Anterior QRS forces in posterolateral infarction.

The QRS loop on the horizontal plane of the vectorcardiogram and the QRS complex in the right praecordial leads of the electrocardiogram were studied in 8o patients with strictly posterior and/or lateral infarction. In all 30 patients with combined posterolateral infarction a ratio RIS greater than I in lead Vi was found. In I9 out of the 23 patients with strictly posterior infarction and in all 9 patients with isolated lateral infarction this ratio was less than i. Posteroinferior infarction (i8patients) behaved like strictly posterior infarction. In posterolateral infarction a pronounced preponderance of the anterior over the posterior QRS loopforces