The earliest anlage of the
semilunar valves was first observed in 2.5 cm CVRL buffalo foetus in aorta (Figure 15) and pulmonary artery.
At early embryonic stages endocardial cushion tissue is positioned in the primitive AVC and OFT, which later on will contribute to formation of the TV and MV and Ao and PT
semilunar valves. Some clinical studies argued that AV valve regurgitation is a common phenomenon during the first trimester of pregnancy [20].
This defect may be found anywhere from just above the
semilunar valves to the more distal ascending aorta and main pulmonary artery.
Medical professionals refer to them as the first heart sound ([S.sub.1]) and the second heart sound ([S.sub.2]), produced by the closing of the atrioventricular valves and
semilunar valves. A third heart sound is normal in children and young adults, but can be indicative of heart failure in people who are older than 40.
A loud, single [S.sub.2] indicates pulmonary hypertension (with RV overload) or congenital heart disease involving the
semilunar valves. Murmurs are graded 1-6/6, and are timed as early, middle or late systolic.
The
semilunar valves are formed from three small tubercles of tissue that are (overriding), a small pulmonary outflow tract, and the inability of the ventricular septum to close.
QAV is a rare abnormal development of
semilunar valves that has been reported in 0.008%, 0.043%, and 1% in, respectively, autopsy series, two-dimensional TTE, and in aortic valve surgery [6].
