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Eur J Cardiothorac Surg 2003;24:886-897
© 2003 Elsevier Science NL

Review

Aortic valve leaflet sparing and salvage surgery: evolution of techniques for aortic root reconstruction

Richard A. Hopkins*

Brown University Medical School, 164 Summit Avenue, Providence, RI 02906, USA

Received 3 April 2003; received in revised form 12 September 2003; accepted 16 September 2003.

* Tel.: +1-401-444-7710; fax: +1-401-444-7711
e-mail: rahopkins{at}lifespan.org


   Abstract
Top
 Abstract
1. Introduction
 2. Functional anatomy of...
 3. Conclusion
 References
 
Over the past 20 years, a series of procedures have been designed to reconstruct the aortic root of patients with aortic insufficiency, in whom the pathology and hence the surgery spares the valve leaflets. Such techniques have various names. Usually ‘valve sparing’ is used in context with chronic aortic dissection or aortic root aneurysm as in patients with Marfan's syndrome. ‘Aortic valve salvage’ tends to be the term of choice for similar surgical reconstruction in the setting of aortic dissection. ‘Aortic valve repair’ is often chosen when direct surgical procedures are performed on the leaflets themselves. All of the techniques have evolved based upon an increased understanding of the functional anatomy of the aortic root complex. The different technical approaches, their applications and results need to be understood by the cardiology community. The failure modes for such techniques are specific and different from prosthetic valve failure modes, but are adequately followed with echocardiography. Over two-thirds of patients remain free of re-development of significant aortic insufficiency at 8–10 years following surgery. The overall patient survival is more dependent upon the underlying cardiovascular status of the patient than the surgical technique itself. Perioperative mortalities vary between 0 and 6% and are comparable to composite valve+graft techniques and isolated aortic valve replacement, in which the operative mortality approximates 3.3–4%. Long-term results are good to excellent and spare the patient anticoagulation and prosthetic valve disease.

Key Words: Aortic valve salvage • Aortic valve repair • Aortic dissection • Marfan's syndrome • Aortic root reconstruction • Aortic valve sparing surgery


   1. Introduction
Top
 Abstract
 1. Introduction
2. Functional anatomy of...
 3. Conclusion
 References
 
Over the past two decades, a series of procedures have been suggested for the treatment of acute and chronic aortic insufficiency, variously named aortic valve re-suspension, valve salvage, valve repair, valve sparing, valve remodeling, and valve reimplantation. The common goal of these procedures is to retain the functioning valve leaflets of the patient while repairing, replacing or stabilizing the other components of the aortic root complex (aortic annulus, aortic sinuses, sino-tubular junction, subvalvular region and ascending aorta), and thus to provide a competent aortic valve with the durability and hemodynamics of native living leaflet tissue with the additional benefit of avoidance of anticoagulation, while reducing the incidence of thrombo-embolism [1]. The availability of such advantageous procedures, if reliable and durable, impacts management strategies for patients with acute or chronic aortic regurgitation as currently recommended by the ACC/AHA; current medical algorithms require symptoms or progression of left ventricular dysfunction with chamber dilatation before surgical referral [2]. The ability to repair and salvage the native aortic valve in certain kinds of aortic insufficiency creates a more compelling option for earlier surgery, in some cases, prior to the deterioration of either systolic or diastolic left ventricular function. It is the goal of this paper to review the evolution of these techniques, to clarify the sometimes confusing vocabulary and to establish parameters for the application of the various methods based upon optimization of the functional anatomy of the aortic root complex.


   2. Functional anatomy of the aortic valve complex aortic root anatomy
Top
 Abstract
 1. Introduction
 2. Functional anatomy of...
3. Conclusion
 References
 
In 1994, Kunzelman and co-authors published an important paper describing the anatomy of the aortic root and the valve relationships therein [3]. The critical finding of the paper was that if the diameter of the aortic root was defined at the mid-sinus as 100%, then the sinus ridge should be 81% of that diameter and the aortic root base 97% of that diameter in the normal aortic root. In other words, the sino-tubular ‘ridge’ is approximately 85% of the diameter of the ‘annulus’ at the base of the root. This analysis of the aortic root quantitative anatomy emphasized the role of DaVinci eddy currents created by the sinuses as defined by the narrowed sino-tubular ridge as being more important than the actual shape of the sinuses (Fig. 1) . The fluid vortices from the eddies between the valve leaflet edges and the aortic wall have two effects:

  1. On valve opening, these eddy currents prevent aortic valve leaflets from impacting the aortic wall.
  2. On valve closure, these eddy currents participate in initiating leaflet closure.



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  		Fig. 1. These diagrams demonstrate the static and basic functional anatomy of the aortic root valve complex. Specifically note that the sino-tubular junction diameter is approximately 15% less than that of the base of the aorta (putative aortic ‘annulus’). The DaVinci sinus currents are depicted which enhance leaflet closure at the end of systole and protect leaflets from wall impact during systole. In addition, movement of the annulus changes the tension/length relationships of the leaflets to enhance function. Difficult to demonstrate in a two-dimensional figure is the time dependent expansion of the aortic root that occurs during the first third of systole and the change in its overall configuration from a truncated cone shape with acorn protuberances of the sinuses to a larger more cylindrical form which would offer less impedance to ejection. FM, free margin; B, base of semi-lunar leaflet insertion; STJ, sino-tubular junction; AA, aortic annulus (defined as the base of the aorta, not the semilunar leaflet attachment scalloped edge).

 
This second effect noted by these authors is likely even more complex than suggested as the fluid vortices initiate valve closure in late systole contributing to a smoother (i.e. less bending stress) and more synchronous closure, likely reducing leaflet material fatigue while optimizing valve mechanics [4].

2.1. Dynamic anatomy of the aortic root
The dynamic aortic root anatomy has been described as designed to ‘reduce cusp stresses and thereby fatigue and eventual structural failure of the valve cusps’ [5–12]. The group from Stanford utilized radiopaque markers in a sheep aortic root model described a series of complex asymmetric deformations during the cardiac cycle, which included atrioventricular base (putative annulus) and sino-tubular junction strains, aortic root elongation, compression, shear and torsion deformities [5]. In a ‘four-dimensional’ study of aortic root dynamics, Lansac and colleagues confirmed that expansion of the aortic root begins at the base during isovolumic contraction and thence evolves to the commissures and ultimately the sino-tubular junction [6]. During the first third of systole, the aortic root reaches its maximal expansion, approaching a cylindrical form, after which it decreases in volume until mid-diastole, as it re-approaches a truncated cone shape by end-diastole. The increase in the aortic root base area of 39% and the commissural increase of 63% during systole would reduce the opposition to ejection, making left ventricular work more efficient. This aortic root expansion is quite significant and demonstrates that the dynamic visco-elastic properties of the aortic root are critical to the impedance-matching characteristics at the ventricular–arterial connection.

The work by both Dagum and Lansac suggest the importance of the inter-leaflet triangles described by Anderson and colleagues, who clearly identified the aortic valve annulus as the functional subaortic region formed by the bases of these three inter-leaflet triangles, rather than the scalloped attachment line of the aortic leaflets [5,6,11,12]. The base of the aortic root thus expands in relation to ventricular mechanics. The upper aortic root begins to expand as the interleaflet triangles distend but the sinuses and sino-tubular junction maximally expand as an aortic related event (i.e. later in systole). In addition, this precise and predictable aortic root expansion dynamic, which follows a specific chronology, also affects the position and degree of tethering of the base of the cusps, moving them three-dimensionally as originally described by Thubrikar [10] (Fig. 1). All of the leaflet sparing reconstructions alter this dynamic aortic root geometry, but in different ways.

2.2. Target disease states for aortic valve sparing/salvage
By and large, these reconstruction techniques are only applicable to aortic insufficiency, as a consequence of three situations:

  1. Aortic root dilatation secondary to ascending aortic aneurysm: mechanism of aortic insufficiency in this disease state is a consequence of the dilatation of the sino-tubular junction with distraction at the commissures of the valve leaflets. With progressive dilatation, the valve leaflets are literally pulled apart from the central coaptation point. This can be made more severe by primary or more often secondary annulus dilatation.
  2. Annulo-aortic ectasia and connective tissue syndromes such as Marfan's and Ehlers-Danlos: the mechanism is dilatation of the sinuses, the sino-tubular junction, as well as the annulus, due to pathologic cystic medial necrosis. Interestingly, the leaflets tend to be spared. The mechanism of aortic insufficiency in the syndromes include progressive dilatation of all components except the leaflets, which ultimately leads to aortic dissection. Annulo-aortic ectasia can occur as a consequence of these specific syndromes.
  3. Aortic root and ascending aortic dissection—acute or chronic: in aortic dissection, there is dilatation of the sino-tubular junction with either or both (a) acute distraction of the valve leaflets; and (b) unhinging and prolapse of the leaflets secondary to sinus wall dissection. In the absence of leaflet damage, the aortic wall and aortic root pathology can often be repaired and the valve reconstructed [13–20].

2.3. Rationale for valve salvage/sparing
The focus on valve sparing operations and the concomitant re-evaluation of the functional anatomy of the aortic root has demonstrated that aortic root deformation often co-exists with architecturally and morphologically normal valve leaflets. Thus, sparing and realigning the leaflets and reconstructing the aortic root has the potential for avoiding prosthetic valve disease including thromboembolism, hemodynamic mismatch, hydraulic dysfunction, and bacterial endocarditis. The risk of early technical failure can be reduced with routine use of intraoperative TEE and adjustments of the reconstruction as necessary to achieve perfect valve function before leaving the operating room [21,22].

2.4. Historical prelude to aortic valve repairs, reconstructions and finally ‘valve sparing’
In 1832, Corrigan first described the ‘permanent patency of the mouth of the aorta’ as a consequence of dilation of the sino-tubular junction co-existing with normal leaflets and pre-morbid diagnosis of aortic insufficiency. In 1913, Tuffier described the first aortic commissurotomy for aortic stenosis [23]. In 1956, Lewis published his technique for aortic valvulotomy and in 1958, Harken reported decalcification/repair for aortic stenosis; poor short and medium term outcomes for the repair methods applied to aortic stenosis were soon well established [24,25]. In 1958, Taylor described a treatment for aortic regurgitation that could be performed off bypass which he termed ‘circumclusion’, which consisted of a suture circumferentially snugging the aortic annulus to reduce the size of the dilated aortic aneurysm [26]. In 1959, Starzl reported a novel technique for the management of aortic regurgitation by creating a bicuspid aortic valve [27]. In 1960, Murphy described a courageous off-bypass annular plication with an umbilical tape technique for syphilitic aortic insufficiency similar to a concept by Hurwitt (1960), who described a series of suture plications of the aortic ‘ring’ for aortic insufficiency, which could also be performed off bypass [28]. In 1958, Garamella published the concept of aortic valve re-suspension for aortic regurgitation due to sub-aortic VSD. This successful re-suspension was critical to the evolution of the understanding of the semilunar valve function [29].

In 1968, Bentall and De Bono reported (in a two page case report), a single patient treated with composite graft and mechanical valve replacement of the aortic root and ascending aorta with coronary reimplantation which became the gold standard for treatment of aortic aneurysm and aortic dissection [30]. In 1980 and 1983, Wolfe published a series of acute ascending aortic dissections treated with valve re-suspension. In his 1983 update, a total of 48 patients were reported of whom 35 had successful valve re-suspension [31,32]. Only one of these patients ultimately required late aortic valve replacement, 17 years following the series (Dr Wolfe, personal communication).

In 1986, Frater described and emphasized the anatomic and mechanical function of the sino-tubular junction and noted that correcting a dilated sino-tubular junction was often sufficient to repair aortic insufficiency in those cases in which valve leaflets and annulus were not enlarged [33].

2.5. Evolution of modern techniques aortic dissection with valve re-suspension
The re-suspension procedure has now evolved for management of all aortic dissections that are limited to the ascending aorta above the sino-tubular junction or involving the non-coronary cusp with aortic valve prolapse with or without minimal involvement of the right and left sinuses. In the classic version of this method, the valve is reconstructed with a single sinus replacement, no coronary reimplantation, re-suspension of the pillars on either side of the non-coronary sinus and, in the current era, biological glues are used (Fig. 2) .



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  		Fig. 2. Wolfe procedure. the non-coronary sinus (which is usually involved with the dissection) is resected and replaced with a tongue of the Dacron tube graft. The aortic valve commissural pillars are re-suspended to the Dacron graft and, when appropriate, glue is used to reinforce, thicken and increase the tensile strength of the proximal aortic wall.

 
2.6. Aortic reimplantation technique of David and Feindel: TD I
In 1992, David and Feindel published a series of 10 patients treated with ‘an aortic valve sparing operation for patients with aortic incompetence and aneurysm of the ascending aorta’ [34]. This 1992 technique, which for the purposes of this review will be designated Tirone David I (TD I), consisted of his classic reimplantation of the aortic valve within a Dacron tube graft. For this procedure, the root is excised leaving coronaries on buttons and leaflets attached to 4–5-mm aortic wall remnants (Fig. 3 A,B). The Dacron tube graft is attached to the aortic root base with pledgeted sutures placed from underneath the leaflet attachments and thus through the fibrous skeleton of the base of the aortic outflow (pseudo-annulus). The valve commissures are re-suspended inside the aortic tube graft, thereby reconstructing the semilunar leaflets inside the tube graft. The operation is completed by attaching the coronary buttons to neo-sinuses and suturing of the distal conduit anastomosis thus establishing a more normal diameter for the ascending aorta (Fig. 3C,D). Features of the TD I reimplantation technique include cylindrical sinus reconstructions, coronary reimplantations, and maximum stabilization of the base of the aortic root (‘annulus’). The original technique does not describe specific sino-tubular junction narrowing. Hvass has reported a variation on this inclusion technique in which a Dacron tube is inserted inside the root proper and sewn to the base of the sinuses (rather than outside as in the David method), the top of the root insert is sutured full thickness to the transversely resected aortic root at the sino-tubular junction and then sewn to another (smaller) tube graft to replace the ascending aorta; such an inside reimplantation method exposes leaflets to Dacron contact and does not stabilize the annulus [35].



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  		Fig. 3. Tirone David I. the sequence demonstrates the surgical approach described initially by Tirone David in 1992, which is now known as the reimplantation technique (TD I). (A) The aneurysmal aortic root is resected. (B) This leaves the semilunar attachments of the normal aortic leaflets intact with a residual sewing margin alongside the pillars and within the sinuses of 3–5 mm. The coronaries are left on buttons. (C) Sutures are placed from below the aortic valve leaflets to the outside through the fibrous base of the aorto-ventricular junction. (D) Then passed through the base of the selected Dacron conduit. This secures the conduit to the fibrous skeleton of the heart at the base of the aorta. (E) The pillars of the valve are re-suspended inside the conduit with continuous suturing analogous to the sub-coronary homograft implantation technique. Coronaries are reimplanted as buttons into their respective sinuses and the distal anastomosis is made, supported with additional Teflon felt strips as needed.

 
2.7. Yacoub aortic root remodeling technique
In 1993, Sarsam and Yacoub published a series of 10 patients with aortic regurgitation treated with what they termed ‘Remodeling of the aortic anulus’ [36].

The first version of the Yacoub ‘remodeling’ technique consisted of replacing all three sinuses with reimplantation of the coronaries utilizing a tripartite crown-shaped Dacron tube graft. It required coronary reimplantation but did not provide stabilization of the aortic base or specific narrowing of the sino-tubular junction (Fig. 4 A–C). In their technique, Sarsam and Yacoub emphasized the sinus excision and the utilization of the Dacron tube graft diameter equal to the aortic root base. The incisions are created to increase the height of the commissural pillars. By definition, the aortic root is reconstructed as a cylinder in this method, the sino-tubular junction is not specifically narrowed, and the base is not stabilized. The advantage of the technique is that it is easier technically than the reimplantation method and provides a simpler method for accurate re-suspension of the pillars. Subsequent modifications by Yacoub include narrowing the sino-tubular junction and allowing the sinus reconstruction to bulge outward more so than in this first version (vida infra).



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  		Fig. 4. Sarsam and Yacoub 1993 technique of remodeling. (A) A tripartite proximal graft is fashioned. (B) The sinuses are resected, leaving the coronaries on buttons and the commissural pillars intact with sewing margins of 4–5 mm. The commissural pillars are re-suspended to 0.1 in their respective sinuses of the Dacron graft, and the flanges each sutured to replace the sinuses. This technique emphasizes sinus excision with stretching of the pillars upward to maintain tension on the semilunar valve suspension mechanism.

 
2.8. Reimplantation versus remodeling
In 1995, David, Feindel and Boss reported the next step in the evolution of the Tirone David techniques. In a paper entitled ‘Repair of aortic valve in patients with aortic insufficiency and aortic root aneurysm’ [37], patients were reported that were repaired by two fundamentally different techniques. The first was the original Tirone David I reimplantation technique, which was applied to patients with dilation of the sino-tubular junction, distortion/dilation of the sinus of Valsalva and annulo-aortic ectasia. The alternative operation procedure described, which this review will title ‘Tirone David II’, was described by the authors as a ‘remodeling’ procedure most applicable to patients without annulo-aortic ectasia, and which they felt addressed the problem of a deformed sinus of Valsalva and some element of correction of the sino-tubular junction. In this series, 45 patients were described with only two mortalities. Nineteen patients had reimplantation by the Tirone David I method and 26 had the Tirone David II remodeling procedure. The aortic valve was reconstructed by replacing all three sinuses and utilizing coronary reimplantation. There was no reinforcement or reduction of the ‘annulus’ and no sino-tubular junction remodeling (i.e. reduction in diameter to 85% of annulus) other than would be provided by the splaying of the tripartite sinus flanges (Fig. 5) .



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  		Fig. 5. 1995 Tirone David II Remodeling. (A) A scalloped sinus replacement is cut from the proximal end of the Dacron graft. (B) This is then sutured into each sinus after excising the aortic root aneurysm. The coronaries are left on buttons, which are then placed into defects created in the respective Dacron sinuses.

 
2.9. Aortic root reimplantation with pseudo-sinus reconstruction: Seattle technique
In 1995, Cochran and colleagues described ‘a variation of the Tirone David method’, in which a modified conduit preparation created outward bulging ‘pseudo-sinuses’ while still sparing the aortic valve [38]. In this Seattle technique of aortic valve sparing/salvage with neo-sinus reconstruction, the aortic valve was reconstructed by replacing all three sinuses with a special technique to allow them to bow outward. This outward bowing was designed to prevent leaflet concussion against the Dacron sinus walls. In the normal aortic root, the leaflets are protected by the dynamic geometry (expansion of sinuses, elongation of leaflets and root, DaVinci currents) (vida supra). This technique stabilizes the ‘annulus’ at the base and includes coronary reimplantation. There is a proximal suture line beneath the leaflets similar to the Tirone David I methodology, and the ‘distal’ suture line above the leaflets is designed to help maximize pillar suspension. The scalloping of the proximal graft is done to create the pseudo-sinuses (Fig. 6) .



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  		Fig. 6. 1995 Seattle Technique. (A) In this method, the proximal Dacron graft is scalloped, but then sutured continuously to the base of the aorta, utilizing sutures brought from underneath the leaflets as horizontal mattress sutures similar to the proximal suture line of the Tirone David I method. This causes bulging of the Dacron replacement in the region of each sinus to be replaced. (B) The semilunar valve is then re-suspended within the Dacron tube graft as a reimplantation. Coronary buttons are sewn. This method is basically a reimplantation method, which involves some remodeling of the sinuses to attempt to create pseudo-sinuses.

 
A hybrid method has been described by van Son and colleagues in which the dilated aortic root is downsized and reconstructed (after removing the coronary buttons) by excising wedges of sinus wall and then reimplanting the reconstructed aortic root inside a Dacron tube graft with attention to restoration of commissural height; the distal root is sutured to the Dacron graft and coronaries reimplanted into Dacron [39]. This hybrid technique spares the leaflets, reconstructs the sinus, allows for control of annular and sino-tubular diameters, while avoiding leaflet-Dacron contact, but does not stabilize the annulus. Others have left ‘cushions’ of aortic wall to theoretically protect against leaflet damage [40,41].

2.10. Aortic root remodeling with annulus stabilization (TD III)
In 1996, Tirone David described yet another variation of his remodeling (TD II) technique for annulo-aortic ectasia (the Tirone David III procedure). In this case, the aortic valve is reconstructed by replacing all three sinuses utilizing coronary reimplantation (Fig. 7 A–E). The major difference is that the ‘annulus’ is buttressed with Teflon felt that, in combination with the fibrous continuity of the ventricle, functions to stabilize the aortic root base. This technique provides easy re-suspension of the pillars similar to the original Yacoub method, and depending on conduit sizing implicitly remodels the sino-tubular junction (Fig. 7F–H). El Khoury and colleagues have reported a similar technique but only reinforced the annulus when it was felt to be significantly dilated; they also recommend leaving some sinuses intact when not involved in dissection or aneurysmal dilatation [42].



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  		Fig. 7. 1996 Tirone David III Remodeling. (A) This method begins with removal of the aortic root and affected ascending aorta. (B) The aorta is transected just above the sino-tubular junction. (C) The aortic root is mobilized to its base and the coronaries are left on their respective buttons. (D) A strip of Teflon felt is used to support the ‘annulus’ in the region of the fibrous continuity of the ventricle to stabilize the aortic root base, particularly useful for patients with annulo-aortic ectasia. (E) The aortic annulus (AA) is sized in this figure as an external measurement from which wall thicknesses are subtracted to define the Dacron graft diameter. Tirone David III Remodeling Aortic Root Procedure: (F) The aortic root is then replaced with a remodeling technique, re-suspending the pillars into cut-outs of the proximal Dacron graft. (G) Attention is paid to adequate re-suspension of the commissural pillars. (H) Coronary buttons are reinserted with continuous suture into defects created in the respective sinuses. A second smaller tube graft can be attached to the Dacron tube graft used for aortic root remodeling to create a smaller sino-tubular ridge. Beveling the distal end of the Dacron tube graft allows attachment to an modestly dilated proximal transverse aorta.

 
2.11. Sino-tubular ridge reconstruction
This method consists of simple replacement of the ascending aorta with a concomitant reconstruction (i.e. narrowing or reduction aortoplasty) of the sino-tubular ridge to repair dilatation causing distraction of the leaflets preventing coaptation in an aortic root. By itself, it can only be used when the leaflets and sinuses of Valsalva are normal and the annulus does not need reconstruction. In this entity, the valve is reconstructed without coronary reimplantation and without sinus replacement. There is no stabilization of the aortic root base and is essentially the Frater approach of enhancing the function of the sino-tubular ridge [33]. Dr David has included this concept in his updated version of the reimplantation method (denoted as a TD IV by Dr Miller) in which he selects a 4-mm larger Dacron graft than his previous sizing and then plicates the graft circumferentially at the neo-sinotubular junction [43]. The TD V or Miller I are reimplantation techniques using an even larger graft (diameter+8 mm) and then ‘necked down’ at both the bottom and top to exaggerate the synthetic pseudosinuses [43,44]. The ‘Jena’ technique has been described as a hybrid method in which the aneurysmal root is reconstructed by plicating and excluding portions of each sinus (‘u’ shaped around coronary ostia or ‘v’ shaped in non-coronary cusp) and the sino-tubular junction rebuilt with a ‘downsized’ Dacron conduit (26–28 mm). This has the advantage of leaving native tissue in potential contact with the leaflets and preserving dynamic expansion and recoil properties of the aortic root proper but does not limit later dilation of annulus or retained root tissue [45].

2.12. Remodeling aortic root for leaflet salvage with maximum stabilization and sino-tubular junction reconstruction
Within the evolutionary approach and greatly influenced by all of above authorities, this author has reconstructed the aortic valve in a method that was independently developed but, in essence, is a variation of the remodeling approach. In this technique (and similar to TD II and Yacoub), all three sinuses are replaced with coronary reimplantation. The base of the aortic root is buttressed circumferentially with felt secured with sutures placed from beneath the valve leaflet base to prevent ‘annulus’ late dilatation and thus, is applicable to patients with connective tissue disorders such as Marfan's. The aortic root base is circumferentially buttressed (Fig. 8) . As in the Yacoub and TD-III techniques, it is easy to emphasize pillar re-suspension. In this technique, the sino-tubular junction is remodeled to approximate the ideal 15% reduction as compared to the diameter of the annulus by choosing the graft diameter to be the desired diameter of the STJ and allowing the sinuses to slightly flange outward by incising the slots for the pillar re-suspensions slightly ‘high’. The slots are kept narrow to emphasize the neo-sinuses. The STJ ‘waist’ is then narrowed with a felt strip. By narrowing the sino-tubular junction, the DaVinci eddy currents are functionally retained and tend to prevent leaflet impact on the Dacron wall. This repair addresses all of the components of the aortic root while sparing the leaflets.



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  		Fig. 8. Hopkins I Method. (A) A narrow strip of Teflon is placed circumferentially around the base of the mobilized aortic root after resecting the pathological aneurysmal tissue. This is secured in place with a series of mattress sutures placed from beneath the aortic valve leaflets in the manner of the Tirone David I reimplantation proximal suture line. The flanges are cut from the proximal end of the Dacron graft to fit and replace the excised aortic root sinuses. The commissural pillars are left with 3–5 mm sewing edges. The upward cuts into the Dacron graft are made relatively long to slightly exaggerate the re-suspension of the commissural pillars and to allow some bulging of the neo-sinuses. (B) The proximal suture line is secured and the sinuses are replaced with the proximal portions of the graft. (C) Once the running suture lines have been completed and the coronary sinus buttons are sutured into their respective sinus defects, a distal collar of Teflon felt is placed just at the top of the commissural pillar suture lines to slightly invaginate or to create a sino-tubular junction waist. The distal anastomosis to the upper ascending or transverse aorta is constructed in the routine fashion, often augmented with Teflon felt strips. Glue is used whenever aortic tissue appears tenuous.

 
2.13. Aortic valve repair and salvage
While the terms ‘salvage’ and ‘sparing’ have been used interchangeably and loosely, the term ‘sparing’ is best reserved for those techniques as reviewed in this manuscript in which the aortic root complex is reconstructed while ‘sparing’ the leaflets. ‘Salvage’ as a term would probably best be utilized for procedures in which techniques that include direct repair of the leaflets are involved and/or acute dissection in which prolapsed leaflets are resuspended and thus ‘salvaged’ not just ‘spared’. Leaflet repairs must re-establish the plane of coaptation. With long-standing lesions, such as sinus of Valsalva aneurysms, there is often an increased amount of tissue in the ‘belly’ of the leaflet cusp with sagging of the cusp leaflet edge and loss of effective coaptation area requiring shortening of the leaflet edges and re-suspension of the pillars [46]. Repair of aortic stenosis by decalcification has been discredited. Other leaflet repair methods for salvage of leaflets include triangular resection for sagging or prolapsing leaflets, Gore-Tex reinforcement, patch repairs, cusp perforations, cusp shaving, commissural plication, pericardial cusp extension, etc.; an extensive description of these are beyond the scope of this paper but have been nicely reviewed and illustrated elsewhere [47,48].

2.14. Failure modes for aortic valve reimplantation and remodeling
Failure of valve sparing operations has been ascribed to methods that fail to stabilize the base of the aorta allowing late dilatation of the aortic ‘annulus’ [49]. The portion of the aortic outflow tract that forms the functional annulus is actually the base of the ‘interleaflet triangles’ below the level of the cusps and thus are part of the ventricular hemodynamics [11,12]. Proponents of the reimplantation technique, particularly in the presence of connective tissue disorders, suggest that stabilization of the annulus is important. Remodeling methods leave the dynamic expansion of these triangles functionally intact, which should be advantageous in optimizing leaflet performance and durability while retaining some of the sequential expansion dynamics of the aortic root complex. The implantation methods support or ‘splint’ these inter-leaflet triangles.

A theoretical alternative cause of failure is accelerated leaflet degeneration as a consequence of systolic contact between leaflet and the wall or buckling of the leaflets due to lack of expansion of the coronary sinuses. Trying to repair aortic roots with annuli greater than 25–27 mm has been related to failure ascribed to leaflet trauma from ‘crowding’ of the cusps within the graft [13,50–52]. These events could occur during reimplantation into a cylindrical graft or with flawed remodeling using too small of a graft. To accommodate and reconstruct the egg shape of the sinuses, a number of innovative prostheses have been developed which incorporate sinuses of Valsalva into the prosthesis itself [53].

Pethig and colleagues, using echocardiography, defined a critical cause of failure resulting from sagging of the leaflet coaptation below the annulus. A type A coaptation is one in which the leaflet coaptation plane was 2 mm above the ‘annulus’ plane base. In type B, the coaptation occurred in the plane of the annulus base and type C is below the plane of the annulus base. In their method, the annulus base was described as the bottom of the Dacron graft. In type A coaptation, there was no regurgitation (n=56); in type B there were two patients with severe AI (n=11) and in type C, all six patients had aortic insufficiency. Thus, this re-emphasizes the importance of re-establishing the normal height of the coaptation plane of the leaflets by adequately re-suspending the pillars. This was a lesson that had previously been learned in the homograft valve sub-coronary implantation era [54].

The early remodeling techniques (e.g. Yacoub, David II) by design, only replace the pathological sinuses with the intent of preserving the dynamic properties of the aorto-ventricular junction. In the short term, this should retain the dynamic properties of the aortic root. But, for patients with connective tissue disorders, this may expose them to the potential failure mode by late dilation of the unsupported components of the reconstructed aortic root and thus remodeling has tended to evolve to include more stabilization of STJ and base.

Dr David has compared his reimplantation technique to his evolving remodeling techniques for patients with aortic root aneurysms and has discovered some disparity in long term durability of the two procedures. While the survival is excellent 8–10 years following surgery, his experience has demonstrated better durability (freedom from developing moderate to severe aortic insufficiency) with the reimplantation technique [49]. He correctly notes that without reinforcement, the aortic root can continue to dilate with many of the remodeling procedures. While the reimplantation procedure has a theoretical disadvantage of valve leaflet impact on the cylindrically reconstructed sinuses, this appears to be less of a problem in reality [49,53,55]. New prostheses are now available that have ‘out-bulging’ sinuses constructed as part of the Dacron conduit [53,56–58]. Increased clearance for the valve leaflets can be achieved surgically, either with the Seattle technique, Zehr's prosthesis [59] or as described by Dr David [49], or sinus grafts attached to smaller tube graft as reported by the Mayo Clinic [50]. However, it is not clear that leaflet impact is the mechanism for the development of late aortic insufficiency in the remodeling procedures but rather is more likely due to a lack of constraint on the residual fibromuscular components of the aortic root complex that exists with the remodeling methods.

Finally, leaflet failure due to friability and post repair degeneration may be inherent or a consequence of thinning.

2.15. Sizing the graft for reimplantation and remodeling
Much emphasis has been placed on selection of graft diameter size for the various techniques. The reimplantation technique has the advantage of stabilizing the entire aortic root complex by securing it inside the Dacron graft, however, the graft sizing for reimplantation is clearly different that for remodeling. For reimplantation, the graft must be large enough to avoid compromising leaflet coaptation edge expansion. David has pointed out that the sino-tubular junction can be readjusted to a smaller size by either plicating or downsizing to a smaller graft at the level of the sino-tubular junction if necessary, given that the reimplantation technique in general requires a somewhat larger graft (30–34 mm), in effect matching the ideal ‘annulus size’ for the aortic valve prior to dilatation [60]. In the remodeling type of techniques, various methods for estimating the valve graft size have been suggested [3,36,60–69]. That of Pepper and Yacoub [62] has been described by Morashita as the circle circumscribing the triangle defined by the three commissures when ‘positioned normally’. David has suggested that the diameter of the aortic annulus should be normalized and then a graft selected which defines a sino-tubular junction that is approximately 15% less than the annulus [60]. This is consistent with the Kunzleman morphometrics [3]. Yacoub's group has also suggested measuring the distance between the commissures, which produces maximal coaptation of the cusps and equating that to the diameter [62,68]. Morashita has recommended an equation based on a triangle circumscribed by a circle of the ST junction in which the diameter equals two-thirds the square root of the internal diameter [63]. Most appropriately, David has pointed out in an editorial that ‘the estimation of diameters of the aortic annulus and sino-tubular junction remains more art than science’ [60]. Sizing for the reimplantation procedure is done differently than for the remodeling in his hands [49]. Conceptually, the reimplantation method is based on the aortic root external diameter (internal diameter+wall thickness), while remodeling is based on internal diameters. For the reimplantation procedure, David describes reconstruction of the aortic root based on the size of the aortic cusps and avoids using grafts smaller than 30 mm in diameter to avoid constraining the aortic sinuses and causing damage to the leaflets [49,60,66]. For reimplantation, this author has followed Dr David's recommendations. For remodeling, we would suggest the following method. After the sinuses have been excised, the true internal diameter of the aortic-ventricular junction ‘annulus’ is measured with a Hegar dilator. The horizontal mattress sutures at the top of each commissural pillar are then used to stretch the pillars superiorly to an apparent appropriate STJ diameter and the coaptation of the leaflets tested with a small amount of saline. That ‘STJ diameter’ is usually equivalent to the internal diameter of the aortic outflow as measured by the Hegar. If the semi-lunar valve cusp coaptation areas appear to be less than optimal, then the next size down graft is usually selected. This very simple method (reminiscent of David's ‘artistic approach’), when combined with placement of a Teflon felt strip at the sino-tubular junction outside the graft and attention to the height of pillar re-suspension seems to reliably result in a sino-tubular junction restoration that approaches the required 15% reduction, while avoiding deformation of sinuses.

2.16. Patient outcomes after aortic root reconstructions with valve sparing or salvage
Perioperative mortality has varied between 0 and 6% [70,71] with a 7-year survival of 72–78±8% [71,72]. Patients with ascending aortic aneurysms have lower survival than patients with aortic root aneurysms, approximating only 36% survival at 8 years [49]. This decreased survival, however, is more likely a consequence of the older age of patients with ascending aortic aneurysm (vs. those with isolated aortic root aneurysms) and their concomitant generalized vascular disease. Reoperation for aortic valve replacement at 7–8 years has been low in most reported series with a freedom from such re-operation approximating 90–97% [68,71,73]. Trivial to mild AI is not uncommon, particularly after 2 years following surgery. However, moderate AI has been relatively uncommon, approximating 6%, although the occasional report approaches as high as 37% [34,55,73–78]. Patients with aortic root aneurysms requiring reconstruction not only have better long term survival, but appear to have a reduced risk of moderate to severe aortic insufficiency developing late with approximately two-thirds having freedom from greater than 2+ aortic insufficiency at 8 years post operatively [49]. For the aortic root aneurysm group, David has reported a superiority of the reimplantation technique (vs. remodeling) in terms of the freedom from the development of late aortic insufficiency; reimplantation resulted in moderate to severe aortic insufficiency in 10% at 8 years versus 45% for remodeling [78]. The Hanover group has similar results for reimplantation with a 3.8% perioperative mortality and 4% reoperation rate for aortic insufficiency at 7 years [73]. Intraoperative transesophageal echocardiography assessment is a critical determinant of short- and long-term durability of the procedure [46,55]. Late failure (AI) in patients with connective tissue disorders seem to occur more often with techniques that do not maximally stabilize the aortic base (‘annulus’) [60,66–69,78–80].

For patients with aortic root aneurysms in which the aortic root complex is left intact and the reconstruction is performed by normalizing the diameter of the sino-tubular junction, the short to medium term functional result is quite good, with over two-thirds of patients remaining free of aortic insufficiency 8–10 years following surgery; but the overall survival of these patients is relatively poor, with only a third of the patients living at 8 years, probably as a consequence of the fact that these patients usually have extensive vascular disease and also tend to be older [46,49].

For comparison to the reconstruction approaches, Dr Gott and his colleagues recently updated the results in aortic root replacement in 235 Marfan patients in which 232 underwent a Bentall composite graft and prosthetic valve replacement of the aortic root. In this group, there were no 30-day mortalities, 83% of the patients in this series were alive at the time of publication, and freedom from reoperation at 20 years was 74% [81]. A Japanese series utilizing a flanged composite graft reported an operative mortality of 8.3% with an actuarial survival at 5 years of 82.7±4.8% [82].

Edwards and colleagues, utilizing the National STS Cardiac Surgery Database were able to establish a normative operative mortality rate for isolated aortic valve replacement of 4%; for patients with elective aortic valve replacement, the operative mortality was 3.3% [83]. These results suggest that, in selected patients, elective aortic valve sparing operations are currently being accomplished in most centers with mortality rates which approach or are better than that for isolated aortic valve replacement.

2.17. Clinical practice options
2.17.1. Age specific
In current practice, aortic leaflet sparing reconstructions are applicable with certain age constraints to treat aortic insufficiency resulting from deformed aortic root due to ascending aortic aneurysm or chronic dissection in which the dilated aortic root co-exists with normal leaflets. Under the age of 70, a valve sparing remodeling operation is performed (TD III, modified Yacoub, or RH method). If there is some ‘floppy’ quality to the leaflets or they appear to have some element of prolapse, then one of the reimplantation methods is likely preferable (TD IV or V, Seattle, von Son). Over the age of 70, patients can be treated without mechanical valves and thus the aortic root is replaced with either a stentless valve [84] (root replacement or subcoronary implantation) or with one of the valve root remodeling or reimplantation operations.

2.17.2. Leaflet involvement
While leaflet repairs are beyond the scope of this paper, elongated cusps can be reduced by various techniques [67,85]. When valve leaflets are thinned with poor material properties, then replacement with a Bentall technique (classically with porcine or mechanical valves), a homograft root replacement or a stentless aortic root replacement should be used (‘stentless Bentall’) [84,86]. Multiple authors have indicated that leaflet abnormalities are a relative contraindication to aortic root reconstruction with leaflet sparing [51,71]. In Marfan's syndrome (or other connective tissue disorder), maximum stabilization seems optimal, and thus the Tirone David I, V (implantation series, or the Seattle, while the Tirone David III (remodeling with annulus reinforcement), modified Yacoub or our technique would be the best remodeling choices. Bicuspid aortic valves have been successfully repaired [87–89] and combined mitral and aortic repairs reported [90,91].

2.17.3. Acute dissection
Surgical therapy for acute ascending aortic dissecting aneurysm usually involves the use of glue with commissural pillar re-suspension, alternately, ascending aortic graft or a reimplantation root with leaflet sparing (TD V) can be used. When two or three sinuses are involved with the dissection, both the modified Yacoub and the Hopkins remodeling techniques can be used (with glue) if leaflets are not unhinged at their base. A root replacement procedure is selected when the root is destroyed [92]. To avoid anticoagulation, this author has salubrious experience with and there is literature support for aortic root replacement with a stentless aortic valve complex and the ascending aorta replaced with a Dacron graft extension as a ‘stentless Bentall’ [84,93].

2.18. Homograft valve procedures
The autotransplant (Ross procedure) has some application in patients under the age of 55, but more often for aortic stenosis than aortic insufficiency, or even best in those patients with combined aortic stenosis/aortic insufficiency [94,95]. It is usually not applicable to long standing pure aortic insufficiency because of architectural mismatch between the native pulmonary valve and the left ventricular outflow tract [96]. It is appropriate for patients with complex multilevel left ventricular outflow tract obstruction and children without connective tissue disorders [54].

Homograft aortic root replacement is used primarily for endocarditis that has destroyed the aortic root in adults or complex multi-level left ventricular outflow tract obstruction in children [97].


   3. Conclusion
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 Abstract
 1. Introduction
 2. Functional anatomy of...
 3. Conclusion
References
 
The evolution of these techniques mirrors the evolving understanding of the functional anatomy of the aortic root complex. For aortic root reconstruction, surgeons and their patients are best served by complete understanding of all the techniques and the variable effects and advantages as described above. Such methods are now well defined such that application has expanded successfully to pediatric and complex aortic root lesions [98,99]. The medium term results appear to validate their use, but the ideal method remains to be demonstrated and the safety and applicability to connective tissue disorders such as Marfan's syndrome remain to be determined with longer term studies [43]. Multiple methods for aortic reconstruction are available, some of the original techniques have been modified or superseded by their own inventors. While it is not clear which concerns are purely theoretical, it does appear that certain principles are emerging which suggest that all components of the aortic root complex must be considered by the surgeon and optimized for the individual patient's functional anatomy. New prosthetics are being developed to improve sinus reconstructions. With attention to the specific anatomy and natural history for each patient, the aortic root complex can be successfully reconstructed with durability and low mortality.


   Footnotes
 
Portions of this manuscript were presented at The American College of Cardiology meeting in Atlanta, Georgia, March 17, 2001.


   References
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 2. Functional anatomy of...
 3. Conclusion
 References
 

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