Vectorcardiographic criteria for diagnosis of high lateral infarction. Supplement for Chou's criteria.

The concept of high lateral myocardial infarction (HLMI) has not been clearly defined, so criteria for its vectorcardiographic (VCG) diagnosis have had no firm basis. However, we have reported that HLMI, expressed as abnormal Q waves in lead aVL on the electrocardiogram, corresponds to necrosis of the area usually supplied by the diagonal branches of the left anterior descending coronary artery. Here, we evaluated conventional VCG criteria for the diagnosis of HLMI on the basis of angiographic findings, and selected the criteria of Chou as typical. The frontal plane VCG was analyzed in 46 patients with HLMI on angiograms; other subjects were 233 healthy controls and 194 patients with left ventricular hypertrophy. Chou's criteria had good specificity, but sensitivity was unsatisfactory (32/46, or 70%). Accordingly, we examined various parameters of the QRS and T loops and found that the addition of four new criteria to Chou's improved sensitivity (46/46, or 100%) without impairment of specificity. The additional criteria are; 1) initial counterclockwise rotation of the QRS loop, 2) the ratio of the maximal QRS magnitude to the maximal T magnitude less than 4.5, 3) direction of the maximal T between +60 degrees and +180 degrees, 4) the QRS-T angle between 40 degrees and 135 degrees, all in the frontal plane.