A potentially curative fetal intervention for hypoplastic left heart syndrome

Advancements in prenatal diagnosis and management of hypoplastic left heart syndrome: A multidisciplinary approach and future directions

Hypoplastic left heart syndrome is a severe congenital defect involving underdeveloped left-sided cardiac structures, leading to significant mortality and morbidity. Prenatal diagnosis using fetal ultrasound and echocardiography enables early detection, family counseling, and improved clinical decision-making. Advanced prenatal interventions, such as fetal aortic valvuloplasty and atrial septostomy, show promise but require careful patient selection. A multidisciplinary approach involving obstetricians, neonatologists, and pediatric cardiologists is vital for effective management. Future directions include refining imaging techniques, such as three-dimensional ultrasound, cardiovascular magnetic resonance imaging, and exploring bioengineering solutions, stem cell therapies, and genetic research. These advancements aim to improve therapeutic options and address current limitations, including transplant scarcity and postoperative complications. Although surgical innovations have improved survival rates, challenges remain, including neurological risks and long-term hemodynamic issues. Ongoing research and technological advancements are essential to enhance outcomes and quality of life for hypoplastic left heart syndrome patients.

Spontaneously Corrected Hypoplastic Left Heart: A Case Report and Exceptional Opportunity to Discuss Etiology with Novel Therapeutic Vision

Hypoplastic left heart syndrome (HLHS) is a relatively prevalent fetal echocardiography finding in complex congenital heart diseases. Current studies indicate that intrinsic and extrinsic mechanisms could be involved in the development of left heart hypoplasia. Left ventricular inflow or outflow disorders may cause left heart hypoplasia. Prenatal aortic valvuloplasty has become more common as a therapeutic strategy. Our case presentation provides an opportunity for a new vision toward the etiology, prevention, and treatment of HLHS. In our patient, prenatal progressive left heart hypoplasia associated with restrictive foramen oval (FO) suggested the likelihood of a flow-mediated mechanism. Additionally, postnatal improvement of the hypoplastic left heart in the presence of a functional perimembranous ventricular septal defect (PM-VSD) reinforced the suspicion of an extrinsic mechanism. Pre- or postnatal interventional creation of an atrial septal defect (ASD) or VSD is our proposed method for HLHS in selected patients.

Novel Insights into the Etiology, Genetics, and Embryology of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a relatively rare severe congenital heart defect (CHD) closely linked to other left ventricular outflow tract (LVOT) lesions including bicuspid aortic valve (BAV), one of the most common heart defects. While HLHS, BAV, and other LVOT lesions have a strong genetic underpinning, their genetic etiology remains poorly understood. Findings from a large-scale mouse mutagenesis screen showed HLHS has a multigenic etiology and is genetically heterogenous, explaining difficulties in identifying the genetic causes of HLHS. In Ohia mice, HLHS shows incomplete penetrance. Some mice exhibited small LV with normal aorta, and others a normal LV with hypoplastic aorta, indicating the LV hypoplasia is not hemodynamically driven. In Ohia mutants, HLHS was found to have a digenic modular construction, with mutation in a chromatin modifier causing the small LV phenotype and mutation in Pcdha9 causing the aorta/aortic valve hypoplasia. The Pcdha9 mutation alone can cause BAV, and in the human genome two common deletion copy number variants spanning PCDHA7-10 are associated with BAV. Hence the digenic etiology of HLHS can account for the close association of HLHS, a rare CHD, with BAV, one of the most common CHD. Functional analysis of Ohia HLHS heart tissue showed severe mitochondrial dysfunction in the small LV, while the normal size RV is also affected but milder, suggesting possible role in vulnerability of surgically palliated HLHS patients to heart failure. These findings suggest insights into the genetics of HLHS may yield new therapies for improving outcome for patients with HLHS.

Hypoplastic left heart syndrome (HLHS): molecular pathogenesis and emerging drug targets for cardiac repair and regeneration

INTRODUCTION

Hypoplastic left heart syndrome (HLHS) is a severe developmental defect characterized by the underdevelopment of the left ventricle along with aortic and valvular defects. Multiple palliative surgeries are required for survival. Emerging studies have identified potential mechanisms for the disease onset, including genetic and hemodynamic causes. Genetic variants associated with HLHS include transcription factors, chromatin remodelers, structural proteins, and signaling proteins necessary for normal heart development. Nonetheless, current therapies are being tested clinically and have shown promising results at improving cardiac function in patients who have undergone palliative surgeries.

AREAS COVERED

We searched PubMed and clinicaltrials.gov to review most of the mechanistic research and clinical trials involving HLHS. This review discusses the anatomy and pathology of HLHS hearts. We highlight some of the identified genetic variants that underly the molecular pathogenesis of HLHS. Additionally, we discuss some of the emerging therapies and their limitations for HLHS.

EXPERT OPINION

While HLHS etiology is largely obscure, palliative therapies remain the most viable option for the patients. It is necessary to generate animal and stem cell models to understand the underlying genetic causes directly leading to HLHS and facilitate the use of gene-based therapies to improve cardiac development and regeneration.