Effects of Calcium Antagonists and Lidocaine on Conduction Delay Induced by Acute Myocardial Ischemia in Dogs

24 open-chest anesthetized dogs with acute myocardial ischemia produced by complete occlusion of the left anterior descending coronary artery (LAD) for 5 or 10 minutes.

Lidocaine (2 mg/kg bolus, 4.3 mg/kg/hr constant infusion), diltiazem (0.4 mg/kg i.v.), or verapamil (0.3 mg/kg i.v.) administered prior to a second LAD occlusion.

Baseline ischemia (first LAD occlusion without drug administration).

Conduction delay in the ischemic zone, measured from the initial deflection of V waves on His bundle electrograms to the major deflection of bipolar electrograms under constant atrial pacing.surrogate