Non-invasive electrophysiologic study with amagnetic transesophageal pacing during unshielded multichannel magnetocardiographic mapping.

Unlabelled: Multichannel magnetocardiographic (MCG) mapping is a non-invasive method, which can provide reproducible three-dimensional (3D) localization of accessory pathways (AP) and ventricular arrhythmias, before ablation procedures. More recently MCG imaging of intra-atrial reentry circuits has also been reported. So far, reported cases of MCG localization and imaging of arrhythmias were investigated during spontaneous rhythm only, although more relevant information can be obtained during dynamic electrophysiologic study (EPS). For cardiac pacing one could use an amagnetic intracardiac catheter; but this, however, would add invasivity to a non-invasive method. The aim of this study was to validate a novel approach for dynamic non-invasive EPS based on MCG in combination with amagnetic transesophageal pacing (TEP).

Method: A tetrapolar 7 French amagnetic catheter was developed, which provides effective TEP (with an average stimulation threshold of 10-15 mA) and simultaneous recording of two esophageal atrial electrograms. MCG data were acquired at rest, with a 36-channel MCG system (sensitivity of 20 fT/Hz(1/2)), for 90 to 300 seconds (sampling rate of 1 KHz; bandwidth of DC Hz to 100 Hz), as a function of the type of pacing procedure. 10 patients were investigated, during both continuous and programmed TEP.

Results and conclusions: MCG during TEP was feasible and reproducible. It provided: 1) more accurate localization of AP during pacing-induced maximal preexcitation; 2) inducibility of supraventricular AR and imaging of atrial reentry circuits, not spontaneously present; 3) stabilization of the heart rate to improve the accuracy of quantitative estimate of ventricular repolarization parameters.