Dr Winnie Sze-Wun Chan
Transcript of Dr Winnie Sze-Wun Chan
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Dr Winnie Sze-Wun Chan Cardiac Team Deputy Team Head Department of Radiology and Imaging Queen Elizabeth Hospital Hong Kong
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Why? Is CT reliable? How to perform the CT study? How to interpret the CT study?
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Compared surgery: Cannot directly visualize valve and annulus during TAVI
Select suitable patients : no suitable valve is available (eg, aortic annulus diameter of <18 mm)
Select best access pathway Predictor: Extent of aortic valve calcification Guidance: Appropriate fluoroscopic
projection angles
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3D MDCT derived measurements are accurate & highly reproducible
Sizing of transcatheter heart valve :
Paravalvular aortic regurgitation (undersizing)
Aortic root injury (oversizing)
Leipsic 2011 , Nguyen 2013 Wilson et al 2012 Blanke et al 2012
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Greater discriminatory value for significant PAR (more than mild) with CT-derived parameters over 2D echo-based sizing
Independent predictor of PAR: Valve size/mean diameter in CT
Wilson at al 2012
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Data Acquisition
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Protocol
Iodinated contrast volume (350mg/ml)
90-100ml
Injection rate
4ml/second
Bolus tracking At ascending aorta, HU >100
ECG -gating Yes for aortic root : Sequential 30%-70% No for peripheral access scan
Slice thickness 0.6mm for aortic root 0.6mm- 1mm for peripheral access
Scanner Dual source CT (Somatom definition, Siemens)
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1 Aortic root Whole aortic arch down to cardiac apex. ECG-gated, Breath-hold Sequential mode, 30%-70%RRi >= 6 segments
2 Peripheral access
Cranially including subclavian artery; Caudally to level of proximal superficial femoral artery Non-ECG gated Flash mode
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Bolus tracking at aorta HU>100
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Reconstruction Automated best-systolic
Multiplanar reconstruction MPR Curved MPR Volume rendering
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Transfemoral : preferred Subclavian artery Edwards Sapien valve can be implanted via a
transapical route. Aortic approach (ascending aorta after mini-
thoracotomy)
Assess route
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Thorax plain BICUSPID-41973261.jpg
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Femoral /Subclavian Arteries
Diameters
Calcifications circumferential
Tortuosity
Others Pseudoanuerysm Dissection Eccentric thrombi
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Moderate-to-severe arterial calcification
3X fold increase in vascular complications (29% vs 9%)
Minimal arterial lumen diameter < external sheath
4X fold (23% vs 5%)
Caution: Calcification is circumferential or nearly circumferential and/or at vessel bifurcations
Bulky atheroma or eccentric calcifications in aortic arch
Rodes-Cabau J et al 2010
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Transapical
LV thrombi
position of the LV apex relative to the chest wall
alignment of the LV axis with LV outflow tract
chest deformities
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COMMON FEMORAL ARTERY PSEUDOANEURYSM
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Aortic root analysis
Importance
Diameters Annulus diameter Prosthesis sizing
Sinus of Valsalva diameter LMCA obstruction when both: left coronary artery height <12 mm and a sinus of Valsalva diameter of <30 mm (67.9% vs 13.3%, P<0.001)
Sinotubular junction (STJ) diameter
Ascending aortic diameter Prosthesis sizing
LVOT diameter
Lengths Native leaflet to L coronary ostium LMCA obstruction when both: left coronary artery height <12 mm and a sinus of Valsalva diameter of <30 mm (67.9% vs 13.3%, P<0.001)
Native leaflet to R coronary ostium Coronary ostial obstruction
Native leaflet to STJ Coronary ostial obstruction
Angle Annular angulation Plan alignment
Plan for C-arm Orthogonal to the annulus For fluoroscopy guidance : prosthesis tilting
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Basal ring: 3 lowest points of the aortic valve cusps (“hinge points”)
annulus has an oval, not a circular shape 2-dimensional echocardiography (TEE or
TTE) typically measure the shorter diameter of the oval aortic annulus
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End systole Greatest annular stretch 20% patients will select smaller valves if use
diastolic measurements Cardiac pulsatility and aortic root compliance
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1. Measurement of the long and short diameters (DL and DS) of the oval aortic annulus. The mean diameter D : averaging the 2 values [D = (DL + DS)/2].
2. Planimetry of the area A of the aortic annulus ; calculation of the diameter with the assumption of full circularity [D = 2*√(A/ π)].
3. Measurement of the circumference C of the aortic annulus and calculation of the diameter D with assumption of full circularity (D = C/π)
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Area Perimeter Long and short diameters
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Change in annular geometry during cardiac cycle
Aortic Stenosis: Higher tensile stiffness of annulus
Bulging of aortomitral continuity towards LA in systole, flatten in diastole
Perimeter integrates annular diameter ; little variation throughout the cardiac cycle
Perimeter-derived diameters are larger than area-derived diameters
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Blanke et al, 2012
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CT based sizing advoates for controlled oversizing to reduce PAR
? Oversizing ~10% >20%: ? Aortic root injury
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Distance of the coronary ostia to the aortic valve plane
aortic cusp length width of the aortic sinus width of the sinotubular junction width of the ascending aorta.
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Avoid coronary obstruction Risk is assumed less with the CoreValve minimum distance of the coronary ostia from
the aortic annulus
Edwards Sapien ( ?minimum 10–14 mm)
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RCA LCA
Lengths to coronary artery ostium
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Determine appropriate projection of aortic annulus
A plane orthogonal to the aortic annulus plane and orthogonal to the commissure between the left coronary cusp and noncoronary cusp
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Fluoroscopy angle : orthogonal to the commissure between the left coronary cusp and noncoronary cusp
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Bicuspid valve
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Diseased aortic cusps are not removed in TAVI
Calcification may hamper the apposition of the prosthesis to aortic root : paravalvular aortic regurgitation (PAR)
**Obstruction of coronary ostia during TAVI
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Quantify : Agatston score, mass, volume
Degree of AR after TAVI
Agatston AVC higher in patients with AR grade>3
Agatston AVC socre >3000 associated with a relevant paravalvular AR , increased trend for second manoeuvres
Koos et al 2011
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Ewe at el. 2011
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Post contrast scan: calcification defined >=800 HU (luminal contrast enhancement 250-760HU)
Measure in volume: mm3
Location
1. Cusp wall ** AUC 0.93 predict paravalvular AR
2. Commissure ** AUC 0.94
3. Cusp body
4. Cusp edge
Ewe et al. 2011
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Device Landing zone calcifications
ie. Native valves and adjacent outflow tract
Need for pacemaker implantation after TAVI
Latsios et al 2010
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Plane of annulus Calcifications – blooming artefact, affect
measurements Perimeter vs Area derived measurements
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Radiation dosage
Relatively high
Less concern in the elderly
Iodinated contrast material
renal impairment in elderly
• Total Radiation dosage : ~ 17 -29mSv
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AORTIC ANNULUS CHANGE TO CIRCULAR SHAPE
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QEH Heart Team
Cardiologists, cardiothoracic surgeons, anesthetists, radiologists, cardiac nurses
TAVI meeting CT, Echo, Angiogram reviewed by team
members jointly before the procedure
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Role of CT in pre-TAVI planning
Aim: Better planning with lesser complications
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Thank you
Department of Radiology and Imaging Queen Elizabeth Hospital Hong Kong