**4. Pathology and physiopathology**

The tendency of mitral valve regurgitation and the adjunct mitral valve prolapse development is inevitably high with the presence of left atrial myxoma either before or after any interventions been made. The development of mitral valve prolapse is due to the persistent rebound pendulum-like motion of the left atrial myxoma on the valve apparatus during each cardiac circle. Echocardiographically, mitral valve prolapse is defined as the upward displacement of the mitral leaflets above 2 mm in diastole [silent] which is usually the case in patients presenting with LAM and above 3 mm [massive] which increases the regurgitant jets seen during the echocardiographic studies. However, mid-systolic click to late systolic murmur is pathognomonic auscultatory findings with mitral valve prolapse and underling regurgitation as it varies from being benign to a gradual or sudden advance stage depending on the prolapse and regurgitation grade either before or after therapeutic interventions with a significant morbidity and mortality rate. Fortunately, apart from the massive prolapse, bacterial endocarditis, thromboembolism, atrial fibrillations, myxomatous degenerations [Barlow's disease] and rheumatic heart diseases play key roles in the resultant regurgitations caused by the left atrial myxoma. Histological features of mitral valve prolapse and regurgitation are marked spongiosa proliferation, mucopolysaccharide acid replacement of the leaflet collagen causing thickening and leaflet redundancy. As a result of the changes made such as fibrotic leaflets, thinning and/or elongation of the chordae tendineae, proper valve coaptation during systole is rendered impossible due to the redundant and elongated leaflets coupled with overshooting into the left atrium and the disrupted tendineae which eventually ruptures leading to regurgitation.

valve during each systolic and diastolic phase coupled with the myxoma body adherence to nearby structures of the mitral valve. The myxoma prolapse from the left atrium toward the left ventricle during the entire cardiac cycle eventually leads to mitral valve regurgitations of varying degrees, cause volume overload propagating both left atrial and left ventricular dilatation, annular dilatation due to the continuous mechanical stretch of the prolapsing tumor on the mitral annulus during each systolic and diastolic phase. However, the extent of valvular obstruction varies with body position as the presence of the myxoma body itself affects transmitral blood flow and also tends to mask mild and moderate to severe mitral regurgitations due to the huge and floating myxoma body where large myxomas with long stalk produces a temporally complete obstruction of the mitral valve orifice resulting in syncope. The continuous pendulum like or "wrecking ball" effect of the myxoma during each cardiac circle against the entirety of the mitral valve apparatus gives raise to regurgitations and its severity is highly dependent on the resultant effect of the myxoma body itself on the mitral valve [26–35]. The grade and severity of the regurgitation is highly dependent on the myxomas body size, stalk length [small, large, prolapsing and non- prolapsing] and to some varying degree body posi-

Mitral Valve Insufficiency, a Constituent of Left Atrial Myxoma: Pathobiology, Physiopathology…

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As widely used and proposed by Carpentier, the anterior leaflet is indicated as A1, A2, and A3 but lacks a clear distinction between A1 and A2 and also between A2 and A3 because of its smooth surface. However, the analogous segments of the posterior leaflets are also indicated as P1 [anterolateral], P2 [middle], and P3 [posteromedial] and highly distinctive from each other [37]. Regurgitations occur when there is an annular dilatation and/or the free edge of one or both leaflets overrides the entire valve orifice during systole, chordae tendineae destruction or rupture, a papillary muscle tear or detachment, architectural left ventricular destruction and acute ischemia as a result of embolization due to the myxoma friability (**Table 1**). Regurgitations caused by LAM express themselves differently according to grades, degree, and size of the myxoma, different loading conditions, body structure, position and other masked underlying pathology so therefore, for a successfully understanding of mitral regurgitation caused by LAM, a clear knowledge of the components and anatomy of the mitral valve apparatus, possible functional alterations, analysis of the leaflet motion, and a proper grading system is essential for a better prognosis after management or repair [1] (**Figure 2**).

tion and the resultant changes of blood flow through the left heart [36].

Type A The manifestation or appearance of mitral regurgitations is as a result of annular dilatation

Type B The manifestation or appearance of mitral regurgitations is as a result of .one of either leaflets overriding

Type C The manifestation or appearance of mitral regurgitations is as a result of restricted leaflet motion during

Type D The manifestation or appearance of mitral regurgitations is as a result of restricted leaflet motion during

**5.1. Carpentier classification**

the annular plane during systole

**Table 1.** Carpentier's classification of regurgitation of the mitral valve.

both systole and diastole

systole only
