Spatial orientation of the vectorcardiogram in patients with myocardial infarction.

We studied the rotation angles on the each of 3 axes and the planarity and roundness of QRS loop when its plane was laid close to horizontal in 4 groups of patients. Thirty five had anterior myocardial infarction, 34 inferior infarction, 15 non Q wave inferior infarction, and 34 were normal subjects. The rotation angles of the QRS loop were significantly different from the controls, on the Y and Z axes in the anterior infarction group, on the Z axis in the inferior infarction group and on the X axis in the non Q wave inferior infarction group (p < 0.01). The planarity index in the inferior infarction group was significantly higher (p < 0.01) than in other groups. The significantly smallest value of the roundness index was noted in the anterior infarction group (p < 0.01). Significant features of the early segmental planarity indexes were shown in the non Q and Q wave inferior infarction groups (p < 0.01). We conclude that the rotation angles and the planarity and roundness indexes are characteristic parameters for the infarct group and may be useful for diagnosing myocardial infarction, which is difficult with electrocardiography and vectorcardiography.