Heart valves

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. 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.

Image:

• Normal mitral valve (e-heart.org).

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.
• 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:

• Dystrophic calcification - 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:

• There should be no neutrophils and no microorganisms.
• An expanded spongiosa layer may be seen in the context of calcification.^{[citation needed]}

DDx:

• Infective endocarditis - inflammatory cells (esp. neutrophils), microorganisms (e.g. cocci).
• Bicuspid aortic valve.
• Rheumatic heart disease.

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 with routine stains.

Localized dystrophic heart valve amyloidosis

General

• Common:
  • ~75-100% of valves with calcific degeneration, i.e. calcific aortic stenosis.
  • ~50% of valves with post-rheumatic sclerosis.
• Not seen in acute disease and healed endocarditis.

Hypothesis:

• Amyloid deposition in the aortic valve is the precursor lesion of calcific aortic stenosis.

Microscopic

Features:

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

DDx:

• Systemic amyloidosis, e.g. senile systemic amyloidosis, AL-amyloidosis.

Stains

• Congo red +ve.

Dystrophic amyloid:

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

Myxomatous degeneration

General

• Usually affects the mitral valve.
• Female > male, disputed by Toronto data.
• Associated with Marfan's syndrome and Turner syndrome (Monosomy X).

Gross

Features:

• 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.

Interpretation of Movat stain:

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

Image:

• 

  Myxomatous valve. Movat stain. (WC/Nephron)

Infective conditions

Rheumatic heart disease

Rheumatic fever redirects here.

• Abbreviated RHD.

General

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

Gross

• "Fish-mouth appearance".
  • Slit-like morphology; elliptical cross-sectional flow area (mitral valve) has an abnormally small semi-minor axis axis due to valve thickening.
  • Image: Fish-mouth appearance - pipe (principia-eng.com).
• Significant valvular thickening.
• Thickening and shortening of the cordae tendinae.

DDx:

• Thickening of the cordae tendinae due to micronodular cirrhosis.

Images

• 

  RHD - showing valvular thickening and thickening of the cordae tendinae. (WC)

• 

  RHD - showing valvular thickening - aortic valve. (WC)

Microscopic

Features:

• 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.
  • This is disputed.

Images

• 

  RHD - intermed. mag. (WC/Nephron)

• 

  RHD - high mag. (WC/Nephron)

• 

  RHD - very high mag. (WC/Nephron)

• 

  Aschoff body (WC/Uthman)

• 

  Anitschkow myocytes (WC/Uthman)

IHC

Features (Aschoff bodies & Anitschkow cells):

• 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.

Organisms associated with particular clinical scenarios:

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

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

• 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.

Clinical

• Diagnosed (clinically) using the Duke criteria.
  • 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.

Treatment:

• Usually medical management.
• Valve replacement.
• Valve repair.
• Valvectomy - for tricuspid valve.

Gross

• Location - left-sided involvement (mitral, aortic) more common than right-sided involvement (pulmonic, tricuspid).
  • This is reversed in IV drug users.
• +/-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:

• Infective endocarditis - aortic valve (flickr.com).

Microscopic

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

Stains

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

Sign out

TRICUSPID VALVE, VALVECTOMY:
- FRAGMENTS OF VALVE WITH INFECTIVE ENDOCARDITIS -- ABUNDANT COCCI
  ORGANISMS IDENTIFIED.
- THIN RIM OF CARDIAC MUSCLE WITHOUT APPARENT PATHOLOGY.

MITRAL VALVE, VALVE REPLACEMENT:
- FRAGMENTS OF VALVE WITH INFECTIVE ENDOCARDITIS -- ABUNDANT COCCI
  ORGANISMS IDENTIFIED.

No microorganisms

AORTIC VALVE (BICUSPID), VALVE REPLACEMENT:
- BICUSPID VALVE WITH CALCIFIC AORTIC STENOSIS AND MILD ENDOCARDITIS.
- NO MICROORGANISMS APPARENT.

Micro

The sections show valve tissue with an attached vegetation with abundant cocci organisms and neutrophils. No calcification is apparent.

No microorganisms

The sections show valve tissue with marked calcification, scattered neutrophils and plasma cells. No microorganisms are identified with routine stains.

Non-infective conditions

Mitral valve prolapse

• Abbreviated MVP.
• AKA floppy mitral valve.

General

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

Clinical:

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

Complications:

• Infective endocarditis.
• Congestive heart failure.
• Sudden cardiac death.
• Thromboembolism.

Gross

Features - any of the following:

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.

Image:

• MVP - intrachordal hooding (e-heart.org).

Microscopic

Features:

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

DDx:

• Myxomatous degeneration.^{[citation needed]}

Nonbacterial thrombotic endocarditis

• Abbreviated NBTE.
• AKA marantic endocarditis.

General

Associations:

• Cardiac catheterization.
• Embolization.
• Malignancy - leading cause, usu. adenocarcinoma.

Note:

• Marantic = wasting away.

Gross

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

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.
• Affects the mitral and aortic valves.
  • Mitral valve most commonly affected.
• It has been suggested that it may be a manifestation of APLA syndrome.

Clinical:

• Usually regurgitation.

Gross

• Vegetations anywhere on the valve surface - often seen on both sides (flow surface & non-flow surface).
• Flat, pale brown/tan, usually small.

Images:

• Libman-Sacks endocarditis (photobucket.com).
• Libman-Sacks endocarditis (utah.edu).

Microscopic

Features:^{[citation needed]}

• Fibrin.
• No microorganisms.
• No inflammation.

Biscupid aortic valve

General

• Aortic valve usually tricuspid.

• Most common congenital heart defect.
  • 1-2% of general population.
    • Male:female ~ 2:1.
• Inherited in autosomal dominant pattern.
  • NOTCH1 gene - implicated.

Significance:

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

Gross

Features - either:

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

Note:

• Raphe ~ suture or seam.

Images:

• Bicuspid valve (ahajournals.org).

Microscopic

Features - section through raphe:

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

Note:

• The clinical impression and gross pathologic impression of bicuspid valve should concur.

DDx:

• Senile calcific aortic stenosis with fusion of leaflets.

Sign out

AORTIC VALVE, VALVE REPLACEMENT:
- BICUSPID VALVE WITH CALCIFIC AORTIC STENOSIS.

Micro

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

Heart valve tumours

Main article: Cardiac tumours

Papillary fibroelastomas are the most common tumour of the valve.

Other

Subvalvular membrane

Subvalvular aortic membrane redirects here.

General

• Rare.
• May lead to sudden natural death.

Clinical:

• Symptoms of aortic stenosis.
• No ejection sound (as in aortic valvular stenosis).

Microscopic

Features:

• Fibrous tissue.

Note:

• Similar to valvular tissue.

Stains

• Movat stain.

Sign out

SUBVALVULAR MEMBRANE, AORTA, EXCISION:
- BENIGN PAUCICELLULAR FIBROUS TISSUE CONSISTENT WITH SUBVALVULAR MEMBRANE.

See also

• Heart.
• Cardiomyopathy.
• Forensic pathology.