Cardiac involvement has been reported in various mucopolysaccharidoses syndromes. Cardiac valve pathology is the most prominent cardiac manifestation of patients with these syndromes. To date, there have been no reports of early childhood onset of high-grade atrioventricular block in patients with Hunter syndrome. We present a case of a 3-year-old boy with Hunter syndrome who was found to have various degrees of atrioventricular block. This case highlights the importance of early routine cardiac screening for conduction abnormalities and close follow-up in patients with mucopolysaccharidoses syndromes.

Right atrial appendage aneurysm is an extremely rare congenital malformation with unknown aetiology. The most common potential complication is atrial arrhythmias including atrial flutter, atrial fibrillation, and atrial tachycardia. These arrhythmias are usually refractory to medication therapy. Radiofrequency catheter ablation has poor efficacy with low success rate and high recurrence rate. Aneurysm resection is the recommended treatment with satisfactory efficacy. We report a child with chaotic atrial tachycardia due to giant right atrial appendage aneurysm who was successfully treated by aneurysm resection.

A 21-year-old man with Wolff–Parkinson–White syndrome and aneurysmal septal dyskinesis underwent radiofrequency catheter ablation of the accessory pathways. Before radiofrequency catheter ablation, the activation wavefront arose from the aneurysmal septum, whereas the propagation of the left ventricle was normalised after radiofrequency catheter ablation. These findings demonstrate the importance of the electro-mechanical interaction in patients with Wolff–Parkinson–White syndrome and ventricular dysfunction.

Premature ventricular contractions are a rare side effect of filgrastim, reported mainly in elderly men. Here we report the case of a 9-year-old child with thalassaemia who developed frequent premature ventricular contractions after three doses of filgrastim were given for deferiprone-induced agranulocytosis. The arrhythmia resolved 3 weeks after discontinuation of filgrastim. Children treated with filgrastim should be carefully monitored for potentially serious arrhythmia.