Morphology of the ventriculoaortic junction in critical aortic stenosis. Implications for hemodynamic function and clinical management.

The clinical presentation of infants with critical aortic stenosis, as well as the results of surgical treatment, differs from obstruction of the left ventricular outflow tract in older children. To investigate a possible anatomic basis for this situation, we performed a detailed morphometric study of 21 hearts from infants who had critical aortic stenosis and 11 normal hearts from infants less than 3 months of age. In each of the hearts with critical aortic stenosis, only one commissure extended to the sinutubular ridge. The other two commissures were represented by folds in the aortic wall that suspended the leaflet below the level of the sinutubular junction. The leaflet thus had a free edge shorter than the circumference of the sinus, in contrast with the normal valve, in which leaflets always were longer than the circumference of their supporting sinus. Analysis of the fibrous triangles on the ventricular aspect of abnormal valves showed a symmetric three-sinus arrangement. In all but one specimen, however, only the triangle related to the mitral valve was fully developed. Although incision of both rudimentary commissures to the aortic wall should achieve some relief of obstruction, these morphologic features strongly mitigate against surgical restoration of normal function or growth in aortic valves having the morphology observed in this series of hearts.     

The morphology of the normal aortic valve as compared with the aortic valve having two leaflets

We studied 30 normal aortic valves and 64 aortic valves with only two leaflets to examine their morphologic components. The components of the aortic valve are the leaflets, the sinuses, and the interleaflet triangles. The first part of our study shows the relationship of these component parts of the normal aortic valve to the other cardiac structures. The second part shows a wide variation in the architecture of valves having two leaflets. Having produced criteria for the number of sinuses and the number of leaflets, we discovered that previous criteria used in the definition of valves with two leaflets are inadequate when the whole valvular complex is considered. Only seven valves in the study have two leaflets supported by two sinuses. The evidence points to the other valves having started with three leaflets but becoming bicuspid during either intrauterine or postnatal life.     

Extensive aneurysms of sinuses of Valsalva precluding valve sparing aortic root reimplantation (David procedure)

A 55-year-old female noticed worsening exertional dyspnoea for two years. She was born with cleft palate and profound deafness. Significant physical findings included dysmorphism with micrognathia and acrocephaly and congenital deafness. Transthoracic echocardiogram revealed aneurysms involving the right and the non-coronary sinuses of Valsalva. Despite that, the native aortic valve retained preserved geometry. Computed tomography (CT)-scan demonstrated multiple aneurysms arising from all three sinuses of Valsalva. This displaced the right ventricle (RV) caudally and indented the RV outflow tract. A valve-sparing root reimplantation was planned. However, intraoperatively the root aneurysms were found to be very extensive such that no healthy tissue remained along the insertion lines of the aortic valve leaflets. The aortic annulus was not dilated (2 cm) and the left ventricular outlow tract was not involved in the disease process. Consequently, despite the presence of macroscopically normal leaflets and relatively undisturbed annular geometry, we were unable to reimplant the native aortic valve and proceeded to a modified Bentall procedure. Histologically, significant medial degeneration with loss of elastin and muscle was identified in the aortic sinus wall. Similar changes were also found affecting the native leaflets coupled with increased fibrous thickening.     

Aortic Valve Replacement with Stentless Porcine Bioprostheses

The implantation of stentless porcine valves (SPVs) is technically more demanding than implantation of stented bioprosthetic valves. Implantation of the Toronto SPV bioprosthesis requires an,understanding of the relationships between the leaflets and the aortic annulus and sinotubular junction. In addition to proper alignment of the three commissures within the aortic root, the diameter of sinotubular junction should not exceed the external diameter of the porcine aortic valve after completion of the operation. The Medtronic Freestyle porcine aortic root bioprosthesis can be used for subcoronary implantation as well as for aortic root replacement. Degenerative calcification of a tricuspid aortic valve is the most common cause of aortic valve disease in older patients. Implantation of stentless valves in the subcoronary position is usually feasible because the geometry of the aortic root is well maintained in these patients. The bicuspid aortic valve is the second most common cause of aortic valve disease in older patients and the most common in younger patients. These patients frequently have dilated aortic root, and the Medtronic Freestyle bioprosthesis is ideal for implantation using the root inclusion technique. Stentless porcine bioprostheses are minimally obstructive and associated with low mean systolic gradients. In addition, they have better hemodynamic performance during exercise than stented bioprostheses. For these reasons, patient-prosthesis mismatch has not been described with stentless valves. Left ventricular function after aortic valve replacement appears to be better with stentless than with stented bioprostheses. Comparative, nonrandomized studies of aortic valve replacement with stented and stentless valves suggest that the risk of cardiac death is reduced with stentless valves and the rates of valve-related complications also appear to be lower. What remains unknown is whether stentless valves are more durable than stented ones.     

Variations within the fibrous skeleton and ventricular outflow tracts in tetralogy of Fallot

We studied 20 hearts with tetralogy of Fallot with particular reference to the morphology of the fibrous continuity between the aortic and atrioventricular valves and of the ventricular outflow tracts. The extent of valvar fibrous continuity varied with the degree of aortic override, with the extent of the perimembranous ventricular septal defect opening between the ventricular inlets, and with the development of the ventriculoinfundibular fold. This, when fused with the septomarginal trabeculation, produced discontinuity between the leaflets of the tricuspid valve and the continuous leaflets of the aortic and mitral valves, as well as a muscular posteroinferior rim to the defect. Rotation of the aortic root ranged through 119 degrees. Aortic override varied from 33% to 94%, with 35% of these hearts having more than half of the aortic circumference connected to the right ventricle. The pulmonary valves had three leaflets in 50%, two leaflets in 45%, and four leaflets in one (5%). All hearts had two main coronary arterial orifices, 45% of which were atypical in location. One heart displayed a transmural course of the left coronary artery arising from the nonfacing sinus. By measurement, the subpulmonary length was, on average, roughly 50% greater than the subaortic length, and, when the selected hearts were sectioned, much of the subpulmonary infundibulum was found to be composed of free-standing musculature rather than true outlet septum. The proportion of total right ventricular length represented by the infundibulum was 0.31 +/- 0.07, confirming that, compared with that of normal hearts, the narrowed infundibulum in tetralogy is longer rather than shorter.     

Sorin Solo stentless valve: extended adaptability for sinotubular junction mismatch

Stentless valve continence is affected by the implantation technique, annular symmetry and dilatation of the sinotubular junction. We tested in vitro how the Sorin Solo stentless pericardial valve adapts to a slightly dilated sinotubular junction. Stentless Sorin Solo aortic valves (25 mm) were sutured into a 32-mm Valsalva graft suspending the commissures into the expandable region of the graft. The neo-aortic root was pressurized and sinotubular junction size progressively decreased by wrapping the neocommissural ridge with Dacron rings. Direct endoscopic view and ultrasound imaging were used to observe geometry and morphology of leaflets, regurgitation, height and level of leaflets coaptation. Fresh porcine valves of the same annular size were used as controls. Solo valves had mild regurgitation at baseline, became continent at 32 mm sinotubular junction size and remained continent at any size of reduction, with optimal coaptation height and level. Porcine valves had severe regurgitation at baseline, became continent at 30 mm and showed mild insufficiency and reduction of the coaptation level at a sinotubular junction of 28 mm. The Solo valve prevents residual valve regurgitation for a wider range of sinotubular junction mismatch when compared with natural porcine valves. This extended tolerance to sinotubular junction mismatch suggests a safe use of stentless valves even in suboptimal geometry roots.     

Coronary arterial and sinusal anatomy in hearts with a common arterial trunk

Eighty-four specimens of common arterial trunk were studied with special reference to the arrangement of the leaflets in relation to the atrioventricular valves, the origin of the coronary arteries in relation to the arterial sinuses, and the epicardial course of the coronary arteries. Fourteen normal hearts were used for comparison. In the hearts with common arterial trunk, the location and level of the coronary artery orifices (as well as the relationship of the truncal root to the area of fibrous continuity with the mitral valve) are different from those in normal hearts. In none of the hearts with common arterial trunk (particularly the 53 hearts with three leaflets in the truncal valve) did the appearance of the truncal valve approximate that of a normal aortic valve. Among the 22 hearts with four leaflets, there was a high incidence of coronary artery orifices in opposite sinuses (17/22 or 77.3%) and a low incidence of coronary artery orifices in adjacent sinuses (2/22 or 9.1%). These results suggest that the formation of the truncal valve is independent of the formation of the coronary orifices. Its leaflets are not predestined to become part of either the aortic valve or the pulmonary valve.     

An aortic valve-sparing operation for patients with aortic incompetence and aneurysm of the ascending aorta.

A number of patients who require an operation for complications of annuloaortic ectasia, such as aortic incompetence or aneurysm of the aortic root (or both), have normal aortic valve leaflets. We have treated these patients by excising the aneurysmal portion of the ascending aorta and sinuses of Valsalva but by leaving the aortic valve leaflets and some arterial wall attached to the left ventricular outflow tract. The aortic valve is reimplanted inside a collagen-impregnated tubular Dacron graft, similar to what is done for implantation of an aortic valve homograft. The coronary arteries are also reimplanted. This operation was performed in 10 patients. All patients had annuloaortic ectasia and five had the stigmata of Marfan syndrome. Four patients had acute aortic dissection. There were no operative deaths, but one patient required composite replacement of the aortic valve and ascending aorta because of persistent aortic incompetence. Postoperative Doppler echocardiography revealed normal aortic valve function in six patients and mild incompetence in three. The preliminary results of this new operation are encouraging. Further investigation is necessary to establish the best size, shape, and type of material that should be used to replace the aortic root while preserving the aortic valve.     

主动脉根部外科解剖及其与毗邻结构关系

目的：测量主动脉根部不同高度的口径大小，并观察主动脉窦与邻近结构的关系。方法：用30例正常成人甲醛固定心脏标本，测量主动脉根部不同高度的口径和主动脉瓣的大小，观察主动脉窦与邻近结构的关系。结果：（1）主动脉窦中部（Sinus)＞主动脉窦管结合部上1cm(STJ1)＞主动脉窦管结合处（STJ0）＞主动脉瓣环基底（Base）。经方差分析检验，P＜0．05，说明主动脉根部4个高度口径大小的差别具统计学意义。（2）主动脉瓣的瓣高、瓣附着缘长和瓣游离缘长的测量结果显示。（3）二尖瓣前瓣中轴线与主动脉窦的关系显示，二尖瓣前瓣中轴线86．6％位于左冠状动脉窦与无冠状动脉窦之间。（4）右心房主动脉隆凸与主动脉窦的关系显示，右心房主动脉隆凸由无冠状动脉窦形成者占73．3％，由无冠状动脉窦和右冠状动脉窦共同形成者占26．7％。（5）左、右肺动脉瓣交界点与主动脉窦的关系显示，左、右肺动脉瓣交界点对向左、右冠状动脉窦之间者占80％。结论：测量结果有助于心外科手术的开展。     

Aortic root dilatation may alter the dimensions of the valve leaflets

Objective: Valve-sparing surgery can be used in patients with dilated aortic roots and aortic insufficiency (AI) but has not become a common practice, in part because the spared valve may be incompetent. Our goal was to study how the dimensions of the aortic root and leaflets have changed in such patients. Methods: Fourteen patients with dilated aortic root and AI were examined by transesophageal echocardiography. The annulus diameter, sinotubular junction (STJ) diameter, sinus height, leaflet free-edge length, and leaflet height were measured. Correlations among these dimensions and with the AI grades were explored. Measurements were also made in 19 normal human aortic valves from silicone molds. Results: There was no evident change in the average diameter of the annulus between the normal valves and those in the dilated aortic roots. The STJ diameter was obviously increased in the dilated aortic roots; the aortic sinuses also appeared to be taller and the leaflets larger than normal. The leaflet free-edge length, the leaflet height, and the sinus height were found to increase with the dilated STJ diameter. The degree of AI was not found to correlate well with any of the dimensions measured. Conclusions: The dimensions of the leaflets may change parallel to aortic root dilatation with AI. Therefore, during valve sparing, it may be necessary to correct both the dilatation of the root and the leaflet free-edge length to achieve a competent valve.     

Comparison of biomechanical and structural properties between human aortic and pulmonary valve.

OBJECTIVE: Pulmonary valve autografts have been reported as clinically effective for replacement of diseased aortic valve (Ross procedure). Published data about pulmonary valve mechanical and structural suitability as a long-term substitute for aortic valve are limited. The aim of this study was to compare aortic and pulmonary valve properties. METHODS: Experimental studies of biomechanical properties and structure of aortic and pulmonary valves were carried out on pathologically unchanged human heart valves, collected from 11 cadaveric hearts. Biomechanical properties of 84 specimens (all valve elements: cusps, fibrous ring, commissures, sinotubular junction, sinuses) were investigated using uniaxial tensile tests. Ultrastructure was studied using transmission and scanning electron microscopy. RESULTS: Ultimate stress in circumferential direction for pulmonary valve cusps is higher than for aortic valve (2.78+/-1.05 and 1.74+/-0.29 MPa, respectively). Ultimate stress in radial direction for pulmonary and aortic cusps is practically the same (0.29+/-0.06 and 0.32+/-0.04 MPa, respectively). In ultrastructural study, different layout and density in each construction element are determined. The aortic and pulmonary valves have common ultrastructural properties. CONCLUSIONS: Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.     

Cause of degenerative disease of the trileaflet aortic valve: review of subject and presentation of a new theory

Risk factors for both atherosclerotic aortic wall disease and degenerative disease of the trileaflet aortic valve are very similar if not identical. This correlation grows even stronger as the person advances in years. Because of this, it is the prevailing view that sclerosis of the trileaflet aortic valve, unless previously affected by septic or rheumatic endocarditis, is a disease similar in origin to sclerosis of the aortic wall, ie, degenerative aortic valve disease is arteriosclerosis of the aortic valve. Our studies challenge these views. The aortic valve is a functional assembly composed of the three cusps, corresponding sinuses, and the sino-tubular junction, characterized not only by morphologic features but also by its functional properties, which together create an environment that is optimal for distribution of diastolic pressure load and assures proper and timely valve opening and closure. Our more recent experiments also demonstrate that loss of aortic wall compliance at the level of the sinuses leads to significant stress-overload on the aortic leaflets and it is likely to start a chain of events, which begins with minor changes in their microstructure, then continues in more evident sclerosis, and finally ends in gross distortion or calcification of the cusps. The loss of the "pull-and-release" process may also play a part in disintegration of bioprosthetic valves and in degeneration of native aortic valves encased in noncompliant prostheses.     

Acquired supravalvular aortic stenosis.

Severe supravalvular aortic stenosis was discovered at reoperation in 3 children with recurrent stenosis of the left ventricular outflow tract. The lesion consisted of gross thickening of the sinus ridge, most marked at the site of the previous aortotomy. The thickening had shortened the free edge of one or more leaflets and had distorted adjacent commissures. Preoperative angiography had indicated valve stenosis, but little commissural fusion was found at operation and the outflow tract obstruction was relieved by inserting a prosthetic patch in the ascending aorta. Recognition of this iatrogenic pathology is important to avoid supravalvular stenosis after aortic valvotomy and unnecessary valve replacement in children requiring reoperation for recurrent left ventricular outflow tract obstruction.     

Clinical introduction of a novel prosthesis for valve-preserving aortic root reconstruction for annuloaortic ectasia

OBJECTIVE: Most patients with annuloaortic ectasia are young. They are at risk for complications related to a lifetime of anticoagulation when composite grafts containing mechanical valves are used for reconstruction. The majority of patients have near normal valve cusps. Valve-preserving techniques have been developed to maintain valve function and avoid anticoagulation. The eddy currents occurring within the sinuses of Valsalva in the natural aortic root have been shown to be important in the smooth, gradual, and gentle closure of the valve. Compliance of the sinuses is important in reducing stress in the leaflets. A novel ascending aortic prosthesis with "built in" compliant sinuses (Robicsek-Thubrikar graft) was developed for clinical aortic root replacement. METHODS: Woven Dacron tubes were used to make the prostheses. Three precisely measured square pieces were cut to make the expandable, individual sinuses. Sewing the individual neo-sinuses to a scalloped end of the Dacron tube graft created the neo-sinotubular junction and sinotubular ridge. Five patients with annuloaortic ectasia underwent valve-preserving aortic root reconstruction. RESULTS: All intraoperative transesophageal echocardiographic images after the valve-preserving procedure showed a normal appearing root with 10% radial expansion of each sinus in systole. The space between the cusps and neo-sinus wall in systole was normal. No patient has more than mild aortic regurgitation. CONCLUSIONS: Valve-preserving aortic root reconstruction with a novel Dacron prosthesis with compliant "built in" sinuses re-establishes normal aortic root geometry with near normal valve motion. This may enhance the durability of the valve-preserving operation.     

Mechanical Stress as Cause of Aortic Valve Disease Presentation of a New Aortic Root Prosthesis

We present an overview of studies on the aortic valve and propose that mechanical stress is a main causative factor in the degenerative valvular disease. In the normal aortic valve, the leaflets have a smooth surface, free of wrinkles and creases, throughout the opening process. This smooth leaflet surface during motion is achieved by the “pull and release” movement of the commissures, which occurs because of the compliance of the aortic root. When the aortic root is stiffened, either by artificial means or by the loss of elasticity due to aging, the leaflet dynamics change significantly. The leaflets develop a significant number of creases and wrinkles during the opening process. In the bileaflet valve, the leaflets develop similar creasing and wrinkling during the opening process. This happens mainly due to the less-than-ideal design of the bileaflet valve and in spite of the compliant aortic root. When the aortic valve is spared using a noncompliant tube graft, a similar phenomenon of leaflet creasing occurs. Because the creasing produces high stresses from bending and buckling, it is damaging to the leaflet tissue and can lead to degenerative and calcific valvular disease. Based on these observations a new aortic root prosthesis with compliant sinuses has been designed for the valve sparing operation.     

Mechanical stress as cause of aortic valve disease. Presentation of a new aortic root prosthesis

We present an overview of studies on the aortic valve and propose that mechanical stress is a main causative factor in the degenerative valvular disease. In the normal aortic valve, the leaflets have a smooth surface, free of wrinkles and creases, throughout the opening process. This smooth leaflet surface during motion is achieved by the "pull and release" movement of the commissures, which occurs because of the compliance of the aortic root. When the aortic root is stiffened, either by artificial means or by the loss of elasticity due to aging, the leaflet dynamics change significantly. The leaflets develop a significant number of creases and wrinkles during the opening process. In the bileaflet valve, the leaflets develop similar creasing and wrinkling during the opening process. This happens mainly due to the less-than-ideal design of the bileaflet valve and in spite of the compliant aortic root. When the aortic valve is spared using a noncompliant tube graft, a similar phenomenon of leaflet creasing occurs. Because the creasing produces high stresses from bending and buckling, it is damaging to the leaflet tissue and can lead to degenerative and calcific valvular disease. Based on these observations a new aortic root prosthesis with compliant sinuses has been designed for the valve sparing operation.     

The mechanism of opening of the aortic valve.

The mechanism of opening of the aortic valve was investigated in dogs by attaching radiopaque markers to the commissures and the leaflets. Analysis of abnormal cardiac cycles demonstrated that, when the ventricular pressure first equalled the aortic pressure, the intercomissural distances increased 9 percent, and the valve opened with a stellate orifice without forward flow and without a rise in aortic pressure. Further opening of the aortic valve was dependent on forward flow over a narrow range. A new mechanism of aortic valve opening is proposed. This mechanism results in minimal flexion stresses on the leaflets and is important for the longevity of the normal aortic valve. It can occur only if the leaflets arise from an expansile aortic root.     

A four-dimensional study of the aortic root dynamics.

OBJECTIVE: Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200Hz) has made time-related 4-D study possible. METHODS: Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. RESULTS: During the cardiac cycle, aortic root volume increased by mean+/-1 standard error of the mean (SEM) 33.7+/-2.7%, with 36.7+/-3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (-2.6+/-0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3+/-2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6+/-2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2+/-2.5%) because most of the significant changes occurred at commissural level (63.7+/-3.6%). CONCLUSION: Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.