Degenerative valvular diseases are the main cause of mitral valve dysfunction in developed countries today and the “pain quotidien” *
* See Glossary .
of the valvular surgeon. They are also the source of regrettable confusion; this is because they are often grouped under the general term “mitral valve prolapse,” which for some authors defines a specific disease, for others a group of several diseases, and for even others a valvular dysfunction. In fact, there are several types of degenerative valvular diseases that can be identified by their clinical and pathological characteristics. Their detection is also possible by echocardiography, although secondary lesions may hide the more characteristic primary lesions. During surgery, the surgeon has the opportunity to examine the entire valve and to confront his or her morphological analysis with the clinical and echocardiographic findings. The three main types of degenerative valvular diseases are Barlow’s disease, fibroelastic deficiency, and Marfan’s disease ( Table 26-1 ).| Barlow | Marfan | Fibroelastic Deficiency | |
|---|---|---|---|
| Age at Diagnosis | <50 years | <50 years | >50 years |
| Genetics | Dominant autosomic transmission | Dominant autosomic transmission | None |
| Patient Characteristics | Normal | Tall stature | Normal |
| Arachnodactylia | |||
| Visual dysfunction | |||
| Interval between Diagnosis and Operation | >10 years | >5 years | <5 years |
| Functional Type | II | I or II | II |
| Valve Morphology: | |||
| Annular dilatation | + + + | + + + | + |
| Leaflets | Thickened ++ | Thickened + | Thin |
| Excess tissue +++ | Excess tissue + + | No excess tissue | |
| Chordae | Heterogeneous | Thin + | Thin + + |
| Elongated | Elongated | Ruptured | |
| Histology: | |||
| Structure | Disorganized | Subnormal | Normal |
| Mucopolysaccharides | ↑↑↑ | ↑ | ↓↓ |
| Collagen | ↓↓ | ↓ | ↓↓ |
| Elastic fibers | ↓↓ | Fragmentation ++ | ↓ |
BARLOW’S DISEASE
Barlow’s disease is the most frequent degenerative valvular disease with a prevalence of 4% to 5% in the general population. Familial cases may be observed with autosomal dominant transmission. Association of this disease with sites of chromosomes 11, 13, and 16 has been described. This disease displays unique clinical and pathological characteristics, compared to other degenerative valvular diseases ( Table 26-1 ). The main clinical characteristic is a midsystolic click and/or a systolic apical murmur, first described by Cuffer and Barbillon. Both of these features were originally thought to be extracardiac until Reid postulated in 1961 that these two auscultatory features could be due to mitral regurgitation. Two years later, Barlow confirmed this hypothesis by left ventricular cineangiography and provided the first well-documented analysis of this disease that was originally believed to be of rheumatic origin. Mucoid degeneration producing billowing leaflets was actually found to be the main histochemical characteristic of the disease. Later, numerous new terms were introduced to describe the same abnormal morphology and dysfunction, such as excessive leaflet motion, mitral valve prolapse, billowing valve floppy valve, valve flail, or prolapsed leaflets. These terms contribute to the confusion in terminology that prevails today. For the sake of clarity, we prefer the term “Barlow’s disease”; this term has the advantage of recognizing the seminal contribution of the author while avoiding confusion with the term “prolapse,” which actually defines a leaflet dysfunction, not a specific disease stage. The term Barlow’s disease should be used exclusively in patients presenting with excess valvular tissue, billowing valves, and myxomatous degeneration whereas leaflet prolapse (type II dysfunction) should be employed to describe an overriding of the free edge of one or both leaflets above the plane of the mitral orifice during systole, a dysfunction that can be seen in other etiologies.
Clinical Presentation
The diagnosis of Barlow’s disease is usually established during the first 2 or 3 decades of life, during a routine clinical examination. It is more prevalent in women and may be diagnosed in a patient presenting with a variety of clinical symptoms, including chest discomfort, palpitations, fatigue and dyspnea (even in the absence of mitral valve regurgitation), neuropsychiatric complaints, and/or transient cerebral ischemia. The characteristic feature of these symptoms is their variability.
On physical examination, the most characteristic findings in Barlow’s disease are the midsystolic click believed to be due to excess valvular tissue. The midsystolic click is frequently followed by a late systolic murmur audible at the apex.
The electrocardiogram is usually normal but some patients may present with ST-T wave depression and/or T wave inversion in the inferior leads. These anomalies may only be observed during changes in position, such as sitting or standing.
The main complication is mitral valve regurgitation, which appears in about 5% of patients after several decades of disease progression. It is usually at this occasion that the patient is examined for the first time.
Echocardiography is the key diagnostic test used for determination of Barlow’s disease ( Fig. 26-1 ). The most characteristic feature is “ excess valvular tissue ” (a) with leaflet thickening predominant near the margin of the leaflets (b) . The excess tissue is responsible for the billowing of the bellies of the leaflets into the left atrium during systole (c) . The surface of coaptation of the leaflets is positioned at a higher level than normal, near the plane of the mitral orifice. Prolapse involving one or several leaflet segments may develop with the leaflet free edge overriding the plane of the orifice, thus producing regurgitation. Leaflet prolapse results from excessive chordae elongation or chordae rupture. Another echocardiographic feature of Barlow’s valve is a severe dilatation of the annulus and an outward displacement of the attachment of the posterior leaflet to the crest of the ventricular wall, creating a well-visualized “cul-de-sac.” *
* See Glossary .
Extensive annular calcification may also occur involving predominantly the posterior annulus with occasional extension to the entire circumference and the head of the papillary muscles (d) . The tricuspid valve often displays similar morphological abnormalities as the mitral valve.
The main pathophysiological characteristic of Barlow’s valve is excess valvular tissue responsible for the billowing of the bellies of the leaflets into the left atrium during systole.
Pathology
The annulus is severely dilatated and circular ( Fig. 26-2 ). Excess leaflet tissue with extensive and irregular billowing of the bellies of the leaflets gives a cauliflower appearance to Barlow’s valve (a, b) . The leaflets are thickened as a result of a myxoid degenerative process that predominantly involves the coaptation zone. The excess tissue is such that the total surface area of the leaflets is usually two to three times greater than the normal surface area with predominant involvement of the posterior leaflet (c) . The anterior leaflet typically measures 38 to 40 mm in transverse diameter and 30 mm or more in height. The increased tension on the excess leaflet tissue (a consequence of Laplace’s law) may produce severe lesions at the attachment of the leaflet to the annulus on both ventricular and atrial sides. On the ventricular side the posterior leaflet attachment to the crest of the ventricular wall is displaced outward, forming the “cul-de-sac” *
* See Glossary .
previously described. On the atrial side, the atrio-valvular junction may be disrupted with tiny cracks (a, arrows) often filled with platelet aggregates that eventually become calcified. Indentations are distended or thickened and fused, and sometimes calcified (d) . The chordae are grossly abnormal: some are elongated, others are shortened, some are thin, and others are thickened. The most characteristic aspect of the marginal and secondary chordae is their chaotic anchorage to the leaflets: their attachment to the ventricular side of the leaflets forms a trabeculated “mesh” that circumscribes small pockets of billowing tissue (e) . Basal chordae are often thicker than normal and may be adherent to the ventricular wall. The papillary muscles may appear normal, but slightly elongated bulky papillary muscles with thickening of the endocardium may be observed. The biological characteristic of Barlow’s valve is myxomatous proliferation. The three-layer leaflet architecture is disrupted by myxomatous tissue ( Fig. 26-3 ). The thickened chordae show a typical sheath of myxomatous tissue surrounding the collagen core.
SURGICAL MANAGEMENT
The optimal reconstructive valve operation in Barlow’s disease is to correct both leaflet prolapse and leaflet billowing.
Valve reconstruction in Barlow’s disease is particularly challenging. The complexity of the reconstruction depends upon the extension of the lesions and whether the goal of the surgeon is to correct only the prolapse or also, and ideally, the billowing.
After decades of experience, we believe that the optimal surgery is to correct both the prolapse and the billowing to prevent recurrent mitral valve regurgitation hopefully for the remainder of the patient’s life.
The complexity of the surgery depends upon the extent of leaflet billowing.
Barlow’s Valve with Posterior Leaflet Billowing and Prolapse and Mild Anterior Leaflet Billowing
In most Barlow’s valves the predominant valve dysfunction involves the posterior leaflet. Segmental valve analysis typically shows a very large P2 segment and less involvement of adjacent segments. The anterior leaflet presents with excess tissue but limited billowing and no prolapse. The commissures are also discretely affected with limited billowing without prolapse. Although the P2 prolapse could theoretically be treated by secondary chordae transposition or artificial chordae, a large resection should be preferred. The goal of this resection is to reduce tension on the remaining leaflet tissue and chordae, thus altering the process of further leaflet billowing and chordae elongation and therefore minimizing the risk of recurrent regurgitation.
The valve reconstruction consists of the following four steps (see Chapter 11 ):
- •
Reduction of the surface area of P2: The extent of the resection is guided by the need both to correct the prolapse and to reduce the amount of tissue. This is achieved by resecting the most affected part of P2 while preserving whenever possible one indentation to facilitate leaflet motion. Whenever the entire P2 segment displays severe degenerative lesions, it should be completely resected provided that the adjacent P1 and P3 segments are not hypoplastic. The height of the preserved P2 leaflet tissue should be ≤15 mm to avoid systolic anterior motion (SAM).
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Reduction of the adjacent P1 and P3 segments: Whenever the height of these segments is ≥20 mm, excess tissue should be reduced by a horizontal resection or plication of the leaflet base. This triangular resection extends to approximately half of the attachment of the leaflet segment.
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Annular leaflet reconstruction: After leaflet resection, the gap between the leaflet remnants is usually smaller than 20 mm. In this setting, a simple annular plication approximates the two leaflet remnants, allowing restoration of leaflet continuity without tension. Whenever the gap is greater than 20 mm, compression sutures and a sliding leaflet plasty are preferred to avoid excessive annular plication, which may compromise the circumflex artery and produce a large cul de sac on the ventricular side.
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Remodeling annuloplasty: After valve reconstruction has been completed, even if the valve appears competent a ring annuloplasty is performed for the following reasons:
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The annulus, involved in the degenerative process, needs to be stabilized in the systolic position.
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The ring reduces tension of the valvular tissue and chordae.
- •
The ring reduces leaflet billowing and further enhances the surface of coaptation.
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The ring ensures the long-term stability of the result.
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Ring selection is an important consideration to avoid SAM, a potential complication in Barlow’s valve reconstruction. The size of the ring, guided by the size of the anterior leaflet, is usually ≥36 mm. Any ring smaller than the surface area of the anterior leaflet greatly increases the risk of SAM. If the anterior leaflet has an abnormal shape, a Classic ring can be selected because the extremities of the ring can be bent to fit the peculiar geometry of this leaflet. Another alternative is the use of a large-size Physio II ring, which has been specifically designed for Barlow’s disease.
Barlow’s Valve with Severe Bileaflet Billowing and Prolapse
Reconstruction of Barlow’s valve with billowing and prolapse of both leaflets is a more complex operation (see Chapters 10 and 12 ). The strategy is to treat not only the leaflet prolapse but also the leaflet billowing so that the process of leaflet stretching and chordae elongation can be altered. This requires a combination of leaflet resection to correct the prolapse and repositioning of each leaflet’s edge low in the ventricular cavity to correct the billowing.
The different steps of the operation are as follows:
- •
Posterior leaflet resection: In the typical setting, the resection involves the entire P2 segment and usually one of the indentations. In addition, the height of the adjacent P1 and P3 segments is reduced by a horizontal triangular or ovoid resection so that the height of these remnants is ≤15 mm.
- •
Reduction of the surface area of the anterior leaflet (see Figure 10-2 ): In the case of anterior leaflet prolapse resulting from localized chordae rupture, a limited triangular resection can be proposed but should not involve more than 10% of the anterior leaflet area. Attempts to resect a larger segment of the anterior leaflet to correct the billowing should be avoided because it may lead to increased leaflet rigidity and does not reposition the free edge at the proper ventricular level.
Leaflet edge repositioning is essential to achieve long-term good results in patients with Barlow’s disease.
- •
Leaflet edge repositioning: Leaflet edge repositioning is a key element of a reconstructive operation in patients with Barlow’s disease. It corrects leaflet billowing in a harmonious manner by repositioning the free edges of all leaflet segments at the same level low in the ventricular cavity. It is also the optimal way to correct anterior leaflet prolapse caused by diffuse chordae elongation. Taking advantage of the quadrangular posterior leaflet resection, which provides extensive access to the subvalvular apparatus, the posterior papillary muscle is addressed first. Three techniques of leaflet edge repositioning are possible depending on the anatomy of the papillary muscle (see Chapter 10 ).
- •
Papillary muscle sliding plasty: This technique is used whenever a papillary muscle, usually the posterior, presents with several heads, with some of them attaching nonelongated chordae while others attach elongated chordae. The papillary muscle is split longitudinally to separate the elongated chordae from the nonelongated chordae. The head supporting the elongated chordae is mobilized downward and reattached to the portion of the papillary muscle supporting the nonelongated chordae, thus effectively shortening the elongated group.
- •
Papillary muscle repositioning: This technique is a variation of the papillary muscle sliding plasty technique. The papillary muscle that attaches all the elongated chordae is mobilized and reattached to a shorter papillary muscle. Usually the shorter papillary muscle is the one that provides chordae to the resected P2.
- •
Papillary muscle shortening: This technique is used when a bulky papillary muscle, usually the anterior with a single head attaching chordae having the same length, is present and cannot be easily repositioned downward. This technique, slightly more difficult than the two other techniques, has the advantage of shortening all the chordae attached to the papillary muscle in a harmonious fashion. The posterior papillary muscle is exposed and shortened first followed by the anterior papillary muscle.
- •
- •
Reconstruction of the posterior annulus (see Chapter 11 ): Compression sutures are placed around the posterior annulus and the gap created by the posterior leaflet after quadrangular resection. The leaflet remnants are then sutured to the annulus and leaflet continuity is restored.
- •
Ring implantation: A remodeling ring annuloplasty is used to reinforce the annulus and the repair of the posterior leaflet; this reduces the tension on the repaired papillary muscle and prevents recurrent annular dilatation. Here again, precise measurement of the anterior leaflet surface area is critical for the ring selection in order to avoid SAM. Excess height of the anterior leaflet should lead the surgeon to modify a Classic ring or to use a Physio II ring.
Management of Annular and/or Papillary Muscle Calcification
Whenever annular calcification is present, the calcium bar is removed en bloc (see Chapter 9 ). The annulus is then reconstructed and the valve is repaired according to techniques described in Chapter 9 . Papillary muscle calcification is usually limited to one of the heads of the papillary muscle. The calcified head is resected and the corresponding chordae are replaced by chordae transposition or artificial chordae.
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