[Non-invasive recording of late ventricular potentials--methodology and first clinical experiences (author's transl)].

Late potentials occurring after the QRS complex were searched for from the body surface using high-gain amplification and signal-averaging techniques with filter settings between 100 and 300 hz at a sampling rate of 10 khz. The number of repetitions of the averaging process ranged between 150 and 300. 52 patients were studied. In 11 control subjects, no late potentials were detected within the ST segment. Late potentials were observed in 3/27 patients without previously documented ventricular tachycardia, all having left ventricular aneurysms. All three patients had evidence of increased ventricular vulnerability (one dying from ventricular tachycardia, one with stimulus-inducible ventricular tachycardia, one with multiple episodes of ventricular fibrillation after surgery). In patients with previously documented ventricular tachycardia and/or fibrillation, late potentials occurred in 7/14 cases (50%), mainly in those with aneurysms (6/8 pts = 75%). Mean onset of late potentials after the QRS complex was 38 +/- 20.1 ms, mean amplitude was 3.9 +/- 2.0 uV, and mean duration was 17.1 +/- 5.4 ms. We conclude that late potentials, which represent late depolarization of a mass of ventricular tissue after slow conduction, herald increased susceptibility to ventricular tachycardia mainly in patients with ventricular aneurysms.