**An Expansible Aortic Ring for a Standardized and Physiological Approach of Aortic Valve Repair**

Emmanuel Lansac1, Isabelle Di Centa2, Rémi Escande3, Maguette Ba3,4, Nizar Kellil3, Eric Arnaud Crozat5, Eric Portocarrero6, Aicha Abed3,4, Anthony Paolitto7, Mathieu Debauchez1 and Anne Meddahi- Pellé3,4 *1Institut Mutualiste Montsouris, Cardiovascular Surgery Department, Paris 2Vascular Surgery Department, Foch Hospital, Suresnes 3Inserm U698, Bioengineering for Cardiovascular Imaging and Therapy Team CHU Xavier Bichat, Paris 4IUT Saint Denis, Paris 13 University 5Cardiac Surgery Department, La Tronche Hospital, 6Cardiac Surgery Nancy Hospital, Nancy, 7CoroNéo Inc, Montreal 1,2,3,4,5,6France 7Canada* 

#### **1. Introduction**

Dystrophy of the ascending aorta is the main etiology of thoracic aortic aneurysms and/or pure aortic insufficiency (tricuspid or bicuspid valves) operated in western countries (Iung et al., 2003; Roberts et al., 2006). It includes two phenotypes depending on whether the sinuses of Valsalva and/or supracoronary aorta are dilated: 1) isolated AI and/or supracoronary aneurysm (sinuses of Valsalva<40 mm); 2) aortic root aneurysms (sinuses of Valsalva>45 mm) (Lansac et al., 2008). Until recently, prosthetic valve replacement was the only surgical option for AI, performing either isolated valve replacement, composite valve and graft replacement or supracoronary graft and/or valve replacement. However, none of the current valve substitutes are ideal options, since mechanical valves require life-long anticoagulation and bioprosthetic valves present the risk of reoperation (Houel et al., 2002). Inspired by mitral experience, reconstructive methods have been developed to treat AI, based on sparing or repairing the native aortic valve, while replacing or stabilizing the other components of the aortic root. The two original valve sparing procedures - remodeling of the aortic root and reimplantation of the aortic valve - focused on root reconstruction to reduce the dilated root diameters in order to restore proper valve function. "Remodeling" technique provides the most physiological reconstruction of the root, but it does not address the dilated annular base (Yacoub et al., 1983). Alternatively, the Reimplantation, as an inclusion technique, provides a subvalvular annuloplasty to the detriment of valve dynamics (David & Feindel, 1992). Numerous technical variations aimed to associate

An Expansible Aortic Ring for a Standardized and Physiological Approach of Aortic Valve Repair 221

Out of main series describing dystrophic aortic roots, aortic annular base diameter superior to 25 mm and sinotubular junction diameter superior to 35 mm are reported and should be

> **Sinotubular junction**

**Interleaflet triangle**

**Aortic root**

**a b c**

**Aortic annular base**

Fig. 1. Anatomy of the ascending aorta and detailed anatomy of the aortic root

Fig. 2. Echocardiographic measurements of aortic root diameters, in long-axis. 1) Aortic annular base diameter (internal diameter), 2) Sinuses of Valsalva (external diameter, from leading edge to leading edge), 3) Sino-tubular junction (external diameter, from leading edge to leading edge), 4) Ascending aorta (external diameter, from leading edge to leading edge) Aortic cusps dimensions vary from one patient to another, as well as from one cusp to another, in height, width, and surface area. In a study of 200 normal hearts, only five hearts

considered as dilated (Gallo et al., 1995; Lansac & Di Centa, 2010c).

**Supracoronary aorta**

> **STJ Aortic root**

> > **d**

preservation of aortic root dynamics with the treatment of dilated native annulus (Aicher et al., 2010; Hopkins, 2003). This results in a lack of standardization and limits their widespread application.

Furthermore, most failures with valve sparing techniques are due to residual cusp prolapse, either as a primary unrecognized lesion or secondary to an induced prolapse after root reconstruction. Despite its more frequent detection intra operatively, cusp prolapse remains challenging to evaluate and treat.

As restorations of both root geometry and cusp coaptation are the prerequisite for a successful valve sparing procedure, we propose a standardized aortic valve repair approach addressing both the aorta and the valve, associating a physiological reconstruction of the aortic root, with cusp resuspension and subvalvular external aortic ring annuloplasty (Lansac et al., 2005a, 2006, 2009, 2010a, 2010b, 2010c, 2011a, 2011b). Depending on the phenotype of the ascending aorta, physiological reconstruction of the root will be achieved through to the Remodeling technique (root aneurysm, sinuses of Valsalva ≥45 mm), or a supracoronary graft (supracoronary aneurysm, sinuses of Valsalva <40 mm). Subvalvular aortic annuloplasty is achieved through external implantation of a calibrated expansible aortic ring that reduces dilated diameters in diastole in order to increase valvular coaptation height, while maintaining root systolic expansibility (Lansac et al., 2009).

#### **2. Anatomical landmarks for aortic valve repair**

#### **2.1 The ascending aorta: Descriptive anatomy**

The ascending aorta may be defined as the ensemble of two distinct entities, separated by the sinotubular junction (STJ): (1) the aortic root, initial portion of the aorta that includes the aortic valve with its crown-shaped annulus, interleaflet triangles, coronary arteries ostia and sinuses of Valsalva and (2) the supracoronary aorta extending above the STJ up to the brachiocephalic trunk (Fig. 1) (Anderson et al., 1991; Lansac & Di Centa, 2010c; Reid, 1970; Robicksek, 1991; Sutton et al., 1995). Coronary arterial ostia are more frequently located below the sinotubular junction, arising within the left and right sinuses of Valsalva and are named accordingly (Muriago et al., 1997; Tops et al., 2008; Turner & Navartnam, 1996). A recent study examining 169 patients using multislice computed tomography, showed that the mean distance from the basal attachment of the cusps to the left and right coronary ostia was 14.4 +/- 2.9 mm and 17.2 +/- 3.3 mm respectively (Tops et al., 2008).

The aortic annulus is not planar since it is formed by the semilunar insertion of the cusps that extend from their basal attachments within the left ventricle (aortic annular base) to their distal attachments at the STJ, forming the commissures (Anderson et al., 1991). This three-dimensional structure of the aortic annulus may be rationalized into two functional diameters of the aortic root, ensuring proper valve function, namely the aortic annular base and the STJ (Anderson et al., 1991; Lansac & Di Centa, 2010c; De Waroux et al., 2007) (Fig. 1). Echographic measurement of the aortic annulus corresponds to the aortic annular base diameter (Fig. 2) (Roman et al., 1987).

Cut-off point of "normal" diameters of the aortic root ensuring valve coaptation can be defined from analysis of main series as an aortic annular base diameter ranging from 21 to 24.5 mm (mean 22.9 mm) and a sinotubular junction diameter ranging from 27.5 to 28.1 mm (mean 27.5 mm) with a normal root ratio STJ/annular base of 1.2. Although difficult to assess precisely, the aortic annular base seems to present a systolic expansion of 6.2% (2.5- 9.6%). Systolic expansion at the sinotubular junction level is reported to be 5.7% (2.8-9.8%) (Lansac & Di Centa, 2010c; Tamas & Nylander, 2007).

preservation of aortic root dynamics with the treatment of dilated native annulus (Aicher et al., 2010; Hopkins, 2003). This results in a lack of standardization and limits their

Furthermore, most failures with valve sparing techniques are due to residual cusp prolapse, either as a primary unrecognized lesion or secondary to an induced prolapse after root reconstruction. Despite its more frequent detection intra operatively, cusp prolapse remains

As restorations of both root geometry and cusp coaptation are the prerequisite for a successful valve sparing procedure, we propose a standardized aortic valve repair approach addressing both the aorta and the valve, associating a physiological reconstruction of the aortic root, with cusp resuspension and subvalvular external aortic ring annuloplasty (Lansac et al., 2005a, 2006, 2009, 2010a, 2010b, 2010c, 2011a, 2011b). Depending on the phenotype of the ascending aorta, physiological reconstruction of the root will be achieved through to the Remodeling technique (root aneurysm, sinuses of Valsalva ≥45 mm), or a supracoronary graft (supracoronary aneurysm, sinuses of Valsalva <40 mm). Subvalvular aortic annuloplasty is achieved through external implantation of a calibrated expansible aortic ring that reduces dilated diameters in diastole in order to increase valvular coaptation

The ascending aorta may be defined as the ensemble of two distinct entities, separated by the sinotubular junction (STJ): (1) the aortic root, initial portion of the aorta that includes the aortic valve with its crown-shaped annulus, interleaflet triangles, coronary arteries ostia and sinuses of Valsalva and (2) the supracoronary aorta extending above the STJ up to the brachiocephalic trunk (Fig. 1) (Anderson et al., 1991; Lansac & Di Centa, 2010c; Reid, 1970; Robicksek, 1991; Sutton et al., 1995). Coronary arterial ostia are more frequently located below the sinotubular junction, arising within the left and right sinuses of Valsalva and are named accordingly (Muriago et al., 1997; Tops et al., 2008; Turner & Navartnam, 1996). A recent study examining 169 patients using multislice computed tomography, showed that the mean distance from the basal attachment of the cusps to the left and right coronary ostia

The aortic annulus is not planar since it is formed by the semilunar insertion of the cusps that extend from their basal attachments within the left ventricle (aortic annular base) to their distal attachments at the STJ, forming the commissures (Anderson et al., 1991). This three-dimensional structure of the aortic annulus may be rationalized into two functional diameters of the aortic root, ensuring proper valve function, namely the aortic annular base and the STJ (Anderson et al., 1991; Lansac & Di Centa, 2010c; De Waroux et al., 2007) (Fig. 1). Echographic measurement of the aortic annulus corresponds to the aortic annular base

Cut-off point of "normal" diameters of the aortic root ensuring valve coaptation can be defined from analysis of main series as an aortic annular base diameter ranging from 21 to 24.5 mm (mean 22.9 mm) and a sinotubular junction diameter ranging from 27.5 to 28.1 mm (mean 27.5 mm) with a normal root ratio STJ/annular base of 1.2. Although difficult to assess precisely, the aortic annular base seems to present a systolic expansion of 6.2% (2.5- 9.6%). Systolic expansion at the sinotubular junction level is reported to be 5.7% (2.8-9.8%)

height, while maintaining root systolic expansibility (Lansac et al., 2009).

was 14.4 +/- 2.9 mm and 17.2 +/- 3.3 mm respectively (Tops et al., 2008).

**2. Anatomical landmarks for aortic valve repair** 

**2.1 The ascending aorta: Descriptive anatomy** 

diameter (Fig. 2) (Roman et al., 1987).

(Lansac & Di Centa, 2010c; Tamas & Nylander, 2007).

widespread application.

challenging to evaluate and treat.

Out of main series describing dystrophic aortic roots, aortic annular base diameter superior to 25 mm and sinotubular junction diameter superior to 35 mm are reported and should be considered as dilated (Gallo et al., 1995; Lansac & Di Centa, 2010c).

Fig. 1. Anatomy of the ascending aorta and detailed anatomy of the aortic root

Fig. 2. Echocardiographic measurements of aortic root diameters, in long-axis. 1) Aortic annular base diameter (internal diameter), 2) Sinuses of Valsalva (external diameter, from leading edge to leading edge), 3) Sino-tubular junction (external diameter, from leading edge to leading edge), 4) Ascending aorta (external diameter, from leading edge to leading edge)

Aortic cusps dimensions vary from one patient to another, as well as from one cusp to another, in height, width, and surface area. In a study of 200 normal hearts, only five hearts

An Expansible Aortic Ring for a Standardized and Physiological Approach of Aortic Valve Repair 223

root and valve dynamics within each phase of the normal cardiac cycle (Gorman et al., 1996; Hansen et al., 1995; Pang et al., 2000). Using this technique we intended to precise the mechanism of aortic root expansion and the shape of the aortic valve orifice at maximum

A significant aortic root expansion occurs during isovolumic contraction and initiates the aortic leaflet separation prior to ejection (2.1 ± 0.5%). This opening is primarily due to commissural expansion, but it is also due to the expansion of the annular base. Both expansions are strongly related to the left ventricular pressure increase (r = 0.95) during IVC. The aortic root volume increases by 33.7 ± 2.7% with a maximal deformation happening during the systole at the commissural level, maximizing left ventricular ejection. These findings also confirm the study of Sutton et al. (Sutton et al., 1995), who described the interleaflet muscular triangles - located under the semilunar attachment of the cusps - as an essential component of the aortic annulus and part of the left ventricular outflow tract. Indeed the aortic root is a junction between the left ventricular and the systemic circulation. Thin cusps separate these two compartments with different hemodynamic systems. The first, left ventricular compartment is situated below the cusps and includes the sigmoidshaped cusp attachments (traditionally described as the annulus), the interleaflet triangles, and the commissures. These structures are related to the left ventricular hemodynamics. The second, aortic compartment, is situated above the cusps, includes the sinuses of Valsalva, the sinotubular junction and ascending aorta, and is related to aortic and coronary flow dynamics. During IVC, aortic root expansion starts at the left ventricular compartment due to volume redistribution in the left ventricular outflow tract. The aortic compartment expansion is delayed at the end of IVC due to a redistribution of volume above the cusps. Confirmation of these bi-compartmental volume dynamics is provided during end-diastole, by the observed re-expansion of the aortic root related to left ventricular compartment

The initiation of cusp separation (i.e., valve opening) is a dynamic process that occurs in the

The shape of the aortic valve orifice remains speculative. Thubrikar et al. (Thubrikar et al., 1977, 1979, 1993), followed by Higashidate et al. (Higashidate et al., 1995), described it as initially stellate, then triangular and circular at maximal opening. These studies were limited by their low data sampling rate (60 Hz), which did not allow for continuous recording of the changes in valve orifice within each phase of the cardiac cycle. Sonometrics analysis at 200 to 800 Hz showed that the shape of the aortic valve orifice progressed from initially stellate to triangular then circular and finally clover shaped at maximum opening following the shape of the three sinuses of Valsalva (Figure 3). At that time, the cusp's free edge area exceeded the commissural area by +16.3 ± 2.0%. This behavior of the valve cusps might explain cases of early cusp deterioration following re-implantation of the aortic valve within a tubular conduit without sinuses of Valsalva (Gallo et al., 1995; Grande-Allen et al., 2000; Leyh et al., 1999) because cusp expansion beyond the commissural level would result in

Furthermore, as previously published, aortic root expansion is also asymmetric, and it induces a tilting dynamic of the aortic valve throughout the cardiac cycle (Dagum et al., 1999; Lansac et al., 2005b). In an ovine model, the aortic root tilt angle between the basal and commissural plane decreases in systole, aligning the left ventricular outflow tract with the ascending aorta in order to maximize ejection. As soon as the valve starts closing and during

diastole, the angle tilts back (as a shock absorber), reducing stress on the cusps.

presence of a negative left ventricular –aorta pressure gradient (-8.5 ± 2.6 mmHg).

opening on an ovine model.

expansion during left ventricular filling.

cusp impact against the wall of the cylindrical conduit.

were found to have cusps of equal size (Roberts, 1970; Silver & Roberts, 1985; Vollebergh & Becker, 1977). Cusp geometry determines cusp coaptation that depends on length of free margin and aortic insertion, intercommissural distance, and cusp height. These values are difficult or impossible to measure by echocardiography or intra-operative measurements. Bierbach et al. have proposed to use the relative height difference between insertion and free margin of the cusp (effective height) as a surrogate parameter of cusp coaptation. In their study effective height has a constant relationship to root dimensions and body size (Bierbach et al., 2010). Authors suggest to measure this parameter as the indicator of configuration and geometric height of a cusp and designed a specific calliper to measure it intra-operatively (Schäfers et al., 2006). Effective height revealed values in healthy adult individuals measured by transthoracic echocardiography in the range of 7 to 12 mm. The three interleaflet triangles are an extension of the left ventricular outflow tract and are composed of aorta's fibrous walls between the expanded sinuses of Valsalva. The two interleaflets triangles placed on both sides of the noncoronary cusp are in fibrous continuity with the menbranous septum, the fibrous trigones and the mitral valve (Sutton et al., 1995). The membranous interventricular septum extends downward and upward corresponding to the interleaflet triangles between the right and non coronary sinuses. It is in close relationship with the atrioventricular node. The bundle of His crosses the right fibrous trigone and passes along the lower edge of the membranous septum. This anatomical landmark is important when performing aortic valve surgery in order to avoid inducing intraventricular conduction abnormalities or heart block (Kunzelman et al., 1994).

#### **2.2 The ascending aorta: A dynamic structure**

Better understanding of aortic valve dynamics recently became a concern because of the increase use of stentless bioprostheses and aortic valve repair and sparing procedures. Although the relationship between the sinuses of Valsalva and the aortic valve had been intuitively shown by Leonardo da Vinci (Robicksek, 1991), the aortic valve has been for a long time regarded as a passive, tri-leaflet structure that moves back and forth according to pressure differences between the left ventricle (LV) and aorta. This concept has led to the development of all mechanical and stented bioprostheses. Several authors have questioned this simplistic view by showing that expansion of the aortic root actively participates in aortic valve opening, reducing shear stress on the cusps (Brewer et al., 1976; Pang et al., 2000; Thubrikar et al., 1977). In 1976, Brewer et al. described the interdependence of aortic valve opening and root expansion in an isolated aortic root model (Brewer et al., 1976). They showed that valve opening was related to the 16% radial displacement of the commissures, which was interpreted as a mechanism to reduce shear stress on the cusps. Using radioopaque markers in dogs, Thubrikar et al. (Thubrikar et al, 1977, 1979) confirmed in vivo that aortic valve opening was related to commissural expansion prior to ejection. They suggested that the mechanism of aortic valve opening was related to the release of the inward pull of the commissures that occurs during isovolumic contraction. Although they did not measure it, they also suggested that the constraining effect of the annular base was part of the mechanism. Limited by their data-sampling rate (60 Hz), all calculations were made on abnormal cardiac cycles under the assumption that a non-ejecting extra systole was equivalent to the isovolumic contraction (IVC). Similarly, Vesely et al. interpreted aortic root dilation prior to valve opening as secondary to passive hemodynamic recoil of the aortic root (Hansen et al., 1995).

Three-dimensional (3D) digital sonomicrometry, characterized by a high rate of data acquisition (200 to 800 Hz), offers opportunity for a precise time-related study of the aortic

were found to have cusps of equal size (Roberts, 1970; Silver & Roberts, 1985; Vollebergh & Becker, 1977). Cusp geometry determines cusp coaptation that depends on length of free margin and aortic insertion, intercommissural distance, and cusp height. These values are difficult or impossible to measure by echocardiography or intra-operative measurements. Bierbach et al. have proposed to use the relative height difference between insertion and free margin of the cusp (effective height) as a surrogate parameter of cusp coaptation. In their study effective height has a constant relationship to root dimensions and body size (Bierbach et al., 2010). Authors suggest to measure this parameter as the indicator of configuration and geometric height of a cusp and designed a specific calliper to measure it intra-operatively (Schäfers et al., 2006). Effective height revealed values in healthy adult individuals measured by transthoracic echocardiography in the range of 7 to 12 mm. The three interleaflet triangles are an extension of the left ventricular outflow tract and are composed of aorta's fibrous walls between the expanded sinuses of Valsalva. The two interleaflets triangles placed on both sides of the noncoronary cusp are in fibrous continuity with the menbranous septum, the fibrous trigones and the mitral valve (Sutton et al., 1995). The membranous interventricular septum extends downward and upward corresponding to the interleaflet triangles between the right and non coronary sinuses. It is in close relationship with the atrioventricular node. The bundle of His crosses the right fibrous trigone and passes along the lower edge of the membranous septum. This anatomical landmark is important when performing aortic valve surgery in order to avoid inducing

intraventricular conduction abnormalities or heart block (Kunzelman et al., 1994).

Better understanding of aortic valve dynamics recently became a concern because of the increase use of stentless bioprostheses and aortic valve repair and sparing procedures. Although the relationship between the sinuses of Valsalva and the aortic valve had been intuitively shown by Leonardo da Vinci (Robicksek, 1991), the aortic valve has been for a long time regarded as a passive, tri-leaflet structure that moves back and forth according to pressure differences between the left ventricle (LV) and aorta. This concept has led to the development of all mechanical and stented bioprostheses. Several authors have questioned this simplistic view by showing that expansion of the aortic root actively participates in aortic valve opening, reducing shear stress on the cusps (Brewer et al., 1976; Pang et al., 2000; Thubrikar et al., 1977). In 1976, Brewer et al. described the interdependence of aortic valve opening and root expansion in an isolated aortic root model (Brewer et al., 1976). They showed that valve opening was related to the 16% radial displacement of the commissures, which was interpreted as a mechanism to reduce shear stress on the cusps. Using radioopaque markers in dogs, Thubrikar et al. (Thubrikar et al, 1977, 1979) confirmed in vivo that aortic valve opening was related to commissural expansion prior to ejection. They suggested that the mechanism of aortic valve opening was related to the release of the inward pull of the commissures that occurs during isovolumic contraction. Although they did not measure it, they also suggested that the constraining effect of the annular base was part of the mechanism. Limited by their data-sampling rate (60 Hz), all calculations were made on abnormal cardiac cycles under the assumption that a non-ejecting extra systole was equivalent to the isovolumic contraction (IVC). Similarly, Vesely et al. interpreted aortic root dilation prior to valve opening as secondary to passive hemodynamic recoil of the aortic

Three-dimensional (3D) digital sonomicrometry, characterized by a high rate of data acquisition (200 to 800 Hz), offers opportunity for a precise time-related study of the aortic

**2.2 The ascending aorta: A dynamic structure** 

root (Hansen et al., 1995).

root and valve dynamics within each phase of the normal cardiac cycle (Gorman et al., 1996; Hansen et al., 1995; Pang et al., 2000). Using this technique we intended to precise the mechanism of aortic root expansion and the shape of the aortic valve orifice at maximum opening on an ovine model.

A significant aortic root expansion occurs during isovolumic contraction and initiates the aortic leaflet separation prior to ejection (2.1 ± 0.5%). This opening is primarily due to commissural expansion, but it is also due to the expansion of the annular base. Both expansions are strongly related to the left ventricular pressure increase (r = 0.95) during IVC. The aortic root volume increases by 33.7 ± 2.7% with a maximal deformation happening during the systole at the commissural level, maximizing left ventricular ejection. These findings also confirm the study of Sutton et al. (Sutton et al., 1995), who described the interleaflet muscular triangles - located under the semilunar attachment of the cusps - as an essential component of the aortic annulus and part of the left ventricular outflow tract.

Indeed the aortic root is a junction between the left ventricular and the systemic circulation. Thin cusps separate these two compartments with different hemodynamic systems. The first, left ventricular compartment is situated below the cusps and includes the sigmoidshaped cusp attachments (traditionally described as the annulus), the interleaflet triangles, and the commissures. These structures are related to the left ventricular hemodynamics. The second, aortic compartment, is situated above the cusps, includes the sinuses of Valsalva, the sinotubular junction and ascending aorta, and is related to aortic and coronary flow dynamics. During IVC, aortic root expansion starts at the left ventricular compartment due to volume redistribution in the left ventricular outflow tract. The aortic compartment expansion is delayed at the end of IVC due to a redistribution of volume above the cusps. Confirmation of these bi-compartmental volume dynamics is provided during end-diastole, by the observed re-expansion of the aortic root related to left ventricular compartment expansion during left ventricular filling.

The initiation of cusp separation (i.e., valve opening) is a dynamic process that occurs in the presence of a negative left ventricular –aorta pressure gradient (-8.5 ± 2.6 mmHg).

The shape of the aortic valve orifice remains speculative. Thubrikar et al. (Thubrikar et al., 1977, 1979, 1993), followed by Higashidate et al. (Higashidate et al., 1995), described it as initially stellate, then triangular and circular at maximal opening. These studies were limited by their low data sampling rate (60 Hz), which did not allow for continuous recording of the changes in valve orifice within each phase of the cardiac cycle. Sonometrics analysis at 200 to 800 Hz showed that the shape of the aortic valve orifice progressed from initially stellate to triangular then circular and finally clover shaped at maximum opening following the shape of the three sinuses of Valsalva (Figure 3). At that time, the cusp's free edge area exceeded the commissural area by +16.3 ± 2.0%. This behavior of the valve cusps might explain cases of early cusp deterioration following re-implantation of the aortic valve within a tubular conduit without sinuses of Valsalva (Gallo et al., 1995; Grande-Allen et al., 2000; Leyh et al., 1999) because cusp expansion beyond the commissural level would result in cusp impact against the wall of the cylindrical conduit.

Furthermore, as previously published, aortic root expansion is also asymmetric, and it induces a tilting dynamic of the aortic valve throughout the cardiac cycle (Dagum et al., 1999; Lansac et al., 2005b). In an ovine model, the aortic root tilt angle between the basal and commissural plane decreases in systole, aligning the left ventricular outflow tract with the ascending aorta in order to maximize ejection. As soon as the valve starts closing and during diastole, the angle tilts back (as a shock absorber), reducing stress on the cusps.

An Expansible Aortic Ring for a Standardized and Physiological Approach of Aortic Valve Repair 225

respectively 26.4mm (25-27.5mm) and 27.3mm (27-28mm), and average sinotubular junction was respectively 45.3mm (39.5-52.4mm) and 31mm (28-35mm). Ratio between the sinotubular junction and aortic annular base diameters was 1.7 in case of root aneurysms,

Surgical emergency operation is indicated in the setting of acute ascending aortic dissection or rupture into the pericardium (acute cardiac tamponade). Operative mortality remains significant and death is almost certain in the case of rupture or acute dissection if not

Based on natural history of ascending aortic aneurysms, prophylactic surgery seems appropriate at 5 to 5.5 cm diameter depending on the etiology. Intervention criteria are summarized in Figure 4 (Hiratzka et al., 2010; Vahanian et al., 2007). Actually, elective surgery of the ascending aorta is much safer than emergency intervention (mortality 4.3%). For patients with Marfan's syndrome and bicuspid valves size criterion is somewhat lower. In those patients, prophylactic repair is warranted for an intervention criterion of 4.5 to 5.0 cm diameter for most authors (Bentall & De Bono, 1968; Yacoub et al., 1998). Dissection or rupture have been stated at sizes less than 5.0 cm in several cases, and an increase rate of aneurysm dilatation greater than 5mm/y is known to lead to an 4.1-fold risk of complications.

Fig. 4. Surgical indications for ascending aorta aneurysms and/or aortic insufficiency

whereas for isolated aortic insufficiency it was 1.1 (Lansac et al., 2008, 2010c).

**3.2 Surgical indications** 

surgically addressed.

Fig. 3. Changes at each level of the aortic root time related to left ventricular and ascending aorta pressures in one sheep, a) during three cardiac cycles and b) detail of one cardiac cycle. c) Dynamic changes of tilt angle of the aortic root time related to left ventricular and aortic pressures. d) cross-sectional area diagram of the aortic root at maximum expansion during ejection (sonomicrometry) showing the clover-shaped orifice of the aortic valve. *Ao* aortic pressure, *LV* left ventricular pressure, *SoV* sinuses of Valsalva, *B* annular base, *STJ* sinotubular, *C* commissures, *AA* ascending aorta, *L* leaflet

Therefore, the durability of native aortic valve seems to rely on a dynamic triad associating 1) systolic expansion of the aortic root, 2) a clover-shaped aortic orifice that embraces the bulging sinuses of Valsalva, and 3) tilting dynamics of the aortic valve (Lansac et al., 2002). Aortic valve surgery should try to preserve these baseline dynamics as much as possible using more physiologically based surgical approaches.
