(1) Larger intramural clefts between cardiomyocyte layers in the right ventricle compared to the left could be the cause of right ventricular arrhythmias in Brugada syndrome. In the Brugada syndrome, the function of the cardiac sodium channel Na_V1.5 is commonly lost in both the left and right ventricle, although arrhythmias preferentially arrise from the right ventricle.

The experiments were conducted on isolated-perfused hearts from wild-type and genetically modified mice, using optical mapping and two-photon microscopy to identify conduction velocities. Cleft differences were similar in both mice groups, but conduction velocities were only impaired during increased pacing of the right ventricle in the genetically modified mouse model. Following acute sodium current inhibition, conduction slowing was also present in right, but not left, ventricular tissue from wild-type mice. Conduction slowing predisposes to functional block and initiation of ventricular arrhythmias.

(3) The novel voltage sensitive dye FluoVolt has several advantages over di-4-ANEPPS in deep tissue imaging of rapidly changing electrophysical signals of intact cardiac tissue. In murine hearts, two-photon excitation of FluoVolt reduced episodes of atrio-ventricular block and improved recording of action potentials, compared to loading with di-4-ANEPPS. FluoVolt records membrane potentials by photo-induced electron transfer.