Mapping cardiac excitation and signal propagation pattern is an important diagnostic and therapeutic approach in clinical cardiac electrophysiology. In this chapter we describe cardiac mapping approaches mainly for in-vitro applications in basic research and drug discovery. The applications use substrate embedded microelectrode array technologies. The mapping of cardiac signal propagation can be performed in cell cultures, in tissue preparations and in complete organs, respectively. Novel approaches integrate cardiomyocytes obtained from embryonic, adult and induced pluripotent cells. These cells -as well as primary cardiomyocytes -can be also used in tissue engineering. On the tissue level, cardiac slices have seen a renaissance within the last decade. The classical organ model for epicardial mapping is the isolated perfused Langendorff heart.At the beginning, this chapter focuses on the methodology while in the second part, applications of cardiac mapping in the various cell and tissue models are discussed.
Microelectrode arraysSubstrate embedded microelectrode arrays (MEAs) allow the recording of cardiac action potentials on up to 256 electrodes simultaneously with high spatial and temporal resolution [1]. The technology has been used to record cardiomyocytes since almost 40 years [2]. In addition to field potential data spatial properties such as conduction velocity and propagation patterns can be addressed. These patterns provide insight into mechanisms of the generation of a variety of arrhythmia forms. Here we discuss recordings obtained from stem cell-derived cardiomyocytes, primary cardiomyocytes, a cardiomyocyte cell line, and surface mappings from atrium and ventricle on isolated hearts.
Passive metal arraysThe voltage change during the action potential of the myocardium and the propagation of the impulse can be detected using extracellular recording electrodes. As extracellular field potential recordings do not require a transmembrane configuration of the recording and reference electrode, the cell membrane stays intact (non-invasive recording) enabling long-term experiments. In clinical electrophysiology, electrode catheters are used to identify spatial and temporal distribution of the electrical potential spread within the myocardium. This approach allows, for example, one to identify arrhythmogenic structures. On the other hand, this method can also be utilized to investigate initiation and repolarization of the underlying action potential in order to obtain information about its shape and amplitude. The composition of cardiac action potentials is well known. The effects of sodium, calcium and potassium channels are reflected in the depolarization, plateau and repolarization.One of the first challenges of the evaluation of cardiac data obtained with the MEA technology was the interpretation of cardiac field potential data. Halbach et al. [3] pharmacologically dissected the different components of the field potential in mouse embryonic heart cells. The authors simultaneously recorded local field an...