[Significance of temperature-controlled energy generation in high-frequency catheter ablation of accessory conduction pathways].

Radiofrequency catheter ablation has become an established treatment modality for definite cure of patients with WPW-syndrome or concealed accessory pathways. On-line monitoring of the induced tissue effects plays an important role concerning the efficacy and safety of this procedure. In a 50 year-old man with recurrent atrioventricular tachycardia, endocardial catheter mapping revealed a left anterolateral concealed accessory pathway. A temperature-guided radiofrequency pulse with a preselected temperature of 70 degrees C was applied during tachycardia when stability of the local electrogram, continuous ventriculoatrial activity during orthodromic tachycardia, and registration of a Kent-potential indicated electrogram criteria for a successful ablation. However, orthodromic tachycardia did not terminate, and catheter tip temperature only reached a plateau of 45 degrees C with maximal power output of 50 watts indicating an insufficient catheter tip-tissue-contact. Therefore, the bending of the catheter curve was slightly straightened during energy application without pushing the catheter forward in order to achieve a better tip electrode contact with the tissue. Simultaneously, a sudden increase in catheter tip temperature was observed accompanied by termination of the tachycardia indicative of the successful ablation of the accessory pathway. At present, a control of radiofrequency catheter induced tissue effects can be best achieved by temperature-guided energy application whereas monitoring of current, voltage, and impedance are insufficient in this respect. In the present case, correction of the catheter placement during energy application could be achieved because of the on-line monitoring of the catheter tip temperature thereby allowing successful ablation of the accessory pathway with a single radiofrequency pulse.