Does dilatation of the sinotubular junction cause aortic regurgitation?

BACKGROUND: Some patients develop aortic regurgitation (AR) in association with dilatation of the sinotubular junction (STJ), despite having normal aortic valve. However, the relationship between dilatation of the STJ and AR is unclear. METHODS: Canine hearts and aortas were isolated. A suture was placed in each commissure and in the sinus of Valsalva at the STJ. These interrupted sutures were drawn horizontally, and strain on the sutures was varied. The sites of the retracted sutures were changed to various positions, and the opening and closing of the aortic valve was observed endoscopically. A beating heart model was used to observe changes in aortic valve function during mechanical retraction of the commissures or sinuses. RESULTS: Opening area of the valve increased when strain on all sutures or commissures was increased. When strain was increased on the sinus alone, coaptation of the valve was not affected. CONCLUSION: We observed endoscopically that mechanical dilatation of the STJ causes AR. These findings suggest that the principal cause of AR associated with dilatation of the STJ is outward deviation of the commissure.