Weisell, Jonna, Ruotsalainen, Anna-Kaisa, Laakso, Hanne, Ylä-Herttuala, Elias, Näpänkangas, Juha, Levonen, Anna-Liisa, Liimatainen, Timo, and Rysä, Jaana
Background: In aortic stenosis (AS), valvular calcification makes valves thicker and stiff causing impairment of the valve function. The aortic valves do not open properly and most of the AS patients have also difficulties in the closing of aortic valves. We used high-resolution cine- magnetic resonance imaging (MRI) to study changes in the mobility of the aortic valves in LDLr-/-ApoB100/100 mice, the model of AS. In addition, morphology of the aortic valves and left ventricular function were determined. Methods: LDLr-/-ApoB100/100 mice were fed a western diet (WD) (42 % kcal from fat) or a normal chow diet (control) for 5 months. The mice were imaged at 7T Bruker Pharmascan using volume transmitter and surface receiver coil. Aortic valve function was examined by imaging the cross section of the aorta at valve level using cine sequence; parameters were; slice thickness 0.6 mm, TR = 8 ms, TE = 2 ms, FOV = 1,5 x 3 cm2, matrix size 192 x 192, 1 slice, and 3 averages. From these images, the area of aortic valve orifice was determined during heart cycle. Heart function was studied from 6-8 cine-images covering the whole heart from apex to aorta; parameters for imaging: TR =8 ms, TE = 2 ms, FOV = 4 x 4 cm2, matrix size 192 x 192, 1 slice, slice thickness 1 mm, 10-14 frames depending on heart rate, and 2 averages. Hematoxylin-eosin staining of aortic valves was conducted. Results: The opening and closing of the aortic valves were evaluated and the data indicated clear functional impairment of aortic valves in WD mice when compared to control mice (interaction P=0.0004), figure 1. MRI showed narrowing (14%, p<0.05) of the orifice area, and this was seen also in histology (34%, p<0.05) indicating more severe AS after WD when compared to controls. Additionally, MRI revealed reduction in EF in mice fed with WD compared to controls (11%, p<0.01). Conclusion: Cine-MRI can be used to detect aortic valve dysfunctionality. In addition, these findings support the use of hypercholesterolemic mice on WD as a model of AS. [ABSTRACT FROM AUTHOR]