Mitral Valve Surgery: A Pathoanatomic Approach



Mitral Valve Surgery: A Pathoanatomic Approach


Vinay Badhwar

Jahnavi Kakuturu

Chris C. Cook



INTRODUCTION

The most prevalent adult valvular heart disease is mitral valve (MV) disease, and its most common presentation is regurgitation.1 Mitral stenosis (MS) is associated with fusion or calcification of the leaflets preventing their adequate opening or closing throughout the cardiac cycle. Mitral regurgitation (MR) may be primary, secondary, or mixed.2 Primary MR is an abnormality of the leaflets or subvalvular chordal apparatus. Secondary MR occurs because of the restriction of leaflet motion, with or without mitral annular dilatation, secondary to ventricular, and papillary muscle pathology. Mixed MR occurs when pathoanatomic features of primary and secondary MR coexist in the same patient. Strategies and techniques of surgical correction of MV disease are tailored to treat the precise pathoanatomy.

Untreated severe primary MR is associated with significant longitudinal morbidity including a 30% incidence of atrial fibrillation and 63% incidence of heart failure.3 Similar sequela accompany severe MS. Once the presence of severe MR has been established, MV surgery is indicated to prevent further left ventricular dilatation and symptoms of heart failure, even in asymptomatic patients. For patients with severe MS who are not candidates for percutaneous mitral balloon commissurotomy (PMBC), mitral valve replacement (MVR) is necessary to treat pulmonary hypertension, symptoms of dyspnea and fatigue, and prevention of secondary right ventricular dysfunction. Whenever anatomically possible and appropriate, MV repair should be performed as it may confer a survival advantage over MVR of 12% to 21% at 15 years.4,5 This chapter will review the indications and pathoanatomic approach to current MV surgery.




ANATOMIC CONSIDERATIONS

For the MV surgeon, it is essential to have a working mastery of echocardiographic structural interpretation, for it is the prediction of pathoanatomic mechanisms and the identification of potential anatomic pitfalls that provides the guidance for surgical strategy.14 Quantitative parameters consistent with severe MR should be identified before anesthetic induction and include a vena contracta width greater than 7 mm, effective regurgitant orifice area greater than 40 mm2, regurgitant volume greater than 60 mL, regurgitant fraction greater than 50%, or the presence of a flail leaflet or ruptured chorda.2 Important for surgical planning is the two-dimensional (2D) or three-dimensional (3D) identification of surgically relevant items such as clefts, annular/leaflet calcification, perforations, or possible coexistent chordal tethering that may impact the tailoring of the precise steps to achieve a successful surgical outcome.

Pathoanatomy at every level of the mitral apparatus may coexist in the same patient, and the preoperative or intraoperative imaging must be carefully reviewed so that the MV surgeon may make an effort to develop the surgical plan before making incision. This is of particular importance when the mechanism is anything more than focal single scallop disease. The MV apparatus is subdivided into the annulus, anterior and posterior leaflets, and the subvalvular chordae tendineae
and papillary muscles. The posterior leaflet is subdivided from lateral to medial into P1, P2, and P3 segments, with corresponding A1, A2, and A3 segments of the anterior leaflet. The anterior leaflet constitutes two-thirds of the valve orifice area and one-third of the annular circumference, while the posterior leaflet constitutes one-third of the valve area and two-thirds of the circumference. The subvalvular apparatus is composed of the anterolateral and posteromedial papillary muscles that give rise to primary chords attached to the free edge of the leaflet, secondary chords attached to the mid-leaflet ventricular surface, and tertiary chords attached to base of the leaflet.






The Carpentier classification is most commonly used to define leaflet motion to describe the possible etiology of MR.2,15 Type 1 is normal leaflet motion, and the MR may be due to congenital clefts, endocarditis/perforation, or annular dilation. Type 2 is excessive leaflet motion, and it is associated with primary degenerative leaflet prolapse or flail leaflet accompanied with chordal rupture. Type 3 is restricted leaflet motion. Type 3A occurs when leaflet motion is restricted in systole and diastole such as with rheumatic disease or radiation, and Type 3B occurs when leaflet motion is restricted in systole only such as with ischemic or nonischemic ventricular secondary MR. Type 3B secondary MR may further be subclassified into grades of severity (1-4) based on the amount of annular dilation, amount of leaflet tethering, and LVEF (Table 88.1).12,13

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May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Mitral Valve Surgery: A Pathoanatomic Approach
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