Dr Winnie Sze-Wun Chan
Transcript of Dr Winnie Sze-Wun Chan
Dr Winnie Sze-Wun Chan Cardiac Team Deputy Team Head Department of Radiology and Imaging Queen Elizabeth Hospital Hong Kong
Why? Is CT reliable? How to perform the CT study? How to interpret the CT study?
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
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
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
Data Acquisition
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)
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
Bolus tracking at aorta HU>100
Reconstruction Automated best-systolic
Multiplanar reconstruction MPR Curved MPR Volume rendering
Transfemoral : preferred Subclavian artery Edwards Sapien valve can be implanted via a
transapical route. Aortic approach (ascending aorta after mini-
thoracotomy)
Assess route
Thorax plain BICUSPID-41973261.jpg
Femoral /Subclavian Arteries
Diameters
Calcifications circumferential
Tortuosity
Others Pseudoanuerysm Dissection Eccentric thrombi
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
Transapical
LV thrombi
position of the LV apex relative to the chest wall
alignment of the LV axis with LV outflow tract
chest deformities
COMMON FEMORAL ARTERY PSEUDOANEURYSM
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
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
End systole Greatest annular stretch 20% patients will select smaller valves if use
diastolic measurements Cardiac pulsatility and aortic root compliance
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)
Area Perimeter Long and short diameters
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
Blanke et al, 2012
CT based sizing advoates for controlled oversizing to reduce PAR
? Oversizing ~10% >20%: ? Aortic root injury
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.
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)
RCA LCA
Lengths to coronary artery ostium
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
Fluoroscopy angle : orthogonal to the commissure between the left coronary cusp and noncoronary cusp
Bicuspid valve
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
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
Ewe at el. 2011
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
Device Landing zone calcifications
ie. Native valves and adjacent outflow tract
Need for pacemaker implantation after TAVI
Latsios et al 2010
Plane of annulus Calcifications – blooming artefact, affect
measurements Perimeter vs Area derived measurements
Radiation dosage
Relatively high
Less concern in the elderly
Iodinated contrast material
renal impairment in elderly
• Total Radiation dosage : ~ 17 -29mSv
AORTIC ANNULUS CHANGE TO CIRCULAR SHAPE
QEH Heart Team
Cardiologists, cardiothoracic surgeons, anesthetists, radiologists, cardiac nurses
TAVI meeting CT, Echo, Angiogram reviewed by team
members jointly before the procedure
Role of CT in pre-TAVI planning
Aim: Better planning with lesser complications
Thank you
Department of Radiology and Imaging Queen Elizabeth Hospital Hong Kong