**2.1 Leaflets**

The leaflets are the valve component that creates the division between the atrium and ventricle. There are two distinct leaflets: the anterior or aortic and posterior or mural. The anterior leaflet is usually comprised of a single trapezoidal-shaped unit. The posterior leaflet is punctuated with multiple slits and clefts that define usually three, but up to six, distinct scallops (Fig. 1). The anterior and posterior leaflets are separated at the commissures but there is usually some continuity of the valve tissue close to the annulus. Further, if one looks

Mitral Valve Subvalvular Apparatus Repair with Artificial Neochords Application 5

mechanical stress on the leaflets. The curvature of the saddle shape or height of the "saddle horn" is reduced in a model of ischemic mitral regurgitation. This may have implications in

Fig. 2. Relational anatomy of the mitral valve: left and right fibrous trigones (LFT and RFT); anterior and posterior mitral leaflets (AL and PL); pulmonic, aortic, and tricuspid valves

The tendinous chords, as functional extensions of the papillary muscles, perform the dual function of maintaining valvular competence by preventing leaflet prolapse and maintaining ventricular geometry by providing cross-ventricular support. The chords originate from the apical portions of the papillary muscles or directly from the posterior ventricular wall. They insert either into the free edge of the leaflets or on their ventricular surface. Chords have been characterized a number of ways. The most useful for repair purposes is to describe the first-degree chords as those inserting into the valve edge and the second-degree chords as those inserting into the underside of the leaflet. Both first-degree and second-degree chords originate from the papillary muscles and third-degree chords

There are two papillary muscles associated with the mitral valve (Fig. 3) When looking from the atrial side, the anterolateral is to the left and the posteromedial is to the right. The muscles are located under their respective commissures. They originate from the lower third of the left ventricular free wall. The papillary muscles are extensions of the ventricular muscle from which they originate. The chords originate from the fibrous tips of these muscles, extending to insert on the mitral leaflets. The blood supply of the anterolateral papillary muscle derives from the left circumflex and/or diagonal systems. The blood supply of the posteromedial papillary muscle derives from the posterolateral coronary branches whether it originates from the left or right coronary system. The papillary muscles adjust tension and stabilize the valve during the cardiac cycle, rather than pulling the chords and leaflets into position. The function of the papillary muscles and their position is greatly dependent on the status of the ventricular myocardium underlying it. Displacement of the papillary muscle by distorted ventricular geometry is one mechanism for the creation of

originate from the ventricular wall and insert into the base of the posterior leaflet.

choosing techniques for annular reduction and stabilization.

(PV, AV, and TV).

**2.3 Tendinous chords** 

**2.4 Papillary muscles** 

mitral regurgitation.

at the chordal distribution, at the commissures, chordae are distributed to both leaflets from a common structural source—so the leaflets form a single functional unit. Nevertheless, it is useful for the purposes of valve repair to differentiate anterior from posterior. However, one must remember that multiple separately suspended distinct units come together to make the valve competent. To describe components of mitral valve repair it is useful to label the scallops by position (Fig. 1); posteriorly from left to right P1, P2, P3, with corresponding regions of the anterior leaflet A1, A2, and A3.

Fig. 1. Photograph of the mitral valve. Note multiple clefts in the posterior leaflet (arrows). The posterior leaflet is divided into 3 scallops or segments (lateral, middle, and medial scallops) identified as P1, P2, and P3. The corresponding segments of the anterior leaflet are labeled A1, A2, and A3.

When in the closed position, the orifice is obscured by the anterior and posterior leaflets. The anterior comprises about one half to two thirds of this area, the posterior comprises about one third to one half of this area. The point of attachment of the anterior leaflet comprises one third of the circumference of the annulus (the fibrous area) and the posterior leaflets comprises two thirds of the circumference of the annulus (the muscular area). The fibrous support of the anterior leaflet is fixed, the muscular support of the posterior leaflet can enlarge and does so when annular dilatation is associated with mitral regurgitation. The leaflets themselves are comprised of clear and rough zones. The clear zone is between the line of closure and the annulus and can be quite thin, almost transparent. The rough zone extends from the line of closure to the free edge, characterized by thicker, nodular ridges which promote sealing of the orifice on valve closure.

#### **2.2 Annulus**

Of the four heart valves, the mitral valve is the only valve that has a distinguishable annulus. However, the presence of a fibrous annular structure is variable and discontinuous. The firmest site of support for the mitral valve is the region of fibrous continuity between the aortic and mitral valves, the extent of which is delineated by the right and left fibrous trigones (Fig. 2). Nevertheless, for surgical purposes, the annulus is considered the area of attachment of the valve leaflets to the atrial muscle. The annulus is a functional component of the mitral valve. The annulus is quite flexible and changes shape throughout the cardiac cycle. With normal systolic function, the annulus will reduce in size by 20% to 40%. Functionally the mitral annulus is not two-dimensional but in fact threedimensional assuming a saddle shape. The curvature imposed by the saddle shape reduces mechanical stress on the leaflets. The curvature of the saddle shape or height of the "saddle horn" is reduced in a model of ischemic mitral regurgitation. This may have implications in choosing techniques for annular reduction and stabilization.

Fig. 2. Relational anatomy of the mitral valve: left and right fibrous trigones (LFT and RFT); anterior and posterior mitral leaflets (AL and PL); pulmonic, aortic, and tricuspid valves (PV, AV, and TV).

#### **2.3 Tendinous chords**

4 Front Lines of Thoracic Surgery

at the chordal distribution, at the commissures, chordae are distributed to both leaflets from a common structural source—so the leaflets form a single functional unit. Nevertheless, it is useful for the purposes of valve repair to differentiate anterior from posterior. However, one must remember that multiple separately suspended distinct units come together to make the valve competent. To describe components of mitral valve repair it is useful to label the scallops by position (Fig. 1); posteriorly from left to right P1, P2, P3, with corresponding

Fig. 1. Photograph of the mitral valve. Note multiple clefts in the posterior leaflet (arrows). The posterior leaflet is divided into 3 scallops or segments (lateral, middle, and medial scallops) identified as P1, P2, and P3. The corresponding segments of the anterior leaflet are

When in the closed position, the orifice is obscured by the anterior and posterior leaflets. The anterior comprises about one half to two thirds of this area, the posterior comprises about one third to one half of this area. The point of attachment of the anterior leaflet comprises one third of the circumference of the annulus (the fibrous area) and the posterior leaflets comprises two thirds of the circumference of the annulus (the muscular area). The fibrous support of the anterior leaflet is fixed, the muscular support of the posterior leaflet can enlarge and does so when annular dilatation is associated with mitral regurgitation. The leaflets themselves are comprised of clear and rough zones. The clear zone is between the line of closure and the annulus and can be quite thin, almost transparent. The rough zone extends from the line of closure to the free edge, characterized by thicker, nodular ridges

Of the four heart valves, the mitral valve is the only valve that has a distinguishable annulus. However, the presence of a fibrous annular structure is variable and discontinuous. The firmest site of support for the mitral valve is the region of fibrous continuity between the aortic and mitral valves, the extent of which is delineated by the right and left fibrous trigones (Fig. 2). Nevertheless, for surgical purposes, the annulus is considered the area of attachment of the valve leaflets to the atrial muscle. The annulus is a functional component of the mitral valve. The annulus is quite flexible and changes shape throughout the cardiac cycle. With normal systolic function, the annulus will reduce in size by 20% to 40%. Functionally the mitral annulus is not two-dimensional but in fact threedimensional assuming a saddle shape. The curvature imposed by the saddle shape reduces

regions of the anterior leaflet A1, A2, and A3.

which promote sealing of the orifice on valve closure.

labeled A1, A2, and A3.

**2.2 Annulus** 

The tendinous chords, as functional extensions of the papillary muscles, perform the dual function of maintaining valvular competence by preventing leaflet prolapse and maintaining ventricular geometry by providing cross-ventricular support. The chords originate from the apical portions of the papillary muscles or directly from the posterior ventricular wall. They insert either into the free edge of the leaflets or on their ventricular surface. Chords have been characterized a number of ways. The most useful for repair purposes is to describe the first-degree chords as those inserting into the valve edge and the second-degree chords as those inserting into the underside of the leaflet. Both first-degree and second-degree chords originate from the papillary muscles and third-degree chords originate from the ventricular wall and insert into the base of the posterior leaflet.

#### **2.4 Papillary muscles**

There are two papillary muscles associated with the mitral valve (Fig. 3) When looking from the atrial side, the anterolateral is to the left and the posteromedial is to the right. The muscles are located under their respective commissures. They originate from the lower third of the left ventricular free wall. The papillary muscles are extensions of the ventricular muscle from which they originate. The chords originate from the fibrous tips of these muscles, extending to insert on the mitral leaflets. The blood supply of the anterolateral papillary muscle derives from the left circumflex and/or diagonal systems. The blood supply of the posteromedial papillary muscle derives from the posterolateral coronary branches whether it originates from the left or right coronary system. The papillary muscles adjust tension and stabilize the valve during the cardiac cycle, rather than pulling the chords and leaflets into position. The function of the papillary muscles and their position is greatly dependent on the status of the ventricular myocardium underlying it. Displacement of the papillary muscle by distorted ventricular geometry is one mechanism for the creation of mitral regurgitation.

Mitral Valve Subvalvular Apparatus Repair with Artificial Neochords Application 7

Cardiac valves can be affected by numerous disease (Tab # 1). Primary valve disease involve the valvular tissue. Secondary valve disease affect the supporting of the valves – that is, the ventricles for the mitral and tricuspid valves and the aorta and pulmonary artery for the aortic and pulmonary valves, respectively. The determination of the etiology of valvular disease is important because it helps to establish the medical treatment, which should

Any of the previously listed disease can cause lesions affecting one or several components of

the heart valves: the annulus, the leaflets, and the supporting structures (Table #2).

**Secondary to Myocardial Disease**  • Ischemic cardiomyopathy • Dilated cardiomyopathy

cardiomyopathy • Myocardial sarcoidosis • Endomyocardial fibrosis • Myocardial tumors

**Aortic\Pulmonary Valves** Annular dilatation Leaflet perforation Leaflet distension Vegetations

Commissure detachment Commissure fusion Calcification

Sino-tubular dilatation

• Hypertrophic obstructive

**4. Etiology** 

precede or follow valve reconstruction.

Lupus erythematoses Valve sclerosis • Degenerative disease Barlow, s disease Marfan,s disease Fibroelastic deficiency • Infective endocarditis

**Primary valve Disease** • Congenital malformation • Inflammatory disease Rheumatic

• Valvular or annular calcification

• Trauma

**5. Lesions** 

• Valvular tumors

Table 1. Etiology of valvular disease.

**Mitral\ Tricuspid Valves** Annular dilatation Leaflet perforation Leaflet tear Leaflet thickening Vegetations Commissure fusion Calcification Chordae rupture Chordae elongation Chordae thickening Chordae fusion

Papillary muscle rupture Papillary muscle elongation Ventricular aneurysm Ventricular fibrous plaque Ventricular dilatation

Table 2. Valvular Lesions.

Fig. 3. Mitral apparatus. ALPM, Anterolateral papillary muscle; PMPM, posteromedial papillary muscle; AoL, aortic leaflet; Ant.Com.L., anterior commissural leaflet; Post.Com.L., posterior commissural leaflet; Ant.Scal. , anterior scallop; Mid.Scal ., middle scallop; h, height of a leaflet; l, length of the attachment of a leaflet; Post.Scal. , posterior scallop; Rt. Trigone, right fibrous trigone; Lt. Trigone, left fibrous trigone; 1, anterior main chorda; 2, posterior main chorda; 3, anterior paramedial chorda; 4, posterior paramedial chorda; 5, anterior paracommissural chorda; 6, posterior paracommissural chorda; 7, anterior commissural chorda; 8, posterior commissural chorda; 9, anterior cleft chorda; 10, posterior cleft chorda.

#### **3. Pathophysiology**

Today, multiple terminologies used to describe mitral pathology. Terms such as prolapse, flail, partial flail, redundant, overshooting, stretching, elongation, floppy, billowing, ballooning, Barlow, dysplasia, myxoid, and myxomatous, for example, have different meanings for different specialists. The confusion comes first from the fact that several of these terms are synonyms. For example, flail leaflet, overshooting leaflet and leaflet prolapse are synonyms. Other synonyms are Barlow, billowing, ballooning, myxomatous valve, and mitral valve prolapse. Another source of confusion comes from the fact that for some specialists a given term such as « prolapse» means a disfunction (leaflet prolapsed) while for others it refers to a disease (mitral valve prolapse). The same chaotic situation applies to the term « floppy valve», which is used to define either a valve morphology, or dysfunction, or a disease. Similar confusion exists in tricuspid and aortic valve diseases, in which many of previously listed terms are used without clear distinction. Clarification can be obtained by using a pathophysiological triad with a sound distinction between the terms describing valve etiology (i.e., the cause of the disease), valve lesions resulting from the disease, and valve dysfunction resulting from the lesions.

> **Etiology - The cause of the disease**  ↓ **Lesions - Result from the disease**  ↓ **Dysfunction - Result from the lesions**

The pathophysiological triad facilitates communication between cardiologists, echocardiographers and surgeons and greatly clarifies clinical investigation.
