Mitral valve motion assessed by high-speed video camera in isolated swine heart

Objective: We have recently reported our isolated and working swine heart model that examines the valve motion precisely by a high-speed digital video camera system. Using this modality, the present study aimed (1) to delineate the motion of the mitral leaflets, chords and annulus throughout the cardiac cycle, and (2) to elucidate the influence of alterations in loading conditions on leaflet excursion. Methods: The valve motion of five isolated and working swine hearts was observed by an endoscope recording the images at 250 frames per second. Modified Krebs-Ringer solution was used as the sole perfusate. The images were obtained in hearts 30 min after reperfusion, changing the left atrial pressure as 4, 8, and 12 mmHg. Results: The motion of the mitral valve in the vicinity of diastole was considered to be well understood by dividing the entire sequence into five stages: 'decoaptation,' 'E excursion,' 'diastasis,' 'A excursion,' and 'coaptation.' Initial separation occurred at both sides of the central tips of the leaflets. The leading edges always followed the mid-portion of the rough zone during opening and closing. The 'strut' second-order chords retained their tension throughout the cardiac cycle and played the role as rotary shafts of the other branching chords. The first-order chords lost their tension during opening, suggesting they mainly are involved in valve competence. Annular constriction occurred coincident with atrial contraction. An increase in preload made the isovolumic relaxation and contraction times shorter. The leaflets opened faster in the rapid-filling phase, whereas they required more time for opening and closing in the atrial-filling phase. Conclusions: The present study revealed the integrated movement of the mitral leaflets, chords and annulus, as well as the impact of altered preload.