The catheter technic for recording the electrical activity of the specialized conducting system in the human heart showed in two patients studied that ventricular pre-excitation was apparently due to a bypass of the His bundle. Intermediate forms of WPW complexes appeared to be combination beats resulting from the activation of the ventricles through impulses traversing both the His bundle and accessory communications. Preferential iatrogenic activation of an intra-atrial (and perhaps even of an atrioventricular) tract appeared to occur in one of the patients. The patients with the WPW (pre-excitation) syndrome and long histories of paroxysmal arrhythmias were successfully treated with a combination of oral propranolol and implanted (transvenous) demand pacemaker.

Selective coronary arteriography produces characteristic ST-T changes associated with significant axis shifts. In patients with normal control AQRS (mean, +88.60; 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. Additional Indexing Words: Block in the superior division of the left br. Block in the inferior division of the left bra S ELECTIVE opacification of the coronary arteries is accompanied by significant * Comparison of magnitude of changes in tables 1 and 2 (without regard to sign): P < 0.001 Circulation, Volume XLI, February 1970 250 by guest on June 25, 2016 http://circ.ahajournals.org/ Downloaded from 9. MAYTIN 0, CASTILLO C, CASTELLANOS A JR.: Circulation, Volume XLI, February 1970 -2"54 by guest on June 25, 2016 http://circ.ahajournals.org/ Downloaded from tion of post-infarction intraventricular block.

No abstract