Feasibility of simultaneous multichannel magnetocardiographic mapping, multiple monophasic action potential recording, and laser photocoagulation of isolated and perfused rabbit ventricular myocardium

Background: Multichannel magnetocardiographic mapping (MCG) has been validated as an accurate non-invasive method for 3D localization of arrhythmogenic substrates suitable for ablation treatment and intracardiac electrophysiology catheters (1,2). High resolution (HR) MCG-guided multiple simultaneous monophasic action potential (multi-MAP) recording and pacing with a special amagnetic catheter (AC) detect local arrhythmogenic mechanisms (3). Laser photocoagulation (LP) providing more controlled and homogeneous myocardial lesions (4), may be an alternative to radiofrequency (RF) ablation, without unwanted electromagnetic noise effect during real-time MCG. Purpose: This study aimed to experimentally test the feasibility of simultaneous multi-MAP recording and LP guided by real-time MCG. Methods: An unshielded 36 channels SQUID system (sensitivity of 30 fT/Hz1/2, at 1 Hz) (CMI, USA) was used to study Langendorff-perfused isolated rabbit heart with MCG (Figure 1A). Four epicardial MAPs were simultaneously recorded (inter MAP distance: 1 mm) with a single multi-MAP AC (bandpass: DC-500 Hz; sampling frequency: 2 kHz) (GE-Prucka Cardiolab). LP was performed with a NdYAG laser (Dornier Medilas 5100) and a catheter system for safe myocardium LP (5). The study was carried out according to NIH guidelines for animal care and use. Results: MCG imaging of rabbit ventricular magnetic field distribution and inverse source localization with the magnetic dipole model are shown in Figure 1B. The morphology of local HR ventricular multi-MAP signals was compatible with myocardial isotropy (Figure 1C). With appropriate cooling of the optic fiber-tissue interface, no epicardial damage was induced by LP, whereas deeper well defined intramural myocardial lesions were appreciable, of different size as a function of the energy delivered (Figure 1D). Multi-MAP recording was not significantly disturbed by LP. Keeping the Medilas unit at least 5 meters away from the MCG sensors, no electromagnetic artifacts were observed during MCG. Conclusion: MCG, multi-MAP recording and well-defined LP lesions of ventricular myocardium were simultaneously feasible on Langendorff-perfused isolated rabbit heart, without major electromagnetic interferences, in an unshielded catheterization laboratory.