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