Perspective
`
`Anatomy of the aortic root: implications for valve-sparing surgery
`
`Efstratios I. Charitos, Hans-Hinrich Sievers
`
`Department of Cardiac and Thoracic Vascular Surgery, University of Lübeck, Lübeck, Germany
`Corresponding to: Efstratios I. Charitos, MD. Ratzeburger Allee 160, 23562, Lübeck, Germany. Email: efstratios.charitos@gmail.com.
`
`Submitted Oct 27, 2012. Accepted for publication Nov 29, 2012.
`doi: 10.3978/j.issn.2225-319X.2012.11.18
`Scan to your mobile device or view this article at: http://www.annalscts.com/comment/view/1400/
`
`Introduction
`
`The aortic root connects the heart to the systemic
`circulation and is a highly sophisticated and complex
`structure. Each component of the aortic root - although
`simple in its macroscopic morphology - has an optimal
`macroscopic and microscopic structure and anatomical
`architecture (1) which contributes to the function of the
`aortic root as a whole: the intermittent, unidirectional
`channeling of large volumes of fluid, while maintaining
`laminar flow, minimal resistance and least possible
`tissue stress and damage, during varying haemodynamic
`conditions and demands (2-4). This well-coordinated
`dynamic behavior of all aortic root components has been
`shown to be of importance for specific flow characteristics,
`coronary perfusion and left ventricular function (5-8).
`On the rare occasions when any aortic root component
`fails, it is the recognition of the complexity, scope and
`superiority of this structure—far better than any man-made
`replacement—that has led to the development of reparative,
`or ‘sparing’, surgical techniques that respect the functional
`and anatomical existence of the individual parts of the
`aortic root (9-12). For the communication and discussion
`of these techniques among surgeons a deep understanding
`of the anatomy of the aortic root and a generally accepted
`nomenclature is of fundamental importance (13-15).
`
`Aortic root anatomy
`
`The aortic root is an ensemble consisting of distinct
`entities: the aortic valve leaflets, the leaflet attachments, the
`sinuses of Valsalva, the interleaflet trigones, the sinotubular
`junction and the annulus (14,16-18) (Figure 1).
`
`Aortic valve leaflets
`
`The three leaflets form the aortic valve and provide its main
`
`sealing mechanism. Anatomically the valve leaflets can be
`divided into three parts:
`v The free margin, with a thickened circular node
`(nodule of Arantius), which provides the coaptation
`area to the corresponding neighboring valve leaflets
`v The “belly” of the leaflet
`v The basal parts of the leaflet or leaflet attachments
`The aortic valve leaflets form the hemodynamic junction
`and physical boundary between the left ventricle and the
`aorta. All the structures distal to the hemodynamic junction
`are subject to arterial pressures, whereas all the proximal
`parts are subjected to ventricular hemodynamics. The
`trileaflet design represents the optimal solution for low
`resistance valve opening (4). No other valve configuration
`can provide these characteristics, a fact prominently
`demonstrated in the setting of a bicuspid aortic valve, in
`which some kind of valve dysfunction or degree of stenosis
`always co-exists depending on the configuration (15).
`Several surgical techniques have been developed for the
`correction of dysfunctional or misaligned leaflets leading
`primarily to aortic insufficiency. The required height and
`size of the leaflets to warrant competent valve function
`are primarily determined by the root size (19-22). These
`considerations seem to be a major determinant for the
`durability of aortic valve repair (23). Another important factor
`for the durability of the repair is adequate tissue quality,
`especially in the setting of bicuspid aortic valve disease.
`
`Leaflet attachments
`
`As the leaflet attachments insert in the wall of the aortic
`root they form a crown shaped, thick fibrous structure, often
`termed the “annulus”. This description is unfortunate as
`the word annulus implies a circular structure in contrast to
`the “crown” shape of the leaflet attachment (14). The points
`
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`Ann Cardiothorac Surg 2013;2(1):53-56
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`54
`
`Charitos and Sievers. Anatomy of the aortic root
`
`A
`
`B
`
`Figure 2 Aortic root vortices visualized using flow-sensitive time-
`resolved ‘4D’ magnetic resonance imaging with flow sensitivity
`in all three directions (adapted from Schmidtke C, Sievers HH,
`Frydrychowicz A, et al. First clinical results with the new sinus
`prosthesis used for valvesparing aortic root replacement. Eur J
`Cardiothorac Surg 2012. [Epub ahead of print].)
`
`that imitates the compliant characteristics of the normal
`aortic root. This would allow for an ideal, and low stress,
`movement of the leaflets and could be a future area of
`interest and research not only for prosthetic material design
`but also for tissue engineering.
`
`The interleaflet triangles
`
`Under each commissure lies one of the three interleaflet
`triangles. Although histologically they consist of thinned
`aortic wall, hemodynamically they are extensions of
`the ventricular outflow tract and reach the level of the
`sinotubular junction in the area of the commissures.
`The triangle between the right- and non-coronary
`sinuses faces the right atrium. It is in direct continuity with
`the membranous septum proximally which contains the
`His bundle. This area is of special importance during aortic
`valve procedures, as injury here can lead to temporary or
`permanent conduction abnormalities, which may require
`the implantation of a permanent pacemaker. Under the left
`and non-coronary triangle, the aorto-mitral curtain leads to
`the anterior mitral valve leaflet.
`
`Sinotubular junction
`
`The distal part of the sinuses toward the ascending aorta
`
`ascending aorta
`
`aortic root
`
`leaflet (cusp)
`commissure
`Sinus of Valsalva
`inter leaflet triangle
`
`sinutubular junction
`
`leaflet attachment
`
`annulus, ventriculo-aortic junction
`
`aortic valve: Three leaflets only
`
`aortic root: All components
`
`(Sinuses of Valsalva, inter leaflet triangles, sinutubular
`junction, leaflet attachments, leaflets, annulus)
`
`Figure 1 Proposed nomenclature for the aortic root components
`(adapted from Sievers HH, Schmidtke C. A classification system
`for the bicuspid aortic valve from 304 surgical specimens. J Thorac
`Cardiovasc Surg 2007;133:1226-33.)
`
`where the leaflet attachments run parallel - distally upstream
`towards the ascending aorta - are called the commissures.
`
`Sinuses of Valsalva
`
`The three bulges of the aortic wall are named the sinuses
`of Valsalva, after the Italian anatomist Antonio Valsalva.
`Two of the three sinuses host the origin of the coronary
`arteries and the sinuses are termed accordingly the left,
`right and non-coronary sinus. They are limited proximally
`by the attachments of the valve leaflets and distally by the
`sinotubular junction. At their base, ventricular musculature
`is partly incorporated. The sinus wall itself is predominantly
`made up of aortic wall, although it is thinner than the
`native aorta (5,24,25). The precise function of the sinuses
`of Valsalva is unclear. There is evidence that the vortices
`created in the sinuses lead to stress reduction on the aortic
`leaflets and support coronary flow (4,5,24). In valve sparing
`aortic valve surgery, maintenance or recreation of the
`sinuses has been shown to effectively recreate the vortices
`in the sinuses and may be beneficial in terms of normal
`leaflet movement and valve durability (5,24-26) (Figure 2).
`However, aortic root reimplantation without recreation of the
`aortic sinuses has not been shown to have deleterious effects
`on valve durability despite abnormal leaflet motion (25). In
`general, there is a need for aortic root replacement material
`
`© AME Publishing Company. All rights reserved.
`
`www.annalscts.com
`
`Ann Cardiothorac Surg 2013;2(1):53-56
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`Annals of cardiothoracic surgery, Vol 2, No 1 January 2013
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`55
`
`together with the commissures form a tubular structure
`called the “sinotubular junction” which separates the aortic
`root from the ascending aorta (Figure 1) (14). In some cases
`dilatation of the sinotubular junction is the cause of central
`aortic insufficiency and replacement of the ascending aorta
`with a short tubular graft can restore valve competence.
`
`The “annulus”
`
`Although the word annulus implies a circular structure,
`no distinct histological entity or anatomical boundary fits
`this description. The circumference defined by the nadirs
`of the semi-lunar leaflet attachments is difficult to define
`as the annulus, because there is no real, anatomically
`or histologically distinct, circular structure. The term
`‘ventriculo-arterial junction’, as a definition of the “annulus”,
`is rather ambiguous as the ‘anatomical ventriculo-arterial
`junction’ represents the junction between the left ventricular
`myocardium and the arterial structure of the aorta. On the
`contrary, the ‘hemodynamic ventriculo-arterial junction’
`is represented by the coronet shaped leaflet insertion,
`and defines the separation level of ventricular and arterial
`hemodynamics. From a strictly anatomic point of view,
`the ‘anatomic/histologic ventriculo-arterial’ as well as the
`‘hemodynamic ventriculo-arterial’ junction lie somewhat
`more distally to the ‘annulus’ (16-18) and define the area of
`interest less precisely.
`Despite the absence of any anatomically or histologically
`distinct circular structure the popularity of the term
`‘annulus’ probably stems from the fact that this is the area
`of the smallest diameter in the blood path between the left
`ventricle and the aorta and determines the fitting position
`of prosthetic valve sizers and, therefore, the size of the
`prosthetic valve to be implanted. In addition to this, the use
`of this definition gives a good impression of the operative
`technique in use, such as the positioning of the prostheses
`‘supra’ or ‘intra-annular’, as this is the level measured by
`echocardiographers as the ‘aortic valve annulus’ and is the
`area which defines the size of the prosthesis to be implanted
`during aortic valve replacement procedures. However
`prosthetic valves are inserted somewhat more proximally,
`more towards the level of the anatomic ventriculo-arterial
`junction, due to the placement of the sutures predominantly
`through the scalloped attachment of the excised leaflets,
`from the nadir of the sinus to midway up the commissures
`(27,28). In order to avoid any misunderstanding due to the
`numerous definition and terms employed, we have recently
`proposed the use of the term ‘annulus’ to describe the
`
`virtual, circular ring defined by the nadirs of the semi-lunar
`leaflet attachments (Figure 1) (14).
`A successful aortic valve repair or sparing operation aims
`not only to correct the failing part of the aortic root, but
`also to restore the intra- and inter- component relationship
`of the aortic root elements to optimal dimensions and
`relations. The aortic annulus geometry and dimensions
`are major determinants of success and, more importantly,
`of the long term durability of aortic root repair. In cases
`with a dilated aortic annulus it can be successfully reduced
`using an internal or external ring (29-31). In the setting of
`valve sparing surgery, the David procedure also reduces the
`dimension of the annulus to fixed dimensions with excellent
`long term results (32).
`
`
`Acknowledgements
`
`Disclosure: The authors declare no conflict of interest.
`
`References
`
`1. Misfeld M, Sievers HH. Heart valve macro- and
`microstructure. Philos Trans R Soc Lond B Biol Sci
`2007;362:1421-36.
`2. Yacoub MH, Cohn LH. Novel approaches to cardiac valve
`repair: from structure to function: Part II. Circulation
`2004;109:1064-72.
`3. Yacoub MH, Kilner PJ, Birks EJ, et al. The aortic outflow
`and root: a tale of dynamism and crosstalk. Ann Thorac
`Surg 1999;68:S37-43.
`4. Thubrikar MJ. The Aortic Valve. 1st ed. Boca Raton,
`Florida, US: CRC Press, Inc., 1981.
`5. Bellhouse BJ, Bellhouse FH. Mechanism of closure of the
`aortic valve. Nature 1968;217:86-7.
`6. Bellhouse BJ, Bellhouse FH, Reid KG. Fluid mechanics of
`the aortic root with application to coronary flow. Nature
`1968;219:1059-61.
`7. Thubrikar M, Piepgrass WC, Bosher LP, et al. The elastic
`modulus of canine aortic valve leaflets in vivo and in vitro.
`Circ Res 1980;47:792-800.
`8. Brewer RJ, Deck JD, Capati B, et al. The dynamic aortic
`root. Its role in aortic valve function. J Thorac Cardiovasc
`Surg 1976;72:413-7.
`9. Carr JA, Savage EB. Aortic valve repair for aortic
`insufficiency in adults: a contemporary review and
`comparison with replacement techniques. Eur J
`Cardiothorac Surg 2004;25:6-15.
`10. Gleason TG. Current perspective on aortic valve repair
`
`© AME Publishing Company. All rights reserved.
`
`www.annalscts.com
`
`Ann Cardiothorac Surg 2013;2(1):53-56
`
`Medtronic, Medtronic Vascular,
`and Medtronic CoreValve - Exhibit 1019 - Page 3
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`56
`
`Charitos and Sievers. Anatomy of the aortic root
`
`and valve-sparing aortic root replacement. Semin Thorac
`Cardiovasc Surg 2006;18:154-64.
`11. Miller DC. Valve-sparing aortic root replacement: current
`state of the art and where are we headed? Ann Thorac
`Surg 2007;83:S736-9;discussion S785-90.
`12. Svensson LG, Deglurkar I, Ung J, et al. Aortic valve repair
`and root preservation by remodeling, reimplantation, and
`tailoring: technical aspects and early outcome. J Card Surg
`2007;22:473-9.
`13. Anderson RH. Demolishing the tower of babel. Eur J
`Cardiothorac Surg 2012;41:483-4.
`14. Sievers HH, Hemmer W, Beyersdorf F, et al. The everyday
`used nomenclature of the aortic root components: the
`tower of Babel? Eur J Cardiothorac Surg 2012;41:478-82.
`15. Sievers HH, Schmidtke C.A classification system for
`the bicuspid aortic valve from 304 surgical specimens. J
`Thorac Cardiovasc Surg 2007;133:1226-33.
`16. Anderson RH. Clinical anatomy of the aortic root. Heart
`2000;84:670-3.
`17. Anderson RH. The surgical anatomy of the aortic root.
`MMCTS 2007;2007:2527.
`18. Frater RW, Anderson RH. How can we logically describe
`the components of the arterial valves? J Heart Valve Dis
`2010;19:438-40.
`19. Bierbach BO, Aicher D, Issa OA, et al. Aortic root and
`cusp configuration determine aortic valve function. Eur J
`Cardiothorac Surg 2010;38:400-6.
`20. Marom G, Haj-Ali R, Rosenfeld M, et al. Aortic root
`numeric model: Correlation between intraoperative
`effective height and diastolic coaptation. J Thorac
`Cardiovasc Surg 2012. [Epub ahead of print].
`21. Schäfers HJ, Schmied W, Marom G, et al. Cusp height in
`aortic valves. J Thorac Cardiovasc Surg 2012. [Epub ahead
`of print].
`22. Marom G, Haj-Ali R, Rosenfeld M, et al. Aortic root
`
`Cite this article as: Charitos EI, Sievers HH. Anatomy of
`the aortic root: implications for valve sparing surgery. Ann
`Cardiothorac Surg 2013;2(1):53-56. DOI: 10.3978/j.issn.2225-
`319X.2012.11.18
`
`numeric model: Annulus diameter prediction of effective
`height and coaptation in post-aortic valve repair. J Thorac
`Cardiovasc Surg 2012. [Epub ahead of print].
`23. Aicher D, Kunihara T, Abou Issa O, et al. Valve
`configuration determines long-term results after repair of
`the bicuspid aortic valve. Circulation 2011;123:178-85.
`24. Schmidtke C, Sievers HH, Frydrychowicz A, et al. First
`clinical results with the new sinus prosthesis used for valve-
`sparing aortic root replacement. Eur J Cardiothorac Surg
`2012. [Epub ahead of print].
`25. Leyh RG, Schmidtke C, Sievers HH, et al. Opening
`and closing characteristics of the aortic valve after
`different types of valve-preserving surgery. Circulation
`1999;100:2153-60.
`26. De Paulis R, De Matteis GM, Nardi P, et al. Opening
`and closing characteristics of the aortic valve after valve-
`sparing procedures using a new aortic root conduit. Ann
`Thorac Surg 2001;72:487-94.
`27. Sutton JP 3rd, Ho SY, Anderson RH. The forgotten
`interleaflet triangles: a review of the surgical anatomy of
`the aortic valve. Ann Thorac Surg 1995;59:419-27.
`28. Sievers HH. Prosthetic aortic valve replacement. J Thorac
`Cardiovasc Surg 2005;129:961-5.
`29. Lansac E, Di Centa I, Raoux F, et al. An expansible aortic
`ring for a physiological approach to conservative aortic
`valve surgery. J Thorac Cardiovasc Surg 2009;138:718-24.
`30. Scharfschwerdt M, Pawlik M, Sievers HH, et al. In vitro
`investigation of aortic valve annuloplasty using prosthetic
`ring devices. Eur J Cardiothorac Surg 2011;40:1127-30.
`31. Rankin JS, Conger JL, Tuzun E, et al. In vivo testing of an
`intra-annular aortic valve annuloplasty ring in a chronic
`calf model. Eur J Cardiothorac Surg 2012;42:149-54.
`32. David TE, Feindel CM, Webb GD, et al. Long-term
`results of aortic valve-sparing operations for aortic root
`aneurysm. J Thorac Cardiovasc Surg 2006;132:347-54.
`
`© AME Publishing Company. All rights reserved.
`
`www.annalscts.com
`
`Ann Cardiothorac Surg 2013;2(1):53-56
`
`Medtronic, Medtronic Vascular,
`and Medtronic CoreValve - Exhibit 1019 - Page 4