Partial Cleft Closure Alleviates a Disproportionate Degree of Force Exerted on Left Atrioventricular Valve Chordae in Ex Vivo Simulation
James Lee, Sumanth Kidambi, Stephen Moye, Robert J. Wilkerson, *Y. Joseph Woo, Michael Ma
Cardiothoracic Surgery, Stanford University, Stanford, California, United States
The surgical management of congenital mitral cleft and various forms of atrioventricular septal defect requires careful titration of its closure to impart the appropriate degree of residual regurgitation v. stenosis. We developed an ex vivo model of this malformation to identify the efficacy of complete versus partial cleft repair on restoring normal leaflet biomechanics.
Fetal bovine mitral valves, including the subvalvar ventricular apparatus, were mounted into a previously validated systemic ventricular heart simulator. Hemodynamic parameters set to physiologic human toddler conditions (heart rate 100 bpm, cardiac output 3.7 L/min, mean arterial pressure 73 mmHg). The cleft model was created by dividing the A2 segment of the anterior mitral leaflet from the leaflet edge to the annulus. Force-sensing neochordae (fiber Bragg grating) were sutured as primary chordae tendineae to each side of the mitral cleft. Complete and partial repair of the mitral cleft was accomplished by using 6-0 monofilament interrupted suture (Figure 1A). Statistical significance was determined using paired t-test.
Complete closure of the mitral cleft resulted in a 26.0% reduction in average force on the neochordae (p=0.004) while partial closure resulted in a 22.8% reduction in average force on the neochordae (p=0.002). Average neochordal forces were significantly lower in the complete closure compared to the partial closure (p=0.01). Partial closure was associated with a 28.3% reduction in maximum neochordae force and complete closure was associated with a 16.3% reduction in maximum neochordae force (Figure 1B). There was no significant difference in maximum neochordae force between the complete and partial closures (p=0.24). The regurgitation fraction was between 9-13% for all three experimental conditions.
Complete and partial closure of mitral cleft were both associated with significant reductions in average and maximum neochordal forces. Complete closure had a significant, but only incremental benefit, compared to partial closure, which may be important clinically in situations where only partial cleft closure can be performed surgically.
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