Difference between revisions of "Heart valves"

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[[Image:Gray497.png|thumb|right|Aortic valve - drawing. (WC/Gray's Anatomy)]]
'''[[Heart]] valves''' are the domain of the cardiac surgeon and their bread & butter.
'''[[Heart]] valves''' are the domain of the cardiac surgeon and their bread & butter.


Line 76: Line 77:
**No fusion.  
**No fusion.  


Note:
*The [[cut-up]] is described in ''[[grossing mitral valves]]''.
===Microscopic===
===Microscopic===
Similar to the aortic valve - layers:
Similar to the aortic valve - layers:
Line 114: Line 117:


==Myxomatous degeneration==
==Myxomatous degeneration==
===General===
{{Main|Myxomatous degeneration}}
*Usually affects the mitral valve.
*Female > male,<ref>URL: [http://emedicine.medscape.com/article/759004-overview http://emedicine.medscape.com/article/759004-overview]. Accessed on: 8 June 2010.</ref> disputed by Toronto data.<ref name=leong>{{cite journal |author=Leong SW, Soor GS, Butany J, Henry J, Thangaroopan M, Leask RL |title=Morphological findings in 192 surgically excised native mitral valves |journal=Can J Cardiol |volume=22 |issue=12 |pages=1055-61 |year=2006 |month=October |pmid=17036100 |doi= |url=}}</ref>
*Associated with [[Marfan's syndrome]] and [[Turner syndrome]] (Monosomy X).<ref>{{cite journal |author=Wigle ED, Rakowski H, Ranganathan N, Silver MC |title=Mitral valve prolapse |journal=Annu. Rev. Med. |volume=27 |issue= |pages=165–80 |year=1976 |pmid=779595 |doi=10.1146/annurev.me.27.020176.001121 |url=}}</ref>
 
===Gross===
Features:<ref name=Ref_PBoD591>{{Ref PBoD|591}}</ref>
*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.<ref>URL: [http://www.mayomedicallaboratories.com/test-catalog/Overview/9832 http://www.mayomedicallaboratories.com/test-catalog/Overview/9832]. Accessed on: 8 June 2010.</ref><ref name=penn_med>Modified Movat's Pentachrome Stain. University Penn Medicine. URL: [http://www.med.upenn.edu/mcrc/histology_core/movat.shtml http://www.med.upenn.edu/mcrc/histology_core/movat.shtml]. Accessed on: January 29, 2009.</ref>
 
Interpretation of Movat stain:<ref name=penn_med/>
*Black = nuclei and elastic fibers.
*Yellow = collagen and reticular fibers.
*Blue = mucin, ground substance.
*Red (intense) = fibrin.
*Red = muscle.
 
Image:
<gallery>
Image:Myxomatous_aortic_valve.jpg | Myxomatous valve. [[Movat stain]]. (WC/Nephron)
</gallery>


=Infective conditions=
=Infective conditions=
==Rheumatic heart disease==
==Rheumatic heart disease==
:''Rheumatic fever'' redirects here.
{{Main|Rheumatic heart disease}}
*Abbreviated ''RHD''.
===General===
*Classically leads to mitral valve stenosis.
**Rheumatic fever accounts for 99% of mitral stenosis.<ref name=Ref_PBoD594>{{Ref PBoD|594}}</ref>
***Caused by ''Streptococcus pyogenes''.<ref name=pmid18306530>{{Cite journal  | last1 = Chopra | first1 = P. | last2 = Gulwani | first2 = H. | title = Pathology and pathogenesis of rheumatic heart disease. | journal = Indian J Pathol Microbiol | volume = 50 | issue = 4 | pages = 685-97 | month = Oct | year = 2007 | doi =  | PMID = 18306530 }}</ref>
*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<ref>URL: [http://en.wikipedia.org/wiki/Ellipse http://en.wikipedia.org/wiki/Ellipse]. Accessed on: 13 November 2010.</ref> axis due to valve thickening.
**Image: [http://www.principia-eng.com/services/construction/IMG_3098.jpg 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]].<ref name=Ref_AoGP25>{{Ref AoGP|25}}</ref>
 
====Images====
<gallery>
Image:Rheumatic_heart_disease,_gross_pathology_20G0013_lores.jpg | RHD - showing valvular thickening and thickening of the cordae tendinae. (WC)
Image:Aortic_stenosis_rheumatic,_gross_pathology_20G0014_lores.jpg | RHD - showing valvular thickening - aortic valve. (WC)
</gallery>
===Microscopic===
Features:<ref name=Ref_PBoD593>{{Ref PBoD|593}}</ref>
*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 [[granuloma]]s.<ref name=pmid3070554>{{Cite journal  | last1 = Love | first1 = GL. | last2 = Restrepo | first2 = C. | title = Aschoff bodies of rheumatic carditis are granulomatous lesions of histiocytic origin. | journal = Mod Pathol | volume = 1 | issue = 4 | pages = 256-61 | month = Jul | year = 1988 | doi =  | PMID = 3070554 }}</ref>
**This is disputed.<ref name=pmid10399163>{{Cite journal  | last1 = Stehbens | first1 = WE. | last2 = Zuccollo | first2 = JM. | title = Anitschkow myocytes or cardiac histiocytes in human hearts. | journal = Pathology | volume = 31 | issue = 2 | pages = 98-101 | month = May | year = 1999 | doi =  | PMID = 10399163 }}</ref>
 
====Images====
<gallery>
Image:Rheumatic_heart_disease_-_intermed_mag.jpg | RHD - intermed. mag. (WC/Nephron)
Image:Rheumatic_heart_disease_-_3_-_high_mag.jpg | RHD - high mag. (WC/Nephron)
Image:Rheumatic_heart_disease_-_3b_-_very_high_mag.jpg | RHD - very high mag. (WC/Nephron)
Image:Aschoff_Body_in_Rheumatic_Myocarditis.jpg | Aschoff body (WC/Uthman)
Image:Anitschkow_Myocytes_in_an_Aschoff_Body,_Rheumatic_Myocarditis.jpg | Anitschkow myocytes (WC/Uthman)
</gallery>
===IHC===
Features (Aschoff bodies & Anitschkow cells):<ref name=pmid3070554>{{Cite journal  | last1 = Love | first1 = GL. | last2 = Restrepo | first2 = C. | title = Aschoff bodies of rheumatic carditis are granulomatous lesions of histiocytic origin. | journal = Mod Pathol | volume = 1 | issue = 4 | pages = 256-61 | month = Jul | year = 1988 | doi =  | PMID = 3070554 }}</ref>
*S100 -ve.
*Muscle specific actin -ve.
*Desmin -ve.
*NF -ve.
*Vimentin +ve.
*CD45 +ve (weak).


==Infective endocarditis==
==Infective endocarditis==
Line 247: Line 162:
===Microscopic===
===Microscopic===
Features:<ref name=pmid3049284/><ref name=Ref_PCPBoD8_296>{{Ref PCPBoD8|296}}</ref>
Features:<ref name=pmid3049284/><ref name=Ref_PCPBoD8_296>{{Ref PCPBoD8|296}}</ref>
*Increased thickness of spongiosa layer.
*Increased thickness of spongiosa layer. ‡
*Thinning of the fibrosa layer.
*Thinning of the fibrosa layer.
*+/-Fibrin deposition - atrial aspect.
*+/-Fibrin deposition - atrial aspect.
Notes:
*‡ The Tthicking may be due to superimposed fibrosis, instead of spongiosa layer thickening.<ref name=pmid24316086>{{Cite journal  | last1 = Roberts | first1 = WC. | last2 = Vowels | first2 = TJ. | last3 = Ko | first3 = JM. | last4 = Hebeler | first4 = RF. | title = Gross and histological features of excised portions of posterior mitral leaflet in patients having operative repair of mitral valve prolapse and comments on the concept of missing (= ruptured) chordae tendineae. | journal = J Am Coll Cardiol | volume = 63 | issue = 16 | pages = 1667-74 | month = Apr | year = 2014 | doi = 10.1016/j.jacc.2013.11.017 | PMID = 24316086 }}</ref>


DDx:
DDx:

Latest revision as of 01:14, 26 July 2016

Aortic valve - drawing. (WC/Gray's Anatomy)

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).

Note:

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.

Image:

Mitral valve

Gross

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

Note:

Microscopic

Similar to the aortic valve - layers:

  1. Atrialis.[3]
  2. Spongiosa.
  3. Fibrosa.

Degenerative conditions

Calcific aortic stenosis

  • Abbreviated CAS.
Main article: Calcific aortic stenosis

Localized dystrophic heart valve amyloidosis

General

  • Common:
  • Not seen in acute disease and healed endocarditis.[6]

Hypothesis:

Microscopic

Features:[6]

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

DDx:

Stains

  • Congo red +ve.

Dystrophic amyloid:[6]

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

Myxomatous degeneration

Main article: Myxomatous degeneration

Infective conditions

Rheumatic heart disease

Main article: Rheumatic heart disease

Infective endocarditis

Main article: Infective endocarditis

Non-infective conditions

Mitral valve prolapse

  • Abbreviated MVP.
  • AKA floppy mitral valve.[7]

General

  • Classically young women.
  • Afflicts ~ 3% of population in the USA.[8]

Clinical:

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

Complications:[8]

Gross

Features - any of the following:[10]

  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.[10]

Image:

Microscopic

Features:[10][8]

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

Notes:

  • ‡ The Tthicking may be due to superimposed fibrosis, instead of spongiosa layer thickening.[11]

DDx:

Nonbacterial thrombotic endocarditis

  • Abbreviated NBTE.
  • AKA marantic endocarditis.[12]

General

Associations:

  • Cardiac catheterization.[13]
  • Embolization.[12]
  • Malignancy - leading cause, usu. adenocarcinoma.[14]

Note:

  • Marantic = wasting away.

Gross

  • Round non-destructive vegetations, usually at the line of closure.[15]

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.[16]
  • Affects the mitral and aortic valves.[17]
    • Mitral valve most commonly affected.[18]
  • It has been suggested that it may be a manifestation of APLA syndrome.[17][18]

Clinical:

  • Usually regurgitation.

Gross

  • Vegetations anywhere on the valve surface[16] - often seen on both sides (flow surface & non-flow surface).[19]
  • Flat, pale brown/tan, usually small.[20]

Images:

Microscopic

Features:[citation needed]

  • Fibrin.
  • No microorganisms.
  • No inflammation.

Biscupid aortic valve

General

  • Aortic valve usually tricuspid.
  • Most common congenital heart defect.[21]
    • 1-2% of general population.[22]
      • Male:female ~ 2:1.[23]
  • Inherited in autosomal dominant pattern.
    • NOTCH1 gene - implicated.[24]

Significance:

Gross

Features - either:

  1. Raphe does not reach the free margin of the cusp.[26]
  2. No raphe - uncommon (~7% of cases).[27]

Note:

  • Raphe ~ suture or seam.[28]

Images:

Microscopic

Features - section through raphe:

  • "No evidence of fusion."[26]
  • Elastic fibres through-out (not interrupted by fibrous tissue). (???)

Note:

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

DDx:

Sign out

AORTIC VALVE, REPLACEMENT:
- BICUSPID AORTIC VALVE WITH CALCIFIC 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

Clinical:

  • Symptoms of aortic stenosis.
  • No ejection sound (as in aortic valvular stenosis).[31]

Microscopic

Features:

Note:

  • Similar to valvular tissue.

Stains

Sign out

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

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. ↑ URL: http://www.e-heart.org/pages/01_cardiac_structure/01_Cardiac_Structure_MV_003.htm. Accessed on: 20 December 2012.
  3. ↑ Chesler, E.; King, RA.; Edwards, JE. (Mar 1983). "The myxomatous mitral valve and sudden death.". Circulation 67 (3): 632-9. PMID 6821906.
  4. ↑ 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.
  5. ↑ 5.0 5.1 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.
  6. ↑ 6.0 6.1 6.2 6.3 Cooper, JH. (Jul 1983). "Localized dystrophic amyloidosis of heart valves.". Hum Pathol 14 (7): 649-53. PMID 6190729.
  7. ↑ Boudoulas, H.; Wooley, CF. (2001). "Floppy mitral valve/mitral valve prolapse/mitral valvular regurgitation: effects on the circulation.". J Cardiol 37 Suppl 1: 15-20. PMID 11433820.
  8. ↑ 8.0 8.1 8.2 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 296. ISBN 978-1416054542.
  9. ↑ Franchitto, N.; Bounes, V.; Telmon, N.; Rougé, D. (Jul 2010). "Mitral valve prolapse and out-of-hospital sudden death: a case report and literature review.". Med Sci Law 50 (3): 164-7. PMID 21133272.
  10. ↑ 10.0 10.1 10.2 Virmani, R.; Atkinson, JB.; Forman, MB. (Aug 1988). "The pathology of mitral valve prolapse.". Herz 13 (4): 215-26. PMID 3049284.
  11. ↑ Roberts, WC.; Vowels, TJ.; Ko, JM.; Hebeler, RF. (Apr 2014). "Gross and histological features of excised portions of posterior mitral leaflet in patients having operative repair of mitral valve prolapse and comments on the concept of missing (= ruptured) chordae tendineae.". J Am Coll Cardiol 63 (16): 1667-74. doi:10.1016/j.jacc.2013.11.017. PMID 24316086.
  12. ↑ 12.0 12.1 Borowski, A.; Ghodsizad, A.; Cohnen, M.; Gams, E. (Jun 2005). "Recurrent embolism in the course of marantic endocarditis.". Ann Thorac Surg 79 (6): 2145-7. doi:10.1016/j.athoracsur.2003.12.024. PMID 15919332.
  13. ↑ Young, RS.; Zalneraitis, EL.. "Marantic endocarditis in children and young adults: clinical and pathological findings.". Stroke 12 (5): 635-9. PMID 7303049.
  14. ↑ Dickens, P.; Chan, AC. (Apr 1991). "Nonbacterial thrombotic endocarditis in Hong Kong Chinese.". Arch Pathol Lab Med 115 (4): 359-61. PMID 2012496.
  15. ↑ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 567. ISBN 978-1416031215.
  16. ↑ 16.0 16.1 Plastiras, SC.; Pamboucas, CA.; Tektonidou, M.; Toumanidis, ST. (Mar 2010). "Real-time three-dimensional echocardiography in evaluating Libman-Sacks vegetations.". Eur J Echocardiogr 11 (2): 184-5. doi:10.1093/ejechocard/jep172. PMID 19946116.
  17. ↑ 17.0 17.1 Lee, JL.; Naguwa, SM.; Cheema, GS.; Gershwin, ME. (Jun 2009). "Revisiting Libman-Sacks endocarditis: a historical review and update.". Clin Rev Allergy Immunol 36 (2-3): 126-30. doi:10.1007/s12016-008-8113-y. PMID 19089657.
  18. ↑ 18.0 18.1 Hojnik, M.; George, J.; Ziporen, L.; Shoenfeld, Y. (Apr 1996). "Heart valve involvement (Libman-Sacks endocarditis) in the antiphospholipid syndrome.". Circulation 93 (8): 1579-87. PMID 8608627.
  19. ↑ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 567. ISBN 978-1416031215.
  20. ↑ URL: http://library.med.utah.edu/WebPath/CVHTML/CV122.html. Accessed on: 6 March 2013.
  21. ↑ 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.
  22. ↑ 22.0 22.1 22.2 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.
  23. ↑ Tzemos, N.; Therrien, J.; Yip, J.; Thanassoulis, G.; Tremblay, S.; Jamorski, MT.; Webb, GD.; Siu, SC. (Sep 2008). "Outcomes in adults with bicuspid aortic valves.". JAMA 300 (11): 1317-25. doi:10.1001/jama.300.11.1317. PMID 18799444.
  24. ↑ Garg, V.; Muth, AN.; Ransom, JF.; Schluterman, MK.; Barnes, R.; King, IN.; Grossfeld, PD.; Srivastava, D. (Sep 2005). "Mutations in NOTCH1 cause aortic valve disease.". Nature 437 (7056): 270-4. doi:10.1038/nature03940. PMID 16025100.
  25. ↑ Braverman, AC.; Güven, H.; Beardslee, MA.; Makan, M.; Kates, AM.; Moon, MR. (Sep 2005). "The bicuspid aortic valve.". Curr Probl Cardiol 30 (9): 470-522. doi:10.1016/j.cpcardiol.2005.06.002. PMID 16129122.
  26. ↑ 26.0 26.1 Rose, Alan G. (2008). Atlas of Gross Pathology with Histologic Correlation (1st ed.). Cambridge University Press. pp. 2. ISBN 978-0521868792.
  27. ↑ Sabet, HY.; Edwards, WD.; Tazelaar, HD.; Daly, RC. (Jan 1999). "Congenitally bicuspid aortic valves: a surgical pathology study of 542 cases (1991 through 1996) and a literature review of 2,715 additional cases.". Mayo Clin Proc 74 (1): 14-26. doi:10.4065/74.1.14. PMID 9987528.
  28. ↑ URL: http://dictionary.reference.com/browse/raphe. Accessed on: 25 February 2012.
  29. ↑ Fedak, PW.; Verma, S.; David, TE.; Leask, RL.; Weisel, RD.; Butany, J. (Aug 2002). "Clinical and pathophysiological implications of a bicuspid aortic valve.". Circulation 106 (8): 900-4. PMID 12186790.
  30. ↑ 30.0 30.1 Turan, AA.; Guven, T.; Karayel, F.; Pakis, I.; Gurpinar, K.; Ozaslan, A. (Mar 2006). "Subvalvular aortic stenosis as a cause of sudden death: two case reports.". Am J Forensic Med Pathol 27 (1): 90-2. doi:10.1097/01.paf.0000203301.96511.f7. PMID 16501359.
  31. ↑ van der Schaar, PJ.; Roos, JP.; Rohmer, J. (May 1969). "Subvalvular membranous aortic stenosis. Results of surgical therapy.". Thorax 24 (3): 276-82. PMID 5817839.
  32. ↑ Dearani, JA.; Croti, UA.; Price, TN.; Braile, DM.. "Subvalvular aortic membrane resection.". Rev Bras Cir Cardiovasc 26 (1): 135-6. PMID 21881724.
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