Detection of late potentials by adaptive filtering

A process called adaptive filtering which permits the observation of small deflections resembling late potentials in individual beats is discussed. Preliminary investigation was done on 12 normal subjects and five patients scheduled for electrophysiology studies (EPSs) who have histories of cardiopulmonary arrest, symptoms of unexplained syncope, or documented malignant ventricular arrhythmias. Two high-frequency ECG signals were acquired for 40 s at a sampling rate of 1000 samples/s per channel. The digitized signals were high-pass filtered, which reduces T waves and low-frequency noise. After selecting primary and reference channels on the basis of noise content, a 400-ms interval inclusive QRS was adaptively filtered. Approximately 40 to 50 beats were adaptively filtered in each case. These signals were averaged to effect further noise reduction