Factors influencing the signal-averaged ECG in healthy subjects in time and frequency domain

The detection of ventricular late potentials in the signal-averaged electrocardiogram (SAECG) is a possible factor in risk stratification of patients after acute myocardial infarction. The influence of clinical and methodological factors that influence the SAECG independently of the cardiac disease seems to be of considerable interest in a prospective study the possible influence of age, gender, heart rate, type of electrical heart axis body weight body height body-mass-index (BMI) and noise ratio, a SAECG has been recorded in 79 healthy subjects (39 female, 40 male) aged 19 to 86 years. The SAECG has been analyzed in lime domain (Simson method) and in frequency domain with spectrotemporal mapping (FFT). Results. 1. Late potentials were found in 6.3% in lime domain and in frequency domain 7.6%. 2. With increasing body height and weight ail time domain parameters tended towards findings typical for late potentials. Frequency domain parameters did not show any changes depending on body height or weight 3. Female subjects presented with a HFQRS significantly shorter than male. On the other hand, female subjects showed a significantly higher percentage of high-frequency content in frequency domain analysis that persisted if body height or weight were taken into account 4. With increasing heart rate, RMS-amplitude increased and LAS-duration decreased. 5 With increasing noise ratio, LAS-duration was significantly longer. 6. Age, type of electrical heart axis and BMI did not show any significant influence on the SAECG. These data suggest that body height body weight heart rate and noise level should be taken into consideration in interpretation of the SAECG in time domain, and gender in frequency domain.