Mitral valve specimen

Question 1

Describe the case for your specimen?

Answer 1

Case: 64yo male had a mitral valve replacement, on a background of mitral regurgitation and aortic stenosis

• Mitral regurgitation -> pansystolic murmur
• Aortic stenosis -> systolic murmur

Question 2

List some risk factors for mitral regurgitation?

Answer 2

Risk: Ehler-Danlos Syndrome, Marfan syndrome, PCKD, Graves’ disease, chest wall deformities (pectus excavatum)

Question 3

Describe the macroscopic appearance of the mitral valve regurgitation?

Answer 3

• Normally: leaflets composed of fibrous skeleton with endocardial surface
• Calcification: large nodular calcific masses -> suggest congenital valve disease
• Mitral valve prolapse: thickened, redundant myxomatous mitral leaflets due to abnormal connective tissue, chordae tendineae elongated -> prone to rupture

Question 4

Describe the microscopic appearance of the mitral valve regurgitation?

Answer 4

• Endothelium infiltrated with T cells, macrophages, foam cells
• Myofibroblasts (differentiated valvular fibroblasts)
• Osteophenotype of myofibroblast
• Calcium nodule formation

Question 5

Describe the pathogenesis of mitral valve regurgitation?

Answer 5

• T lymphocytes and macrophages infiltrate endothelium -> release cytokines -> act on fibroblasts to promote cellular proliferation and extracellular matrix remodelling
• Valvular fibroblasts in fibrosa layer differentiate into myofibroblasts (smooth muscle characteristics)
• LDL taken into subendothelial layer -> oxidatively modified and taken up by macrophages -> form foam cells
• Valvular myofibroblasts differentiate into osteoblast phenotype -> promotes calcium nodule formation
• Valve cusps progressively thicken -> fibroses and calcifies