Papillary Muscle Noncompaction: A Unique Mechanism for Mitral Regurgitation in Children

Background: Noncompaction Cardiomyopathy (NCCM) is a primary genetic cardiomyopathy with variable clinical and Echocardiographic (echo) features. Association with Mitral Regurgitation (MR) was reported but the mechanism of this association has not been well described in pediatric patients. Aims: To describe clinical and echo features of MR in NCCM. Methods: All pediatric patients with NCCM associated with MR and preserved ventricle function seen in one center from January 2015 to March 2020 were included. Clinical and echo features were described. Results: Twelve patients were identified (66% females), 8 (66%) presented with heart failure due to severe MR , and 4 were asymptomatic with mild-moderate MR. Echo features in all patients showed Papillary Muscle Noncompaction (PMNC). The Papillary Muscle (PM) base was discontinuous with the endocardium in 5 patients (41%) and PM were not well differentiated from the noncompacted myocardium in 3 patients (25%)There were variable degrees of chordal elongation and malcoaptation of the leaflets in all patients. Five patients (41%) had associated congenital heart disease including ventricular septal defects in 4 and patent ductus arteriosus in one patient. Conclusion: PMNC causes MV chordal abnormalities that lead to malcoaptation of the mitral leaflets resulting in MR. NCCM needs to be considered when evaluating patients with MR.