Cardiac and hemodynamic effects of the selective bradycardic agent KC 8857 during exercise-induced myocardial ischemia.

The effects of an in vitro bradycardic agent without negative inotropism, KC 8857 (3,7-di-(cyclopropylmethyl)-9,9-tetramethylene-3,7-diazabicyclo-[3.3.1]- nonane dihydrochloride), were tested in chronically instrumented dogs in a model of exercise-induced myocardial ischemia. KC 8857 was i.v. infused during critical stenosis of the circumflex branch of the left coronary artery which led to exercise-induced myocardial dysfunction. KC 8857 caused a decrease in heart rate, left ventricular dp/dtmax and calculated myocardial oxygen demand at rest and during exercise. Since positive dp/dtmax values at a given heart rate were not altered by KC 8857 it may be assumed that myocardial function was restored mainly by the decrease in heart rate.