Transposition of Great Arteries (TGA)

Transposition of Great Arteries (TGA)

• The pulmonary artery arises from the left ventricle, and the aorta exits from the right ventricle
• There is no communication between the systemic and pulmonary circulations
• Life-threatening at birth
• Survival depends on an open ductus arteriosus and foramen ovale initially
• Accounts for 5% to 7% of congenital heart defects
• More common in males
• ASD or VSD may be present

Transposition of Great Arteries (TGA) - Associated Defects and Treatments

• Associated defects include septal defects or PDA
• The most common defect is a patent foramen ovale
• PDA-associated defects at birth may include VSD
• VSD increases the risk of heart failure
• A VSD allows blood flow from the left ventricle into the pulmonary artery and then to the lungs

TGA Clinical Manifestations

• Cyanosis soon after birth progresses to hypoxemia and acidosis
• Cyanosis does not improve with oxygen administration
• Cyanosis may be less apparent with a large VSD
• Infants take a long time to feed and need frequent rest periods because of rapid respiratory rate and fatigue
• Growth failure may be evident as early as 2 weeks of age if corrective surgery is not performed
• Congestive Heart Failure may develop immediately or over days or weeks
• Tachypnea (60 breaths/ min) is present without retractions or dyspnea unless CHF is present
• If a VSD is present, there is a systolic murmur and a loud S2 that sounds like a single sound

TGA Diagnostic Evaluation

• Chest radiograph reveals a classic egg-shaped heart on a string with enlarged ventricles and increased pulmonary vascular markings.
• ECG reveals right ventricular hypertrophy and shows the abnormal position of the great arteries rising from the ventricles and any associated defects.
• Blood tests reveal an increased hematocrit and hemoglobin or polycythemia and acidosis.

TGA Therapeutic Management

• Prostaglandin E1 is given to maintain a patent ductus arteriosus until a balloon atrial septostomy can be done as a palliative procedure
• Balloon atrial septostomy (Rashkind procedure) is performed during cardiac catheterization
• Balloon atrial septostomy permits oxygenated and unoxygenated blood to mix during cardiac catheterization or under echocardiographic guidance
• A balloon atrial septostomy increases mixing by opening the atrial septum
• CHF is treated with diuretics and digoxin
• Corrective surgery (arterial switch) is performed in the neonatal period
• The arterial switch involves transecting the great arteries
• Arterial switch also involves anastomosing the pulmonary artery to the proximal aorta (just above the aortic valve) and anastomosing the ascending aorta to the proximal pulmonary artery

TGA Postoperative Complications

• Right ventricular failure and rhythm disturbances can occur
• Loss of normal sinus rhythm, baffle leaks, and ventricular dysfunction can also occur
• Survival without surgery is impossible
• Stenosis of the pulmonary artery or aorta may occur in the vessels beyond the valves or coronary artery obstruction
• Arrhythmias, tricuspid valve insufficiency, right ventricular dysfunction or failure, and sudden death may be long-term complications with formerly used surgical procedures

Total Anomalous Pulmonary Venous Return (TAPVR)

• PV fails to join the left atrium
• PV abnormally connects to the systemic venous circuit via the right atrium, such as the SVC
• Abnormal attachment results in mixed blood returning to the right atrium and shunted from right to left through ASD
• Mixed blood must pass through the foramen ovale to provide systemic circulation
• Condition severity increases with pulmonary vein obstruction

TAPVR Classification

• Supracardiac: attachment above the diaphragm (SVC)
• Infradiaphragmatic: attachment below the diaphragm (IVC)
• Cardiac: direct attachment to the heart (RA or coronary sinus)

TAPVR Clinical Manifestations

• Mild cyanosis and tachypnea are typical
• Signs of CHF (tachypnea, dyspnea, tachycardia, and enlarged liver) occurs
• Pulmonary edema develops along with poor growth and frequent respiratory infections
• A systolic murmur is heard in the pulmonic area
• S2 has a wide, fixed split when there is no pulmonary vein obstruction
• A precordial bulge may be palpated

TAPVR Diagnosis & Treatment

• ECG reveals right ventricular hypertrophy
• Echocardiogram reveals a dilated right atrium and ventricle, smaller left-sided chambers, dilated pulmonary arteries, and a patent foramen ovale
• Echocardiogram determines the type of pulmonary drainage and if the pulmonary venous return is obstructed
• Prostaglandin E1 is given to maintain the patent ductus arteriosus
• Diuretics are given to treat CHF
• Surgery is performed to move or create a conduit to connect the pulmonary veins to the left atrium
• Corrective repair is performed during early infancy
• Pulmonary vein is anastomosed to the back of the left atrium, ASD is closed, and the anomalous pulmonary venous connection is ligated

TAPVR Postoperative complications

• Reobstruction, bleeding, dysrhythmias (heart block) can occur
• Pulmonary artery hypertension can also occur
• Persistent heart failure

Truncus Arteriosus

• Failure of normal septation and division of the embryonic bulbar trunk into the pulmonary artery and the aorta leads to the development of a single vessel that overrides both ventricles
• Blood from both ventricles mixes in the common great artery, leading to desaturation and hypoxemia

Truncus Arteriosus - Types

• Type I - a single pulmonary trunk arises near the base of the truncus and divides into the left and right pulmonary arteries
• Type II - left and right pulmonary arteries arise separately but are in close proximity and at the same level from the back of the truncus
• Type III - pulmonary arteries arise independently from the sides of the truncus

Truncus Arteriosus - Manifestations

• Cyanosis develops soon after birth
• Congestive Heart Failure develops within 2 weeks after birth
• CHF is characterized by tachypnea, dyspnea, retractions, poor feeding, poor growth, clubbing, increased pulse pressure, bounding peripheral pulses, widened pulse pressure, and frequent respiratory infections.
• A systolic click may be heard in the apex and pulmonic area.
• The VSD produces a harsh systolic murmur in the lower sternal border

Truncus Arteriosus - Diagnosis and Repair

• Chest radiograph shows cardiomegaly, increased pulmonary vascular markings, and sometimes a right aortic arch
• ECG reveals bilateral ventricular hypertrophy
• Echocardiogram shows a VSD, a large single great artery, and one semilunar valve
• Repair involves closing the VSD so that the truncus arteriosus receives the outflow from the left ventricle
• Pulmonary arteries are excised from the aorta and attached to the right ventricle by means of a homograft.

Truncus Arteriosus - Postoperative Complications & Treatments

• Persistent heart failure can occur
• Bleeding
• Pulmonary artery hypertension can also be a complication
• Dysrhythmias and residual VSD can occur post op
• One or more conduit replacements may be needed later in childhood
• CHF is treated with diuretics and digoxin
• Rastelli procedure is performed to close the VSD, enabling the left ventricle to empty into the single large great artery
• Prophylaxis for infective endocarditis is needed for life

Hypoplastic Left Heart Syndrome (HLHS)

• Under-development of the left side of the heart, which results in a hypoplastic left ventricle and aortic atresia.
• The mitral and aortic valves are absent or stenosed.
• An abnormally small left ventricle and small aorta is common
• Most blood from the left atrium flows across the patent foramen ovale to the right atrium, to the right ventricle, and out the pulmonary artery

HLHS: Clinical Manifestations

• Mild cyanosis
• Signs of Heart Failure until the PDA closes
• Tachycardia, tachypnea, dyspnea and retractions
• Decreased peripheral pulses
• Poor peripheral perfusion
• Pulmonary edema
• CHF leads to shock, acidosis, and death if left untreated
• S2 is single and loud
• No heart murmur is present.

HLHS: Diagnostic Evaluation

• Chest radiograph shows cardiomegaly and increased pulmonary venous congestion
• ECG shows right ventricular hypertrophy
• Echocardiogram shows the small left ventricle and enlarged right ventricle
• HLHS is commonly diagnosed prenatally

HLHS: Therapeutic Management

• Neonates require stabilization with mechanical ventilation and inotropic support preoperatively
• Prostaglandin E1 infusion maintain ductal patency and ensure adequate systemic blood flow
• Norwood procedure is the first stage approach
• Pulmonary artery is anastamosed to the aorta creating a new aorta
• Shunting occurs to provide pulmonary blood flow
• (Modified Blalock-Taussig shunt), and creation of a large ASD.
• Modification done via the use of a right ventricle-to-pulmonary artery homograft conduit instead of a shunt to supply pulmonary blood flow (Sano procedure)
• Imbalance of systemic and pulmonary blood flow, bleeding, low cardiac output, and persistent heart failure.
• Bidirectional Glenn shunt procedure or a hemi-Fontan operation is performed
• The SVC is anastomosed to the right pulmonary artery so SVC flow bypasses the right atrium and flows directly to the lungs
• Procedure is usually done at 3 to 6 months of age to relieve cyanosis and reduce the volume load on the right ventricle
• The final repair is a modified Fontan.
• Transplant of the heart in the newborn is another option for infants

HLHS: Problems & Complications

• Shortage of newborn organ donors creates a rejection risk
• There are long-term problems with chronic immunosuppression infection.
• Risks include; Worsening ventricular function, Tricuspid regurgitation, Recurrent aortic arch narrowing, and Dysrhythmias and developmental delays
• Potential for complications
• The mortality for the latter two operations is less than 5%.