Butterworth Bi-directional and BiSpec/sup TM/ filters in the assessment of ventricular late potentials: a comparative study

The Ventricular Late Potentials (VLP) are low amplitude signals originating from electrically unstable regions of damaged myocardium. Due to low amplitude, VLP are detected on the body surface by statistical techniques and band-pass filtering to reduce the baseline noise and exclude high-energy components. The BiSpec/sup TM/ filter is currently in use as an alternative for VLP analysis but no clinical study validating its application has been performed so far. To accomplish this task a clinical study was conducted to compare the BiSpec 40 Hz filter (BS) and four pole 40-250 Hz band-pass Butterworth bi-directional filter (BD) regarding their diagnostic properties. 170 patients were studied retrospectively without bundle branch blocks with signal-averaged ECG, using the Predictor SAECG System (ART, Texas) and divided into three groups. The variables analyzed were DUR, RMST, RMS40 and LAS40. Significant differences were found between BS and BD for RMST in all groups (p<0.001), DUR in GI (p<0.05) and LAS40 in GII (p<0.05). The distribution of diagnostic results were significantly different in GII and GIII (p<0.05) and linear correlation were <0.7 in GI and GII. Sensitivity was lower for BS than BD (p<0.05). This study demonstrates that BS and BD provide significantly different diagnostic results and suggests that normality intervals should be re-evaluated for BS.