Aortic Valve Anatomy #1 — Aortic Leaflet

1. Fundamental leaflet structure

Each leaflet is defined by several key anatomic components [1,2]:

1. Hinge line: the semilunar basal attachment of the leaflet to the aortic root
2. Body: the main mobile portion of the cusp
3. Free margin: the unsupported edge that participates in leaflet apposition
4. Lunula: the thin coapting zone near the free edge
5. Nodulus of Arantius: the central thickening that reinforces leaflet closure

These elements are not merely descriptive landmarks. The nodulus of Arantius buttresses the central zone of apposition, while the scalloped hinge lines create the characteristic crown-like arrangement of the leaflets and define the boundaries of the interleaflet triangles [1,2]. Thus, normal valve competence depends not only on leaflet tissue itself, but also on how leaflet geometry is integrated into the surrounding root. (PubMed)

2. Relationship of the three cusps to surrounding anatomy

The RCC and LCC are associated with the right and left coronary sinuses, from which the right coronary artery and left coronary artery arise, respectively, whereas the NCC does not give rise to a coronary artery [1,3]. The leaflet attachments extend in semilunar fashion from their nadirs toward the commissures at the level of the sinotubular junction, creating the familiar crown-like insertion pattern of the native aortic valve [3]. This configuration explains why the “aortic annulus” is better understood as a functional rather than purely anatomic ring. (PubMed)

Several adjacent structures are particularly important surgically:

• The RCC–NCC region is closely related to the membranous septum and conduction tissue
• The LCC–NCC region is related to the aorto-mitral curtain
• The interleaflet triangle between the RCC and NCC serves as an important landmark for the atrioventricular conduction bundle [1,3]

These relationships are essential during valve-sparing root surgery, cusp repair, and complex root reconstruction. (PubMed)

3. Interleaflet triangles and the functional aortic root

Aortic valve competence cannot be understood by examining the leaflets alone. The interleaflet triangles, created by the scalloped arrangement of the leaflet hinge lines, are central components of root anatomy and valve mechanics [1,2]. These triangles extend toward the sinotubular junction and help define the continuity between the leaflets and the root wall. Their morphology also influences the distinction between normal tricuspid valves and congenitally malformed variants such as bicuspid or unicuspid valves [7]. (PubMed)

Modern aortic valve surgery therefore emphasizes the concept of the functional aortic annulus, which includes the ventriculo-aortic junction, virtual basal ring, leaflet insertion line, and sinotubular junction [3]. De Paulis and Salica described these structures as the “skeleton” of the aortic valve, highlighting that durable repair requires restoration not only of leaflet morphology but also of the proportional geometry of the root [3]. (PubMed)

4. Geometric requirements for normal competence

Normal aortic valve function depends on balanced geometric relationships among the cusps, commissures, and root dimensions [3-5]. In practical surgical terms, successful repair requires:

• sufficient leaflet tissue
• symmetric cusp motion
• stable commissural orientation
• appropriate sinotubular junction size
• adequate coaptation height

Berdajs emphasized two particularly important repair targets:

1. the level of valve coaptation should be positioned at least 8 mm above the aortic root base, and
2. the coaptation height should be at least 5 mm [4].

These quantitative principles remain highly relevant in valve-preserving root reconstruction and cusp repair. (PubMed)

5. Importance of the sinotubular junction

The sinotubular junction (STJ) is a major determinant of leaflet coaptation and overall root mechanics [3,5]. Experimental work has shown that if the STJ is excessively dilated, commissural displacement leads to leaflet tethering and central regurgitation; conversely, excessive reduction of the STJ can produce cusp prolapse and eccentric regurgitation [5]. Thus, normal competence depends on preserving the correct proportional relationship between the STJ and the basal components of the root. (PubMed)

This principle is especially important in reimplantation and remodeling procedures. In such settings, a technically excellent cusp repair can still fail if root geometry—particularly the STJ dimension—is not physiologically restored [3-5]. (PubMed)

6. Insights from contemporary three-dimensional analysis

Recent three-dimensional imaging studies have further refined our understanding of normal aortic root anatomy [6]. The normal root is not perfectly symmetric; rather, subtle asymmetry appears to be a native feature of physiologic design. Three-dimensional CT analysis has shown that the normal aortic root demonstrates measurable asymmetry in sinus and leaflet geometry, with implications for both surgical reconstruction and prosthetic design [6]. Such findings support the principle that successful repair should aim to recreate physiologic geometry, not merely a simplified circular configuration. (ncbi.nlm.nih.gov)

7. Surgical perspective

From a surgeon’s standpoint, the aortic leaflets should be viewed as part of a dynamic root-leaflet complex rather than isolated cusps. The key operative concept is that leaflet competence is a geometric achievement. Even histologically normal leaflets may become incompetent if the commissures are displaced, the interleaflet triangles are distorted, or the STJ and basal ring lose their physiologic relationship [3-5,7]. Conversely, durable repair becomes possible when leaflet free margins, coaptation zone, and root dimensions are restored in a balanced manner. (PubMed)

Summary

In summary, the normal aortic valve consists of three semilunar leaflets whose structure is defined by the hinge line, body, free margin, lunula, and nodulus of Arantius [1,2]. These leaflets function within a three-dimensional root architecture shaped by the interleaflet triangles, commissures, ventriculo-aortic junction, virtual basal ring, and sinotubular junction [1-3]. Contemporary surgical understanding recognizes that durable valve competence depends on preserving or reconstructing this integrated geometry, with particular attention to coaptation height and sinotubular junction proportion [3-6]. (OUP Academic)

References

[1] Ho SY. Structure and anatomy of the aortic root. Eur J Echocardiogr. 2009;10(1):i3-i10.

[2] 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(2):419-427.

[3] De Paulis R, Salica A. Surgical anatomy of the aortic valve and root-implications for valve repair. Ann Cardiothorac Surg. 2019;8(3):313-321.

[4] Berdajs DA. Aortic root morphology: a paradigm for successful reconstruction. Interact Cardiovasc Thorac Surg. 2016;22(1):85-91.

[5] Maselli D, De Paulis R, Scaffa R, Weltert L, Bellisario A, Salica A, Ricci A. Sinotubular junction size affects aortic root geometry and aortic valve function in the aortic valve reimplantation procedure: an in vitro study using the Valsalva graft. Ann Thorac Surg. 2007;84(4):1214-1218.

[6] Yang DH, Kim DH, Handschumacher MD, Levine RA, Kim JB, Sun BJ, Jang JY, Kim N, Baek S, Kang JW, Song JM, Kang DH, Lim TH, Song JK. In vivo assessment of aortic root geometry in normal controls using 3D analysis of computed tomography. Eur Heart J Cardiovasc Imaging. 2017;18(7):780-786.

[7] Tretter JT, Spicer DE, Mori S, Chikkabyrappa S, Redington AN, Anderson RH. The significance of the interleaflet triangles in determining the morphology of congenitally abnormal aortic valves: implications for noninvasive imaging and surgical management. J Am Soc Echocardiogr. 2016;29(12):1131-1143.