[Diagnosis of limited septal infarction associated with a posterior or postero-inferior infarction. Value of vectorcardiography and clinical, coronary angiographic and developed correlations].

In patients with posterior or postero inferior infarction, a limited septal infarction may be detected by vectorcardiography, septal extension being a sign of disease of the left anterior descending artery. In order to confirm this hypothesis, 31 posterior or postero inferior infarction with septal extension were selected by vectorcardiography from more than 500 ECGs recorded after the acute phase of a clinically and biologically documented infarction. The following criteria were chosen: 1. Anterior deviation of the QRS, associated or not with superior deviation of the initial deflection lasting over 25 ms and clockwise rotation of the frontal loop (posterior infarct: 9 cases, postero inferior infarct: 22 cases). 2. Abnormalities of the initial phase of the QRS in the horizontal plane, associated with a reduced amplitude and duration of the initial deflection. The clinical, ECG, vectorcardiographic and angiographic (14 cases) features of these 31 postero septal infarcts were compared with those of 31 posterior septal infarcts were compared with those of 31 posterior or postero inferior infarcts (24 coronary angiographies). 1. From the clinicl point of view, in the acute phase postero septal infarction did not differ from posterior infarction and the early prognosis was favourable. On the other hand, with an average follow-up of 2 years, the outcome of postero septal infarction was statistically more complicated than that of strict posterior infarction (52 p. 100 compared to 19 p. 100, p < 0.01). 2. From the electrocardiographical point of view, septal extension of posterior infarction was only suspected in 25 p. 100 cases. In the acute phase, ST depression in V2 to V5 sometimes associated with reduction of the R wave in the right precordial leads and QS waves in V4R, suggesting a "rudimentary" or "subendocardial" infarct. 3. From the angiographic point of view, although disease of the posterior vessels was equally common in posterior and postero septal infarction (86 p. 100 compared to 92 p. 100 NS), stenosis of the left anterior descending artery was statistically more common in postero septal infarction than in posterior infarction (86 p.100 compared to 29 p. 100, p < 0.001). Thallium myocardial scintigraphy, when performed, showed the double myocardial lesion in the antero septal and postero inferior walls in postero septal infarction. These results validate the vectorcardiographical criteria retained for diagnosis of postero septal infarction and confirmed the superiority of the vectorcardiogramme over the electrocardiogramme in the diagnosis of double infarction. Therefore, the vectorcardiogramme in the diagnosis of double infarction. Therefore, the vectorcardiogramme allows selection of the patients with postero diaphragmatic infarction with a limited septal extension, for whom coronary angiography should be proposed. A "postero septal" infarct diagnosed on vectorcardiogramme has a high probability of stenosis of the left anterior descending artery.