We found two unique clinical viewpoints in this case. The first is the boy had been on central ECMO support for a sudden worsening of hemodynamic and respiratory status due to cardiomyopathy caused by refractory AT despite the first attack, and the second is he underwent surgical resection of LAA to treat AT on ECMO support.
Atrial tachycardia is rare in children. The median age at diagnosis is 7.2 years with the most commonly occurring from birth to 1 year, and most patients are treated with antiarrhythmic medications (ATP, amiodarone, β-blocker), cardioversion or catheter ablation [1]. Antiarrhythmic agents are well effective to recover normal sinus rhythm in most cases [1]; however, AT may cause cardiomyopathy when arrhythmic episode repeats frequently. When medical treatments as above would not be effective, mechanical hemodynamic support by ECMO should be considered for a rescue therapy because AT may cause cardiomyopathy when AT would not be recovered to sinus rhythm for a certain period of time [2, 6]. Remarkably decreased left ventricular ejection fraction suggested cardiomyopathy, which required prompt treatment in this child. Several pediatric cases showed that ECMO support was performed for cardiomyopathy associated with refractory AT [1, 2] and refractory arrhythmias [2, 6,7,8]. There have been no reports of patients requiring ECMO within a few days after the first attack. In this case, he had already had a severe cardiac failure on arrival at ED, which dramatically progressed leading to pulmonary edema despite treatment such as amiodarone infusion, bolus of ATP, and electric cardioversion. Our choice to induce ECMO as a rescue therapy for refractory AT was considered to be reasonable in this case. If we had hesitated to introduce ECMO, cardiac arrest and neurological sequelae would have been more likely to occur. In fact, Kang et al. reported a case of a 13-year-old girl who died of serious neurological complications after requiring ECMO due to circulatory collapse during the administration of amiodarone for treating refractory AT [1]. We also selected central ECMO with thoracotomy instead of peripheral ECMO. Although peripheral ECMO via inguinal approach does not require a thoracotomy, it not only increases left ventricular afterload, but also exacerbates pulmonary edema and delays recovery of left ventricular function due to inadequate left atrium (LA) decompression [9]. In contrast, central ECMO solves these problems, and Kotani et al. reported that ECMO with early LA decompression increases the rate of recovery of lung and left ventricular function [9]. After all, the establishment of ECMO before the collapse contributed to the neurological prognosis, and the choice of central ECMO, which is possible to drainage blood from both atriums, instead of peripheral ECMO may have resulted in a faster weaning from ECMO and ventilator because of avoiding the damage to the heart and lungs [9]. Although bleeding complications are a greater problem with central ECMO than with peripheral ECMO, we think that the advantages of central ECMO outweighed the disadvantages of hemorrhage since the left ventricular function was significantly impaired in this case and peripheral ECMO could have worsened the condition of the heart and lungs due to increased left atrial and ventricular pressure with increased afterload.
In the second unique situation, surgical ablation was performed under ECMO support in this case. As a therapeutic option, catheter ablation is considered in the case of refractory AT, but it was difficult to perform catheter ablation in this case because of the rapid deterioration of his condition. Previous reports have shown that the atrial appendage is the source of focal AT in 11% of cases [1]. For refractory AT of LAA origin, Khan et al. reported a successful case of radiofrequency ablation on ECMO support [2], but Phillips et al. described that catheter ablation of focal AT resulting from LAA, especially distal point, was difficult due to the complex anatomy of LAA, and surgical appendectomy or thoracoscopic surgery may be required [10]. Pokushalov et al. reported a case of hemodynamically stable that ineffective catheter ablation followed by successful surgical ablation [4]. In this case, the chest had already been opened for central ECMO, and it was reasonable to perform surgical ablation during ECMO support as a rescue treatment because it was very difficult to plan catheter ablation in this situation.
Finally, he was completely recovered from hemodynamic and respiratory failure by multidisciplinary treatment. ECMO support and surgical ablation played the main role in treating AT.