Voltage sensitive dye di-4-ANNEPS prolongs impulse conduction through ventricles, but not through AV node in isolated rabbit heart

Voltage sensitive dyes are widely used for recording of action potential in various cardiac studies. The elementary condition for its application is the fact that measured electrophysiological parameters would not be affected by the measuring procedure itself. The RR interval prolongation in the presence of the most frequently used voltage sensitive dye di-4-ANEPPS has been reported, but its exact mechanism is not known. In this study, the impact of di-4-ANEPPS on impulse conduction through the atrioventricular (AV) node and through cardiac ventricles in isolated rabbit heart was examined. The impulse conduction through AV node in the presence of di-4-ANEPPS was prolonged only during dye loading in the 14th, 16th and 17th minute. Only sporadic AV blocks were observed. In comparison, the prolongation of impulse conduction through cardiac ventricles was observed from the 13th minute of loading and persisted to the end of this phase as well as over the whole wash out phase.