Overview
Definition:
Congenital Heart Disease (CHD) refers to structural abnormalities of the heart or great vessels present at birth
Critical Congenital Heart Disease (CCHD) is a subset of CHDs requiring intervention in the first year of life, often presenting with significant hypoxemia or hemodynamic compromise
Pulse oximetry screening is a non-invasive method to detect CCHD in asymptomatic newborns prior to discharge.
Epidemiology:
CHDs affect approximately 1% of live births worldwide
Of these, CCHDs account for about 25-30%
In India, the prevalence may vary, but robust screening is crucial due to the large birth cohort
Late diagnosis significantly increases morbidity and mortality.
Clinical Significance:
Early detection of CCHD through routine screening dramatically improves outcomes by allowing timely intervention, reducing complications like hypoxic brain injury, pulmonary hypertension, and death
This screening program is a cornerstone of modern neonatal care and a critical topic for pediatric residents preparing for DNB and NEET SS examinations.
Screening Protocol
Timing:
Screening should be performed after 24 hours of age or before discharge, whichever is later
If the infant is discharged before 24 hours, screening should occur within 48 hours of discharge or at a follow-up visit.
Procedure Steps:
Obtain pulse oximetry readings from a pre-ductal (right hand) and post-ductal (foot) site
Readings should be taken when the infant is calm and not crying
Ensure proper sensor placement and a stable waveform.
Pass Criteria:
A screen is considered passed if the SpO2 reading in both the right hand and foot is ≥ 95% and the difference between them (absolute difference) is < 3%.
Fail Criteria:
A screen is considered failed if the SpO2 reading in either the right hand or foot is < 95% OR the absolute difference between the right hand and foot SpO2 is ≥ 3%.
Repeat Screening:
If the initial screen fails, repeat the pulse oximetry after 1 hour
If the second screen also fails, proceed to further evaluation
If the SpO2 is < 90% on the initial screen, immediate further evaluation is warranted without repeating.
Diagnostic Approach Post Fail
Initial Evaluation:
If the screening test fails, a thorough clinical assessment for signs of CHD is essential
This includes evaluating for cyanosis, tachypnea, grunting, retractions, poor feeding, lethargy, and differential pulses.
Further Investigations:
The primary investigation following a failed screen is echocardiography
This imaging modality can confirm the presence, type, and severity of CCHD
A chest X-ray may be considered if respiratory distress is evident, but it is not definitive for CHD.
Differential Diagnosis:
Conditions mimicking CCHD include sepsis, respiratory distress syndrome, pneumonia, transient tachypnea of the newborn, meconium aspiration syndrome, and other causes of hypoxemia not related to structural heart defects
Careful clinical correlation is vital.
Referral Criteria:
Infants with a failed pulse oximetry screen require prompt evaluation by a pediatric cardiologist or in a facility equipped for neonatal cardiac assessment and management
Any infant with suspected CCHD should be urgently referred.
Specific Chds Detected
Ductal Dependent Lesions:
Examples include Tetralogy of Fallot, Transposition of the Great Arteries, Critical Pulmonary Stenosis, Tricuspid Atresia, Hypoplastic Left Heart Syndrome, and Interrupted Aortic Arch
These rely on the patent ductus arteriosus for systemic or pulmonary blood flow.
Other Significant Chds:
Ventricular Septal Defect (large VSDs), Atrial Septal Defect (large ASDs), Patent Ductus Arteriosus (significant PDAs), Coarctation of the Aorta (though less likely to present with severe hypoxemia initially unless severe).
Importance Of Timing:
The ductus arteriosus begins to close shortly after birth, especially with increased oxygenation
Detecting these ductal-dependent lesions before complete closure is critical for initiating medical management (prostaglandin infusion) and planning surgical or interventional correction.
Management Of Cchd
Medical Management:
Prostaglandin E1 (PGE1) infusion is critical for ductal-dependent lesions to maintain ductal patency and adequate systemic or pulmonary blood flow
Dosage is typically 0.05-0.1 mcg/kg/min, titrated to effect
Supportive care includes oxygen, management of heart failure symptoms, and adequate nutrition.
Surgical Or Interventional Management:
The specific intervention depends on the type of CCHD
Options include balloon atrial septostomy, ductal stenting, surgical repair (e.g., VSD closure, TOF repair), or palliative staged procedures (e.g., Norwood procedure for HLHS)
Decisions are made by a multidisciplinary cardiac team.
Postoperative Care:
Requires intensive monitoring in a pediatric cardiac intensive care unit, managing hemodynamics, fluid balance, respiratory support, and pain control
Long-term follow-up with a pediatric cardiologist is essential.
Key Points
Exam Focus:
Understand the exact criteria for passing and failing the pulse oximetry screen
Know the typical age for screening, the specific sites for measurement (pre- and post-ductal), and the critical role of PGE1 in ductal-dependent lesions
Recognize the common CCHDs that can be detected.
Clinical Pearls:
Always perform the screen after 24 hours of age
Rule out transient causes of hypoxemia before proceeding with definitive cardiac workup
Echocardiography is the gold standard for diagnosing CCHD
Prompt recognition and referral are life-saving.
Common Mistakes:
Performing the screen too early (before 24 hours)
Misinterpreting readings or failing to check pre- and post-ductal differences
Delaying echocardiography after a failed screen
Not initiating PGE1 infusion promptly for suspected ductal-dependent lesions
Confusing CCHD with other causes of neonatal respiratory distress.