Voltage-sensitive dye mapping of activation and conduction in adult mouse hearts

A custom-made apparatus based on a charge-coupled-device camera has been us ed to monitor changes in fluorescence from Langendorff-perfused adult mouse hearts stained with a voltage-sensitive dye, di-4-ANEPPS. With this approa ch it is possible to monitor activation of the ventricles at high temporal (375 mus/frame) and spatial resolution (72x78 pixels, 100x100 mum/pixel). I n sinus rhythm, activation occurred with a complicated breakthrough pattern on both ventricles, and a total activation time of 3.51+/-0.16 ms (32 degr eesC). A stimulus applied near the apex of the left ventricle resulted in a single activation wave front with a total activation time of 8.18+/-0.25 m s. Pacing from a site near the middle of the left ventricular epicardial su rface revealed anisotropic conduction, indicating that conduction occurs pr eferentially in the direction of the predominant fiber orientation. The tot al activation time in this configuration was 5.44+/-0.24 ms. The difference in total activation time between sinus rhythm and epicardial stimulation s uggests an important role for transmural conduction (the Purkinje system) i n the mouse heart. These findings provide much of the necessary background needed for studying conduction abnormalities in genetically altered mice an d suggest that the comparison of sinus rhythm and epicardial pacing can be used to reveal transmural conduction abnormalities. (C) 2000 Biomedical Eng ineering Society. [S0090-6964(oo)01408-9].