Endothelial-to-Mesenchymal Transition as Underlying Mechanism for the Formation of Double-Chambered Right Ventricle

Predictive modeling of endocardial fibroelastosis recurrence in patients with congenital heart disease

BACKGROUND

Endocardial fibroelastosis (EFE) is a major effector in the maldevelopment of the heart in patients with congenital heart disease. Despite successful surgical removal, EFE can redevelop, but the underlying cause of EFE recurrence remains unknown. This study aimed to identify hemodynamic predictors and genetic links to epithelial/endothelial-to-mesenchymal transition (EMT/EndMT) alterations for preoperative risk assessment.

METHODS

We assessed the impact of preoperative hemodynamic parameters on EFE recurrence in a cohort of 92 patients with congenital heart disease who underwent left ventricular (LV) EFE resection between January 2010 and March 2021. Additionally, whole-exome sequencing in 18 patients was used to identify rare variants (minor allele frequency <10-5) in high-expression heart (HHE) genes related to cardiac EMT/EndMT and congenital heart disease.

RESULTS

EFE recurred in 55.4% of patients, within a median of 2.2 years postsurgery. Multivariable analysis revealed specific hemodynamic parameters (mitral valve inflow and area, LV filling pressure, and aortic valve gradient and diameter) as predictors, forming a predictive model with an area under the receiver operating characteristic curve of 0.782. Furthermore, 89% of the patients exhibited damaging variants in HHE genes, with 38% linked to cardiac EMT/EndMT Gene Ontology processes and 22% associated with known congenital heart disease genes. Notably, HHE genes associated with cardiac EMT/EndMT were significantly associated with faster EFE recurrence in a multivariate analysis (hazard ratio, 3.56; 95% confidence interval, 1.24-10.17; P = .018).

CONCLUSIONS

These findings established a predictive scoring system using preoperative hemodynamic parameters for EFE recurrence risk assessment. Alterations in HHE genes, particularly those linked to cardiac EMT/EndMT, exacerbate the risk of recurrence.

Progressive Right Ventricular Obstruction Caused by a Double-Chambered Right Ventricle Resulting in Shunt-Reversal via a Concomitant Congenital Ventricular Septal Defect and Subsequent Erythrocytosis in a Dog

A 3-year-old Chihuahua was presented because of exercise intolerance, respiratory distress, and syncopal episodes. At the age of 10 weeks, the dog was diagnosed with a congenital small left-to-right shunting ventricular septal defect and a mild right ventricular outflow tract obstruction via echocardiography. At that time, the dog was asymptomatic, but the breeder’s veterinarian heard a murmur. Both cardiac defects were judged to be clinically non-relevant at that time. However, at 3 years of age, echocardiography revealed a severe right ventricular obstruction, known as a double-chambered right ventricle, along with right-to-left shunting via the ventricular septal defect. Because of chronic hypoxemia due to the right-to-left shunting, erythrocytosis developed. Flow reversal via the shunt was caused by a progressively worsening right ventricular obstruction leading to a supra-systemic right ventricular systolic pressure. Because of the poor prognosis, the dog was euthanized, and the heart was submitted for post-mortem examination. Gross pathologic findings revealed the close proximity of the right ventricular obstructive lesion to the ventricular septal defect. Histopathology revealed localized muscular hypertrophy and severe endocardial fibrosis. The suspected pathogenesis of the progressive obstruction was infiltrative myocardial fibrosis due to turbulent blood flow from the left-to-right shunting ventricular septal defect, as described in humans.

Case report: Active clinical manifestation of endocardial fibroelastosis in adolescence in a patient with mitral and aortic obstruction–histologic presence of endothelial-to-mesenchymal transformation

This is the first description of active clinical manifestation of endocardial fibroelastosis (EFE) and remodeling of the endocardium via endothelial-to-mesenchymal transformation (EndMT) in an adolescent with Shone’s variant hypoplastic left heart complex (HLHC) and a genetic heterozygous ABL1 variant. While EFE has not been typically associated HLHC or Shone’s syndrome, in this patient flow alterations in the left ventricle (LV), combined with genetic alterations of intrinsic EndMT pathways led to active clinical manifestation of EFE in adolescence. This case emphasizes that new therapies for EFE might need to focus on molecular factors influenced by intrinsic and extrinsic stimuli of EndMT.