Di-4-ANEPPS Slows Cardiac Conduction Velocity

Abstract

One of the most widely used voltage-sensitive dyes for optically mapping cardiac conduction is di-4-ANEPPS. Previous studies suggest that di-4-ANEPPS broadens the QRS; however, little is known about its effects on myocardial conduction. We hypothesized that di-4-ANEPPS suppresses cardiac conduction velocity (CV). CV was quantified in Langendorff-perfused guinea pig hearts using unipolar electrode and optical recordings. Electrode recordings from the anterior epicardium revealed that di-4-ANEPPS (7.5 µM) slowed cardiac transverse CV significantly from 23±4 cm/s to 18±3 cm/s (p<0.05). To investigate a possible concentration dependent effect of di-4-ANEPPS, CV and anisotropy was quantified using optical signals recorded from the anterior epicardium of both the right and left ventricle (RV, LV) at different concentrations of di-4-ANEPPS. Increasing the concentration of di-4-ANEPPS from 1.9 to 15 µM reduced transverse CV by 7±2 cm/s in the RV (p<0.05) (n=4) and 4±2 cm/s in the LV (p<0.05) (n=4). The decrease in longitudinal CV trended towards significance in both the RV (14±7 cm/s, p=0.08) and the LV (15±9 cm/s, p=0.07). The anisotropic ratio of CV was not affected by di-4-ANEPPS concentration. Connexin43 conductance was not significantly changed by di-4-ANEPPS at 15 µM evident from dual patch clamp experiments on HeLa cell-pairs overexpressing rat connexin43 (n=5), suggesting that decreased gap junction conductance is not the underlying mechanism. These data suggest that the perfusion of di-4-ANEPPS into whole heart tissue slows CV in both the right and left ventricles and this effect does not appear to be connexin related. Investigators should take the effect of di-4-ANEPPS on conduction into account when interpreting data obtained with this dye.