Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3711_Библиотеки_им_академика_М_И_Перельмана

The three leaets of the aortic valve are attached to the aor­toventricular junction. The collagenous condensation at the point of attachment of each leaet has been termed the annu­lus brosis. There is, however, no true “ring” of the annular tissue supporting the leaets in a straight circular plane. The hemodynamic stresses on the leaets, therefore, are counter­acted at several structural levels. The margin of coaptation of a competent valve is more than a nite point of contact. It extends along the whole margin of the leaet in length and several millimeters in depth. Beneath the apices formed by leaet attachment, the so-called commissures, there are sub­commissural or interleaet triangles. The wide base of these triangles follows the ventricular contraction pattern and allows optimal retraction of leaets during systole. The sino­tubular bar marks the junction with the ascending aorta. It is thicker than the adjacent sinuses. It is circular with areas of increased collagen. It acts as a suspension post that supports the peripheral attachments (the commissures) of the valve leaets. The parabolic shape of the leaets resembles a sus­pension bridge. Their attachments to the sinotubular bar are several millimeters above the level of coaptation. As these support poles stretch outward by as much as 16–44% during early systole, the leaet edges (the cables) become straighter, aiding in the opening of the valve.

The aortic root is also a complex hemodynamic system. Its component parts change in size and shape during the car­diac cycle. Its distal portion is exposed to the aortic pressure. It expands to allow leaet retraction. Its base is exposed to ventricular dynamics. It contracts during the peak of systole to decrease the distance the leaets have to close and to reduce the stress forces applied to leaets in early diastole.

In type I, there is no median raphe at the junction of two cusps. As a result, there are two rather symmetric aortic sinuses and leaet base attachment. The valve orice is cen­tral. The commissural triangle is rather well developed. The leaets are suspended at the sinotubular bar and have ade­quate depth. In type II, which is more prevalent, a median raphe is present. The cusps are asymmetric, and the fused leaet is longer and shallower and takes up more of the cir­cumference of the valve. In contrast to the normal tricuspid valve, the leaet edges are excessive and sagging. As a result, there is increased folding and crossing and a compensatory extension of the area of leaet approximation from their edges (doming). The opening of the valve is eccentric due to discrepancy in leaet sizes. The orice also has an elliptical rather than a circular opening. The resultant distortion in blood ow pattern exaggerates turbulence and predisposes to degenerative changes. Frequently, there is commissural fusion that limits the leaet movement and exaggerates the eccentricity of valve opening and the decrease in its effective orice diameter. The narrowed opening, often combined with annular hypoplasia, impairs the ability of the leaets to escape systolic or diastolic pressure load, further exaggerat­ing the stress on the valve. The subcommissural triangle is severely attenuated. It limits leaet movement in early sys­tole and the change in orice conguration necessary for appropriate leaet coaptation at the end of systole. The leaf­let edges are suspended below the sinotubular bar. This, combined with redundant leaet edges, results in shallow sinuses, decreases coaptation area, and exaggerates leaet­deforming dynamic forces [3].

To achieve optimal short- and long-term results, surgical intervention should be timed appropriately. The decision relies on achieving the goals of valve surgery, which include relief of symptoms, restoration of exercise capacity, improved quality of life, and, most importantly, protection of the myo­cardium from chronic pressure and/or volume overload. Most of the reported guidelines for the timing of valve surgery are based on studies that use mortality rates as a

The introduction of and renement in valvuloplasty tech­niques has prompted critical evaluation of these older guide­lines for timing of surgical intervention on the diseased aortic valve. The availability of a surgical alternative that avoids valve replacement or anticoagulation has liberalized the older rigid criteria [4]. Although large-scale, long-term data on repaired valves are not available, there is unquestionable evidence that valvuloplasty extends the functional longevity of the native aortic valve and may safely delay the need for replacement, thus justifying earlier surgical intervention. Waiting for symptoms to appear or for ejection fraction to decrease prolongs the duration of ventricular pressure and volume overload and may lead to irreversible ventricular dysfunction [5].

3. Reconstructive steps should be preceded by relief of

4. Isolated repair of only one leaet or cusp without

7. Centralizing blood ow through the valve decreases tur­bulence and extends the longevity of the repair; there­fore, tricuspidization of the valve is advantageous when possible.

11. Realization that there is a dynamic interplay between the valve and the aortic root that is essential for valve func­tion has refocused attention on the importance of repair­ing all the root components, namely, the annulus, the sinus, the cusps, and the sinotubular junction.

All valvuloplasties are performed through an oblique aor­totomy above the sinotubular bar. Antegrade and retrograde blood cardioplegia is used. Placement of commissural sutures aids exposure. Axial traction (perpendicular to the annulus plane) applied to the commissural sutures allows assessment of the valve leaets and annulus. In addition, a centrally placed suture helps in evaluating the structure, the deciency, and the redundancy of the different cusps by trac­tion on the suture and pushing the leaets gently toward the ventricle.

In regurgitant valves, there is a variable degree of annular dilatation that is accelerated in patients with bicuspid valves or distorted septo-aortic angle. Signicant dilatation (Z≥+

Management of the dilated sinus consists of sinus wall plica­tion at mid-distance between the involved two commissures. In occasional cases, when the valve opening is not at the cen­ter, asymmetric plication may centralize blood ow through the valve. Severe dilatation of the sinuses may necessitate reduction of the sinus wall by resection of a triangular piece [10] (Fig. 36.3). Restrictive sinus wall, on the other hand, limits cusp movement, attenuates the Eddie currents, and leads to dysplasia of the leaet. Management consists of sinus enlargement with a triangular patch (Fig. 36.1). The

There is no ideal patch material. Several commercially available patches have been used. Most of these, however, develop brosis and calcication, limiting the functional life of the valvuloplasty. Autologous pericardial patient debrided thoroughly from all fat and adventitial tissue, treated with glutaraldehyde 0.625% for 2minutes and rinsed thoroughly has proven to be the best option.

Management of dilated sinotubular junction is plication at the intercommissural point. It is tightened until the junction­to- annulus diameter ratio is 1.3:1 or the normal diameter pre­dicted from nomograms is achieved. Another approach is to reduce the diameter of the ascending aorta at the dilated junction by resecting a triangular piece of the aortic wall. Anastomosis to reestablish aortic continuity is reinforced with a circular pericardial strip (Fig.36.9) [17].

The techniques of aortic valvuloplasty are in evolution. Several series have reported results using one or more of the techniques mentioned here. None of these results, however, reects the present knowledge of the surgical anatomy or the outcome of valve repair when these technical steps are used in combination.

A review of our total experience with these different approaches revealed a signicant drop in pressure gradient across the valve, a decrease in aortic regurgitation as judged by grade and by ratio of the regurgitant jet to aortic annulus diameter, and a decrease in indexed left ventricular end­diastolic volumes [20].