Characterizing valve dynamics in mice by high-resolution cine-MRI

In calcific aortic valve disease (CAVD), progressive valvular sclerosis and calcification cause narrowing of the orifice and an impairment of the valve's function. We applied high-resolution cine-MRI to perform quantitative analysis of the dynamics of the aortic valve in a mice model of CAVD.

LDLr^-/- ApoB^100/100 mice were fed a Western diet (WD) or a standard diet (control) for 22 weeks. The mice were imaged in a 7 T horizontal MRI scanner, and aortic valve dynamics was examined by imaging the cross-section of the aorta at valve level using cine sequences. From these images, the area of the aortic valve orifice was determined during the heart cycle. MRI results were compared with echocardiographic and histopathologic results. The data revealed evidence of clear aortic valve dysfunction in WD mice as compared with control mice (interaction P < 0.001). MRI showed narrowing (14%, P < 0.05) of the orifice area, and this was also seen in histology (34%, P < 0.05), indicating more severe aortic stenosis after WD than in controls. Additionally, MRI revealed a reduction in the ejection fraction (EF) (-11%, P < 0.01), a result confirmed with echocardiography (-27%, P < 0.001) in mice fed with WD. EF detected by MRI and echocardiography also correlated strongly with the degree of stenosis assessed by histology.

Cine-MRI can be used for quantitative analysis of the aortic valve orifice over the cardiac cycle in mice. MRI showed the cusps clearly, and we were able to detect aortic valve dysfunction over time through the cardiac cycle.