Exercise-induced QRS Axis Shift and Its Clinical Significance

Abstract

Exercise tests occasionally induce a QRS axis shift. Reviewing single Master's two-step test electrocardiograms of 1810 patients, we examined the incidence of the QRS axis shift and the relations of the QRS axis shifts to ischemic heart disease. The QRS axis shift was 30 degrees or more to the right in 38 (2.1%), 15 to 29 degrees to the right in 304 (16.8%), less than 15 degrees to the right or to the left in 1375 (75.9%), 15 to 29 degrees to the left in 81 (4.5%), and 30 degrees or more to the left in 12 patients (0.7%). The frequency of positive Master's tests and clinical ischemic heart disease were both significantly greater in the patients with QRS axis shifts of 30 degrees or more to the right (15.8% and 26.3%, respectively) and the patients with those of 30 degrees or more to the left (33.3% and 50.0%, respectively) than in the patients with shifts less than 15 degrees (6.5% and 8.5%, respectively). These results indicate that the exercise-induced QRS axis shift is a useful clue for the diagnosis of ischemic heart disease.