The purpose of the present study was to determine if our recently introduced novel working rat heart preparation could be used to study wall stress-induced dysrhythmias. A double cannula, which consisted of an outer cannula that, was inserted in the aorta and an inner cannula that was advanced into the left ventricle was used. The perfusion flowed through the inner cannula into the left ventricle and was ejected from there into the aorta. Afterload was changed suddenly from 60 to 160 Hg of pressure by turning a valve so that the fluid was diverted to a column set at a different height. A sudden increase of aortic pressure that lasted for 10 sec caused cardiac ectopic beats. Wall stress-induced dysrhythmias were more sustained during perfusion with low potassium and low magnesium Krebs-Henseleit solution. Bradykinin (1 microg) or epinephrine (10 microg) was injected as a bolus via an in-line injection port placed at the inner cannula. Bradykinin significantly reduced the incidence of ectopic beats and epinephrine increased the incidence of nonsustained runs of VT. This "working" heart preparation is a convenient tool to study wall stress-induced dysrhythmias.