Observations with endocardial electrography on ventricular tachycardia by intracoronary saline in dogs

Selective injection of 1.5 ml of 10% saline into the left circumflex coronary artery (LCX) was carried out during sinus rhythm twice in each of 15 mongrel dogs anesthetized with sodium pentobarbital, and multiple endocardial recordings including His bundle electrogram (HBE) were made. Ventricular tachycardia (VT) was elicited in all of the 15 dogs both in the first and second injections. The cycle length of sinus rhythm before injection was 468 +/- 88 msec (mean +/- S.D.). The coupling interval between the last depolarization of the left ventricle (LV) of sinus origin and the first premature LV depolarization of the VT was 395 +/- 57 msec. Coupling interval between the first and the second LV depolarizations was 348 +/- 78 msec. Significant difference was noted between any pair of these values (p less than 0.01). No bundle branch re-entry in the beginning of VT was observed. The site of origin of the VT was referred to the LV in 13 dogs. Rapid pacing during paroxysm of VT applied at the apex of the LV made no marked influence upon VT after pacing. The calcium channel blocker, diltiazem failed to block the production of VT. The Mechanism for genesis of this VT may not be re-entry but rather enhanced automaticity independent of the calcium inward current.