Congenital Heart Defect: Truncus Arteriosus

Truncus Arteriosus

• Rare congenital heart defect (CHD) where a single artery (truncus) arises from the heart instead of separate pulmonary artery and aorta.
• Mixed oxygenated and deoxygenated blood is circulated to the systemic and pulmonary systems.

Key Features

• Single Great Artery: A single artery overrides both ventricles, supplying blood to coronary arteries, pulmonary arteries, and systemic circulation.
• Ventricular Septal Defect (VSD): Large, nonrestrictive VSD present, allowing communication between the right and left ventricles.
• Truncal Valve: A single valve, often with 3 cusps (can have 2 or 4), located at the root of the truncus arteriosus. This valve may have regurgitation or stenosis.
• Pulmonary Arteries: Pulmonary arteries arise from the truncus arteriosus, not a separate pulmonary trunk. Location and origin vary depending on the type of truncus.
• Aortic Arch: Aortic arch may have variations, including a right-sided aortic arch in 1/3 of patients.

Associated Defects

• Right aortic arch
• Secundum atrial septal defect (ASD)
• Coronary artery anomalies
• DiGeorge syndrome
• Interrupted aortic arch

Embryology

• Failure of the aorticopulmonary septum to fully develop and divide the common truncus arteriosus into the aorta and pulmonary trunk.

Echo Findings

• Dilated single great artery overriding both ventricles.
• Large, unrestricted VSD.
• Assessment of pulmonary artery anatomy and truncal valve morphology (cusp number, regurgitation, stenosis).
• Possible presence of a right aortic arch or coronary anomalies.

Classification Systems

Collet & Edwards

• Type 1: Main pulmonary artery (MPA) branches into left and right pulmonary arteries.
• Type 2: Separate pulmonary arteries branch close to the truncus.

Van Praagh

• Type 1: Portion of MPA present, branches into pulmonary arteries.
• Type 2: No MPA, separate branch pulmonary arteries arise from the truncus.
• Type 3: Only one pulmonary artery branch arises from the truncus.

d-Transposition of the Great Arteries (d-TGA)

• d-TGA is a congenital heart defect where the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle.
• This results in two separate circulatory loops, one systemic and one pulmonary.
• The aorta is anterior and right, while the pulmonary artery is posterior and left.
• Requires a shunt (patent foramen ovale, atrial septal defect, patent ductus arteriosus) for life.
• Presents with cyanosis within the first day of life due to parallel circulatory systems.
• May hear systolic murmurs due to VSD or outflow tract obstruction.

Associated Anomalies in d-TGA

• Ventricular septal defect (VSD)
• Coronary artery anomalies
• Pulmonary stenosis
• Left ventricular outflow tract obstruction (LVOTO)
• Atrial septal defect (ASD)
• Patent ductus arteriosus (PDA)

Echo Features in d-TGA

• Abnormal ventriculo-arterial connections
• Parallel great arteries
• Associated shunts

Surgical Procedures for d-TGA

• Balloon septostomy
• Atrial switch (Mustard/Senning)
• Arterial switch (Jatene)

d-TGA Initial Stabilization

• Prostaglandin E1: keeps the ductus arteriosus open
• Balloon septostomy: creates or enlarges a shunt

d-TGA Atrial Switch

• Reroutes systemic and pulmonary venous return
• Corrects blood flow at the atrial level.
• Complications: right ventricular dysfunction, tricuspid regurgitation (TR), baffle leaks, arrhythmias.

d-TGA Arterial Switch

• Preferred surgery
• Switches the aorta and pulmonary artery to restore normal circulation
• Current preferred surgery
• Corrects ventriculo-arterial connections
• Complications: coronary artery obstruction and stenosis at anastomosis sites.

Incidence

• 3% of all congenital heart defects
• 20-22 per 100,000 live births

Key Features

• Parallel circulations with no oxygenation without a shunt.
• Profound cyanosis at birth.
• Echo: Parallel great arteries, rightward aorta, abnormal ventriculo-arterial connections.

Associated Lesions

• VSD
• Coronary artery anomalies
• Coarctation
• ASD.

Treatment

• Medical: Prostaglandin E1 to keep ductus arteriosus open, balloon septostomy
• Surgical: Atrial switch (Mustard or Senning), Arterial switch (Jatene), Lecompte maneuver.

Congenitally Corrected Transposition of the Great Arteries (CC-TGA)

• AV and VA discordance, but corrected circulation.
• Ventricles are inverted: right ventricle (on the left) is systemic, and the left ventricle (on the right) is subpulmonary.

CC-TGA Etiology

• Results from abnormal (L-looping) embryologic development.

CC-TGA Physiology

• Hemodynamically corrected, but structurally abnormal.
• May lead to right ventricular failure.

Associated Anomalies in CC-TGA

• VSD (60%)
• Tricuspid valve abnormalities (up to 90%)
• Left ventricular outflow tract obstruction.

Echocardiographic Features in CC-TGA

• Discordant atrioventricular and ventriculo-arterial connections.
• Systemic RV connected to the aorta.

Surgical Procedures for CC-TGA

• Double Switch: Combines atrial and arterial switch to redirect blood flow and make the left ventricle the systemic ventricle.

CC-TGA Incidence

• 0.5% of all congenital heart defects.

CC-TGA Key Features

• Asymptomatic early in life.
• Can be undiagnosed until adulthood.
• Echo: Discordant atrioventricular and ventriculo-arterial connections.
• Right ventricle becomes systemic and the left ventricle is subpulmonary.

Associated Lesions in CC-TGA

• VSD
• Systemic tricuspid valve abnormalities
• Left ventricular outflow tract obstruction.

CC-TGA Treatment

• Medical: Treat heart failure, reduce afterload
• Surgical: Tricuspid valve repair or replacement.

Explore the complex nature of truncus arteriosus, a rare congenital heart defect characterized by a single great artery supplying both systemic and pulmonary circulation. This quiz delves into its key features, including the presence of a ventricular septal defect and truncal valve abnormalities. Test your knowledge on this unique cardiovascular condition and its implications.