Monitoring of lesion formation during catheter ablation is difficult to accomplish. To achieve that goal, monitoring of intracardiac local electrograms (LEGs) was performed during laser application by using an open-irrigated electrode laser mapping and ablation (ELMA) catheter provided with pin electrodes at its tip in a dog model. A total of 112 laser impacts were aimed at the atrial (15 W/5-30 s, n560) and at the ventricular free walls (20 W/20-50 s, n552) in 12 dogs. Amplitudes of potentials

more »

... in the LEG gradually dwindled and were abolished in 8-13 s (9.9¡1.6) and in 25-32 s (28.1¡1.9) after radiation. Lesions achieved were correlated with the LEG recorded during formation of each lesion. After permanent abolishment of potentials, lesions were transmural. Radiation limited to 3-5 s allowed for complete recovery of potential amplitudes and did not produce lesions. In contrast to that, continuation of radiation .5 s beyond 13 s or 35 s, occasionally caused myocardial and collateral damages or malignant arrhythmias. A light-guide protection system (LPS) and transesophageal light sensor (TLS) helped avoid such damage. During laser application LEGs recorded via the pin electrodes mounted at the ELMA catheter tip allowed for monitoring of lesion formation. KEYWORDS. laser catheter ablation, monitoring of laser lesion formation, open-irrigated electrode laser mapping and ablation catheter, voltage of local intracardiac potential amplitudes.