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Noninvasive Evaluation of the Aortic Root with Multi-Slice Computed Tomography

Implications for transcatheter aortic valve replacement

Percutaneous transcatheter aortic valve replacement has emerged as a novel procedure in the treatment of aortic stenosis (AS). Particularly in patients with high perioperative risk, the procedure may become a reliable alternative and improve prognosis. However, detailed information of the aortic annulus anatomy and its relation with the coronary arteries is needed in order to avoid complications such as paravalvular leakage and coronary occlusion.
Non-invasive Imaging: Cardiac Computed Tomography


In the current study by Tops et al, the feasibility of Multi-Slice Computed Tomography (MSCT) to obtain this information was explored. A total of 169 patients, of which 19 with moderate to severe AS, was evaluated with 64-slice MSCT. Subsequently, the authors performed a detailed systematic analysis of the aortic valves, annulus and its relation with the coronary artery ostia. First, the aspect of the aortic valve (bicuspid or tricuspid) and the presence of aortic valve calcifications was assessed.

The latter was evaluated both visually and quantitatively using the Agatston score. Then, the aortic root was evaluated by measuring its diameter in both diastole and systole. Also, the diameter of the Sinus of Valsalva and sinotubular junction and their distances from the annulus were assessed, as these variables are important for prosthesis sizing. Subsequently, the relation between the aortic annulus, coronary leaflet and coronary ostia was assessed by determining the distances between the annulus and the ostia of the left and right coronary artery. Also the length of the coronary leaflet as well the distance between the tip of the left coronary leaflet and ostium left coronary artery was determined (the latter both in diastole and systole).  These variables may help in estimating the risk of coronary occlusion. Finally, the authors analyzed the left ventricular outflow tract and interventricular septum.

In addition to the MSCT, 2D echocardiography was performed to evaluate ejection fraction, aortic annulus diameter and aortic stenosis. In 2 patients, a bicuspid valve was detected and these patients were excluded from further analysis. Aortic calcifications were present in 44 (27%) resulting in a mean Agatston score of 819, while mean calcium volume of the aortic calcifications was 663 mm3. Mean diameter of the aortic annulus was 26.3 mm on the coronal view, whereas the mean diameter was lower on the sagittal view (23.5 mm). Interestingly, in 47% of patients, the difference between coronal and sagittal diameter exceeded 3.0 mm indicating an oval rather than circular shape of the annulus.

Agreement with echocardiography was good, although the observed diameter on echocardiography tended to be smaller as compared to the MSCT measurements. Mean distance between the aortic annulus and the left and right coronary arteries was 14.4 mm and 17.2 mm, respectively. In almost half of patients (n=82), the left coronary leaflet was longer than the distance between the annulus and left coronary ostium. For the right coronary leaflet and artery, this phenomenon was noted in only 10% of patients. Finally, a sigmoid aspect of the interventricular septum was observed in 7% of patients. In a next step the authors compared finding between patients with and without AS.

Conclusion:

Not surprisingly, the extent of aortic valve calcifications was significantly higher in AS patients. No differences were observed with regard to the diameter of the annulus, sinus of Valsalva or sinotubular junction. Importantly however, the percentage of patients with a longer left coronary leaflet than the distance from the ostium and thus at potential risk for coronary occlusion was significantly higher in the patients with AS (76%) as compared to the patients without AS (46%). Accordingly, the authors conclude, MSCT may provide important information on the aortic annulus prior to percutaneous transcatheter aortic valve replacement. Knowledge of individual variations in aortic annulus diameter may be of value for prosthesis sizing and avoid paravalvular leakage. In addition, the individual patient’s risk of coronary occlusion during valve replacement may be assessed. However, future prospective studies in patients undergoing percutaneous transcatheter aortic valve replacement are needed to further explore the potential of this particular application of MSCT.

References


Tops LF, Wood DA, Delgado V, et al., J Am Coll Cardiol Img 2008; 1 : 321-30
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.