Maximal spatial ST-vector patterns in patients with acute anteroseptal myocardial infarction

Seventy patients with acute myocardial infarction were studied by serial vectorcardiography. Eleven out of 70 patients had acute myocardial infarction, which consistently met the vectorcardiographic QRS-loop criteria of anteroseptal myocardial infarction within the 21 days follow-up period. From the first vectorcardiographic tracings three types of the maximal spatial ST-vector were seen. Their directions belonged to one of the following octants: (1) right-anterior-superior, (2) left-anterior-superior, or (3) left-anterior-inferior. The directions were the same as the types of initial activity of the normal depolarization process of the interventricular septum revealed by the intracardiac mapping in dogs. The subsequent vectorcardiograms showed no change in direction of the maximal spatial ST-vector in all patients except one. This study suggested that there are three types of the maximal spatial ST-vector concealed in patients with first acute anteroseptal myocardial infarction. Each type of the maximal spatial ST-vectors is capable of causing S-T segment elevation from leads V1 to V3 in the acute electrocardiogram. Why the subgroup of the right-anterior-superior maximal spatial ST-vector in patients with acute anteroseptal myocardial infarction had poor outcomes during the acute stage needs further investigation.