# Tetralogy of Fallot: Genetic, Epigenetic and Clinical Insights into a Multifactorial Congenital Heart Disease

## TL;DR

This review explores the genetic and epigenetic factors behind Tetralogy of Fallot, a heart defect, and how they influence its varied symptoms and treatment.

## Contribution

The paper integrates recent genomic and clinical findings to highlight the interplay of genetic and epigenetic mechanisms in Fallot-type heart defects.

## Key findings

- Variants in genes like NOTCH1, FLT4, and GATA6 are linked to conotruncal development and heart defects.
- Epigenetic factors such as DNA methylation and non-coding RNA influence the variability of Fallot-type malformations.
- New candidate genes and regulatory networks are emerging as key contributors to cardiac morphogenesis.

## Abstract

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease, classically characterized by right ventricular outflow tract obstruction, ventricular septal defect, overriding aorta, and right ventricular hypertrophy. Recent advances in molecular and genomic research indicate that TOF is part of a phenotypic continuum encompassing Trilogy, Tetralogy, and Pentalogy of Fallot, in which the variability of anatomical presentation reflects shared genetic and epigenetic mechanisms with highly variable penetrance and expressivity. Variants in NOTCH1, FLT4, KDR, GATA6, and TBX1 highlight key pathways in conotruncal development and endothelial–mesenchymal transition, yet these well-known genes explain only a fraction of the genetic landscape. Emerging studies have identified additional candidate genes and networks involved in cardiac morphogenesis, including transcriptional regulators, signaling mediators, chromatin-remodeling factors, and splicing-associated genes such as PUF60 and DVL3. Epigenetic mechanisms, including DNA methylation, histone modifications, and non-coding RNA expression, further modulate phenotypic expressivity and contribute to variability along the Trilogy–Tetralogy–Pentalogy spectrum. This review integrates current genomic and clinical evidence to provide a comprehensive overview of the molecular architecture of Fallot-type conotruncal malformations, emphasizing the interplay between genetic and epigenetic mechanisms, genotype–phenotype correlations, and implications for diagnosis, risk stratification, counseling, and personalized management in the era of precision cardiology.