Cyanotic Heart Defects (CHDs)

Cyanotic Heart Defects (CHDs)

• Congenital cardiac malformations affecting atrial walls, ventricular walls, heart valves, or large blood vessels
• Common causes: genetic defects, maternal conditions (e.g., diabetes), and spontaneous genetic mutations
• Pathophysiology: right-to-left cardiac shunt, leading to deoxygenated blood entering the systemic circulation, resulting in hypoxemia and cyanosis

Symptoms and Diagnosis

• Symptoms: cyanosis, failure to thrive, characteristic heart murmurs, and symptoms of heart failure
• Diagnosis: confirmed through echocardiography, with low oxygen saturation and characteristic x-ray findings

Treatment and Prognosis

• Heart defects requiring treatment are repaired via catheter procedures or surgery
• Supportive medical therapy is required in patients with heart failure or if surgery cannot be performed
• If untreated, most cyanotic heart defects are fatal within the first year of life

Associated Conditions and Risk Factors

• Tetralogy of Fallot
• DiGeorge syndrome
• Down syndrome
• Maternal risk factors: alcohol consumption, phenylketonuria, and diabetes
• Tricuspid valve atresia
• Total anomalous pulmonary venous return
• Heterotaxy syndromes
• Persistent truncus arteriosus
• Hypoplastic left heart syndrome

General Pathophysiological Processes

• Right-to-left cardiac shunting: deoxygenated blood entering the systemic circulation, leading to cyanosis
• Fetal and postnatal circulation: changes in blood flow and oxygenation during development

Topic-Specific Notes

Tetralogy of Fallot

• Definition: simultaneous occurrence of four defects: RVOTO, RVH, VSD, and overriding aorta
• Epidemiology: most common cyanotic CHD
• Etiology: typically sporadic, associated with genetic disorders (DiGeorge syndrome, Down syndrome)
• Pathophysiology: anterior and superior deviation of the infundibular septum during fetal development
• Clinical findings: cyanosis, RVOTO, and characteristic cardiac examination findings
• Treatment: surgical repair, PGE1 infusion, and treatment of tet spells

Transposition of the Great Vessels (TGV)

• Definition: anatomical reversal of the aorta and pulmonary artery
• Etiology: failed spiraling of the aorticopulmonary septum during fetal development
• Pathophysiology: complete isolation of the pulmonary and systemic circuits, leading to cyanosis
• Clinical findings: postnatal cyanosis, tachypnea, and single, loud S2
• Treatment: mixing of the two parallel circulations, balloon atrial septostomy, and surgical repair

Tricuspid Valve Atresia

• Definition: absent or rudimentary tricuspid valve
• Pathophysiology: RV hypoplasia, RA dilation, and interatrial and interventricular communications
• Clinical findings: cyanosis, tachypnea, and cardiac examination findings
• Treatment: cardiopulmonary stabilization, PGE1 infusion, and surgical palliation

Ebstein Anomaly

• Definition: malformed tricuspid valve leaflets displaced into the RV
• Pathophysiology: incomplete delamination during valve development, leading to tricuspid regurgitation and RV atrialization
• Clinical findings: cyanosis, cardiomegaly, and cardiac examination findings
• Treatment: surgical repair

Total Anomalous Pulmonary Venous Return (TAPVR)

• Definition: all four pulmonary veins draining into the systemic venous circulation
• Pathophysiology: venous mixing, leading to right-to-left shunting and cyanosis
• Clinical findings: cyanosis, respiratory failure, and cardiac examination findings
• Treatment: surgical repair

Persistent Truncus Arteriosus

• Definition: underdevelopment of the aorticopulmonary septum, resulting in a single trunk
• Pathophysiology: deoxygenated and oxygenated blood mix via a VSD
• Clinical findings: cyanosis, respiratory distress, and cardiac examination findings
• Treatment: surgical repair

Hypoplastic Left Heart Syndrome (HLHS)

• Definition: spectrum of disease consisting of severe hypoplasia of the left ventricle
• Pathophysiology: hypoplastic left ventricle is nonfunctional, with RV becoming the primary supply for pulmonary and systemic circulations
• Clinical findings: cyanosis, tachypnea, and cardiac examination findings
• Treatment: initial medical management, PGE1 infusion, and surgical repair