Direct thermography-a new in vitro method to characterize temperature kinetics of ablation catheters

For the treatment of increasingly complex cardiac arrhythmias, new catheter designs as well as alternative energy sources are constantly being developed. However, there is presently no in vitro method available for assessment of the temperature changes induced at various myocardial levels during energy delivery. Therefore, our study was aimed at developing an in vitro model to record and display the temperature kinetics during ablation in the entire muscle cross section. A sapphire glass pane was inserted into one wall of the in vitro experimental set-up. Due to its thermodynamic properties, the temperature distribution in an adjacent cross section of the cardiac muscle can be measured exactly (+/- 1 A degrees C) through this pane by means of a thermography camera. Computer-supported image processing enables the colour-coded and two-dimensional display of the temperature kinetics during the energy application at any location of the myocardial cross section (+/- 0.5 mm). This new measuring methodology was validated by direct temperature measurements utilizing several intramyocardial thermo elements. This new method allows a temporal and spatial analysis of the temperature phenomena during ablation without the interference and spatial limitation of intramyocardial temperature probes. New ablation technologies can thus be evaluated, independent of the catheter configuration or source of energy used.