Aortic Regurgitation

This title is a comprehensive resource of aortic regurgitation suitable for both the novice and experienced practitioner. Detailed attention is given to the recently growing field of aortic valve-sparing surgery and aortic valve repair. Guidelines are also provided for general practitioners on how to treat patients after various aortic procedures. Also included are many operative photos, original medical illustrations and schematics. 

Aortic Regurgitation synthesizes current knowledge of aortic valve repair into an easy-to-follow, illustration-rich text. It is therefore an indispensable guide suitable for use by cardiologists and trainees in cardiology, cardiac surgeons, echocardiographers, general practitioners and radiologists.    

• Language: English
• Publisher: Springer
• Release date: Apr 25, 2018
• ISBN: 9783319742137

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© Springer International Publishing AG, part of Springer Nature 2018

Jan Vojacek, Pavel Zacek and Jan Dominik (eds.)Aortic Regurgitationhttps://doi.org/10.1007/978-3-319-74213-7_1

1. Leonardo

Pavel Zacek¹  

(1)

Department of Cardiac Surgery, Charles University, Faculty of Medicine in Hradec Králové, University Hospital Hradec Králové, Hradec Králové, Czech Republic

Pavel Zacek

Email: [e-mail]

One may feel almost embarrassed when having realised how much of the dynamic performance of the aortic valve was clear to Leonardo da Vinci more than five centuries ago. Drawings performed in sepia ink depict the aortic valve opened and closed, geometry of the aortic root with a trefoil of bulging sinuses of Valsalva and, above all, trajectories of blood flow in systole and diastole. Spirals of vortexes inside of aortic sinuses, drawn by Leonardo’s hand, were rediscovered only recently thanks to magnetic resonance imaging [1].

Leonardo dedicated himself to anatomical studies in three periods: first in years 1487–1495 in Milan at the court of Ludovico Sforza, and later in years 1505–1509, when he entered the service of Cesare Borgia and resided in Venice, Florence and again in Milan. Third period of Leonardo anatomical studies started after leaving Milan in 1509. In these years, he collaborated with Marcantonio della Torre who was professor of anatomy in Pavia and Padua. Leonardo performed about 30 autopsies from which 10 were focused on the heart and vessels. In Florence, in the hospital Santa Maria Nuova, he witnessed a peaceful decease of a centenarian and immediately after that he performed his autopsy. In his notes he described precisely the signs of advanced atherosclerosis and rightly denoted it to be the cause of death. Autopsies were for non-physicians strictly forbidden by the Church but later Leonardo obtained permission thanks to his reputation. Nevertheless, after returning to Rome he faced accusations of unseemly conduct and ceased performing human autopsies. He, however, dissected also animals (cows, sheep, birds, frogs) and compared the anatomical findings. Leonardo created 240 anatomical drawings and wrote about 13,000 words of notes but he has never published his work.

Amazing drawings of aortic valve are dated 9th January1513. Besides undisputable beauty of art, the educated spectator will be astounded by precision of medical observation and exact description of flow pattern across the aortic valve. Leonardo, evidently due to his studies of hydrodynamics, could predict correctly the behaviour of lateral strata of the blood flow that are slowed by contact with valve and bent into the sinuses of Valsalva where they lead to expansion and coaptation of the valve leaflets in diastole. Brilliancy of this deduction keeps to raise admiration, when reminding the contemporary technical conditions of autopsy as well as plenitude of other tasks occupying simultaneously Leonardo’s mind. From the text of his notes it cannot be elicited unequivocally whether he really performed or only designed an experiment in which a hollow glass model of the aorta was created on a basis of wax cast of the aortic root interior. Grass seeds were added into the water for visualisation of the currents. It was not until 1968 that similar experiment was performed by Bellhouse [2].

The extent of Leonardo’s work remained hardly apprehensible for next generations. Great talent of art has intersected with brightness of mind, technical aptitude and analytical and combination capacity. Insatiable curiosity has driven him into ever new fields while artistic skills enabled him to perfectly depict his new knowledge. Roaming among many subjects of interest often hindered finishing his projects but, on the other hand, rewarded him with a wide interdisciplinary perception. Despite astounding modernity of his anatomical studies , Leonardo, however, has not advanced from Galenic conception that assumed the arterial blood flow to be a unidirectional stream of nutrition and heat from liver towards tissues. Another century would have to pass before William Harvey in1628 described the systemic circulation.

Leonardo’s work has been hidden for mankind for several centuries. Francesco Melzi, his disciple and heir, failed to prepare its publication. His descendants sold the drawings that were later divided in technical and artistic and purchased to collectors. Anatomical studies were acquired by Charles II Stuart in 1690 for the Royal Collection. Only in the second half of twentieth century, translated and provided with comments, they have appealed the attention of especially medical community. Nowadays, various authors can only speculate how much time had Leonardo lacked for his own invention of blood circulation, or how could have the general knowledge of his achievements influence the development of medicine [3–5].

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Leonardo da Vinci (1452–1519). Aortic valve (28.3 × 20.4 cm, ink drawing, paper). With kind permission of the Royal Collection Trust/© Her Majesty Queen Elizabeth II 2016

References

1.

Gharib M, Kremers D, Koochesfahani MM, K M. Leonardo’s vision of flow visualization. Exp Fluids. 2002;33:219–23.Crossref

2.

Bellhouse BJ, Bellhouse FH. Mechanism of closure of the aortic valve. Nature. 1968;217(5123):86–7.Crossref

3.

Boon B. Leonardo da Vinci on atherosclerosis and the function of the sinuses of Valsalva. Neth Heart J. 2009;17(12):496–9.Crossref

4.

Robicsek F. Leonardo da Vinci and the sinuses of Valsalva. Ann Thorac Surg. 1991;52(2):328–35.Crossref

5.

Wells FC, Crowe T. Leonardo da Vinci as a paradigm for modern clinical research. J Thorac Cardiovasc Surg. 2004;127(4):929–44. https://​doi.​org/​10.​1016/​j.​jtcvs.​2004.​02.​002.CrossrefPubMed

© Springer International Publishing AG, part of Springer Nature 2018

Jan Vojacek, Pavel Zacek and Jan Dominik (eds.)Aortic Regurgitationhttps://doi.org/10.1007/978-3-319-74213-7_2

2. Clinical and Surgical Anatomy of the Aortic Root

Horia Muresian¹ 

(1)

Cardiovascular Surgery, University Hospital of Bucharest, Bucharest, Romania

Keywords

Aortic rootAortic valveCoronary artery variationsAortic root remodelling/reimplantationCardiac ultrasoundBicuspid aortic valveQuadricuspid aortic valve

The right and the left ventricles of the human heart propel the blood into corresponding arterial conduits: the pulmonary trunk and the aorta, respectively. The junction between each ventricle and its complementary arterial channel is accomplished by means of complex structures constituting the so-called arterial roots . Although following similar constructural design, the aortic and the pulmonary roots differ significantly in their gross anatomy, histology and function , reflecting the particular haemodynamic conditions of the systemic and of pulmonary vascular circuits [1]. The aortic root accommodates the origin of the coronary arteries also. The right ventricle functions as a volume pump, whereas the left ventricle as a pressure pump. As a consequence, the aortic root appears thicker, stouter and contains more fibro-elastic tissue.

The general design of the arterial roots consists of a complex trifoliate valvar system (the valve cusps or more correctly: the valve leaflets) and associated dilations called sinuses . The transition between the ventricles and arterial roots appears more evident at the level of the pulmonary root , where the valve leaflets take off from the free-standing infundibular musculature (Fig. 2.1) [2].

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Fig. 2.1

Gross anatomy of the pulmonary root and valve. Different from the aortic root, the valve leaflets of the pulmonary valve take off from a sleeve of free-standing infundibular musculature. (a) Intraoperative aspect of the pulmonary autograft harvested during the Ross procedure. Note that there is no evident basal ring and that the pulmonary root is easily distortable. (b) Anatomical specimen of a formalin fixed adult human heart opened longitudinally and depicting the right ventricular (RV) outflow tract, pulmonary valve and root. Note the particular disposition of the RV trabeculae and the insertion of the pulmonary valve leaflets directly on myocardium

The muscular portion of the aortic root represents only roughly two-thirds of its circumference, the remainder portion being fibrous (Fig. 2.2a, b). The distal limit of the arterial roots is marked by the supravalvar crest, clinically and surgically called the sinotubular junction (STJ) . Of all the "annuluses and rings" described at the level of the arterial roots, the only evident is the STJ. The STJ is a circular junction of the aortic valve commissures. Normally, the coronary ostia are located below the STJ (Fig. 2.3).

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Fig. 2.2

(a) Gross anatomy of the aortic root and valve. Fresh anatomical specimen demonstrating the muscular portion of the aortic root as seen from the inside (left) and from the outside (right). Underneath the right (R) and left (L) aortic sinuses lies the muscular portion of the ventricular septum. The origins of the two major coronary arterial trunks are apparent both from the inside and outside. Note the close relationship with the anterolateral commissure of the mitral valve and the corresponding papillary muscle (ALPM). L, R aortic sinuses, left and right, RCA right coronary artery, LCA left coronary artery, ALPM anterolateral papillary muscle, LAA left atrial appendage. (b) Gross anatomy of the aortic root and valve. Inferior (ventricular) view of the aortic root and valve. The fibrous portion of the aortic root is evident, as is the mitral-aortic curtain. The mitral and tricuspid subvalvar apparatus was removed and only the valve leaflets were left in place. The muscular portion of the aortic root appears as a rim, occupying roughly 2/3 of the circumference (arrows). L, R, Non aortic sinuses, left, right and non-facing, M mitral valve, Tri tricuspid valve, RCA right coronary artery, LCA left coronary artery

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Fig. 2.3

Superior view of the aortic root and valve. The aortic root is opened just distal to the sinotubular junction (STJ) . Cx circumflex branch of the left coronary artery circling around the mitral annulus (M), LAD left anterior descending artery, Tri tricuspid valve, RCA right coronary artery, PT pulmonary trunk, L, R and Non aortic sinuses and valvar leaflets: left, right and non-facing (non-coronary). The STJ is the prominent ridge indicated by the arrow

The left ventricle expels the blood into the already-filled aorta where the entire blood column is maintained at a high pressure. Consequently, each stroke volume must first accommodate into the aortic root and then has to progress distally through the aorta and its main branches. This is made possible by distension of the aortic root both in longitudinal and radial directions, followed by its elastic recoil with consequent squeezing and distal advancement of the blood column. The backflow of blood into the left ventricle is restricted by its kinetic energy and by closure of the valve leaflets. By the same mechanism of distension and recoil, the pulse wave is transmitted distally.

The aortic root must also absorb and even the complex to-and-fro and torque movements of the ventricular base [3]. This is accomplished by the sinuses and interleaflet trigones—which depict both a static asymmetry and a different distensibility (Fig. 2.4). On the other hand, the aortic root is solidly attached to the cardiac base, especially by means of a direct continuity with the left and right fibrous trigones.

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Fig. 2.4

Aortic root dynamics . The aortic root absorbs the to-and-fro and torque movements of the ventricular base. The sinuses and the interleaflet trigones have a static asymmetry and depict a different distensibility. Green arrow demonstrates the longitudinal deformation (mostly at the level of the aortic sinuses); the shear strain and torsional deformation is suggested by the arched blue arrow (mostly at the level of the interleaflet trigones). The initial circumferential deformation at the level of the base of the aortic root is the result of the nonuniform distensibility of the three aortic sinuses: the left more than the right, more than the non-facing (L > R > NF). However, the aortic root adapts these complex differences and the resultant circumferential deformation at the level of the STJ is uniform

The connection between the left ventricular myocardium and the aortic fibro-elastic tissue is represented by the anatomical ventriculo-arterial junction . This landmark is apparent only in correspondence with the muscular portion of the aortic root. The semilunar attachment of the three aortic valve leaflets skirts between the STJ and an area under the anatomical ventriculo-arterial junction; the circle joining these lowest points is traditionally known as "the basal ring" (BR) although this notion designates an imaginary circle [4]; it is still used, however, in the absence of a distinct proximal limit of the aortic root (Fig. 2.5).

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Fig. 2.5

Aortic root—anatomical and echocardiographic landmarks . The aortic root was opened along the left ventricular outflow tract. The greater part of the septum was removed along with the right aortic sinus. The left (L) and non-facing (NF) sinuses and leaflets are apparent as well as their continuity with the anterior mitral leaflet (AML). A portion of the right atrium (RA) with the opening of the coronary sinus (CS) and the initial tract of the right coronary artery (RCA) is visible. The membranous septum is marked with a black circle. The most apparent landmark is represented by the sinotubular junction (white arrows). The basal ring (BR) is but an imaginary plane joining the deepest portions of the aortic valve leaflets (yellow dotted line and corresponding arrow). The ventriculo-arterial junction would correspond to the red dotted line (and arrow) but is practically unapparent at the level of the fibrous portion of the aortic root. The insertion of the valve leaflets skirts between the STJ and the BR in a curved manner and drawing the form of a three pointed coronet; it crosses the anatomical ventriculo-arterial junction. This is the functional, haemodynamic ventriculo-arterial junction: proximal to it the haemodynamic parameters are of ventricular type; distal to it, of aortic type. The resultant interleaflet triangles represent prolongations of the left ventricular outflow tract and due to their particular anatomical relationship, are in potential contact with the pericardial cavity (the outside of the heart). Other relevant measurements include the dimensions of the aortic root at the level of the sinuses

The haemodynamic ventriculo-arterial junction is represented by the attachments of the aortic leaflets: the pressure profile distal to it is characteristically aortic, while proximal to it, typically ventricular. The remnants of the leaflets are then used by the surgeon to anchor prostheses used to replace the diseased valve. It is these semilunar remnants that the surgeon then describes as "the annulus ". The valve leaflets are enclosed by three corresponding sinuses, possessing distensibility in radial and longitudinal directions. The walls of the sinuses are primarily composed of elastic tissue and are thinner than the walls of the ascending aorta [5]. The aortic valve leaflets and sinuses are usually named according to the origin of the coronary arteries (right, left and non-coronary) although the most pertinent and useful nomenclature is offered by the so-called Leiden convention [6] and will be followed here (right-facing sinus or sinus #1; left-facing sinus or sinus #2; non-facing sinus NF sinus) (Fig. 2.6).

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Fig. 2.6

Numerical nomenclature of the aortic sinuses and valvar leaflets (the Leiden convention). In order to avoid confusions and for a better communication, especially in the case of congenitally malformed hearts, a numerical nomenclature of the aortic sinuses and corresponding leaflets appears more appropriate. A schematic view depicts the aortic and pulmonary arterial roots, as viewed from above. The spatial coordinates are given in the right upper corner. The sinuses and leaflets of the two arterial roots are either adjacent (facing sinuses) or non-adjacent (non-facing). For a hypothetical observer located at the level of the non-facing aortic sinus, the right-handed sinus is called sinus #1 or right (aortic) sinus and the left-handed sinus is called sinus #2 or left (aortic) sinus. It is also more appropriate calling the remaining sinus non-facing (NF) and not "non-coronary sinus" especially due to the fact that confusion might appear with the coronary sinus—the venous collector of the heart

The valve leaflets depict a concave outline and possess a fibrous layer (the fibrosa) towards the aortic aspect and an underlying layer of loose connective tissue (the spongiosa) towards the ventricular aspect. Both surfaces are covered by endocardium. Similar to the mitral valve, the aortic valve leaflets do not coapt with their free margins; instead, the free margins are located above the line of closure, are thinner (the so-called lunulas ), may be fenestrated, and usually contain a collagenous aggregation (the node of Arantius ). The systolic dilation of the aortic root with the consequent straightening of the valve leaflets and the inertia of the free margins provided by the presence of the nodes of Arantius, and the vortices created in the sinuses minimize the fluttering of the valve leaflets during ventricular ejection and prevent the valve leaflets from contacting the wall of the aortic root. In the meantime, the valve leaflets are ready to close as soon as the haemodynamic conditions change.

The three interleaflet triangles are the remainder portions of the aortic root and represent extensions of the ventricular cavity in potential communication with the pericardial cavity. The triangles are composed mostly of fibrous tissue and represent the less distensible and less extensible portion of the aortic root anchoring the aortic root to the tauter part of the left ventricular base (the left and the right fibrous trigones) [7].

Dilation of the interleaflet triangles may occur, however, in disease: annuloectatic or aortic aneurysm; consequently, the basal portion of the aortic root including the triangles must be stabilized in aortic valve repair procedures. This is well demonstrated by the David procedure as compared with the Yacoub technique [8]. Each of the three interleaflet triangles establishes particular anatomical relationships of clinical relevance. The interleaflet triangle between the non-facing and the right aortic sinuses is continued in apical direction by the membranous septum. This area can be recognized in a living patient as corresponding to the normally occurring gap between the septal and the anterior leaflets of the tricuspid valve. Intraoperatively, the membranous septum can be identified by backlighting. The insertion of the valve leaflets divides the membranous septum into an atrioventricular and an interventricular portion. The bundle of His courses below the membranous septum from the area of the triangle of Koch. The same pathway is followed by the atrioventricular node artery; distortion or interruption of this artery can occur in mitral valve surgery and especially when the artery originates in the left coronary artery [9, 10]. Extensive calcifications of this area may also complicate with conduction disturbances. The triangle between the left and the non-facing aortic sinuses is in direct continuity with the mitral-aortic curtain and with the aortic leaflet of the mitral valve. The triangle between the left and the right aortic sinuses directly overlies the muscular portion of the aortic root. This is the safest area for performing incisions necessary for enlargements of the aortic root as in the Konno procedure or for the myotomy/myectomy operation (the Morrow procedure).

Among all cardiac structures, the aortic root is located centrally and consequently establishes salient anatomical relationships with almost all the remainder cardiac elements [11] (Fig. 2.7). The least covered part is the left aortic sinus (sinus #2).The aortic, mitral and tricuspid valvar "rings" are closely related although not in the same plane as previously taught. The right fibrous trigone and adjacent fibrous structures (the tendon of Todaro and the membranous septum) constitute the central fibrous body of the heart cementing the three valvar rings. The root of the pulmonary trunk is loosely connected to the aortic root allowing the surgical separation of the two, however, not beyond the level of the outlet septum (see below). This makes possible the harvesting of the pulmonary root during the Ross operation. On the other hand, the outlet septum represents a small, circumscribed area; in root enlargement procedures (such as Konno), incisions must be performed strictly at this very level, as otherwise they may lead to the outside of the heart [2] (Fig. 2.8).

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Fig. 2.7

The major anatomical relationships of the aortic root. Superior view of the aortic root. The roofs of the left and right atria were removed. The greater part of the atrial septum was also removed, leaving in place only the area of the fossa ovalis. The aortic root is centrally located, establishing anatomical relationships with practically all the remainder cardiac elements. Note the oblique disposition of the aortic and pulmonary roots (as clearly apparent in echocardiographic imaging). L, R and NF left, right and non-facing aortic sinuses and leaflets, RCA right coronary artery, LAD left anterior descending artery, Cx circumflex branch, IAS interatrial septum, RA right atrium, MI mitral valve, RAA, LAA right and left atrial appendages, Conus pulmonary infundibulum and conus branch (from the RCA), PT pulmonary trunk

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Fig. 2.8

Particular anatomical relationships of the aortic root and the root enlargement procedures . The particular anatomical details are demonstrated in this oblique section through the aortic root. The position of the membranous septum is shown by the grey circle. The Nicks and Manouguian procedures (N and M) allow limited enlargements of the aortic root by cutting through the fibrous portion. The incisions into or through the muscular portion of the ventricular septum (Morrow and Konno, K) must avoid the origin of the right coronary artery, the membranous septum or getting on the outside of the heart (white arrows). L, R, NF aortic sinuses and leaflets, left, right and non-facing, CS coronary sinus ostium, PT pulmonary trunk

The aortic and mitral valves share the base of the left ventricle. The anterior mitral leaflet (together with the mitral-aortic curtain) alternatively delimitates the inflow from the outflow compartments of the left ventricle during cardiac cycle. The long axis of the right ventricular inflow compartment (perpendicular to the tricuspid annular plane) and of the left ventricular inflow (perpendicular to the mitral annular plane) and outflow compartments (perpendicular to the aortic annular plane) are not parallel but converge towards the apex of the heart. The aorto-mitral angle delineated between the aortic and mitral annular planes changes during the cardiac cycle. More obtuse values of this angle are encountered in mitral insufficiency. Postsurgical excessive mitral annular and aorto-mitral angle reduction predisposes to the systolic anterior motion of the mitral valve (SAM).

The dimensions of the aortic root must be assessed in both static and dynamic circumstances as well as in normal and in disease [12, 13] (Fig. 2.9).

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Fig. 2.9

The normal asymmetry of the aortic root. This is apparent both in static dimensions and volumes, as well as in their distensibility. The static volumes appear larger for the right sinus, than the non-facing, than the left. The distensibility is major for the right sinus, than the left, than the non-facing. The resultant aortic tilt angle (more reduced in humans than in other mammalian species) might have a role in the dynamics of the aortic root: during left ventricular ejection, the aortic root becomes straighter while the angle increases during diastole—a mechanism probably aiding in reducing the stress on the leaflets. L, R, NF left, right and non-facing sinuses of the aortic valve, ms membranous septum, Mitral mitral valve, BR basal ring, STJ sinotubular junction, RCA right coronary artery

The various diagnostic methods and techniques usually take into account the following: the basal ring (BR), the aortic sinuses, and the STJ, the ascending aorta and the left ventricular outflow tract (LVOT) (Fig. 2.10). As previously mentioned [4], the BR represents an imaginary circle joining the lowest portions of the aortic valve leaflets [14]. In aortic insufficiency, the BR is displaced towards the left ventricle; in aortic stenosis and retraction of the leaflets, the BR shifts towards the aorta. In some cases, the BR is difficult or impossible to define (Fig. 2.11). Some authors prefer measuring the most distal portion of the left ventricular outflow tract (LVOT) at the level of the mitral-aortic hinge. Even this landmark is not fixed: the hinge is displaced towards the free margin of the anterior mitral leaflet in case of mitral insufficiency [15] (Fig. 2.12). The direct measurement using a Hegar probe during surgery is probably the most reliable, accurate and valid method. Bicuspid aortic valve (see below) brings additional particulars in the delineation and measurement of the BR. The proper gauging of the BR is important in aortic root replacement/remodelling as a proper ratio between the BR and the STJ must be maintained or restored [16].

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Fig. 2.10

Diameters and measurements for gauging of the aortic root. Diagnostic imaging techniques and intraoperative assessment ask for precise landmarks and measurements. The following parameters are determined: the basal ring (BR), the diameter at the level of the sinuses (Sin), the sinotubular junction (STJ), the ascending aorta (AA). Not infrequently and also during surgery it is important to measure the diameter of the left ventricular outflow tract (LVOT) skirting between the ventricular septum and the anterior mitral leaflet (AML). LA left atrium, LV left ventricle

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Fig. 2.11

Aortic valve stenosis . Distortion of the aortic root and valve is readily apparent in aortic stenosis . The aortic leaflets are retracted and calcified. Sclerosis and calcifications extend into the sinuses, interleaflet triangles and towards the membranous septum (ms) eventually determining atrioventricular block. Not least, the mitral valve is affected. This represents an example of difficult or impossible determination of the diameter of the BR or Sin level. L, R, NF left, right and non-facing sinuses of the aortic valve, ms membranous septum, AML anterior mitral leaflet

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Fig. 2.12

The diameter of the left ventricular outflow tract . The dimensions between the septum and the mitral-aortic hinge represent a fair measurement of the LVOT. However, the most prominent portion of the septum may not be at the level of the insertion of the aortic leaflet but lower towards the LV and this holds even more true in cases with a prominent septal spur or in hypertrophic cardiomyopathy. On the other hand, the mitral-aortic hinge may be displaced: towards the free margin of the anterior mitral leaflet in mitral insufficiency or towards the aorta, in cases of aortic and/or mitral stenosis. Surgeons measure best the diameter of the LVOT by using a Hegar probe

The assessment of the aortic root at the level of the sinuses also asks for particular observance. The usual image is that of a pear-shaped aortic root with two opposite sinuses. This sinus-to-sinus diameter does not represent the cross section passing right through the middle of the aortic root; the actual section dividing the root in two halves is the sinus-to-opposite commissure diameter (Fig. 2.13). Moreover, due to the normal asymmetry of the aortic root, there are many more such diameters to be taken into account. Reimplantation/resuspension of the aortic valve asks for a precise calibration. The diameter of the STJ and the height of the aortic valve leaflets (2/3 of the height) represent the main landmarks in surgery (not least, the height of the commissures must be also thoroughly determined). However, especially in aortic root aneurysm, the valve leaflets are asymmetric and larger than usual [17]. A thorough clinical judgment must follow all such measurements.

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Fig. 2.13

The diameter of the aortic root at the level of the sinuses. The section cutting the aortic root in two symmetrical halves would skirt from the middle of one sinus to the opposite commissure; consequently, the classical view of the aortic root with two (almost) symmetrical sinuses does not pass through the middle of the root. Moreover, due to the natural asymmetry of the aortic root, and not least, in disease, the three sinus-to-commissure diameters are unequal. The coaptation zone of the three aortic leaflets usually does not lie in a median position. In aortic root dilation/aneurysm, the leaflets are larger than usual and depict even more asymmetry. Therefore, a thorough clinical judgment and surgical experience must follow the measurements, as it is well known that the reimplantation of the aortic valve asks as reference either the diameter of the STJ or 2/3 of the double leaflet height

The evaluation of the diameter at the level of the STJ (commissural level) is more straightforward. It is worthwhile to mention the proper ratio of 1.1/1 between the BR and the STJ—a detail to be followed in aortic root remodelling/replacement. With BR dilatation (annuloectasia) the stress on the leaflets is increased up to 70%. The dilation of the STJ increases the stress by only 15% [18]. Annular ectasia plus root widening imply that surgery should be considered at earlier stages of dilation. It is also well known that the relative size of the aortic root is more important than the absolute size in predicting complications [19].

The most important anatomical relationships of the aortic root are presented in Fig. 2.7. With the heart in anatomically correct orientation [20], the salient correlated cardiac structures are as follows. The pulmonary infundibulum and trunk lie anteriorly. The pulmonary valve is at a higher level than the aortic valve. The two arterial trunks are closely related at the level of the commissure between the right and left aortic sinuses (sinus #1 and #2). The muscular portion of the ventricular septum lies immediately below the right aortic valve leaflet; incisions for myotomy/myectomy are driven between the ostium of the right coronary artery and the right/left valvar commissure. The left aortic sinus (sinus #2) is covered by the left atrial appendage, epicardial fat and is in relation with the great cardiac vein. The common trunk of the left coronary artery emerges and divides after variable distance, into the circumflex branch and the anterior interventricular artery. The lowest portion of the left aortic sinus is firmly attached to the left fibrous trigone. In a similar manner, the non-facing (non-coronary) sinus is attached to the right fibrous trigone. At this very level, the atrial septum and the ventricular septum converge. The mitral-aortic curtain skirts between the left and right trigones and corresponds to the interleaflet triangle between the left and non-facing sinuses (L/NF). The trigones and the curtain constitute the fibrous portion of the BR of the aortic root; the left atrial (LA) myocardium is inserted on this fibrous part, too. Surgical separation of the LA from the aortic root can be easily achieved during surgery, down to the adjoining portion of the aortic and mitral rings. The membranous septum corresponds to the right/non-facing (R/NF) interleaflet triangle. The only fibrous portion of the tricuspid ring is at the level of the membranous septum. Just under the non-facing sinus of the aortic root, and visible from the right atrium, is the triangle of Koch (delimitated by the orifice of the coronary sinus, the tendon of Todaro and the septal leaflet of the tricuspid valve).

The muscular portion of the aortic root which actually represents the most distal extension of the LVOT is vascularized by anterior and posterior septal branches originating from the left, right or both coronary arteries . Small collateral left atrial branches follow the insertion of the LA myocardium and travel across the mitral-aortic curtain. The aortic sinuses are vascularized by small arterial branches with origin either in the main coronary trunks or in the atrial and infundibular branches. The right coronary artery gives off branches which vascularize both the aortic and pulmonary roots. The arteries to the aortic root can easily bleed with extensive dissection and such bleeding may resemble an anastomotic leak after aortic root replacement or reimplantation of the coronary buttons. Incisions for enlargement of the aortic root performed at the level of the fibrous portion as in the Nicks [21] or Manouguian procedures [22] interfere less with the vascularization of the aortic root. Aortoventriculoplasty —the Ross-Konno procedure [23]—implies ampler incisions in the muscular portion of the aortic root and septum with interruption of one or more septal arteries; the clinical consequences are still difficult to predict especially in a paediatric patient population (depending also on the number and calibre of the arteries interrupted). The vascularization of the aortic root is synthetically presented in the Table 2.1.

Table 2.1

The vascularization of the aortic root [24]

R, L, NF right, left and non-facing sinuses of the aorta, Right SANB right sinoatrial node branch (right atrial branch), Left SANB left sinoatrial node branch, RCA right coronary artery, LCA left coronary artery

The function of the aortic root, both in normal and disease, cannot be entirely separated from that of the mitral valve: the mitral and the aortic valves constitute a dual structure located at the base of the left ventricle allowing both the inflow into and, respectively, the proper outflow from the left ventricle; the valves also share a common fibrous portion (see above). The mitral-aortic curtain represents a flexible element interposed between the left ventricular inflow and outflow compartments. The anterior intertrigonal segment and the mitral-aortic curtain represent dynamic structures. The normal function of the aortic valve depends more on haemodynamic factors but it must be taken into account in a more general context of adjacent anatomical elements that together constitute the aortic root. The synchronous dynamic physiology of the aortic and mitral valves has recently been revealed with changes occurring in a reciprocal fashion [25]. The aorto-mitral angle changes during the cardiac cycle although such changes are not mediated through the anatomic fibrous continuity. Postsurgical excessive reduction of the aorto-mitral angle predisposes to systolic anterior motion of the mitral valve. The left-sided heart valves depict characteristics related to the particular haemodynamic conditions in the systemic division of the circulation. Besides their tauter appearance and higher pressure gradients these elements must experience, the mitral and the aortic valves are intimately coupled both from an anatomical and from a functional point of view—asking for a more elaborate clinical approach and requiring further investigation as well. An important issue is that the opening and closing of the aortic valve is modified after the valve-sparing procedures [26, 27]; indeed, the scope of the remodelling/resuspension techinques addressed to the aortic root, is that of restoring a functionally appropriate valvar system and not an anatomically perfect valve [28].

Particular problems are encountered with bicuspid, unicuspid or quadricuspid aortic valves. The bicuspid aortic valve (BAV) is the most frequent congenital anomaly of the aortic valve [29]. The entire anatomy, histologic structure and function of the aortic valve and root are altered: the aortic valve leaflets are not equal (a raphe may or may be not present), their histologic appearance is modified (fibrosed or calcified) [30], the aortic root depicts major modifications as the sinuses are either present or absent, the distensibility of the sinuses is altered, the coronary ostia may depict modifications in their position, and the resultant orifice of the valve is asymmetric with an eccentric jet of blood. Various classifications for the BAV have been proposed during the time [31, 32]. There is also a difference between the congenital and acquired forms of BAV [33]. Individuals with BAV develop aortic valve and aortic wall disorders at a younger age as compared with individuals with tricuspid aortic valve. The shorter left main coronary artery that the BAV patients possess may contribute to the progressive course of aortic dilatation [34].

The major characteristics taken into account for a valid classification of the BAV disease are: (1) the number of raphes; (2) the spatial position of the leaflets or raphes; (3) the functional status of the valve [32]. However, the analysis of the morphological appearance of the valve must also include: the number of leaflets, number of raphes, size of the leaflets (equal or non-equal), number of commissures, the circumferential distances among the three commissures, number of aortic sinuses, the position of the coronary ostia (and the presence of any coronary arterial variation) and the "potentially tricuspid" status of the valve. The entire aortic root and valve must be considered when surgery is contemplated. Any classification system may have limitations especially with calcification of the valve (Table 2.2). For a surgical perspective, it is more important to distinguish between the purely bicuspid versus the potentially tricuspid aortic valves [36]. In the first case, there are two equal leaflets, no raphe(s) and two commissures. The potentially tricuspid aortic valve, although depicting two leaflets, may have one or two raphes, the leaflets are non-equal and there are three commissures (with one or two underdeveloped).

Table 2.2

Bicuspid aortic valve classification [35]

R right aortic leaflet, L left aortic leaflet, NF non-facing (non-coronary) aortic leaflet, E aortic sinus effacement, AA ascending aorta dilatation, Men more frequent in men

aA raphe may or may not be present between the fused leaflets

bA raphe is always present. Forms without raphe between the L and NF leaflets were not encountered

The most common complication is aortic stenosis. Only some 15% of individuals with BAV still have a normally functioning valve in the fifth decade [37, 38]. Aortic insufficiency may be present with or without aortic stenosis [39]. Infective complications (endocarditis) are more common with BAV disease and the clinical outcome tends to be worse than in normal valves. The prevalence of dilation of the aortic root is higher in individuals with BAV, ranging between 7.5 and 79% [40, 41]. Three different shapes of proximal aorta in BAV were described and correlated to the type of BAV cusp configuration [42]. Incidence is higher in patients with type 2 BAV (fusion of R + NF leaflets, see Table 2.2). Coarctation of the aorta, another major abnormality associated with BAV is regarded as a part of the diffuse aortopathy that characterizes the BAV. Less common associated congenital anomalies with BAV include: ventricular septal defects, Ebstein’s anomaly, hypoplastic left heart syndrome, abnormal coronary anatomy, patent ductus arteriosus, atrial septal defects and bicuspid pulmonary valve. Surgery is indicated at lower degrees of