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) Injection rate 90-100ml 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 Scanner 0.6mm for aortic root 0.6mm- 1mm for peripheral access 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
Assess route Transfemoral : preferred Subclavian artery Edwards Sapien valve can be implanted via a transapical route. Aortic approach (ascending aorta after minithoracotomy)
Thorax plain BICUSPID-41973261.jpg
Femoral /Subclavian Arteries Diameters Calcifications Tortuosity Others circumferential 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 Sinotubular junction (STJ) diameter Ascending aortic 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) 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 Native leaflet to STJ Coronary ostial obstruction 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 (D L and D S ) of the oval aortic annulus. The mean diameter D : averaging the 2 values [D = (D L + D S )/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)
Long and short diameters Area Perimeter
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)
Lengths to coronary artery ostium RCA LCA
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