Significant increase of aortic root volume and commissural area occurs prior to aortic valve opening

Background and aim of the study: The increased use of autologous, homologou s or heterologous aortic root demands a detailed knowledge of its anatomy a nd function. The advent of 3-D digital sonomicrometry offered the opportuni ty to acquire precise information on the foot and leaflet movements during the cardiac cycle. Methods: Under cardiopulmonary bypass, sonomicrometry crystals were implant ed in the aortic root and valve of eight sheep. Crystals were sutured at ea ch commissure (n = 3), the top of the sinotubular junction (n = 3), lowest point of the annulus (n = 3), and leaflet tip (n = 3). 3-D coordinates of e ach crystal were recorded, together with left ventricular and aortic root p ressures and EGG. When the animal had returned to a stable hemodynamic cond ition, the maximum and minimum distances between two crystals, and areas be tween three crystals, were calculated. Changes in root volume and leaflet p osition were time-related to the pressure changes. Results: The most significant change between maximum and minimum distance b etween crystals during the cardiac cycle occurred at the commissural level. Similarly, the triangle defined by the three commissural crystals showed t he greatest change in area (47%). The root volume increased by an average o f 22%; about 40% of this increase occurred during the isovolumic phase. The aortic leaflets began to open before ejection. Conclusion: We postulate that aortic valve opening is initiated by the outw ard pull of the commissures. These findings should impact on aortic root su rgery.