Overview
Definition:
Transposition of the Great Arteries (TGA) is a critical congenital heart defect where the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle, leading to parallel circulations rather than the normal series circulation
Balloon Atrial Septostomy (BAS), often referred to as the Rashkind procedure, is a palliative interventional cardiac catheterization technique used to create or enlarge an atrial septal defect (ASD) to improve mixing of oxygenated and deoxygenated blood.
Epidemiology:
TGA is one of the most common cyanotic congenital heart diseases, accounting for approximately 5-7% of all congenital heart defects
The incidence is about 20-30 per 100,000 live births
It is more common in males
In some cases, TGA is associated with other cardiac anomalies such as ventricular septal defect (VSD), atrial septal defect (ASD), or patent ductus arteriosus (PDA).
Clinical Significance:
TGA results in severe cyanosis at birth due to the unoxygenated blood returning from the body entering the systemic circulation directly via the aorta, and oxygenated blood from the lungs returning to the lungs via the pulmonary artery
Adequate mixing of blood at the atrial level is crucial for survival
BAS is a vital, life-saving intervention that provides temporary palliation, allowing for improved oxygenation until definitive surgical repair can be performed.
Clinical Presentation
Symptoms:
Severe cyanosis, often apparent within minutes to hours of birth
Respiratory distress may be present, but often the infant appears relatively well initially, with cyanosis being the dominant feature
Rapid breathing and poor feeding can also occur
If a large VSD or PDA is present, the cyanosis may be less severe initially, but heart failure can develop later.
Signs:
Marked cyanosis (often central, with a saturation below 75%)
A single, loud second heart sound (S2) is typical
A systolic murmur may be present if there is an associated VSD or increased pulmonary blood flow
Retractions and grunting may indicate respiratory distress
Peripheral pulses may be weak or bounding depending on the associated lesions.
Diagnostic Criteria:
Diagnosis is typically made based on clinical suspicion in a cyanotic neonate, confirmed by echocardiography
Echocardiography clearly demonstrates the discordant origin of the great arteries from the ventricles and the presence or absence of other intracardiac anomalies
Electrocardiogram (ECG) may show right ventricular hypertrophy in some cases.
Diagnostic Approach
History Taking:
Focus on the timing of cyanosis onset (immediately after birth vs
delayed)
Note any associated symptoms like poor feeding, tachypnea, or lethargy
Family history of congenital heart disease
Maternal health during pregnancy (e.g., gestational diabetes, rubella infection).
Physical Examination:
Assess for central cyanosis, tachypnea, retractions
Auscultate for heart sounds (single S2 is key) and murmurs
Palpate peripheral pulses for character
Assess for hepatomegaly or ascites if heart failure is developing.
Investigations:
Echocardiography: The gold standard for diagnosis, demonstrating discordant ventriculoarterial connections, great artery origins, and associated defects
Chest X-ray: May show a narrow mediastinum ("egg-on-a-string" appearance) in complete TGA, but can be variable
ECG: May show right axis deviation and right ventricular hypertrophy
Pulse oximetry: Essential for assessing systemic oxygen saturation.
Differential Diagnosis:
Other causes of cyanotic congenital heart disease in the neonate, including Tetralogy of Fallot, Tricuspid Atresia, Pulmonary Atresia with intact ventricular septum, Truncus Arteriosus, Total Anomalous Pulmonary Venous Connection (TAPVC), and persistent pulmonary hypertension of the newborn
The rapid onset of cyanosis without significant respiratory distress strongly suggests TGA.
Management
Initial Management:
Immediate stabilization is critical
Maintain adequate oxygenation and ventilation
Administer intravenous prostaglandins (e.g., alprostadil) to maintain ductal patency, which allows for some mixing of oxygenated blood from the pulmonary artery to the systemic circulation
Prevent hypothermia and hypoglycemia.
Medical Management:
Prostaglandin E1 infusion is the cornerstone of initial medical management to keep the ductus arteriosus open
This provides a critical pathway for oxygenated blood to reach the systemic circulation
Fluid management is important to prevent dehydration and maintain cardiac output.
Surgical Management:
Balloon Atrial Septostomy (BAS) is an interventional procedure performed in the cardiac catheterization laboratory
Under fluoroscopic guidance, a balloon-tipped catheter is advanced across the foramen ovale or an existing ASD
The balloon is then inflated to tear or enlarge the atrial septum, creating a larger ASD
This facilitates more effective mixing of oxygenated and deoxygenated blood between the atria, significantly improving systemic oxygen saturation
This is a palliative step before definitive surgical correction (e.g., arterial switch operation).
Supportive Care:
Close monitoring of vital signs, oxygen saturation, and fluid balance is essential
Respiratory support may be required
Nutritional support for adequate caloric intake
Management of any co-existing medical conditions
Post-procedural care after BAS includes monitoring for complications and assessment of improved saturation.
Complications
Early Complications:
Complications of BAS can include damage to the tricuspid valve, persistent atrial flutter or fibrillation, perforation of the atrial septum, bleeding at the catheterization site, and paradoxical embolism
Inadequate mixing leading to persistent cyanosis can also occur.
Late Complications:
The primary goal of BAS is palliation
Late complications are primarily related to the underlying TGA and its natural progression or complications of the definitive surgical repair
These can include supraventricular tachycardias, pulmonary stenosis, or residual shunting.
Prevention Strategies:
Meticulous technique during catheterization to minimize trauma to cardiac structures
Careful selection of patients for BAS
Prompt recognition and management of arrhythmias or bleeding
Early definitive surgical correction is the best strategy to prevent long-term complications of uncorrected TGA.
Prognosis
Factors Affecting Prognosis:
The presence and severity of associated intracardiac defects (e.g., VSD, pulmonary stenosis) significantly impact prognosis
The effectiveness of blood mixing achieved by BAS and the timing of definitive surgical repair are crucial
Early diagnosis and intervention are key.
Outcomes:
Without intervention, TGA is uniformly fatal
With prompt medical management (prostaglandins) and palliative procedures like BAS, survival to surgical repair is significantly improved
The arterial switch operation, when performed early, offers excellent long-term outcomes with a near-normal life expectancy for many patients.
Follow Up:
Patients require lifelong cardiology follow-up after definitive surgical repair
This includes regular clinical assessments, ECGs, and echocardiograms to monitor for arrhythmias, valve function, and any residual hemodynamic abnormalities.
Key Points
Exam Focus:
Understand the hemodynamics of TGA and the rationale for BAS
Recognize the classic presentation of severe cyanosis
Know the role of prostaglandins and the immediate goal of BAS (improving atrial mixing)
Recall that BAS is a palliative step before arterial switch operation.
Clinical Pearls:
Severe cyanosis at birth with minimal respiratory distress is highly suggestive of TGA
Always consider the need for prostaglandin infusion immediately upon suspecting TGA
The Rashkind procedure aims to create a functional ASD to allow shunting
The single loud S2 is an important physical finding.
Common Mistakes:
Delaying prostaglandin administration in a cyanotic neonate
Misinterpreting the chest X-ray findings
Overlooking the need for effective atrial mixing when a VSD is also present
Confusing TGA with other cyanotic heart diseases without proper echocardiographic confirmation
Failing to recognize the palliative nature of BAS and the necessity of surgical repair.