The aortic valve (AV) is a semilunar valve positioned at the end of the left ventricular outflow tract (LVOT) between the left ventricle and aorta. Proper functioning of this valve is critical in maintaining efficient cardiac function. This chapter explores the anatomical and physiologic properties of the AV.
Embryologic development of the AV is closely associated with development of the LVOT. In the primary heart tube, blood travels from the primitive ventricle into the bulbous cordis and out the aortic roots. The midportion of the bulbous cordis, the conus cordis, develops into the outflow tracts of the ventricles. The distal portion of the bulbous cordis, the truncus arteriosus (TA), develops into the proximal portion of the aorta and pulmonary arteries. During the fifth week of development, pairs of opposing swellings appear in the conus cordis and TA (Fig. 31-1). These conotruncal, or bulbar, ridges grow toward each other and fuse to form the aorticopulmonary (AP) septum. The AP septum divides the conus cordis into the left and right ventricular outflow tracts and the TA into the ascending aorta and pulmonary trunk.
Schematic representation of development of the left and right ventricular outflow tracts and aortic and pulmonary valves. (Top left) Cross-section through the cordis showing the conotruncal ridges beginning to develop. (Top right) Aorticopulmonary septum forming from fusion of the conotruncal ridges and subendocardial swellings beginning to develop into the aortic and pulmonary valve leaflets. (Bottom left) Left and right ventricular outflow tracts separated by the aorticopulmonary septum and further development of the subendocardial swellings. (Bottom right) Aortic and pulmonary valves in the adult. (Reproduced with permission of the Cleveland Clinic, Cleveland, OH.)
When partitioning of the TA is nearly completed, the AV begins to develop from three swellings of subendocardial tissue (see Fig. 31-1). Two swellings arising from the fused truncal ridges develop into the right and left AV leaflets. A third dorsal swelling develops into the posterior leaflet. These swellings are reshaped and hollowed out to form the three thin-walled cusps of the fully developed AV. The pulmonary valve develops in a similar manner.
The AV separates the terminal portion of the LVOT from the aorta. The normal AV consists of three semilunar leaflets or cusps projecting outward and upward into the lumen of the ascending aorta (Fig. 31-2). The space between the free edge of each leaflet and the points of attachment to the aorta comprise the sinuses of Valsalva. Because the coronary arteries arise from two of the three sinuses, the sinuses and the respective leaflets are named the right coronary, left coronary, and posterior (noncoronary) sinuses and leaflets. The ostia of coronary arteries arise from the upper part of the sinuses, with the ostium of the left coronary artery positioned slightly ...