[Surface recording of abnormal post-QRS micropotentials. Description and frequency in ventricular tachycardias after myocardial infarction].

In order to study abnormal post-QRS micropotentials, so called late potentials, and to determine their frequency in post myocardial infarction ventricular tachycardia (VT), high amplification electrocardiogrammes were recorded in 180 patients classified in 3 different groups: Group A comprising 36 patients who developed sustained VT after myocardial infarction; Group B comprising 124 patients with myocardial infarction uncomplicated by VT. This group was subdivided into subgroup B1 (retrospective study of 35 patients with chronic myocardial infarction, dating on average 10 months--range 7 days to 8 years) and subgroup B2 (prospective study of 89 patients investigated on the 7th and 60th days after infarction); Group C comprising 20 young, normal control subjects. Using computer assisted high amplification electrocardiography, all patients underwent at least 3 successive recordings of the following parameters: averaging 100 cycles; sampling: 1 kHz; band pass 20-300 Hz and 80-300 Hz; gain setting 10,000 and 25,000. Late potentials usually appears, after the end of the S wave, as high frequency oscillations with an amplitude (10 to 20 microV) significantly greater than that of the background noise. Our recordings also showed: the frequent presence, especially in intraventricular blocks, of fragmentation of the end of the R wave and of the S wave or terminal potentials; the presence of an abnormal giant low frequency high amplitude wave (40 to 80 microV) in 5 patients with a large left ventricular aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)