions, the latter in particular in patients withstentless surgical valves. Pre-procedural CT plays alimited role in THV sizing, but a key role in thediscrimination of patient specific risk for coronaryocclusion. Vascular access should be reported as forTAVI/TAVR in native aortic valves (see Vascular Ac-cess section). Please refer to Table 8 for a summary ofrecommendations.

8.2. ASSESSMENT FOR RISK OF CORONARY ARTERY

OBSTRUCTION. Implantation of a THV within astented surgical valve is technically different fromTAVR in native aortic valves, as the stented bio-prosthetic valves provides the scaffold for THVanchorage. The THV displaces the bioprostheticleaflets into an open position with the THV frame andoverlying bioprosthetic leaflets forming a ‘covered’cylinder. The anatomical orientation of the cylinder isbeing dictated by the orientation of the surgical valve.Frequently, the surgical valve is implanted in a can-ted fashion in regard to the long axis of the aorticroot, with the potential for close proximity of thebioprosthetic leaflets/THV to the coronary ostia and


FIGURE 9 Examples of Hypo-Attenuated Leaflet Thickening in Both Self-Expandable (Upper Row) and Balloon-Expandable Device

(Lower Row) With Varying Degree of Thickening: Limited to Base, i.e., <25% Leaflet Involvement (Left Column) and Near Complete

Leaflet Involvement, i.e., >75% (Right Column)

TABLE 8 Summary of Recommendations for the Reporting of Post TAVI/TAVR and Pre-VIV Scans


Recommendation*

Post TAVR

At present, routine CT imaging following TAVI/TAVR is not recommended Strong

CT should be considered in the setting of clinical concern for valve thrombosis, infective endocarditis, or structural valve degeneration Strong

Leaflet thickening should be described based on location, extent in length and overall thickness Strong

Restricted motion should be reported as present or absent Strong

Valve-in-valve

When available the size of the surgical valve in situ should be obtained from the patient records. When this is not possible, internal diameter may bemeasured and used for calculating the valve to be inserted

Strong

The relationship of the uppermost aspect of the surgical valve struts to the STJ and to the coronaries should be described Strong

When the surgical valve struts end below the level of the coronary ostia, virtual transcatheter valve to coronary ostia distances do not need to be measured. Strong

Stentless surgical valve in valve procedures should be interpreted and reported as for native TAVI/TAVR cases regarding risk of coronary occlusion Strong


CT ¼ computed tomography; SOV ¼ sinus of valsalva; STJ ¼ sinotubular junction; TAVI ¼ transcatheter aortic valve implantation; TAVR ¼ transcatheter aortic valve replacement.



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FIGURE 10 Workflow for Assessment of Coronary Obstruction Risk in Patients Undergoing Transcatheter Valve-in-Valve Procedure

Virtual THV to coronary (VTC) distance should be assessed in patients with stented valves and coronary artery orifices originating at the level

of the prosthetic heart valve.


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subsequent risk of coronary obstruction despite alarge aortic root. Conceivably, the distortion is notadequately described by the coronary artery heightand sinus of Valsalva width. To account for thisanatomical distortion, the concept of predicting thedistance from the anticipated, expanded THV frameto the coronary artery orifice, also referred to as thevirtual THV to coronary (VTC) distance was intro-duced (106). This concept was validated in a recentVIVID multicenter analysis, which demonstrated theVTC to be the only independent predictor of coronaryobstruction, with a VTC of less than 4 mm indicatingan increased risk of coronary artery obstruction (105).

It is recommended that the VTC is assessed for theright coronary artery and the left main coronary ar-tery, if the posts extend to or above the level of theorifices (Fig. 10). If the coronary arteries originateabove the posts, obviously no VTC is required.

The VTC can be assessed using either a multiplanarreformat (MPR) capable of producing a circular regionof interest (ROI), or an advanced post-processingplatform capable of simulating a virtual cylinderwith a defined diameter and height (106) (Fig. 11). TheMPRs should be carefully aligned with the orientationof the surgical valve. The ROI is drawn at the level ofthe coronary artery orifice and the distance from theROI to the orifices is assessed with a caliper tool andreported in [mm]. Dependent on the configuration of


the aortic root, the sinus wall or STJ can come intocloser proximity to the expanded THV above theostium. For this reason, VTC assessment should notbe confined to the level of the ostium but additionalmeasurements should be employed above the ostiumto identify the risk of potential sealing.

Sinus of Valsalva (SOV) width and coronary ostiaheight can also be measured but the VTC has beenshown to provide incremental risk discrimination asthe other measurements do not take into account theSHV tilting/canting. VTC distances <4mm should behighlighted as being at high risk of procedure relatedcoronary obstruction (105).

Implantation of a THV within a stentless surgicalvalve is biomechanically similar to TAVR in nativestenosis due to the absence of a rigid scaffold. How-ever, stentless surgical valves are often employed insmall root anatomies. This, in combination withanatomical distortion increases the risk of coronaryobstruction. Stentless surgical valve cases should beinterpreted similar to native aortic stenosis casesregarding risk of coronary occlusion, with the sinusdimensions and coronary heights measured and re-ported as described earlier.

8.3. THV SIZING. If unknown, the size of a SAVR canbe estimated from measuring the internal area ofthe basal SAVR ring on the CT reconstructions and


FIGURE 11 Pre-Procedural Assessment of Virtual THV to Coronary Artery Distance in Patients Undergoing Transcatheter Valve-in-Valve

Procedure

The example shown here features a stented valve with a non-planar basal sewing ring. Steps 3 to 6 account for identifying alignment with the

three most basal points. In case of a planar basal ring, these steps can be omitted.



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TABLE 9 Pertinent Components of a Comprehensive Pre-TAVR/TAVI CT Report

Category Items

Aortic root findings 1 Valve morphology [tricuspid, congenital bicuspid according to e.g.,Sievers classification, functional/acquired bicuspid]

2 Calcium distribution [symmetric, asymmetric, bulky, bulky at freeedge]

3 Aortic annular dimensiona Overall image quality [good, fair, poor]b When assessed (systole/diastole, reconstruction phase)c Annular area [mm2]d Annular perimeter [mm]e Optional min and max diameter [mm]

4 Presence of annular and subannular calcificationa Extent [crescent non-protruding vs. bulky protruding, intramural]b Location

5 LM height [mm]6 RCA height [mm]7 SoV averaged [mm]8 STJ [mm], report if calcified9 Optimal coplanar projection [LAO/RAO and corresponding CRA/CAU

angulation]

Aorto/ilio/femoralvasculature

1 Pathologies of the ascending aorta2 Pathologies of the aortic arch, descending thoracic/abdominal aorta3 Iliofemoral vasculature

a Minimal diameters with locationb Extent [mild, moderate, severe] and location of calcification/pla-

que; particular emphasis on horse-shoe, circumferential patternc Tortuosity

4 Common femoral artery access sitea Calcium (posterior, anterior; anterior has implication for closure

system)b Report findings in regard to the level of the femoral head (upper

third, center, lower third)c Level of femoral bifurcation if at level of femoral head

1 Subclavian arterya Minimal diameterb Calcification, in particular at ostiumc Tortuosity

2 Other access approaches such as trans-aortic, trans-carotid or trans-caval depending on site preferences

Other cardiacfindings

Report relevant cardiac findings, such as chamber size, myocardial scar,evidence of other valvulopathies including MAC

Other findings Report relevant extra-cardiac pathologies and relevant incidental findings

Impression 1 Valve morphology, annular area, relevant root features (e.g., adverseroot features such as calcification, low coronary artery height, non-spacious sinus of Valsalva)

2 Comment on feasibility of trans-femoral access; adverse featuressuch as horse-shoe/circumferential calcium, severe tortuosity,anterior common femoral artery calcium

3 Relevant incidental findings.


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cross-referencing with published reference charts(107,108). However, reference charts are currentlylimited to two publications and do not reflect thecomplete complement of available SAVRs, withdifferent measurement techniques used in both ofthese. When using reference charts careful adherenceto the measurement technique employed in therespective papers is required to allow for accurateestimation of the valve size.

8.4. REQUIREMENTS FOR CT DATA ACQUISITION

AND RECONSTRUCTION. As anatomical informationof both the aortic root and aorto/ilio/femoral vascu-lature is required pre-VIV, the requirements for CTdata acquisition and reconstruction are similar tothose for planning of TAVR in native aortic valve.The contrast-enhanced, ECG-synchronized cardiacCT acquisition should cover at least the aortic root.In stented surgical valves, the lack of dynamism dueto the rigid bioprosthetic heart valve scaffold re-quires only a single ECG-synchronized frame. How-ever, acquisition and reconstruction of the entirecardiac cycle allows for additional CT data whichmay be beneficial in case of motion or misregistra-tion artifacts. Of note, in the setting of stentedsurgical valves with radiopaque scaffolds, a non-contrast CT dataset may be sufficient for assess-ment of coronary obstruction risk, as coronary arteryorifices can be identified based on surroundingepicardial fatty tissue. In patients with stentlesssurgical valves, acquisition protocols for nativeaortic stenosis should be employed, and contrastenhancement is required.

9. REPORTING

All measurements of the aortic root and access routeshould to be stored as screenshots in the picturearchiving and communication system (PACS) forfuture review and reference. Screenshots shouldideally include MPR reference images with cross-hairs displayed, which allows to comprehend theorientation and location of the imaging plane onwhich the measurement was taken. Pertinentcomponents of a comprehensive report are listed inTable 9.

10. SUMMARY

CT imaging plays an important role in proceduralplanning for TAVI/TAVR and should be a fully inte-grated component of any TAVI/TAVR program. Theuse of CT in TAVI/TAVR is multifaceted and


should include appropriate image acquisition andreconstruction as well as the comprehensive assess-ment the aortic root and vascular access. Importantly,the individuals responsible for the interpretation ofthe CT examination should be part of the Heart teamto ensure appropriate incorporation of the data fromthe CTA into the patient selection process and pro-cedure planning.

ADDRESS FOR CORRESPONDENCE: Dr. PhilippBlanke, St. Paul’s Hospital and University of BritishColumbia, Radiology, 1081 Burrard Street, Vancouver,BC V1Z 1Y6, Canada. E-mail: [email protected].


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