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Atrioventricular block in situs ambiguus and left isomerism (polysplenia syndrome)
Insights
Polysplenia syndrome, a form of situs ambiguus, is linked to advanced atrioventricular block in children. This specific heart block pattern suggests left isomerism in pediatric patients with heart disease.
Area of Science:
- Pediatric Cardiology
- Electrophysiology
- Congenital Heart Disease
Background:
- Situs ambiguus, specifically left isomerism (polysplenia syndrome), is a complex congenital condition.
- Advanced atrioventricular block (AV block) can present in various forms, including Wenckebach block and complete heart block.
Observation:
- Three pediatric patients with situs ambiguus and left isomerism presented with advanced atrioventricular block.
- One patient exhibited complex bradyarrhythmia with Wenckebach block.
- Two patients displayed congenital AV block with narrow QRS, specific ventricular and atrial rates, and unusual superiorly directed P wave axes.
Findings:
- The observed ECG pattern of complete AV block with narrow QRS and unusual P wave axis in infants and children is highly suggestive of left isomerism.
- This specific ECG presentation was not found in over 400 adult patients with complete AV block.
- The incidence of complete AV block in left isomerism is approximately twenty percent.
Implications:
- Early recognition of this specific ECG pattern in pediatric patients can aid in diagnosing left isomerism.
- This finding highlights the importance of considering situs abnormalities in the evaluation of congenital heart block.
- Further research into the cardiac manifestations of polysplenia syndrome is warranted.
Abstract:
Three patients are described who had situs ambiguus and left isomerism (polysplenia syndrome) and advanced atrioventricular block. One presented with a complex bradyarrhythmia with Wenckebach block. The other two had congenital atrioventricular block with a narrow QRS at a ventricular rate of 80 per minute, an atrial rate of 150' per minute, and both had a P wave axis directed superiorly and to the right in one, and superiorly to the left in the other. This ECG pattern was not observed in more than 400 adult patients with complete A-V block treated in our service. It is our opinion that in infants and children with heart disease the presence of complete A-V block with narrow QRS and an unusual P waves axis directed superiorly is strongly suggestive of left isomerism. The incidence rate of complete A-V block in left isomerism is nearly twenty percent of the cases described.