The effect of varying filter techniques on late potential parameters of signal averaged electrocardiographic records

Signal average electrocardiographic parameters were obtained in 54 patients and 128 normal subjects using two filtering techniques and lead systems. Filtered QRS duration (TQRS), root mean voltage in the terminal filtered QRS (RMS), and terminal QRS duration under 40 microvolts (LAD) were compared. TQRS was significantly different for all subjects. RMS values were different for normal subjects and EPS positive subjects. It is concluded that variation in filtering can modify results and that standards appropriate for the filter must be employed clinically