Experience of computer-assisted ECG recording in 242 exercise tests.

242 computer-assisted exercise tests were studied. The computer performs simultaneous averaging of a 6- or 12-lead ECG, keeps track of the work load and time and labels all ECG records. Less than 1 per cent of atrial and ventricular extrasystoles were included in the computer average together with ordinary beats, while 80 per cent of all beats were averaged. Averaging reduced the peak-to-nadir QRS amplitude by 3-4 per cent at a sampling rate of 400/s and by 8-9 per cent at 200/s. Q waves with small beat-to-beat variation were usually well preserved after averaging while more variable QRS details often decreased in width or amplitude. The averaging program performed adequately on most kinds of arrhythmia. Averaging should not be used on pacemaker ECGs. Caution must be exercised in the presence of very frequent ventricular extrasystoles.