Genesis of 5th sound. A comparative phonomechanographic and echographic study

846 children between the ages of 6 and 12 were examined by phonocardiogram. The 5th sound was noted in 30.8% of the subjects examined. It appeared as a single or double vibration of approximately 65 msec from the third sound and corresponds to a small wave "H" of apexcardiogram at approximately 50 msec from the end of "E" wave. From the comparative poligraphic and echocardiographic study, the 5th sound corresponds to one or more added waves (G and G1) between point F and point A of the echogram of the anterior mitral leaflet; they are in exact chronological correspondence with the "H" wave of the APG. The 5th sound is evident and also the added waves of the anterior mitral leaflet (G, g1) when the frequency of the heart is slow. When the frequency increase, the 5th sound blends with the 3rd that appears prolonged and G, G1 waves become a single wave until its disappearents.