# Case Report: Bradycardia in neonatal lupus: differential diagnosis between atrioventricular block and premature atrial contractions with block

## TL;DR

This case report highlights the importance of distinguishing between different types of heart rhythm issues in a neonate with lupus to ensure proper treatment.

## Contribution

The paper presents a rare case of neonatal lupus with atrial tachycardia and emphasizes the diagnostic distinction between AV block and PACs with block.

## Key findings

- The neonate had bradycardia due to premature atrial contractions with block, not high-degree AV block.
- Atrial tachycardia developed at 23 days, a rare manifestation in neonatal lupus.
- Fixed RR intervals and unfixed PP intervals helped differentiate the arrhythmias.

## Abstract

Neonatal lupus may be associated with severe cardiac conduction problems, including high-degree or complete atrioventricular (AV) block, necessitating immediate pacemaker implantation during the neonatal period. However, cardiac manifestations of neonatal lupus may extend beyond AV block. Our case was a full-term female neonate, who presented with fetal arrhythmia and bradycardia with a heart rate of approximately 70–75 beats per minute after birth. Neonatal lupus was diagnosed later due to positive maternal and neonatal anti-SSA/Ro antibody. High-degree AV block was considered initially but bigeminy premature atrial contractions (PACs) with block was confirmed through a detailed evaluation of an electrocardiogram, which demonstrated unfixed PP intervals and fixed RR intervals. Atrial tachycardia (AT) developed when the neonate was 23 days old. The key point that differentiates high-degree AV block from PACs with block is the PP interval. The PP interval is fixed in high-degree AV block and unfixed in PACs with block. Careful differential diagnosis is required in neonates with bradycardia because it may lead to very different management. Our case presents a good illustration of why these arrhythmias need to be differentiated. Furthermore, our case may be the first of neonatal lupus with AT.