High speed cine-radiographic study of aortic valve leaflet motion

The leaflets of the aortic valve move extremely rapidly during opening and closing. To analyse this movement, radiopaque markers were placed on the aortic valves of four dogs during cardiopulmonary bypass. One to five months later the dogs were studied using x-ray, and the marker motion was recorded on cine-film at 500 frames/second. Simultaneous aortic pressure varied from 70/30 to 188/152 mmHg and heart rate from 33 to 150 bpm. Analysis of 19 systolic periods and 2500 cine-frames indicated that leaflet motion occurred in four phases: 1--rapid movement during initial opening, 2--a little movement near maximal excursion, 3--a slow movement during early closing and 4--a rapid movement to complete closure. Phases 1 and 4 averaged 17.6 and 16.5 msec respectively, and were independent of heart rate, whereas the length of phases 2 and 3 varied with heart rate. The leaflets moved 82% of their maximum excursion during rapid opening and 53% during rapid closure. Leaflet curvature reversed in both the radial and the circumferential directions during opening. The leaflet profile in the radial direction changed as follows: during rapid opening, the belly of the leaflet moved outward, first causing the leaflet to straighten and then to conform to the profile of blood flow. During closure the belly of the leaflet moved centrally, causing the leaflet to curve toward the ventricle. The leaflet profile in the circumferential direction indicated that during opening the midpoint of the leaflet leads the motion towards the aortic wall.(ABSTRACT TRUNCATED AT 250 WORDS)