After recovery from an initial episode of rheumatic fever, approximately 60 to 65% of patients will develop heart valve disease (rheumatic heart disease, RHD) and possibly secondary conditions such as atrial fibrillation, endocarditis, and heart failure.¹ Rheumatic heart disease is one of the leading noncommunicable diseases in developing countries with a global prevalence of up to 19.6 million in 2005 and an incidence of 282,000 new cases per year.²

In Western countries, economic and sociopolitical changes together with prophylactic initiatives led by the American Heart Association and the World Heart Federation contributed to eliminate rheumatic fever by the 1980s (current prevalence in the United States is 0.05/1000). Much of the morbidity and mortality due to RHD has been proven to be effectively prevented by secondary prophylaxis including long-acting penicillin, oral anticoagulants, and surgical interventions.³ However, the costs of prophylaxis continue to burden low-income and middle-income countries as well as certain concentered populations of higher-income countries (demographic shifts due to immigration).⁴ In this context, an estimated of up to 468,164 patients die each year from RHD and or its clinical complications. Interestingly, recent echocardiographic data have shown that the true prevalence of the disease is significantly higher than the current global estimate if we take into consideration subclinical RHD.⁵

Rheumatic heart disease is unarguably the most common cardiovascular disease among individuals aged <25 years worldwide, and has a peak age group of 25 to 35 years (female predominance) in developing countries⁶ (Fig. 36-1). Conversely, patients with RHD in industrialized countries are either old (mostly above 50 years of age) or young immigrants. In this setting, the mitral valve is affected in 50% of patients and results in mitral regurgitation, mitral stenosis, or both.⁷ In younger patients, mitral regurgitation is predominant, but mitral stenosis becomes more prevalent with age and calcification of tissues. Regurgitant mitral valves are edematous with fibrotic thickening, and annular dilatation and anterior leaflet pseudoprolapse are often seen, whereas stenotic mitral valves present with stiff, nonpliable, and severely restricted leaflets, fusion of the subvalvular apparatus and commissures and often annular calcification⁸ (Fig. 36-2). Clinical assessment and two-dimensional echocardiography are paramount to detect and assess mitral stenosis, particularly in asymptomatic patients.⁹

The main consequence of RHD and more particularly rheumatic mitral valve disease (RMVD) is mitral stenosis.¹⁰ This circumstance results in an increase of diastolic gradients across the mitral valve with invariable measurements of the mitral area due to moderate-to-severe commissural fusion. From a hemodynamic standpoint, transvalvular flow and heart rate are considered to play an important role in the perioperative management of patients with RMVD.¹¹ Mean mitral gradient increases in parallel with cardiac output (importance of atrial contraction) or with fast heart rates.

Increasing mitral gradients trigger left atrium enlargement due to chronic escalating left atrial pressures. This in turn favors the occurrence of atrial fibrillation leading to annular dilatation and thrombus formation. The logical rise in pulmonary artery pressure leads to pulmonary hypertension and late in the course to right ventricular hypertrophy, right ventricular dilatation, secondary tricuspid regurgitation and eventually right ventricular dysfunction (inherent surgical risk). This is important to understand why patients undergoing mitral valve repair often receive adjuvant tricuspid valve repair and a Maze procedure.¹² Finally, it is important to emphasize on the role of rhythm control therapies and central vasodilators during the preoperative period and medical optimization for surgery.

Although mitral stenosis was the first mitral valve dysfunction treated surgically (Elliot Carr Cutler performed a closed transventricular mitral commissurotomy with a cardiovalvulotome in 1923), nowadays most of the patients with mitral valve stenosis receive a percutaneous balloon valvuloplasty unless the lesions are not amenable to balloon dilatation (or there is a high risk of embolic events), there is concomitant regurgitation, or a previous balloon valvuloplasty has failed.¹³ When surgery is indicated, mitral valve repair is always preferred to mitral valve replacement due to lower perioperative mortality rates,^14,15 superior preservation of left ventricular function,¹⁶ lower thromboembolic complications¹⁷ and risk of endocarditis (critical in patients with deficient socio-economic conditions), and greater long-term durability.¹⁸ This is particularly important in young patients. However, although repair rates have been shown to be near a 100% in prolapsing valves or patients with isolated annular dilatation, repair techniques are feasible in only 50 to 75% of patients with RMVD (percentage varies according to age, leaflet dysfunction and degree of calcification).^19,20 This difference is attributable to the vast spectrum of lesion complexity found in patient with RHD and therefore the need for more complex surgical techniques that often cannot guarantee long-term durability. In addition, when deciding about repair versus replacement, the evoluting nature of the rheumatic process, which implies a progressive distortion of the subvalvular apparatus even beyond a successful repair, needs to be part of the equation. In this context, it is crucial to distinguish between the lesions in patients from developing countries (the histological rheumatic process is active) and that of patients from industrialized countries were the process is controlled.

From a strictly technical point of view, several aspects have recently transformed the field of mitral valve repair in patients with RMVD. The first one is introduction of polytetrafluoroethylene neochordoplasty to either replace diseased chords or reinforce leaflet segments which has significantly impacted surgical outcomes.²¹ Neochordoplasty has actually replaced many of the subvalvular techniques originally described and promoted by Carpentier such as chordal shortening, chordal transfer, or papillary muscle reposition.²² Additionally, although leaflet extension is not a new technique,²³ the relatively recent introduction of gluteraldehyde-fixed pericardium has avoided shrinkage, thickening and calcification of the autologous pericardium potentially leading to more durable results.²⁴

Type I Dysfunction

Two mechanisms may lead to type I dysfunction²⁵ in patients with RHD. The first one is rapid left ventricular dilatation and subsequent mitral annular dilatation due to pancarditis (early stages), which often impacts left ventricular contractility due to an acute inflammatory reaction (myocarditis). The second mechanism is annular dilatation secondary to chronic atrial fibrillation. Atrial fibrillation (very common in patients with RHD) impairs atrial contraction thus increasing left atrial pressures. This in turn results in left atrial dilatation and pure mitral annular dilatation.

Type II Dysfunction

The most frequent lesions encountered leading to type II dysfunction²⁵ are true prolapse and pseudoprolapse of the anterior leaflet. In the setting of true prolapse of the anterior leaflet, the leaflet overrides the coaptation plane during systole resulting in mitral regurgitation. Causes of true anterior prolapse in patients with RMVD include elongation or rupture (secondary to an acute inflammatory reaction) of the chordae tendinae or papillary muscles, or secondary rupture caused by bacterial endocarditis (facilitated and exacerbated by a dysfunctional rheumatic valve as occurs in patients with severe underlying degenerative mitral valve disease).

In the setting of anterior leaflet pseudoprolapse, as opposed to true anterior leaflet prolapse, the anterior leaflet does not override the plane of coaptation during systole (minor prolapse of the free edge of A2 due to distention and posterolateral displacement of the paramedical chordae). This lesion is often found in patients with opposing dysfunction, this being a combination of type IIIb dysfunction of the posterior leaflet (restricted motion) and consequent anterior leaflet pseudoprolapse (also known as type IIa/IIIp). In this case, mitral regurgitation is secondary to the lack of coaptation between the anterior and the posterior leaflets, which permits full unfolding of the anterior leaflet (there is no coaptation surface against the posterior leaflet) without overriding the plane of coaptation or annular plane.

Type III Dysfunction

Type III is the most frequent dysfunction²⁵ in patients with RMVD. In the early stages of rheumatic valve involvement, mild degrees of leaflet fibrosis (incipient symmetric bileaflet restriction) might create mild mitral regurgitation and very subtle hemodynamic changes. Moreover, mitral regurgitation at this stage might be often aggravated by certain degree of annular dilatation. When the inflammatory process induces a more significant fibrotic reaction both leaflets present greater degrees of restricted motion with important hemodynamic consequences. This circumstance might certainly impede leaflet coaptation in systole leading to severe mitral regurgitation. However, in this setting, the more advanced fibrotic thickening of both leaflets as well as the fusion of both commissures and the subvalvular apparatus also impedes leaflet opening in diastole resulting in mitral stenosis. When restricted motion mainly affects valve opening during diastole owing to isolated commissural fusion or further rheumatic changes pure mitral stenosis is predominant.

The use of a prosthetic-ring or prosthetic-band annuloplasty is currently a standard technique in all patients receiving mitral valve repair (obviously pediatric patients are an exception requiring biodegradable or pericardial rings or bands) regardless of the etiology of mitral valve disease.²⁶ Except in rare cases of pure mitral stenosis (with preserved ventricular function and mild atrial enlargement and therefore no secondary annular deformation), annular dilatation is present in the majority of patients with RMVD and mandate correction with a prosthesis size based on the surface of the anterior leaflet or on the intertrigonal distance (any discrepancy between two sizes should lead the surgeon to choose the larger size always). The use of ring annuloplasty has been shown to reduce the incidence of both mitral and tricuspid regurgitation (and subsequent reoperations) in patients with RMVD. In the setting of pure mitral stenosis with obvious annular dilatation, ring annuloplasty contributes to prevent commissural leaks by providing better surface of coaptation between both leaflets (commissurotomy might result in valve regurgitation in the presence of severe annular dilatation).