Elorm Agra

PhD Thesis defense presentation

Date: Monday July 19th, 2020

Time: 3:00 pm to 5:00 pm

Location: https://zoom.us/j/93882265128

Meeting ID: 938 8226 5128

Passcode: Elorm_A

Committee members:

Muralidhar Padala, PhD (advisor)

Lakshmi Prasad Dasi, PhD 
John Oshinski, PhD 
Hanjoong Jo, PhD 
Robert Taylor, MD/PhD
Robert Guyton MD (Emory Dept of Surgery) 

Title: Subannular approaches for mitral valve repair to correct functional mitral regurgitation 

Abstract:

Functional mitral regurgitation (FMR) is a valvular heart disease that affects 35% of the 5.5 million Americans living with heart failure. In this disease, the native geometry and mechanics of the mitral valve are perturbed with increased interpapillary muscle separation, decreased closing forces, increased chordae tendineae tethering forces and tethered valve leaflets. The gold standard repair for FMR, undersizing ring annuloplasty (URA) results in 34% recurrence of the disease after one year and 58.8% after two years. This may be due to an unnatural configuration of the mitral valve induced by URA with further tethering of the posterior leaflet. In addition, the natural slack present in the rough zone of the mitral leaflets is lost due to the displacement of papillary muscle (PM) tips outside the mitral corridor. Subannular repairs such as PM approximation and PM basal hoisting may be a more physiologic approach to repairing FMR either in isolation or in combination with URA. In preliminary studies from the lab we found improved leaflet mobility and coaptation resulting in 0% FMR recurrence at 3 months with PM approximation compared with UMA.  

Thus, I hypothesize that relocating the displaced papillary muscles laterally inward or basally towards the annulus will relieve leaflet tethering, reduce chordal forces, and improve leaflet mobility to restore native mitral valve geometry and motion. Specifically, PM approximation should relieve tethering in marginal chordae, restoring the vertical shelf formation of the rough zones of each scallop of both leaflets despite poor closing forces. However, PM basal hoisting may relieve tethering of both marginal and strut chordae but have focal improvements in leaflet geometry. I propose to test this in 3 aims. Aim 1: Create an ex vivo benchtop model of FMR with a dilated ventricle that mimics human-like mitral valve tethering Aim 2: Investigate the impact of PM approximation (lateral relocation) and PM hoisting (basal relocation) on mitral valve geometry, hemodynamics and kinematics in the setting of mitral valve tethering Aim 3: Investigate the impact of PM approximation and relocation (basal hoisting) on mitral valve chordal force balance and biomechanics.