Quantitative analysis of the high frequency components of the terminal portion of the high-resolution surface QRS was performed in 119 normal subjects (N), 62 patients with ventricular tachycardia (VT) including 20 patients with sustained VT or VF (VTs/VF) and in 565 ischemic and nonischemic cardiac patients (NO-VT). High-resolution surface ECG (SAECG) was obtained during sinus rhythm with noise level below 0.4 microV by ART-1200EPX. The vector magnitude of the filtered and signal-averaged standard bipolar orthogonal leads X, Y, Z (V = square root of X2 + Y2 + Z2) were used for analysis. Total duration of the QRS (QRST), the duration of the low amplitude (40 microV) signals in the terminal portion of the QRS (D40) and the amplitude of the signals in the last 40 ms (V40) were measured at filter settings of both 25Hz and 40Hz by the computer. Specific values for each of the indices were identified at both 25Hz and 40Hz filterings, which could separate N as well as NO-VT from VTs/VF. They were greater than or equal to 120 ms for QRST, greater than or equal to 34 ms for D40 and less than or equal to 25 microV for V40 at 25Hz, greater than or equal to 120 ms for QRST, greater than or equal to 39 ms for D40 and less than or equal to 20 microV for V40 at 40 Hz filtering.(ABSTRACT TRUNCATED AT 250 WORDS)