[Diagnosis of posterior infarction. Value of vectorcardiography. Apropos of 108 cases, 31 of which had exclusively posterior necrosis].

An analysis of the vectorcardiogram results (VCG) in 77 cases with a posterior extension of an infarct and 31 cases with an exclusively posterior infarction (EPI) has allowed us to distinguish some diagnostic criteria relative to the extension, or localisation, of an infarct in the posterior segment. The maximum anterior vector (MAV) appears late (36.5 ms +/- 5), and the amplitude of its projection onto Z is increased; the maximum vector (V max) appears early (41.5 ms +/- 4.5), and its orientation is anterior (+ 24 degrees +/- 11); the interval separating MAV from V max is reduced to 5 ms; the transition from before backwards is late (50 ms +/- 6); the ratio of anterior surface to posterior surface is increased (1.45); there is a terminal delay, most frequently occuring in the right posterior quadrant in 78 percent of cases; and finally, the T loop approaches the Z axis. Repeat electrocardiograms in patients with EPI show the most frequent changes to be represented (in 25 cases out of 31) by the following formula: AQRS " 0 degrees, R/S greater than or equal to 1 in V2, RV2 greater than RV6. The diagnosis of an exclusively posterior infarction can therefore be made with a high degree of certainty when these electrocardiographic abnormalities are associated with the clinical picture of coronary insufficiency.