Heart valves

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Heart valves are the domain of the cardiac surgeon and their bread & butter.

Clinical

General

  • Insufficiency (regurgitant flow) - murmur in diastole.
  • Stenosis (decreased flow area) - murmur in systole.

Pathology

Which valves cause the most trouble?

  • Mostly those on the left side (subjected to higher pressures), i.e. mitral valve (or left atrioventricular v.) and aortic valve.

Aortic stenosis - cause?

  • Mostly "calcific aortic stenosis".

Quick approach to valves

Gross

  • Calcification?
    • Consider calcific stenosis.
  • Vegetations?
    • Consider infective endocarditis.
  • Thin (see-through)?
    • Consider myxomatous change.

Microscopic

  • Inflammation?
    • Consider endocarditis.
  • Anitschkow's cells (caterpillar cells)?
    • Rheumatic heart disease.
  • Aschoff bodies?
    • Rheumatic heart disease.
  • Thickening of spongiosa (layer)?
    • Myxomatous change?

Normal histology

Aortic valve

General:

  • Covered by endothelium.
  • Mostly avascular (nutrients supplied by diffusion).

Terminology:

  • Base - closest to the aortic wall.
  • Free edge - closest to the centre of the valve/interacts with other valve cusps.

Three layers (from proximal (ventricular side) to distal (valsalva side)):[1]

  1. Ventricularis.
    • Elastic tissue.
  2. Spongiosa.
    • Loose connective tissue.
  3. Fibrosa.
    • Mostly collagen, thickest part in a normal valve.

Notes:

  • The loading of the ventricular aspect is tensile and the valsalva side compressive. Thus, it makes sense that the tissue on the ventricular aspect is good in tensile loading and the tissue on the valsalva side good in compression. The elastic tissue can be thought of as rebar... the collagen as concrete.

Mitral valve

Gross

  • Cordae tendinae.
    • Should be thin.
    • No fusion.

Histology

  • Similar to the aortic valve.

Calcific aortic stenosis

General

  • Somewhat similar to atherosclerosis; however, considered a separate entity.[2]
  • Mitral valve is usually normal.

Microscopic

Features:[3]

  • Affects the valsalva side of the valve.
    • It affects the fibrosa.
  • Primarily at the base of the valve, i.e. there is relative sparing the free edge.

Myxomatous degeneration

General

Gross

Features:[7]

  • No commissural fusion.
    • Commissural fusion typical of rheumatic heart disease.
  • Thickened.
  • Rubbery consistency.
  • Reactive/secondary changes.
    • Fibrosis due to prolapse/abnormal contact of valve with other structures.
    • Clots/organized thrombus - due to stasis.

Microscopic

  • Thinning of fibrosa layer.
  • Thickening of spongiosa layer with mucoid (myxomatous) material. (key feature).
  • +/-Secondary changes (due to valvular dysfunction): thrombi, fibrosis.

Staining

  • Movat stain.
    • Acid fuchsin, alcian blue, crocein scarlet, elastic hematoxylin, pathology consultation, and saffron.[8][9]

Interpretation of Movat stain:[9]

  • Black = nuclei and elastic fibers.
  • Yellow = collagen and reticular fibers.
  • Blue = mucin, ground substance.
  • Red (intense) = fibrin.
  • Red = muscle.

Image:

Rheumatic heart disease

General

  • Classically leads to mitral valve stenosis.
    • Rheumatic fever accounts for 99% of mitral stenosis.[10]
  • Disease less frequent today - as streptococcal pharynigits is treated.

Gross

  • "Fish-mouth appearance".
  • Significant valvular thickening.
  • Thickening of the cordae tendinae.

Microscopic

Features:[12]

  • Caterpillar cell (AKA Anitschkow cells)
    • Abundant eosinophilic cytoplasm.
    • Moderately-poorly defined cell border.
    • Well-defined central ovoid nucleus with a prominent wavy ribbon-like chromatin -- looks vaguely like a caterpillar with some imagination.
    • Pathognomonic for rheumatic fever.
  • Aschoff bodies:
    • Usually in the heart itself,
    • Jumbled collagen, eosinophilic, and
    • Surrounded by lymphocytes (T cells) +/- plasma cells.

Images:

Endocarditis

General

  • Infection of the endocardium - often involves the valves (which are covered by endocardium).
  • Before the time of antibiotics -- 100% fatal.

Clinical

  • Diagnosed (clinically) using the Duke criteria.[13][14]
    • Positive blood cultures.
    • Cardiac involvement - vegetation.
    • +/-Febrile.

Microscopic

  • Inflammatory infiltrate (key feature @ low power):
    • +/-Plasma cells.
    • +/-Neutrophils.
  • Microorganisms - key feature (diagnostic).
    • Hard to see (even at high power).

Stains

  • GMS (Gomori Methenamine-silver stain).
    • Look for fungi.
  • Gram stain.
    • Look for bacteria.

Non-bacterial thrombotic endocarditis

General

  • Abbreviated NBTE.
  • May be associated with catheterization.

Microscopic

Features:

  • No inflammation.
  • No organisms.

Biscupid aortic valve

General

  • Aortic valve usually tricuspid.
  • 1-2% of general population.[15]
  • Inherited in autosomal dominant pattern.
  • Most common congenital heart defect.[16]

Significance

  • Associated with ascending aortic aneurysms - x10 risk of dissection vs. normal population[15]
  • 30% develop serious morbidity.[15]
  • Associated with early development of calcific aortic stenosis.

Tumours

Main article: Cardiac tumours

Papillary fibroelastomas are the most common tumour of the valve.

See also

References

  1. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 558. ISBN 0-7216-0187-1.
  2. ↑ Otto CM (September 2008). "Calcific aortic stenosis--time to look more closely at the valve". N. Engl. J. Med. 359 (13): 1395-8. doi:10.1056/NEJMe0807001. PMID 18815402.
  3. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 590. ISBN 0-7216-0187-1.
  4. ↑ URL: http://emedicine.medscape.com/article/759004-overview. Accessed on: 8 June 2010.
  5. ↑ Leong SW, Soor GS, Butany J, Henry J, Thangaroopan M, Leask RL (October 2006). "Morphological findings in 192 surgically excised native mitral valves". Can J Cardiol 22 (12): 1055-61. PMID 17036100.
  6. ↑ Wigle ED, Rakowski H, Ranganathan N, Silver MC (1976). "Mitral valve prolapse". Annu. Rev. Med. 27: 165–80. doi:10.1146/annurev.me.27.020176.001121. PMID 779595.
  7. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 591. ISBN 0-7216-0187-1.
  8. ↑ URL: http://www.mayomedicallaboratories.com/test-catalog/Overview/9832. Accessed on: 8 June 2010.
  9. ↑ 9.0 9.1 Modified Movat's Pentachrome Stain. University Penn Medicine. URL: http://www.med.upenn.edu/mcrc/histology_core/movat.shtml. Accessed on: January 29, 2009.
  10. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 594. ISBN 0-7216-0187-1.
  11. ↑ URL: http://en.wikipedia.org/wiki/Ellipse. Accessed on: 13 November 2010.
  12. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 593. ISBN 0-7216-0187-1.
  13. ↑ http://www.medcalc.com/endocarditis.html
  14. ↑ Durack DT, Lukes AS, Bright DK (March 1994). "New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service". Am. J. Med. 96 (3): 200-9. PMID 8154507.
  15. ↑ 15.0 15.1 15.2 Vallely MP, Semsarian C, Bannon PG (October 2008). "Management of the ascending aorta in patients with bicuspid aortic valve disease". Heart Lung Circ 17 (5): 357-63. doi:10.1016/j.hlc.2008.01.007. PMID 18514024.
  16. ↑ Siu SC, Silversides CK (June 2010). "Bicuspid aortic valve disease". J. Am. Coll. Cardiol. 55 (25): 2789–800. doi:10.1016/j.jacc.2009.12.068. PMID 20579534.
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