The genesis of QRS changes produced by selective coronary arteriography.

Selective coronary arteriography produces characteristic ST-T changes associated with significant axis shifts. In patients with normal control AQRS (mean, +88.60; SD -t12.20) left coronary injections induced an important leftward deviation of the AQRS: mean, +8.2.; SD, +49.10 (P < 0.001). Right coronary artery opacification changed the AQRS from a control mean of +66.50; SD, +17.20 to a mean of 89.3°; SD, +16.70 (P < 0.001). Left axis shifts after left coronary artery injections were significantly more marked than right axis deviation after right coronary injections. Important increases (beyond 0.02 sec) in ventricular activation time were not observed. These electrocardiographic abnormalities were attributed to the transient ischemic or toxic effect produced by the bolus of dye. This could result in different degrees of complete or incomplete block in the divisions of the left branch or in an extensive peripheral block affecting large areas of the subendocardial regions of the heart.