Changed Duration of Ventricle Repolarization in Dog Heart under Conditions of Increased Preload

The duration of repolarization of subendocardial, intramural, and epicardial layers of dog ventricles was studied under conditions of volume overload of the heart in situ. Increased preload was modeled by rapid intravenous infusion of saline and rheopolygluquine. The activation-recovery interval was measured by flexible intramural electrodes inserted into the right and left ventricles. The level of preload was evaluated by the increase in left-ventricular end-diastolic pressure. The increase in preload from 11±6 to 26±10 mm Hg led to a significant (p