Diagram of the heart and great vessels showing locations of the mitral and other cardiac valves.

mvschematic

Normal mitral valves open widely and allow rapid inflow of blood from the left atrium to the left ventricle in diastole. During systole, increasing ventricular pressure closes the mitral valve and opens the aortic valve. Chordae tendineae restrain the mitral leaflets.

normaldiag

The mitral valve apparatus between the left atrium and left ventricle includes two major leaflets hinged at the annulus fibrosus and restrained by chordae tendineae attached to two papillary muscles. The leaflets are thin and translucent in the basal area and thicker in the contact zones.

normalheart

Photographs through the left atrium of a normal dog heart mounted on a pulse duplicator show the mitral valve in diastole and systole. The aortic (A, anterior) and mural (M, posterior) leaflets only close 60-70% of the valve orifice. Commissural cusp tissue (C) closes the remainder. The line of closure in dogs is C-shaped but species differences occur. Click forward arrow to see valve motion. (From Frater RWM and Ellis FH Jr. J Surg Res 1:171-178, 1961).

pulsedupFrater

Post mortem human heart mounted on a pulse duplicator showing alternate opening and closing of the mitral valve (rightward) and the aortic valve (upper left). Film courtesy of Julio C. Davila, MD & Joseph Sunner RPB.

A pulse duplicator pump and transparent ports in the left atrium and left ventricle allow filming of mitral and aortic valve motion in a postmortem heart perfused with saline. A-reservoir. B-peripheral resistance simulating chamber. C-strain gauge. D-aortic viewing chamber. E-atrial viewing chamber. F-postmortem heart with left ventricle attached to pump outflow nipple. Systolic pump pressure was generated by a piston driven by an eccentric cam.

(From Davila JC et al. Annals of Surgery April 1956, p546)

pulsedup-Davila