Multifocal atrial tachycardia has certain electrocardiographic similarities to atrial fibrillation. The mechanism of atrial fibrillation is heterogenous but in some cases may arise from a single ectopic driver with fibrillatory conduction to the rest of the atria. This has led to the speculation that multifocal atrial tachycardia may have a similar mechanistic unifocal site that disperses through the atrium in a fibrillatory pattern. Ivabradine has been reported to be efficacious in an adult with paroxysmal atrial fibrillation as well as in children with junctional or ectopic atrial tachycardias. This is the first report of successfully using ivabradine, a novel anti-arrhythmic If blocking agent, to convert multifocal atrial tachycardia in a 5-month-old critically ill infant to a pattern indicating a single ectopic atrial focus. This allowed the patient’s single atrial focus to be ablated with return to sinus rhythm and decannulation from ventriculoarterial extracorporeal membrane oxygenation. This case suggests that multifocal atrial tachycardia may arise from a single automatic focus with downstream fibrillatory conduction to the atria.

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.