[Abnormal filter setting or Brugada syndrome?]

26-year old patient was admitted to our department with suspected Brugada syndrome (BrS). He complained of recurrent dizziness due to which he was taken by a team of rescuers to the district hospital, where the recorded ECG demonstrated isolated 3–7 mm ST segment elevation in leads V1–V3. Coronary angiography performed in this hospital was normal. Then patient was transferred to our department for consideration of ICD implantation. ECG registration in our hospital with 0.05 Hz (3.2 s) filter showed sinus bradycardia with 1–2 mm ST segment elevation in precordial leads. A detailed analysis of all ECG's proved that the district hospital ECG was performed in manual mode with the application of 1.5 Hz (0.1 s) low frequency high-pass filter. To confirm the effect of incorrect filter as the cause of misdiagnosis we repeated ECG recording using the recorder which allows to apply the same settings 1.5 Hz (0.1 s) as in district hospital and reconstructed ECG with repolarisation abnormalities. Negative ajmaline test (1 mg/kg) additionally reaffirmed an exclusion of dynamic form of BrS.