Morphological findings in 192 surgically excised native mitral valves

Abstract

Introduction: Mitral valve disease (MVD) is a significant clinical problem that is becoming more common in the 21st century. The pathogenesis of MVD seems to be changing and is not well understood.

Patients and methods: The present study details the morphological findings in 192 native mitral valves excised over a one-year period at the Toronto General Hospital, Toronto, Ontario. The mean patient age was 59.7+/-12.3 years at operation.

Results: There were 106 men (55.2%) and 86 women (44.8%) in the present study. The most frequent changes in the surgically excised valvular leaflets were fibrosis (78.6%) and thickening (66.2%). Fusion (32.3%) and calcification (25.2%) were common changes at the commissures. Chordae tendineae most often showed evidence of thickening (47.9%) and fibrosis (37.0%). In total, 110 valves showed mitral incompetence (57.3%), 72 showed mitral stenosis (37.5%), and 10 showed a combination of stenosis and incompetence (5.2%).

Conclusions: In the present series, MVD was most frequently caused by postinflammatory (rheumatic) valve disease (RVD) (35.9%), followed by myxomatous degeneration (33.3%). Patients with RVD were usually female (66.7%), while those with myxomatous degeneration were more likely to be male (76.6%). RVD remains a significant problem even though the incidence of acute rheumatic fever with cardiac involvement has declined in Canada. This most likely reflects the current sociodemographic composition of the referral population.

Figure 1

A to C A postinflammatory (rheumatic) mitral valve, excised from a 31-year-old man. A Flow surface. The specimen shows nodular calcification (black arrow), thickening and fibrosis of the leaflets. Two chordae tendineae have been pushed through the orifice (white arrow). B Nonflow surface. Shortening and fusion of the chordae tendineae can be seen (asterisks). C Transverse section through a commissure, showing ulceration (u), calcification (m), inflammation (i) and old hemorrhage (h) into this commissural region of the leaflets (hematoxylin and eosin stain, original magnification ×16). D A postinflammatory (rheumatic) mitral valve, excised from a 43-year-old man. On the flow surface, the valve shows loss of scallops on the posterior leaflet (black arrowhead)

Figure 2

A postinflammatory (rheumatic) mitral valve, excised from a 56-year-old woman. A Flow surface. Mild commissural fusion can be seen (white arrows). B Nonflow surface. The specimen shows fibrosis and fusion of some of the chordae tendineae. No calcification is seen, and some chordae tendineae, especially from the posterior leaflet, appear virtually unremarkable (white arrowheads). A papillary muscle tip, with attached strips of chordae tendineae, is also seen. This mitral valve shows relatively mild changes compared with the usual gross findings in a rheumatic mitral valve as seen in Figure 1

Figure 3

A to C A myxomatous mitral valve, excised from a 63-year-old man. A Flow surface. The segments of the posterior leaflet show thickening, fibrosis, ‘hooding’ (asterisks) and myxomatous change. B Nonflow surface. One segment shows atypical chordal attachments, with the chordae attached to the basal regions of the free margin (white arrow). The cut edges have a thick, myxoid (edematous) appearance (red arrowhead). C Section through the posterior mitral leaflet, showing thickening and fibrosis (black arrowheads), myxomatous change (white asterisks) and elastosis (black arrows) of the leaflet (Movat pentachrome stain, original magnification ×16). D Section through a myxomatous posterior mitral leaflet showing fibroelastic deficiency, excised from a 55-year-old man. (Movat pentachrome stain, original magnification ×25). The higher magnification inset of the boxed area shows loss of elastic tissue and accumulation of mucopolysaccharides (area between the red arrows) (original magnification ×200)

Figure 4

A mitral valve from a 33-year-old woman, showing infective endocarditis. The flow (A) and nonflow (B) surfaces show evidence of pre-existing myxomatous change, infected vegetations (white arrows) and tissue destruction. C A section through the cusp showing extensive tissue destruction (black asterisk) (Movat pentachrome stain, original magnification ×16). D This magnified section of the boxed area in C shows colonies of Gram-positive bacteria (black arrow) (Gram stain, original magnification ×200)

Figure 5

A mitral valve from a 37-year-old woman showing fibrosis and thickening. This mitral valve had been repaired 19 years before excision, for reasons related to the patient’s tetralogy of Fallot. A A synthetic chorda tendinea can be seen, covered by significant circumferential fibrosis (white arrow). B Section through the posterior leaflet (Movat pentachrome stain, original magnification ×16). The inset, polarized and magnified from the boxed area, shows the synthetic fabric of the suture (black arrow) and fibrosis surrounding the suture (original magnification ×200)