Aims: Precise assessment of aortic root dimensions is essential in patients scheduled for transcatheter aortic valve replacement to avoid complications such as valve migration, annulus rupture, paravalvular regurgitation or obstruction of coronary ostia. Various two-dimensional imaging modalities including echocardiography, fluoroscopy and multidetector computed tomography (CT) are being used to evaluate the anatomy in the screening process, with limited abilities to describe three-dimensional structures. Aim of our study was to assess the aortic root geometry using a new dedicated CT reconstruction tool (3mensio, Netherlands).
Methods and results: One hundred and twenty five consecutive patients scheduled for transcatheter aortic valve replacement with pre-interventional ECG-gated contrast cardiac CT were included. Aortic annulus was defined as ring through the nadirs of all three aortic cusps. Outflow tract dimensions were calculated 5 mm below the aortic annulus. Maximum (max.) and minimum (min.) diameters, perimeter, area and virtual diameters based on the perimeter and area, assessed in both locations, as well as height of coronary ostia were analysed. Parameter detection was complete for all patients. Average max. and min. diameters of the aortic annulus were 26.1±2.7 mm and 20.0±2.2 mm with a mean eccentricity index of 1.3. Mean outflow tract dimensions were 28.0±4.9 mm and 18.7±3.1 mm for the max. and min. diameter, respectively, with a significantly higher eccentricity index of 1.5 compared with the annulus. Mean perimeters of aortic annulus and outflow tract were 73.8±7.2 mm and 76.0±12.2 mm (p<0.05), mean areas 416.2±78.4 mm2 and 416.8±127.7 mm2 (p=ns). In 68 patients (54%), the aortic annulus area exceeded the outflow tract area with a mean difference of 53.2±34.4 mm2, in 57 patients (46%) the outflow tract area exceeded the annulus area, by 72.1±104.3 mm2 on average. Mean distances between annulus and coronary ostia were 14.6±3.5 mm and 17.1±3.4 mm for the left and right coronary arteries. Virtual diameters for annulus and outflow tract were 23.5±2.3 mm and 24.2±3.9 mm for the perimeter based calculation, and more similar for the area based calculation with 22.9±2.1 mm and 22.8±3.3 mm, respectively (p=ns).
Conclusions: There is a significant mismatch of aortic annulus and outflow tract dimensions, with a higher eccentricity and relevant area differences in specific cases, which might affect the procedural outcome, particularly in cases with deep valve implantations. For both locations, oval shapes are predominant, which must be considered for valve design and screening criteria.