Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3752_Библиотеки_им_академика_М_И_Перельмана

Dmax, Dmean, area and perimeter once the tracing is made. If these features are not available, diameter (D) can be calcu­lated from circumference (D = circumference / π). (π = Pi). Area is calculated from π.D 2 /4.

The Aortic annulus is not orthogonal to the body axis/planes. For a successful implantation, the prosthetic device needs to be deployed coaxially to the centerline of the aorta. Inappropriate deployment might lead to complications [ 41 ]. This plane can be achieved on both CT workstation and fl uo­roscopy units. However to achieve the same plane in fl uoros­copy unit, multiple aortograms are to be performed in a stepwise approach.

This situation offers an opportunity for pre-procedural CT to help predict the co-planar angles of deployment prior to the procedure. At here are innumerable co-planar angles of deploy­ment typically ranging from RAO Caudal to LAO Cranial. Pre­procedural co-planar angle guidance has been shown to help reduce procedure fl uoroscopy time and the volume of contrast needed for the procedure [ 42 , 43 ]. Binder et al. have demon- strated signifi cant correlation (r = 0.682, p < 0.001) between the predicted optimal deployment projections using 3D

Apart from annulus sizing, assessment of the aortic annulus, left ventricular outfl ow tract and aortic valve leafl ets is equally important for a successful TAVI procedure. Valve calcifi cations may be distributed focally or diffusely over the surface of the valve cusps or they may present along the leafl et edges. Presence of severe calcium is likely to cause important peri and post pro­cedural complications. Post dilatation techniques might need to be employed in patients with severe calcifi cation.

In TAVI cohorts, it is not uncommon to see sub annular or LVOT calcifi cation (Figs. 15.4 and 15.5 ) or aorto-mitral calci- fi cation as a continuum (Fig. 15.4a, b ). Distribution of calcium in each of these locations has been shown to have important prognostic implications. In a study by Barbanti et al., 31 con­secutive TAVI patients who had LVOT/annular/aortic con­tained/noncontained rupture were caliper-matched to control group of 31 patients without annular injury [ 45 ]. They observed at least 2 features were signifi cantly associated with

annular rupture: 1. Moderate/severe LVOT/subannular calcifi ­cation ((odds ratio, 10.92; 95 % CI, 3.23–36.91; P < 0.001) and

Aortic valve calcifi cations (AVC) distribution is better visualized on the cross-sectional view of the sinus of Valsalva. AVC can be assessed qualitatively as mild, moderate or severe

11.38; 95 % confi dence interval (CI) 2.33–55.53; P = 0.001)] was noted. It is not only the amount of calcifi cation but location/distribution at each separate cusp or commissure has been found to be associated with PAR [ 48 ]. Their study identifi ed signifi cant association for the right and left coro­nary cusp, for right-left and left non coronary commissure, and there was no signifi cant association for non-coronary right commissure and for non-coronary cusp. Interestingly a number of other studies evaluating patients who under­went TAVI using a self-expanding system,, did not fi nd an association between PAR and the degree of calcifi cation [ 49 , 50 ]. It is likely the distribution of radial force at differ- ent locations due to the nature of the device with balloon expandable at the annulus whereas the self- expandable at the ascending aorta cause varied propensity towards devel­opment of PAR.

A coronary ostial cut off of 10 mm was suggested by the American College of Cardiology Foundation/ American Association for Thoracic Surgery/Society for Cardiovascular Angiography and Interventions/Society of Thoracic Surgeons expert consensus [ 15 , 51 ]. However, in a study of reported cases of coronary obstruction, the mean height was 10.3 mm (range 7–12 mm) and 60 % of cases with obstruction had a height >10 mm [ 52 ]. In a multi- center registry study, it was observed majority of the patients who had coronary obstruction (~80 % overall and 96 % of women) had a left ostial height <12 mm [ 53 ]. Further, adding to the complexity and importance of ostial measurements, in the same registry study, even though the coronary ostial heights were more than >12 mm, 21.4 % had a coronary obstruction implying that there are factors beyond ‘safety cutoff’ of coronary ostial height that might

It is also interesting to note that coronary obstruction was more often observed in patients with balloon expandable devices than those who had self-expandable devices [ 53 , 54 ]. It is unknown whether makeup of the device or mechanism of deployment has any role in the observed obstructions. Other causes which predispose to coronary obstruction include bulky calcifi cation of the native aortic leafl ets, long mobile leafl ets and specifi cally presence of leafl et length more than the coronary ostial heights.

Access routes can be broadly classifi ed into retrograde (transfemoral [TF], transaortic, transsubclavian etc.), ante­grade (tranapical) approach or a combination of both (trans­caval-transaortic). Each of the access sites for delivery of TAVI has advantages and limitations.

Accurate measurements of lumen diameter are obtained through multiplanar reformations. Due to MDCT volumetric acquisition, orthogonal planes to the center line of arterial lumen can be obtained to determine the true short and long axis diameter measurements. Modern post processing work stations have curved planar reformations tool which would help in extracting the entire course of the vessel and thus a visual and quantitative measurements could be obtained. A potential limitation in assessment of arterial lumen arises

ral artery area ratio (SFAAR – sheath area to the femoral

minimal lumen area [MLA]) in 255 patients and found SFAAR of 1.35 was predictive of vascular complications (sensitivity 78.6 %, specifi city 62.9 %) [ 63 ]. In comparison, although a diameter ratio cutoff of 1.45 was predictive but it had lower sensitivity and specifi city (64.2 % and 67.4 %, respectively). These fi ndings highlight the importance of lumen diameter and area measurements and their relation to sheath diameter/areas in predicting vascular complications.

of circumferential ilio-femoral calcifi cations was an impor­tant risk factor for vascular complications and also an inde­pendent predictor of increased mortality after TF-TAVI [ 65 ]. Further, incorporation of this MSCT derived parameter in the workup algorithm of patients with a sheath-to- iliofemoral artery ratio – SIFAR ≥1 on angiographic screening improved the specifi city for prediction of major vascular complications to 62 % without altering the sensitivity (100 %).

Chiam et al. assessed iliofemoral dimensions and charac­teristics by ultrasonography in 549 Asian patients [ 68 ]. They observed female gender, lower body surface area, and pres­ence of diabetes mellitus; dyslipidemia and smoking history were independent factors for smaller iliofemoral dimensions. Thus for the same degree of tortuosity, a smaller intraluminal diameter might predispose to increased vascular risk, if TT/ AD index is incorporated.

Alternative access routes should be considered in patients where reconstructed CT images reveal unfavorable ilio- femoral anatomy. Description of various access sites is beyond the scope of this chapter; however, the underly­ing principles would remain the same as mentioned above. Access routes need to be assessed holistically depending upon patient’s condition and also the device that is likely to be deployed with minimal complications (Fig. 15.11 ).