In vivo cinematographic analysis of behavior of the aortic valve

In open-chest dogs direct-cinematographic high-speed recordings of aortic valve movement were made using a thin flexible fiberscope. Simultaneously ECG, ascending aortic flow (electromagnetically), and the pressures in the aorta, left ventricle, and left atrium were recorded. Replacement of blood by a transparent liquid (Tyrode solution) was done with two roller pumps, one connected to the left atrium and the other to the femoral artery. Free outflow occurred through a cannula in the pulmonary artery. Comparison of the film frames with the aortic flow signals revealed that 1) the valve was completely open at the moment that aortic flow had reached about 75% of its maximum value; 2) the opening time was 32 ms; 3) valve closure started before the onset of aortic flow deceleration; 4) at least 80% of the closure was completed before aortic flow becomes zero; 5) complete valve closing coincided with the moment of maximum backflow in the valve; 6) the shape of the valvular orifice at complete opening was almost circular; and 7) fluid viscosity had no significant effect on valve closure.