Management of cardiac arrhythmias in paediatric patients with TANGO2-deficiency disorder

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: TANGO2-deficiency disorder (TDD) is a rare paediatric condition caused by bi-allelic mutations in the TANGO2 gene. TDD is characterised by susceptibility to metabolic crises with rhabdomyolysis, encephalopathy, lactic acidosis, hypothyroidism and difficult to manage tachyarrhythmias. AIM: We describe the electrocardiographic (ECG) findings at baseline and during metabolic crises in patients with TDD. METHODS: Retrospective, single-centre, case series study of patients with TDD (<18 years), with ECG and subcutaneous Holter monitoring, both during metabolic crises and compensated phases. RESULTS: During the period 2013-2021, 12 patients with TDD were found (median age 6.8 years, IQR 2-11.5 years). In the inter-crisis period, bradyarrhythmias were evidenced: 2/12 patients presented sinus bradycardia, 2/12 pauses of 4 and 10 seconds, 1/12 Wenckebach type block; and tachyarrhythmias: 1/12 presented paroxysmal supraventricular tachycardia and 1/12 flutter. 25% had long QT during non-acute phases (median QTc max 476 ms, IQR 456ms-530ms). There were 14 hospitalisations for metabolic crises. 57.1% had QTc interval prolongation, 35.7% ventricular tachycardias (4/14 monomorphic VT, 1/14 torsade de prongs) and 1/14 Brugada type 3 pattern. Three patients died in the context of severe metabolic acidosis and multi-organ involvement (2/12 due to VT and 1/12 due to cardiogenic shock, bradycardia associated with QTc of 635ms and severe ventricular dysfunction). CONCLUSIONS: In paediatric patients with TDD, the most frequent ECG abnormality was QTc interval prolongation with or without metabolic crises. There is a high risk of tachyarrhythmias, mainly VT, being the main cause of death in children with TDD. Subcutaneous Holter monitoring is recommended. During metabolic crises, there should be close ECG monitoring.