In vitro laser photocoagulation of ventricular myocardium during multichannel MCG mapping and multi-MAP recording with amagnetic catheters

Laser photocoagulation (LP) of myocardium is an alternative to radiofrequency (RF) for ablation of cardiac arrhythmias. It produces homogeneous clear-cut lesions of coagulation necrosis in a controlled fashion, without unwanted effect on the heart. This study was aimed to test the possibility to perform simultaneously LP and multiple monophasic action potential (multi-MAP) recording with amagnetic catheters (AC) during multichannel MCG mapping (MMCG). Experimental set-up: Langendorff-perfused isolated rabbit heart. A 9 channels system (sensitivity is 20 fT/Hz1/2, at 1 Hz) (CMI, USA) was used for MMCG. 4 MAPs were recorded with a single multi-MAP AC, (bandpass DC-500 Hz; sampling frequency of 1-2 kHz) (GE-Prucka Cardiolab). LP was performed with Nd:YAG laser (DornierMedilas 5100) and a catheter system for safe myocardium LP, as defined by Weber. MMCG provided adequate imaging of rabbit ventricular magnetic field distribution. Due to the geometrical limi-tation of the experimental set-up, multiMAP recordings and LP were performed only from the right ventricle and atrium. The quality of right ventricular MAP signals was acceptable, although the baseline was sometime unsta-ble. The size and macroscopic features of LP-induced myocardial lesions were similar to those reported by We-ber. With proper cooling of the optic fiber-tissue interface, no epicardial damage was observed, in spite of effec-tive LP of the deeper myocardial layers. Multi-MAP recording was not disturbed by laser photocoagulation. To avoid magnetic artifacts the laser unit had to be at least 5 meters away from the MMCG instrumentation. We conclude that the three techniques can be simultaneously used, without major interferences, and that LP can be the proper energy for MMCG-guided ablation of arrhythmia