Overview
Definition:
Pulmonary atresia with ventricular septal defect (PA-VSD) is a complex cyanotic congenital heart disease characterized by complete obstruction of the pulmonary valve annulus and outflow tract, coupled with a defect in the interventricular septum allowing shunting of blood between the ventricles
Blood flow to the pulmonary circulation relies on systemic-to-pulmonary collateral arteries (SPCA) or a patent ductus arteriosus (PDA).
Epidemiology:
PA-VSD accounts for approximately 1-3% of all congenital heart defects
It is one of the more severe forms of cyanotic heart disease, often presenting with significant hypoxemia
The incidence varies, but it is a critical condition requiring prompt diagnosis and management.
Clinical Significance:
This condition is life-threatening without surgical intervention
Understanding staged palliation is crucial for pediatric cardiologists and cardiac surgeons as it involves a series of operations to gradually establish adequate pulmonary blood flow and eventually a single ventricle physiology, aiming to improve survival and functional status in affected infants and children
Success impacts long-term morbidity and quality of life.
Clinical Presentation
Symptoms:
Severe cyanosis at birth or shortly thereafter
Progressive dyspnea
Tachypnea
Poor feeding
Failure to thrive
Palpitations if significant shunting occurs
Murmur may be absent or soft due to lack of pulmonary valve flow.
Signs:
Profound cyanosis (peripheral and central)
Tachycardia
Tachypnea
Poor peripheral perfusion
Clubbing of fingers and toes may develop over time
A single S2 may be heard, with absence of a loud P2
A systolic murmur may be present if there are associated obstructions or collateral flow
Signs of congestive heart failure may be present in some cases.
Diagnostic Criteria:
Diagnosis is primarily based on echocardiography, which reveals the absence of pulmonary valve leaflets or atretic annulus, presence of a VSD, and assessment of pulmonary arteries and collateral flow
Cardiac catheterization may be used for detailed anatomical assessment and hemodynamic evaluation, especially for planning surgical intervention.
Diagnostic Approach
History Taking:
Detailed perinatal history for maternal infections or exposures
History of cyanosis since birth, its severity and variability
Presence of associated symptoms like poor feeding or respiratory distress
Family history of congenital heart disease.
Physical Examination:
Thorough cardiovascular examination focusing on cyanosis, vital signs, peripheral pulses, and auscultation for murmurs and heart sounds
Assessment for any signs of respiratory distress or failure to thrive.
Investigations:
Echocardiography is the cornerstone for diagnosis, visualizing the VSD, pulmonary atresia, collateral circulation (SPCA), and the size of branch pulmonary arteries
Chest X-ray may show reduced pulmonary vascular markings and cardiomegaly
Electrocardiogram (ECG) can reveal right ventricular hypertrophy or strain patterns
Cardiac MRI or CT angiography can provide detailed anatomy of pulmonary arteries and SPCA
Cardiac catheterization is essential for pre-operative assessment of pulmonary artery anatomy, collateral flow, and pressures, guiding surgical strategy.
Differential Diagnosis:
Other cyanotic congenital heart diseases with decreased pulmonary blood flow, such as Tetralogy of Fallot with pulmonary atresia, Tricuspid atresia, Pulmonary stenosis with VSD, Transposition of the great arteries with VSD and pulmonary stenosis
Critical evaluation of pulmonary artery anatomy and collateral supply is key to differentiating.
Management
Initial Management:
Immediate stabilization is critical
Maintain ductal patency with prostaglandin E1 infusion (e.g., 0.05-0.1 mcg/kg/min) to ensure systemic-to-pulmonary flow if the PDA is the primary source of pulmonary perfusion
Supplemental oxygen should be used judiciously as it can reduce systemic vascular resistance and worsen cyanosis.
Medical Management:
Primarily supportive
Prostaglandin infusion is the mainstay until surgical palliation
Antibiotic prophylaxis for infective endocarditis is important due to the VSD
Management of congestive heart failure if present (though less common in severe PA-VSD without significant regurgitant flow).
Surgical Management:
Staged palliation is the standard approach
The specific strategy depends on the anatomy of the pulmonary arteries and collateral supply
Stage 1: Newborn period - Pulmonary artery reconstruction (if feasible), Blalock-Taussig (BT) shunt placement from subclavian to pulmonary artery, or an RV-to-PA conduit if a viable pulmonary valve annulus is present
The goal is to achieve adequate pulmonary blood flow for oxygenation
Stage 2: Infancy - Often involves widening the pulmonary artery or completing a conduit if a partial conduit was placed initially
May include closure of the VSD if it aids in creating a more balanced circulation, or if it’s part of a single-ventricle repair pathway
Stage 3: Fontan Procedure - Typically performed between 2-5 years of age
This involves creating a connection between the vena cava and pulmonary arteries, establishing a cavopulmonary connection (e.g., bidirectional Glenn shunt or lateral tunnel Fontan), leading to total cavopulmonary connection (TCPC) to divert deoxygenated systemic venous blood directly to the pulmonary arteries without passing through the heart
The VSD is usually closed during the Fontan procedure if not closed earlier.
Supportive Care:
Close monitoring of oxygen saturation, heart rate, and respiratory status
Nutritional support to promote growth
Strict fluid balance management
Education of parents regarding the condition and long-term care plan.
Complications
Early Complications:
Shunt thrombosis or stenosis (BT shunt)
Pulmonary hypertension from excessive flow
Arrhythmias
Hemorrhage
Myocardial dysfunction
Chylothorax.
Late Complications:
Pulmonary arteriovenous malformations (AVMs)
Protein-losing enteropathy (PLE) post-Fontan
Liver dysfunction
Arrhythmias (atrial flutter/fibrillation)
Progressive ventricular dysfunction
Pulmonary venous obstruction
Thromboembolism
Development of pulmonary edema due to inadequate systemic venous pressure regulation.
Prevention Strategies:
Careful surgical technique for shunt placement and conduit creation
Optimal balancing of pulmonary blood flow to avoid over-circulation
Regular echocardiographic surveillance for shunt integrity and pulmonary artery growth
Early recognition and management of AVMs
Prophylactic measures for PLE and thrombotic events.
Prognosis
Factors Affecting Prognosis:
Size and continuity of branch pulmonary arteries
Presence and adequacy of collateral circulation
Success of surgical interventions (shunt patency, conduit function)
Development of complications like PLE or liver disease
Overall ventricular function
Adherence to follow-up protocols.
Outcomes:
With modern staged palliation, survival rates have significantly improved
Many children can achieve a functional single ventricle physiology, allowing for improved exercise tolerance and quality of life
However, long-term management requires lifelong cardiology follow-up due to the inherent risks of Fontan circulation.
Follow Up:
Lifelong, comprehensive follow-up with a pediatric cardiologist specializing in adult congenital heart disease is essential
This includes regular clinical assessments, ECGs, echocardiograms, and Holter monitoring
Screening for complications such as liver disease, protein-losing enteropathy, and AVMs is critical.
Key Points
Exam Focus:
PA-VSD is a cyanotic heart defect requiring staged palliation
Prostaglandin E1 is crucial for ductal patency in neonates
Staged palliation aims for a Fontan circulation
Key surgical stages include BT shunt/RV-PA conduit, potentially Glenn, and finally Fontan
Complications like PLE and AVMs are crucial to remember for exam questions.
Clinical Pearls:
Always consider PA-VSD in a neonate with severe cyanosis and a soft murmur
Echocardiography is paramount for initial diagnosis and planning
The success of palliation hinges on the anatomy of the pulmonary arteries and effective management of collateral flow
Recognize that even after Fontan completion, significant long-term risks remain.
Common Mistakes:
Over-oxygenation in cyanotic infants
Delaying prostaglandin infusion when ductal dependence is suspected
Inadequate assessment of pulmonary artery anatomy pre-operatively
Misinterpreting echocardiographic findings regarding collateral supply
Underestimating the long-term management needs post-Fontan circulation.