Histological appearance and echocardiogram of the MV and chordae tendineae. A: Myxomatous degeneration. The structure of the valve is crumbly and the main changes are myxoid degeneration and no inflammation. A': Myxomatous degeneration of idiopathic RMCT. The parasternal left ventricular long-axis view shows elongated subvalvular chordae, and a floppy and soft valve associated with posterior small tendon rupture. B: Chronic rheumatic valvulitis. Fibrous tissue hyperplasia of the valve, glass-like degeneration, and vascular proliferation, with a small amount of lymphocytic infiltration can be seen. B': Chronic rheumatic valvulitis. The parasternal left ventricular long axis view shows marked thickening of valve leaflets, and the arrow shows ruptured posterior tendons. C: Infective endocarditis. Valve tissue necrosis, thrombosis associated with a large amount of neutrophil infiltration, and neoplasms can be seen. C': Infective endocarditis (TEE): Intraoperative ultrasound shows marked thickening of mitral valve leaves and non-uniform, non-uniform echo dense and valve prolapse. The arrow indicates the site of chordae rupture and mitral valve prolapse.