Magnetic guidance system for cardiac electrophysiology
a prospective trial of safety and efficacy in humans
Mitchell N. Faddis, MD, PhD, FACC*,*,
Jane Chen, MD, FACC*,
Judy Osborn, RN*,
Michael Talcott, DVM*,
Michael E. Cain, MD, FACC* and
Bruce D. Lindsay, MD, FACC*
* Washington University School of Medicine, St. Louis, Missouri, USA
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Figure 1 Magnetic catheter and magnetic guidance system (MGS) (A) Photographs of the 7F magnetic catheter. A closeup of the catheter tip is shown on the right. A permanent magnet embedded within the tip of the catheter interacts with a prevailing magnetic field. A standard, platinum 4-mm-tip electrode and a proximal ring electrode are used for endocardial recording and pacing. The scale bar is 20 mm. (B) A photograph of the MGS. This system consists of a housing that surrounds the patient's torso; the system also contains an electromagnetic array, a digital biplanar fluoroscope, a standard fluoroscopy table, and a graphical workstation for catheter navigation. The system is shown with the fluoroscopy table withdrawn from the electromagnet housing.
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Figure 2 Magnetic navigation. (A) Photograph of catheter navigation with the magnetic guidence system. The catheter is guided by drawing a magnetic field vector on a graphical digitization tablet at the side of the fluoroscopy table as shown. The magnetic field vector is drawn and displayed overlying two orthogonal fluoroscopic views to specify a unique three-dimensional magnetic field vector. The magnetic field is then activated through the digitization tablet, and the catheter aligns parallel with the selected magnetic field vector. (B) Orthogonal fluoroscopic views used to specify the magnetic field vector. The images displayed (left anterior oblique [left], right anterior oblique [right]) show the magnetic catheter aligning parallel to the chosen magnetic field vector to reach the His bundle recording site in a patient.
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Figure 3 Electrogram recordings with a magnetic catheter. Surface electrocardiograms (ECGs) and intracardiac electrograms recorded from a single patient with Wolff-Parkinson-White syndrome are shown. Intracardiac recordings made with both a standard 4-mm-tipped ablation catheter and the magnetic catheter at the high right atrium (HRA), right ventricle apex (RVA), His bundle (His), and ventricular insertion of the accessory pathway are shown. Electrograms were recorded sequentially from the recording sites and are displayed in registry with the surface ECGs. Surface and intracardiac electrograms were not compromised by the magnetic field. The vertical scale is 5 mV, and the horizontal scale is 400 ms.
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Figure 4 Tricuspid annulus recording sites. The distribution of recording sites located around the tricuspid valve are shown schematically. Each recording site was targeted in the left anterior oblique fluoroscopic projection. Recording sites were categorized by the analogous hour position on a clock face. All navigation attempts to sites around the tricuspid annulus were successful. An example of a recording site at the lateral (Lat) aspect (9:00) on the tricuspid valve annulus (TVA) is shown in right anterior oblique (left) and left anterior oblique (right) images. The septal (Sep), anterior (Ant), and posterior (Post) tricuspid annulus are indicated for orientation.
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Figure 5 Pulmonary vein mapping with a magnetic catheter. The magnetic catheter was introduced into the left atrium through a trans-septal sheath for left atrial mapping in a patient with a left posterolateral accessory pathway. Navigation of the magnetic catheter to each pulmonary vein is shown in left anterior oblique images: (A) left superior pulmonary vein; (B) right superior pulmonary vein; (C) left inferior pulmonary vein; (D) the right inferior pulmonary vein.
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Figure 6 Magnetic catheter recordings in a patient with Wolff-Parkinson-White syndrome. The magnetic catheter was introduced into the left atrium by a trans-septal sheath and directed onto the site of a left posterolateral accessory pathway. The right anterior oblique (left) and left anterior oblique (right) projections are shown of the magnetic catheter positioned at the accessory pathway recording site. Catheters are also shown recording from the right ventricular apex, the His bundle recording site, and within the coronary sinus. Electrogram recordings were made with the magnetic catheter at the accessory pathway site during sinus rhythm and during orthodromic atrioventricular re-entrant tachycardia. Concurrent proximal His (pHis) and distal His (dHis) readings are shown. The vertical scale is 3 mV, and the vertical scale is 400 ms. NSR = normal sinus rhythm; SVT = supraventricular tachycardia.
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