Dr.SreeLekshmy.S, Dr.Krishnakumar (pediatric cardiology), Dr.Jayasree, Dr.Sheela Namboothiri(pediatric genetics)
DrC Jayakumar
A term Asymmetrical SGA male ba born to a primi mother at 38weeks with a birthweight of 2.12kg, cried at birth and was referred inview of antenatally detected congenital heartblock and large membranous VSD.
At admission ba had respiratory distress and bradycardia (HR-60/min).
General examination revealed dysmorphic facies with down slanting eyes, micro retrognathia, overlapping fingers and short big toe.
Systemic examination revealed soft pansystolic murmur in the
lower left sternal border.
Ba was started on HFNC in view of respiratory distress.
ECHO showed a normal sequential chamber relationship with Large inlet VSD; laminar flow, enlarged LA &LVand bradycardia from complete heart block.
Oral ociprenaline was started in view of congenital heart block and heart rate was maintained between 60-70/min.
Diuretics were added in view of congestive cardiac failure and titrated to effect. Later on day 3 of admission respiratory support escalated to bubble CPAP with PEEP 5 fio2 21%.
Total fluids were restricted to 110ml per kg per day in view of VSD with CHF as per pediatric cardiology recommendation
In view Dysmorphic facies and hemivertebrae and heart block Anti RO and Anti LA antibody was done turned out to be negative.
FISH test to rule out TRISOMY 18was negative but Microarray sent was positive for Trisomy 18.
Respiratory distress increased on day12 and raising PCo2 and respiratory acidosis with increased Fio2 requirements ba was intubated and connected to SIMV mode with Pip 16 fio2- 26% Peep-6.
In view of negative balance with raising urea IV furosemide was tapered from 3mg per kg per day to 2mg per kg per day then to 1mg per kg per day . Joint cardiac committee discussion was done and planned to do Pulmonary artery banding with Permanent pacemaker implantation after stabilisation at a later date.
Discussion:
Congenital Heart Block (CHB) refers to a condition where the electrical conduction system of the heart is impaired from birth, leading to a delay or complete block in the transmission of electrical signals from the atria to the ventricles. This can cause a variety of arrhythmias, most commonly a slow heart rate or complete heart block.
1. Etiology (Causes)
Maternal Autoantibodies:
The most common cause of congenital heart block is maternal autoimmune diseases, particularly Systemic Lupus Erythematosus (SLE) and Sjogren’s syndrome.
These conditions are associated with anti-Ro (SSA) and anti-La (SSB) antibodies, which can cross the placenta and damage the fetal conduction system.
Genetic Factors:
In some cases, CHB may be associated with inherited genetic conditions, but this is less common than the autoimmune cause.
Idiopathic: In some instances, the exact cause is unknown.
2. Pathophysiology
The heart’s electrical conduction system, which controls the heart’s rhythm, consists of the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, and Purkinje fibers. In congenital heart block, the conduction of electrical impulses is impaired at the AV node or lower levels of the conduction system.
Type I: First-degree heart block – Prolonged PR interval with normal conduction.
Type II: Second-degree heart block – Some atrial impulses are not conducted to the ventricles (e.g., Mobitz type I or II).
Type III: Third-degree (complete) heart block – No atrial impulses are conducted to the ventricles. The ventricles generate their own rhythm, typically slower than normal.
3. Clinical Presentation
Symptoms: Often related to bradycardia (slow heart rate). Infants may present with poor feeding, fatigue, cyanosis, and heart failure symptoms if the block is severe.
• In mild cases, some patients might be asymptomatic, and the condition is discovered incidentally on an ECG.
Fetal Diagnosis: CHB can be diagnosed in utero through prenatal ultrasound, where a slow fetal heart rate (usually below 60-70 beats per minute) may be detected. In cases of severe third-degree block, the fetus may also show signs of hydrops fetalis (fluid buildup in tissues).
4. Diagnosis
• ECG: The hallmark of congenital heart block on an ECG is a prolonged PR interval. In third-degree block, there will be complete dissociation between the atria and ventricles (no conduction of atrial impulses to the ventricles).
Fetal Monitoring: In cases of suspected maternal autoimmune disease, fetal echocardiography and fetal ECG may be performed to assess the heart rate and detect abnormalities.
Serology: Testing for anti-Ro and anti-La antibodies in the mother is essential if an autoimmune cause is suspected.
5. Management
Monitoring and Follow-up: Mild forms of congenital heart block may require only periodic monitoring, while severe cases might need more intensive management.
Pacemaker: In cases of third-degree heart block, especially in symptomatic infants, a pacemaker may be required to maintain an adequate heart rate. This is often a long-term treatment.
Maternal Treatment: If the heart block is suspected to be related to maternal autoimmune disease, treating the underlying maternal condition (e.g., with corticosteroids) may be beneficial to prevent further complications.
6. Prognosis
Mild Heart Block (First-degree or occasional second-degree): These cases may resolve or remain stable throughout life with no significant symptoms or complications.
Severe Heart Block (Third-degree block): The prognosis depends on the severity of the block and the presence of other associated complications, such as hydrops or heart failure. Early pacemaker insertion often results in a good outcome.
Fetal Heart Block: The prognosis is worse in severe cases diagnosed before birth, particularly in the presence of hydrops or when a pacemaker is not available or effective.
7. Complications
Heart failure: Especially in newborns with severe block, where there is inadequate ventricular rate and cardiac output.
Infections: Children with pacemakers are at increased risk for infections, such as endocarditis.
Arrhythmias: Long-term risk of developing other arrhythmias, especially if the conduction system continues to degenerate.
