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Ann Thorac Surg 2007;84:1214-1218
© 2007 The Society of Thoracic Surgeons

Original Articles: Cardiovascular

Sinotubular Junction Size Affects Aortic Root Geometry and Aortic Valve Function in the Aortic Valve Reimplantation Procedure: An In Vitro Study Using the Valsalva Graft

Daniele Maselli, MD*, Ruggero De Paulis, MD, Raffaele Scaffa, MD, Luca Weltert, MD, Alessandro Bellisario, MD, Andrea Salica, MD, Alessandro Ricci, MD

Department of Cardiac Surgery, European Hospital, Rome, Italy

Accepted for publication May 11, 2007.

* Address correspondence to Dr Maselli, U.O. Cardiochirurgia, European Hospital, Via Portuense 700, Rome, 00149, Italy (Email: dmaselli{at}tiscali.it).


Dr De Paulis discloses a financial relationship with Vascutek.

 

   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
Background: Sinotubular junction (STJ) size in aortic valve reimplantation procedures is usually predetermined on the basis of experience or intraoperative mathematical calculations. Given the small coaptation reserve of aortic valve leaflets, small errors can produce an incompetent aortic valve. We tested in vitro the effect of geometrically changing the relationship between aortic annulus size and STJ size on aortic root geometry and aortic valve function.

Methods: Twenty-five–millimeter diameter scalloped porcine aortic roots were reimplanted into 32-mm Valsalva grafts (Vascutek, Renfrewshire, Scotland), suspending commissures into the expandable region of the graft itself. Neoaortic roots were pressurized up to 100 mm Hg. Sinotubular junction size was then changed by wrapping the neocommissural ridge with Dacron rings of decreasing size. Geometry of the aortic root, anatomy of aortic valve leaflets, and extent of their coaptation were analyzed by direct endoscopic view and by ultrasound imaging techniques.

Results: Pressurizing unwrapped aortic root resulted in centrifugal displacement of commissures, aortic leaflets tethering and bending, and central aortic regurgitation. By reducing STJ size, coaptation height of aortic valve leaflets first increased to reach a maximum for an STJ size corresponding to 30 mm, and then decreased for further reduction of STJ size. Excess reduction of STJ size also resulted in prolapsed aortic leaflets and eccentric aortic regurgitation.

Conclusions: In the reimplantation procedure performed with a Valsalva graft, aortic valve function and leaflet coaptation can be optimized by optimizing STJ size.

Aneurysms or dissection of the aortic root can severely impair aortic valve competence without affecting macroscopic appearance of the leaflets. On the basis of this finding, aortic valve–sparing surgical techniques to replace the aortic root and restore normal anatomic and possibly functional relationships between aortic root components have been developed in the last decade [1, 2].

Correct matching between native and synthetic aortic root components, which is crucial to achieve a good result in valve-sparing aortic surgery, relies predominantly on selection of the correct size of the graft used to replace the aortic root. Size of the graft determines size of the neosinotubular junction (STJ), which has a recognized role in determining aortic valve competence [3]. Formulas have been developed to adapt STJ size to both annulus diameter and average height and free edge length of aortic leaflets [4–8].

The objective of the present study is to evaluate the effect of changing the STJ size on aortic root geometry and aortic valve competence in pressurized neoaortic roots obtained by reimplanting porcine aortic roots into a synthetic graft with preformed sinuses of Valsalva.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
Porcine hearts procured from the local slaughterhouse were preserved with ice, transferred to our laboratory, and processed within 4 hours. Isolated aortic roots were obtained by the same technique commonly used for human homograft preservation, and only perfect valves with no fenestration and no regurgitation were accepted for the study. Aortic annulus diameter was sized by Hegar’s dilators; the height of the commissures and native STJ were sized by a clinical tape. Native sinuses of Valsalva were resected, valve remnants were trimmed to a final thickness of 2 to 3 mm, and the muscular septum and the anterior mitral valve leaflet were trimmed to a minimum.

Six 25-mm porcine aortic roots were implanted into 32-mm Valsalva grafts (Vascutek, Renfrewshire, Scotland). The graft consists of three segments joined together: the collar with horizontal corrugations, the skirt with radially expandable vertical corrugations, and the body with horizontal corrugations (Fig 1). The annulus is located at the joint between the collar and the skirt, and the STJ is located at the joint between the skirt and the body of the graft. In a 32-mm graft they both measure 32 mm. Sinotubular junction height of the graft equals, by design, the diameter of the graft itself; in other words, the STJ of a 32-mm graft is located 32 mm above the annulus. In a 32-mm Valsalva graft (Vascutek), size of the fully expanded skirt is about 40 mm. Interrupted mattress 2-0 Ethibond (Ethicon, Somerville, NJ) sutures were used to fix, on a straight nonscalloped line, the "aortic annulus" to the graft annulus. Sutures were tied on a 25-mm Hegar’s dilator to achieve a constant aortic annulus size of 25 mm. The commissures were then suspended in the expandable portion of the graft by mattress 4-0 polypropylene sutures, and the sinus remnants were fixed to neosinuses by 5-0 polypropylene running sutures. Commissural height of porcine valves used in this study was 19.7 ± 3.7 mm. Owing to this mismatch in STJ height, it was always possible to implant the neocommissural ridge of porcine roots into the expandable portion of the graft, obtaining a pathologically oversized STJ size.


Figure 1
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  		Fig 1. The Valsalva graft is illustrated. The graft is formed by three units: the bottom portion with horizontal corrugations is called the collar; the central portion with vertical corrugations that allow radial expansion under pressure and mimics the sinuses of Valsalva is called the skirt, and the upper portion with horizontal corrugations is the body of the graft. The junction between the collar and the skirt is the aortic annulus, and the junction between the skirt and the body is the sinotubular junction. In a 32-mm Valsalva graft they both measure 32 mm.

 
Neoaortic roots were immersed in a saline bath at a constant temperature of 37°C and mounted in the test circuit illustrated in Figure 2. A centrifugal pump-driven (Bio-Medicus, Minneapolis, MN) perfusion circuit (Carmeda Bioactive Surface; Medtronic, Minneapolis, MN) was primed with saline solution, and its arterial branch was connected to a Y-shaped cannula commonly used for port-access procedures (Ethicon Cardiovations, Somerville, NJ). The Y cannula was modified by inverting the barbed tubing connection site with the hemostasis valve, the side branch of the Y cannula was used for tubing connection, and the hemostasis valve was used to insert a 4.0-mm zero-degree endoscope (Wolf Medical Instruments Corp, Vernon Hills, IL), connected to a Teknocam 3000 P camera (Teknomedical, Tuttlingen, Germany), into the cannula.


Figure 2
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  		Fig 2. The test circuit. See text for description. (B = basin; CP = centrifugal pump; E = endoscope; echo = echocardiography equipment; M/V = display monitor and video recording; P = echocardiography probe; PC = personal computer for off-line image analysis; PM = pressure monitoring; VG = Valsalva graft; YC = y cannula.)

 
Neoaortic roots were joined to the cannula by a properly designed connector. Aortic root grafts were instrumented by a pressure-monitoring set (Truware PX-600; Edwards Lifesciences, Irvine, CA) for continuous pressure monitoring (Hewlett Packard Viridia 24 C, Boeblingen, Germany) and perfused to reach a constant internal graft pressure of 100 to 110 mm Hg. Saline recirculation through the circuit was ensured by the porosity of the graft and obtained by connecting the venous branch of the perfusion circuit to the basin.

The STJ was subsequently reduced by sequentially placing around the expandable portion of the graft, at the level of the reimplanted commissures, rings of polyethylene terephthalate fiber (Dacron) of decreasing size that, by preventing skirt expansion, realized a new STJ (Fig 3). Each aortic root was tested at basal STJ size and then at STJ sizes of 32, 30, and 28 mm.


Figure 3
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  		Fig 3. Method to reduce sinotubular junction size is illustrated. The implanted aortic root is pressurized (left), and sinotubular junction size is reduced by banding the neocommissural ridge with Dacron rings of decreasing size (center, right).

 
A qualitative appraisal of aortic leaflet coaptation in pressurized roots was made on images obtained by the endoscopic camera. Images were displayed online by a monitor (Sony, Tokyo, Japan) and recorded onto professional videotape (Panasonic AG5700E, Matsushita, Japan). Images of the coaptation profile of the valve were obtained at a pressure of 100 mm Hg and transferred to a personal computer for off-line analysis.

Long-axis and short-axis views of the aortic root were acquired by a 5.2-MHz ultrasound probe (C 3540; Philips, Bothell, WA) connected to a Sonos 5500 HP machine (Hewlett Packard, Andover, MA). Maximal sinus size, diameter of the neo-STJ, coaptation height, and coaptation level of aortic valve leaflets were measured. Diameter of the neo-STJ was measured at the internal plane connecting the three commissures; usually looking at them from the outside, this corresponds to the lower border of the ring as illustrated in Figure 3. Coaptation height was the distance along which aortic valve leaflets coapted, coaptation level was the distance between the aortic annulus plane and the superior edge plane of the aortic valve leaflets. The amount of aortic regurgitation was qualitatively assessed by direct visualization of the regurgitant jet and classified as mild (jet diameter < 2.0 mm), moderate (jet diameter 2 to 5 mm), and severe (jet diameter > 5 mm). Central or eccentric direction of the regurgitant jet was recorded.

Data entry was carried out directly at the time of experiment by two independent observers to minimize observation-related errors. No discrepancy was found in the double dataset process.

Measures are reported as mean ± standard deviation. Analysis of variance was applied first to assess individual differences between variables. The analysis was performed with Bonferroni, Duncan, and Tukey models, and all tests showed the existence of a significant difference in sinus dimension (p < 0.001), STJ dimension (p < 0.001), coaptation height (p < 0.01), and coaptation length (p < 0.01). One-tail homoscedastic Student’s t test was then performed to explore the difference between groups, as stated in Table 1. All statistical analyses were performed using SPSS Statistical Package 13.0 (SPSS Inc, Chicago, IL).


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  		Table 1 Effect of Sequential Wrapping Procedures on Aortic Root Geometry
 

   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
All valves were successfully mounted and instrumented in the test circuit. Effects of sequential wrapping maneuvers on aortic root geometry are reported in Table 1 and in Figure 4. A significant reduction of STJ size was achieved by wrapping, with a Dacron ring of the same size as the graft (32 mm), the neocommissural ridge. Dimension of sinuses significantly decreased from abnormal to normal range values. In the further steps of STJ reduction, a trivial reduction of the maximal sinus diameter was found.


Figure 4
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  		Fig 4. Aortic root dimensions according to sinotubular junction size for a 32-mm Valsalva graft. Effect of sinotubular junction size reduction on aortic root geometry. (SD = sinus dimension; STJD = sinotubular junction dimension.)

 
Progressive reduction of STJ size resulted in an increased height and decreased level of aortic valve leaflet coaptation; optimal values were obtained for an STJ of 30 mm. Further reduction of the STJ size resulted in prolapse of aortic valve leaflets and consequent reduction of both coaptation height and level (Fig 4, Table 1).

Aortic regurgitation was present at baseline, and its amount was significantly decreased when an STJ of 32 mm was realized, disappearing at an STJ of 30 mm. An eccentric aortic regurgitation was observed at an STJ of 28 mm.

At baseline a significant aortic regurgitation was associated with tethering and tilting of the free edge of aortic leaflets into the sinus (Fig 5A). When the STJ size was reduced to 32 mm, aortic leaflet tethering and bending improved but was still evident and associated with a mild aortic regurgitation (Fig 5B). Tethering, bending, and regurgitation disappeared at an STJ of 30 mm (Fig 5C).


Figure 5
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  		Fig 5. Coaptation profile of a 25-mm porcine aortic root implanted in a 32-mm Valsalva graft. (A) Without a sinotubular junction banding ring, commissures are displaced centrifugally, a central orifice is evident, and leaflet tethering and outward bending of the leaflet free margin are evident. (B) With a 32-mm sinotubular junction banding ring, the central orifice is reduced compared with A, and leaflet tethering and free margin bending are also reduced but not eliminated. (C) With a 30-mm sinotubular junction ring, the central orifice has disappeared, and leaflet coaptation is optimized.

 

   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
Results of the present study suggest that in the reimplantation procedure with a Valsalva graft, progressive reduction of the STJ size can be obtained by implanting the commissures in the skirt of the graft and by subsequently banding it with rings of decreasing size. Reduction of the STJ to a certain level results in optimization of the level and height of aortic leaflet coaptation. In our experiments with a 25-mm aortic valve, the maximal height of coaptation, which in fact reflects the amount of the leaflet surface involved in coaptation, was achieved for an STJ of 30 mm. Also, the level of coaptation, which reflects the distance between the aortic annulus plane and aortic leaflet edge plane, decreased to reach the ideal level, at the center of the sinuses, for the same value of STJ size. It should be noted that given a mean wall thickness of the porcine aortic root of 2 mm, 4 to 5 mm must be subtracted from the measured external diameter of the STJ to obtain the effective internal diameter of the STJ. In other words, the optimal ratio between the aortic annulus and the neo-STJ is approximately 1:1.

Sinotubular junction size plays a crucial role in the optimization of aortic valve competence after aortic valve reimplantation procedures but could also affect durability of the repair. An STJ size bigger than needed in fact was invariably associated with tethering and bending of the free margin of aortic leaflets, which reduced the coaptation reserve, causing valve regurgitation. Mild aortic regurgitation, clinically considered an acceptable result, was invariably associated with tethering and bending of aortic cusps (Fig 5A). Absence of aortic regurgitation or presence of a small regurgitant jet yields a good result if accompanied by a correct level and height of coaptation of the leaflets.

A considerable number of attempts to define standard rules for the correct sizing of the neo-STJ in valve-sparing aortic procedures have been made in the last several years. Kunzelman and colleagues [9] analyzed the mathematical relationship between normal nonpressurized human aortic root components and found that STJ and aortic valve annulus diameters are, respectively, 81% ± 2% and 97% ± 2% of the diameter at the sinus level. They described a formula to anticipate diameter of the neoaortic root at the sinus level based on measurement of the perimeter (the sum of the free margin length and of the attached edge length) and height of the aortic valve leaflets.

From the consideration that determination of graft size by measuring the various components of the aortic root is not entirely reliable, and that most patients with aortic root aneurysms have slightly elongated aortic cusps and may have a dilated aortic annulus, David and associates [4] suggested an empiric principle: the diameter of the aortic annulus and of the STJ should be similar and fixed to 1.5 to 1.6 times the average height of the cusps and 0.8 to 0.9 times the average length of their free margin. David [10] specified many times that these principles cannot be a substitute for experience and that more art than science is important to achieve a good result. In the Stanford modification [6, 11] of the so-called David V, a large graft is used to reimplant the aortic valve and to create pseudosinuses and a small graft is used to create a new STJ. The original David’s formula is used to calculate diameter of both grafts, and STJ size is predetermined [2].

A recent study showed that both free margin length and height of aortic valve leaflets may change parallel to aortic root dilatation [12] and that restoring annulus diameter, STJ diameter, and sinus height can be insufficient to restore aortic valve competence. From these results, a reference table has been proposed [8] to match dimensions of neoaortic root components.

Although mathematical models can help in selection of the graft, the final result derived from that model might not be fully predictable. If the model is wrong, or if it is incorrectly applied, the aortic valve has to be replaced. By our method the size of the STJ can be customized under transoesophageal echo guidance and fixed when an ideal level and height of coaptation are achieved and aortic regurgitation disappears. The adjustable STJ principle can represent the solution for both overestimation and underestimation of the neo-STJ, which can respectively result in a residual aortic regurgitation or improper coaptation level of the aortic valve leaflets [13]. Our results provide a scientific base for the adjustable STJ principle and support its clinical application [14, 15].

Another important aspect that comes from this experiment is that the optimal ratio between aortic annulus diameter and STJ diameter in a reconstructed aortic root is 1:1. Because the Valsalva graft has, by design, a proportion of 1:1 between the annulus and the STJ (Fig 1), a simple method of sizing can be considered. In fact by adding 5 mm to the size of the annulus, the correct graft size is selected (eg, 30 mm for a 25-mm aortic valve, as in our experiment). The collar of the graft is trimmed to a minimum (right at the junction between the collar and the skirt), and annular sutures are placed. At that point the surgeon needs only to correctly place the commissures at the level of the STJ (30 mm for a 30-mm graft) to obtain the best result.

This is an in vitro study based on static pressurization of isolated fresh porcine aortic roots. Pulsatile flow would probably have magnified tilting of aortic leaflets and regurgitation amount [16].


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Sarsam MAI, Yacoub M. Remodeling of the aortic valve anulus J Thorac Cardiovasc Surg 1993;105:435-438.[Abstract]
  2. David TE, Feindel CM. An aortic valve-sparing operation for patients with aortic incompetence and aneurysm of the ascending aorta J Thorac Cardiovasc Surg 1992;103:617-622.[Abstract]
  3. Furukawa K, Ohteki H, Cao Z, et al. Does dilatation of the sinotubular junction cause aortic regurgitation? Ann Thorac Surg 1999;68:949-954.[Abstract/Free Full Text]
  4. David TE, Ivanon J, Armstrong S, Feindel CM, Webb GD. Aortic valve-sparing operations in patients with aneurysm of the aortic root or ascending aorta Ann Thorac Surg 2002;74(Suppl):S1758-S1761.[Abstract/Free Full Text]
  5. Svensson LG. Sizing for modified David’s reimplantation procedure Ann Thorac Surg 2003;76:1751-1753.[Abstract/Free Full Text]
  6. Demers P, Miller DC. Simple modification of "T.David-V" valve sparing aortic root replacement to create graft pseudosinuses Ann Thorac Surg 2004;78:1479-1481.[Abstract/Free Full Text]
  7. Gleason TG. New graft formulation and modification of the David reimplantation technique J Thorac Cardiovasc Surg 2005;130:601-603.[Free Full Text]
  8. Labrosse MR, Beller CJ, Robicsek F, Thubrikar MJ. Geometric modeling of functional trileaflet aortic valves: development and clinical applications J Biomech 2006;39:2665-2672.[Medline]
  9. Kunzelmann KS, Grande J, David TE, Cochran RP, Verrier ED. Aortic root and valve relationships: impact on surgical repair J Thorac Cardiovasc Surg 1994;107:162-170.[Abstract/Free Full Text]
  10. David TE. Aortic valve-sparing operations Ann Thorac Surg 2002;73:1029-1030.[Free Full Text]
  11. Miller DC. Valve-sparing aortic root replacement in patients with the Marfan syndrome J Thorac Cardiovasc Surg 2003;125:773-778.[Free Full Text]
  12. Thubrikar MJ, Labrosse MR, Zehr KJ, Robicsek F, Gong GG, Fowler BL. Aortic root dilatation may alter the dimensions of the valve leaflets Eur J Cardiothorac Surg 2005;28:850-856.[Abstract/Free Full Text]
  13. Pethig K, Milz A, Hagl C, Harringer W, Haverich A. Aortic valve reimplantation in ascending aortic aneurysm: risk factors for early graft failure Ann Thorac Surg 2002;73:29-33.[Abstract/Free Full Text]
  14. Maselli D, Minzioni G. A technique to reposition sinotubular junction in aortic valve reimplantation procedures with the De Paulis Valsalva graft Eur J Cardiothorac Surg 2006;29:107-109.[Abstract/Free Full Text]
  15. Maselli D, Guarracino F, Bajona P, Bellieni L, Minzioni G. Adjustable sinotubular junction for aortic valve reimplantation procedures Ann Thorac Surg 2007;83:700-702.[Abstract/Free Full Text]
  16. Nötzold A, Scharfschwerdt M, Thiede L, Hüppe M, Sievers H. In-vitro study on the relationship between progressive sinotubular junction dilatation and aortic regurgitation for several stentless aortic valve substitutes Eur J Cardiothorac Surg 2005;27:90-93.[Abstract/Free Full Text]



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This Article
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Right arrow Author home page(s):
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Andrea Salica
Alessandro Ricci
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