Arrhythmias presenting in neonatal lupus.

Area of Science:

• Immunology
• Cardiology
• Neonatology

Background:

• Congenital heart block is a severe manifestation of Neonatal Lupus (NL).
• Anti-Ro/SSA antibodies are implicated in the pathogenesis of NL.
• Current understanding of congenital atrioventricular (AV) block requires refinement regarding detection timing and reversibility.

Purpose of the Study:

• To explore the direct electrophysiological effects of anti-Ro/SSA and anti-p200 antibodies on the fetal heart.
• To differentiate between potentially reversible incomplete AV block and irreversible complete AV block in utero.
• To propose a refined definition for congenital AV block, encompassing in utero and neonatal periods.

Main Methods:

• Perfusion of human fetal hearts with anti-Ro/SSA antibodies.
• Investigation of antibody cross-reactivity with cardiac calcium channels (T- and L-type).
• Analysis of calcium accumulation in rat heart cells induced by anti-p200 antibodies.

Main Results:

• Anti-Ro/SSA antibody perfusion induced transient heart block in human fetal hearts.
• Antibodies may directly affect cardiac electrophysiology via calcium channel interactions.
• Incomplete AV block shows potential for reversibility with fluorinated steroid therapy, unlike complete AV block.

Conclusions:

• Anti-Ro/SSA antibodies are a likely direct cause of fetal heart block through electrophysiological mechanisms.
• Early detection and differentiation of AV block (complete vs. incomplete) are critical for neonatal lupus management.
• A revised definition of congenital AV block, including the neonatal period, is proposed for accurate diagnosis and research.