Abstract 2705: Effect of Inotropy and Chronotropy on Stitch Tension in the Edge-to-Edge Mitral Repair
Background: Our prior studies suggest that mitral annular septal-lateral (SL) diameter is the chief determinant of “Alfieri stitch” tension, but hemodynamic parameters may also play a role. To study the effects of inotropic and chronotropic stimulation on stitch tension and annular SL diameter, we approximated the central edge of the mitral leaflets with a miniature force transducer to measure leaflet tension (T) at the leaflet approximation point.
Methods: Eight sheep were studied under open-chest conditions immediately after surgical placement of a miniature force transducer to approximate the leaflets and implantation of radiopaque markers on the LV and mitral annulus (MA). Chronotropic stimulation was induced with atrial pacing at 130 min-1 (n=5) while inotropic state was increased with IV CaCl2 bolus (n=8). Hemodynamic data, stitch tension, and 3-D marker coordinates were obtained throughout the cardiac cycle before and during each intervention. Marker 3-D coordinates were used to calculateseptal-lateral (SL) diameter.
Results: Peak stitch tension (TMAX) under was observed in diastole and temporally correlated with peak annular SL (SLMAX) size.
Conclusion: Isolated increase in heart rate or inotropic state did not alter peak stitch tension; enhanced contractile state decreased SL diameter minimally. These data suggest that geometric (SL diameter) rather than hemodynamic parameters are the main determinants of “Alfieri stitch” tension. This implies that any interventional or surgical edge-to-edge repair performed without concomitant annular reduction or annuloplasty exposes the leaflet junction to high forces which portend limited repair durability