2.5 Electrical mapping of ex vivo heart preparations
A multi-electrical array (MEA) mapping system (EMS64-USB-1003, MappingLab Ltd., UK) was employed to record extracellular potentials (ECP) from the epicardium. Two 64 channel MEAs (MappingLab Ltd., UK) were employed for left atrial and left ventricular simultaneous recordings. ECP signals were recorded at a 10 kHz sampling using synchronized 64 channel EMS64-USB-1003 recording systems and recorded using EMapRecord 5.0 software (MapingLab Ltd., UK) and stored in a computer for subsequent off-line analysis. Electrocardiograms (ECG) were continuously recorded by two ECG electrodes (MappingLab Ltd., UK) positioned on the right atrium and left ventricle respectively.
The epicardial isochronal activation map during sinus rhythm or imposed pacing was plotted as time differences between the earliest activation site and the individual activation site on each channel. Activation times were calculated as the point of maximal negative slope of activation waveforms. The conduction velocity (CV) was calculated from the difference in timing and the known distance between the recording points using EMapScope 5.0 software (MappingLab Ltd.).