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 morphology

Aortic valve

General

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

Gross

Terminology:

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

Cusps:

  • Left - has LMCA ostium.
  • Right - has RCA ostium.
  • Posterior (non-coronary cusp).

Microscopic

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.

Microscopic

Similar to the aortic valve - layers:

  1. Atrialis.
  2. Spongiosa.
  3. Fibrosa.

Degenerative conditions

Calcific aortic stenosis

  • Abbreviated CAS.

General

  • Somewhat similar to atherosclerosis; however, considered a separate entity.[2]
  • Mitral valve is usually normal.
  • Most common cause of aortic stenosis.

DDx of aortic stenosis:

  1. Calcific aortic stenosis.
  2. Bicuspid aortic valve with calcific aortic stenosis.
  3. Rheumatic heart disease.

Clinical (mnemonic SAD):

  • Syncope.
  • Angina.
  • Dyspnea (shortness of breath) - first symptom.

Microscopic

Features:[3]

  • Dystrophic calcification[4] - 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.

Note:

DDx:

Sign out

AORTIC VALVE, VALVE REPLACEMENT: 
	- CALCIFIC AORTIC STENOSIS.

Micro

The sections show valve tissue with marked calcification of the fibrosa layer. No neutrophils are identified. No microorganisms are identified.

Localized dystrophic heart valve amyloidosis

General

  • Common:
  • Not seen in acute disease and healed endocarditis.[7]

Hypothesis:

Microscopic

Features:[7]

  • Pink amorphous material - key feature.
    • Usually around the calcific foci.

DDx:

Stains

  • Congo red +ve.

Dystrophic amyloid:[7]

  • Alcian blue -ve.
  • Periodic acid-Schiff -ve.

Myxomatous degeneration

General

Gross

Features:[11]

  • 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.[12][13]

Interpretation of Movat stain:[13]

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

Image:

Infective conditions

Rheumatic heart disease

  • Abbreviated RHD.

General

  • Classically leads to mitral valve stenosis.
    • Rheumatic fever accounts for 99% of mitral stenosis.[14]
      • Caused by Streptococcus pyogenes.[15]
  • Disease less frequent today - as streptococcal pharynigits is treated.

Gross

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

DDx:

  • Thickening of the cordae tendinae due to micronodular cirrhosis.[17]

Microscopic

Features:[18]

  • Caterpillar cells (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.
    • Surrounded by lymphocytes (T cells) +/- plasma cells.

Notes:

  • Anitschkow cells are thought to be histocytes and Aschoff bodies are thought to be granulomas.[19]
    • This is disputed.[20]

Images:

IHC

Features (Aschoff bodies & Anitschkow cells):[19]

  • S100 -ve.
  • Muscle specific actin -ve.
  • Desmin -ve.
  • NF -ve.
  • Vimentin +ve.
  • CD45 +ve (weak).

Infective endocarditis

Bacterial endocarditis and subacute bacterial endocarditis redirect here.
  • Abbreviated IE.

General

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

Organisms

Most common organism overall:

  • Staphylococcus aureus.[21]

Organisms associated with particular clinical scenarios:

  • IV drug users / normal valves = Staphylococcus aureus.[22]
  • Previously damaged valve = Streptococcus viridans.
  • Prosthetic valves = Staphylococcus epidermidis.[23]

Organisms that less commonly cause IE are known as the HASEK group:[22]

  • Haemophilus (Haemophilus parainfluenzae, Haemophilus aphrophilus, Haemophilus paraphrophilus).
  • Actinobacillus (Actinobacillus actinomycetemcomitans, Aggregatibacter aphrophilus).
  • Cardiobacterium hominis.
  • Eikenella corrodens. †
  • Kingella (Kingella kingae).

Notes:

  • Enterococci are not included in this list but are lumped with the HACEK organisms.[22]

Clinical

  • Diagnosed (clinically) using the Duke criteria.[24][25]
    • Positive blood cultures.
    • Cardiac involvement - vegetation.
    • +/-Febrile.

Subdivided into:

  1. Acute IE.
    • Classically due to Staphylococcus aureus.
  2. Subacute IE.
    • Classically due to Streptococcus viridans.

Gross

  • Location - left-sided involvement (mitral, aortic) more common than right-sided involvement (pulmonic, tricuspid).
    • This is reversed in IV drug users.[22][26]
  • +/-Valvular destruction.
    • More common in acute IE.
  • +/-Distant emboli, e.g. splenic infarct.
    • More common in acute IE.
  • +/-Valvular vegetations.
    • Irregular ball of loosely adherent tissue - dull, irregular surface.
    • On the ventricular aspect in aortic valve IE.
    • Larger in acute IE.

Image:

Microscopic

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

Stains

Non-infective conditions

Mitral valve prolapse

  • Abbreviated MVP.
  • AKA floppy mitral valve.[27]

General

  • Classically young women.
  • Afflicts ~ 3% of population in the USA.[28]

Clinical:

  • Pansystolic murmur.
  • +/-Left ventricular hypertrophy - secondary to MVP.

Complications:[28]

Gross

Features - any of the following:[30]

  1. "Intrachordal hooding" = ballooning/bulging of leaflet between chordal attachments.
  2. Hooding or doming of the body of the leftlet into the left atrium.
    • Extreme concavity of the valve when seen from the left ventricle.
  3. Elongated leaflets/large valve area.
  4. Dilated valve annulus.
  • Thickening of the valve.
  • +/-Left ventricular hypertrophy.

Note - location:

  • Posterior leaflet pathology more common than anterior leaflet pathology.[30]

Image:

Microscopic

Features:[30][28]

  • Increased thickness of spongiosa layer.
  • Thinning of the fibrosa layer.
  • +/-Fibrin deposition - atrial aspect.

DDx:

Nonbacterial thrombotic endocarditis

  • Abbreviated NBTE.
  • AKA marantic endocarditis.[31]

General

Associations:

  • Cardiac catheterization.[32]
  • Embolization.[31]
  • Malignancy - leading cause, usu. adenocarcinoma.[33]

Note:

  • Marantic = wasting away.

Gross

  • Round non-destructive vegetations, usually at the line of closure.[34]

Microscopic

Features:

  • Vegetation without inflammation and microorganisms.

Libman-Sacks endocarditis

General

  • Associated with systemic lupus erythematosus.
    • Seen in approximately in 1/10 SLE cases by echocardiography.[35]
  • Affects the mitral and aortic valves.[36]
    • Mitral valve most commonly affected.[37]
  • It has been suggested that it may be a manifestation of APLA syndrome.[36][37]

Clinical:

  • Usually regurgitation.

Gross

  • Vegetations anywhere on the valve surface[35] - often seen on both sides (flow surface & non-flow surface).[38]

Image:

Microscopic

Features:[citation needed]

  • Fibrin.
  • No microorganisms.
  • No inflammation.

Biscupid aortic valve

General

  • Aortic valve usually tricuspid.
  • Most common congenital heart defect.[39]
    • 1-2% of general population.[40]
      • Male:female ~ 2:1.[41]
  • Inherited in autosomal dominant pattern.
    • NOTCH1 gene - implicated.[42]

Significance:

Gross

Features - either:

  1. Raphe does not reach the free margin of the cusp.[43]
  2. No raphe - uncommon (~7% of cases).[44]

Note:

  • Raphe ~ suture or seam.[45]

Images:

Microscopic

Features - section through raphe:

  • "No evidence of fusion."[43]
  • Elastic fibres through-out (not interrupted by fibrous tissue). (???)

DDx:

Heart valve 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. Novaro, GM.; Griffin, BP. (May 2003). "Calcific aortic stenosis: another face of atherosclerosis?". Cleve Clin J Med 70 (5): 471-7. PMID 12779138.
  5. Kristen, AV.; Schnabel, PA.; Winter, B.; Helmke, BM.; Longerich, T.; Hardt, S.; Koch, A.; Sack, FU. et al. "High prevalence of amyloid in 150 surgically removed heart valves--a comparison of histological and clinical data reveals a correlation to atheroinflammatory conditions.". Cardiovasc Pathol 19 (4): 228-35. doi:10.1016/j.carpath.2009.04.005. PMID 19502085.
  6. 6.0 6.1 Falk, E.; Ladefoged, C.; Christensen, HE. (Jan 1981). "Amyloid deposits in calcified aortic valves.". Acta Pathol Microbiol Scand A 89 (1): 23-6. PMID 7223424.
  7. 7.0 7.1 7.2 7.3 Cooper, JH. (Jul 1983). "Localized dystrophic amyloidosis of heart valves.". Hum Pathol 14 (7): 649-53. PMID 6190729.
  8. URL: http://emedicine.medscape.com/article/759004-overview. Accessed on: 8 June 2010.
  9. 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.
  10. 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.
  11. 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.
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