Abstract 18388: Novel Study of the Dynamic Changes in Mitral Valve Annular and Leaflet Parameters Under Varying Loading Conditions: A Three-Dimensional Echocardiographic Study

Abstract

Background: The impact of changing loading conditions on mitral valve (MV) coaptation is controversial. Previous studies assessed the MV at mid or end-systole only, hence MV dynamic changes throughout systole are poorly understood. We used three-dimensional echocardiography (3DE) to explore dynamic changes in MV annular and leaflet parameters during loading stress and inotropy in an animal model. Methods: In open chest model, 8 pigs and 4 dogs were imaged epicardially. 3DE was performed at baseline, with dobutamine infusion, volume infusion and aortic constriction, with a return to baseline hemodynamics between each intervention. The 3DE datasets were analyzed offline using TomTec semi automated MV software. Leaflet (AL) and annular area (AA) were reported as % change from baseline in 5 systolic intervals (1-5; each representing 20% of systole). ANOVA was performed between each intervention and baseline, at the 5 intervals, with Dunnett’s correction. Results: At baseline, MV peak % change of AL and AA occurred during the 4th and 5th intervals respectively. Compared to baseline, dobutamine infusion % change AL was reduced (-5.9% ± 3.8 vs -9.4% ± 6.1, p<0.01) in the 3rd interval, whilst % change AA was reduced throughout systole. With volume loading, % change AL and AA were significantly reduced during intervals 2 to 5. In contrast, with aortic constriction % change AL (-5.9% ± 3.8 vs -2.4% ± 4.8, p<0.05) and %change AA (-1.6% ± 3.8 vs 1.5% ± 5.7, p<0.05) were increased at the 3rd interval (see Figure). Conclusion: Peak MV annular contraction and leaflet apposition occurs in late systole. MV leaflet coaptation area improves in response to increased contractility and pre-load by increasing annular contraction and reducing unopposed leaflet surface. In contrast, increased afterload has the opposite effect on annular and leaflet size, potentially worsening coaptation. The timing of peak annular contraction and leaflet apposition has implications for the design of future MV studies.