Multiple simultaneous Monophasic Action Potential recordings with a single biomagnetically localizable amagnetic catheter

A further development of a multipurpose catheter, designed to be biomagnetically localizable for magnetocardiographically (MCG) guided intracardiac electrophysiological recordings and ablation of cardiac arrhythmias (USA Patent N. 5,056,517 and EUR Patent N. 0428812), is described. Methods: The 7F (French) catheter's tip features five non-polarizable amagnetic electrodes, arranged in such a way that, differently connected to external power sources, two orthogonal or parallel current dipoles can be generated in the patients heart. Alternatively a magnetic dipole can be induced as well. This assembly can be localized by MCG mapping and inverse solution, with a three-dimensional (3D) accuracy of 10 mm, without the use of fluoroscopy. On the basis of preoperative MCG 3D localization, the catheter can be driven, under fluoroscopic control, as close as possible to the arrhythmogenic zone. MCG mapping is then performed under pacing, with fine adjustments of the catheter, until the 3D co-ordinates of its moving tip will fit those generated by the spontaneous arrhythmia. Once reached the area of onset of the arrhythmia the same electrodes are used to record simultaneously four monophasic action potentials (MAP) with a spatial resolution of 4 mm2. Alternatively two electrodes can be used for local pacing and two for simultaneous MAP recordings. MAP signals are differentially amplified, low-pass filtered at 1Kh and digitized at the sampling frequency of 4 KHz. All digitized waveforms are simultaneously displayed on the PC monitor and written on hard disk or magneto-optic disk. MAP duration at 50% and 90% levels of repolarization and local conduction times between the MAP's onset are automatically calculated. Results: In 10 patients, the average local variation coefficients of MAP duration, at 50% and 90% of repolarization, were 4.5% and 5.2% respectively. Local activation time was automatically computed with 1 msec. resolution. This allowed the detection of local repolarization homogeneity and of areas of slow conduction or focal block. Conclusion: MCG mapping, in combination with this new amagnetic catheter, provides non fluoroscopy-dependant single-catheter intracardiac mapping of local electrophysiological abnormalities right on a predefined arrhythmogenic area.