A 23-year-old man was referred to our center for atrial flutter ablation. After arrhythmia termination sinus node dysfunction unmasked and persisted after 2 months drug-free follow-up. Secondary causes such as antiarrhythmic drug consumption, organic heart disease, or electrolyte disturbance could be excluded. Standard 12-lead ECG showed a coved-type ST elevation in V1-V3, which increased after flecainide provocative test. Following an unexpected sick sinus syndrome, a Brugada-type ECG should be noted.