Gliding window fast Fourier transform analysis--a new method for discovering the contribution of higher frequencies in signal-averaged ECG.

Objective: An attempt to detect the 'parasitic contribution' of high frequencies in the electrocardiogram signal.

Design: A new method--gliding window fast Fourier transform analysis (GWFFTA)--was developed. It was applied in healthy subjects and in patients with acute myocardial infarction.

Setting: Faculty of Medicine and University Hospital.

Patients: The GWFFTA was used in 29 healthy volunteers and in a group of 30 patients with myocardial infarction, on day 7 to 14 after admission to a coronary unit.

Intervention: Noninvasive examination, performed under standard conditions.

Main Results: GWFFTA provides better reproducible results compared with 'classic' fast Fourier transform analysis. The parasitic contribution of high frequencies within QRS complex and ST segment in patients with acute myocardial infarction is independent of presence or absence of late potentials. Contribution of high frequencies are three times higher in patients with acute myocardial infarction than in healthy probands.

Conclusions: GWFFTA is a reproducible method of detection of high frequencies during whole heart activation. Contribution of high frequencies in patients with acute myocardial infarction reflects the state of the entire myocardium. It is also confirmed by the lack of correlation with the presence or absence of late potentials. Late potentials are more reflective of focal changes.