Parachute mitral valve with mitral stenosis

Congenital mitral stenosis (MS) results from a variety of anatomic anomalies in the pediatric population, and it is commonly associated with parachute mitral valve (PMV),1, 2 an abnormality in which the mitral valve (MV) chordae insert into a single papillary muscle (anterolateral papillary muscle [ALPM] or posteromedial papillary muscle [PMPM]).³ Parachute-like asymmetric mitral valve (PLAMV)⁴ is a similar anomaly in which chordae are distributed unequally between two identifiable papillary muscles. Usually the dominant papillary muscle is normal and the other is elongated and displaced toward the mitral valve annulus. Although both mitral valve anomalies have predominant unifocalization of chordae, “true” PMV has only one papillary muscle to which all chordae are attached. When both types of PMV occur, the chordae are short and thickened, limiting movement of normal mitral valve leaflets³ and resulting in functional and hemodynamic abnormalities.⁵ Although clinical presentations may be similar, “true” PMV and PLAMV are defined separately, because the valves originate and develop in different ways morphogenetically.⁶

PMV is associated with other cardiac anomalies,⁷ which significantly affect patient outcome.⁸ These associations may determine whether a patient requires univentricular palliation, in which an atrial septectomy is performed, making the tricuspid valve the systemic atrioventricular valve and thus rendering the functional outcome of the PMV less important. In patients with “true” PMV or PLAMV and a biventricular circulation, the degree of MS or mitral regurgitation (MR) is of paramount importance.

Historically, “true” PMV and PLAMV have been grouped together and analyzed as a single lesion. The influence of PMV type and dominant papillary muscle on associated lesions, palliation strategies, and outcomes in patients who maintain a biventricular circulation has not been previously analyzed. The objectives of this study were as follows: (1) to describe and compare the morphologic features and associated lesions of the two PMV and dominant papillary muscle types, (2) to assess for predictors of univentricular palliation in the entire PMV cohort, (3) to describe the interventions and midterm outcomes of patients who maintained biventricular circulation, and (4) to assess for predictors of MS on initial echocardiogram, progressive MS and MR, and mortality in the biventricular cohort.