The diagnostic and therapeutic aspects of loss-of-function cardiac sodium channelopathies in children

Background
Loss-of-function sodium channelopathies manifest as a spectrum of diseases including Brugada syndrome (BrS) and cardiac conduction disease.

Objective
To analyze the diagnostic and therapeutic aspects of these disorders in children.

Methods
Patients aged ≤16 years with genetically confirmed loss-of-function sodium channelopathies (SCN5A mutation), presenting with cardiac symptoms, positive family history, and/or abnormal electrocardiogram (ECG), were included. Abnormal ECG consisted of type 1 BrS ECG and/or prolonged conduction intervals (PR interval/QRS duration > 98th percentile for age).

Results
Among the cohort (n = 33, age 6 ± 5 years, 58% male subjects, 30% probands), 14 (42%) patients were symptomatic, presenting with syncope (n = 5), palpitations (n = 1), supraventricular arrhythmias (n = 3), aborted cardiac arrest (n = 3), and sudden cardiac death (n = 2). Heart rate was 91 ± 26 beats/min, PR interval 168 ± 35 ms, QRS duration 112 ± 20 ms, and heart-rate corrected QT interval 409 ± 26 ms. Conduction intervals were prolonged in 28 (85%) patients; 6 of these patients also had spontaneous type 1 BrS ECG. Eight fever-associated events occurred in 6 patients; 2 of these were vaccination-related fever episodes. Treatment included aggressive antipyretics during fever in all patients; antiarrhythmic treatment included implantable cardioverter-defibrillator (n = 4), pacemaker (n = 2), and beta-blockers, either alone (n = 3) or in combination with device (n = 2). During follow-up (4 ± 4 years), 2 previously symptomatic patients had monomorphic ventricular tachycardia; there were no deaths.

Conclusions
Diagnosis of loss-of-function sodium channelopathies in children relies on cardiac symptoms, family history, and ECG. Fever and vaccination are potential arrhythmia triggers; conduction delay is the commonest finding on ECG. Beta-blockers have a role in preventing tachycardia-induced arrhythmias; implantable cardioverter-defibrillator should probably be reserved for severe cases.