Asthmatic attacks were induced in 11 asthmatics by the inhalation of the antigenic extracts. The electrocardiograms were obtained before, during and after the attacks for comparison. The significant changes during the asthmatic attack were as follows: (1) taller and more peaked P-waves in leads II, III and aVF, and the shifting of the mean vector of P-waves on the frontal plane towards the right; (2) generalized low amplitude of QRS-complexes, especially marked in left precordial leads and shifting of the mean vector of QRS-complexes on the frontal plane towards the right; (3) respiratory changes in QRS-amplitude which was lower during the inspiratory phase and taller during the expiratory phase; (4) clockwise rotation of the heart along the longitudinal axis. The above findings were observed in all cases and could be explained by the hyperinflation of the lung and "strain" of the right side of the heart by the increased pulmonary artery pressure, which was observed during cardiac catheterization.
Ectopic beats were observed in 2 cases among 11, while the air way obstrution was becoming progressively severe, but disappeared after the air way obstruction reached a maximum. From the present study, it was also believed that there seemed to be no direct cardiac danger of the provocative study by the inhalation of the antigenic extracts.