Remaining challenges in direct cardiac mapping

Summary form only given. While electrical and optical cardiac mapping techniques have provided important information about cardiac electrophysiology, both techniques have limitations. It is possible that some of these limitations can be overcome by improvements in both mapping technologies as well as by using them in combination. For example, recent evidence suggests that greatly decreasing the size of the electrode and its intramural carrier can minimize the amount of distortion they produce. Mathematical analysis of the extracellular potentials may provide an opportunity to reconstruct the transmembrane action potentials, as suggested by the ability of the activation-recovery interval to estimate the refractory period. Techniques to track cardiac motion may eliminate the need for electro-mechanical uncouplers in optical mapping. Application of fiber optic technology may allow intramural optical recording. Electrical and optical mapping would be even more powerful if the two techniques were combined. For example, the use of microelectronic techniques would allow several electrodes to be placed close together with an optical fiber nearby on a very small carrier introduced intramurally. The extracellular electrodes would be used to calculate the extracellular Laplacian, which reflects the flow of the transmembrane current, while the optical fiber can record a signal proportional to the transmembrane voltage. Thus, transmembrane voltage, current, and membrane conductivity could be followed dynamically during normal cardiac activity, arrhythmias, and defibrillation shocks.