Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-06-01
2003-03-04
Bennett, Henry (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06527724
ABSTRACT:
The subject matter of the present invention consists of an improved amagnetic electrocatheter for single-catheter multiple monophasic action potential recording with a high spatial resolution, directly from the arrhythmogenic substrate of a cardiac arrhythmia, and the threedimensional electro-anatomical integration of the electrophysiological information obtained on a heart model of the examined patient, andor on bi- and threedimensional magnetic resonance imaging.
The monophasic action potential recording (MAP) is a method that allows to bridge the gap between in vitro experimental electrophysiology (transmembrane action potential recording) and clinical electrophysiology. In fact, MAP allows a clinical diagnosis of the alterations in the cardiac electrogenesis, as lack of repolarization homogeneity, triggered activity, early or late afterpotentials, focal conduction abnormalities with microre-entry phenomena.
The catheter subject matter of the present invention is a multipurpose device derived from the experience with another previously patented amagnetic electrocatheter (IT 1,219;855-A EP 0,428,812 U.S. Pat. No. 5,056,517 JP 2554105), of which it constitutes an improvement.
In particular, EP 0,428,812 describes a cardiac electrocatheter which comprises a distal and proximal electrode of non-ferromagnetic, non-polarisable material adapted to being connected to external pacing devices through insulated twisted wires.
Multiple simultaneous MAP recordings are essential in order to improve the diagnostic specificity of the method.
As it is known, with the previously patented amagnetic catheter only a single MAP per catheter could be recorded. Therefore, the insertion of multiple catheters and/or the carrying out of sequential recordings, prolonging the study duration and the radioscopy times, were required. Moreover, spatial resolution was not well-defined for multiple recordings thus carried out.
The improved amagnetic electrocatheter subject matter of the present invention, by virtue of the peculiar configuration thereof and of the nature of the materials used for the construction thereof, can be used for single-catheter multiple monophasic action potential recording, although being localizable by surface magnetocardiographic mapping (MCG), with high spatial resolution and without fluoroscopy.
The electrocatheter according to the invention can have different embodiments. The most specific and innovative feature of the present device is the presence of multiple distal and proximal electrodes critically located in order to generate, sequentially or simultaneously, multiple electric or magnetic dipoles of variable intensity and geometry. This feature permits a highly accurate three-dimensional localization of the distal end (tip) of the catheter by MCG, visualizing the positioning thereof almost in real time inside a three-dimensional model of the heart of the patient under examination, interactively analyzable by the operator.
This permits to drive the catheter, by a numerical spatial control of the distal end thereof, until the three-dimensional coordinates fit at the best those of the arrhythmogenic area, with minimum use of fluoroscopy.
The magnetocardiographic driving method of the catheter onto the arrhythmogenic substrate is carried out as follows.
Prior to the invasive electrophysiological study, a magnetocardiographic study (mapping) of the patient is carried out in order to assess, even by reiterated gauging, the distribution characteristics of the magnetic field generated by the arrhythmogenic structure susceptible of catheter ablation, and the reproducible threedimensional alocalization thereof.
On the basis of such preoperating information, the amagnetic catheter is inserted under fluoroscopic control and driven in close proximity of the presumably arrhythmogenic area. Then the catheter is repositioned under magnetocardiographic spatial control, until the threedimensional coordinates of the distal end thereof fit at the best those of the target arrhythmogenic area.
Upon reaching the presumed arrhythmogenic area, the simultaneous single-catheter multiple MAP recording provides the following new electrophysiological information referring to the underlying myocardial area:
1. Estimate of the local repolarization scattering;
2. Estimate of the local conduction speed;
3. Identification of the route of the depolarization front;
4. Presence of early andor late afterpotentials;
5. Presence of areas of focal block, with or without micro re-entry; and
6. Electro-anatomical integration of the aforesaid information with the three-dimensional coordinates of the catheter distal end (tip).
Once the arrhythmogenic nature of the substrate under examination has been confirmed by high-resolution MAP mapping, energy can be outputted by laser emission with fiberoptics coaxial to and centered with respect to the area defined by the MAP recording. This allows modifying the electrogenesis of the underlying myocardium, monitoring the effects thereof according to the aforesaid parameters and to the characteristics of the arrhythmia under examination.
In case the effectiveness of a functional exclusion of the substrate under examination has been documented, this can be effectively ablated with a suitable energy output.
Hence, the electrocatheter subject matter of the present invention is aimed at the implementation of an entirely innovative approach to the electrophysiological study and to the ablation of the cardiac arrhythmiae, with high spatial resolution and minimal invasivity.
By virtue of their characteristics, the variants of the electrocatheter according to the invention are localizable by magnetocardiographic mapping, at the same time being apt to record multiple MAPs, to implement intracardiac stimulation (pacing) and to output energy by laser emission.
In its broader definition, the electrocatheter according to the invention comprises a plurality of distal electrodes, constructed of a non-ferromagnetic and non-polarizable conductor material, shaped in such a manner as to generate simultaneously or sequentially electromagnetic fields of dipolar configuration and with different geometry, at least a more proximal electrode, such electrodes being located at the end of multiple wires, of a non-ferromagnetic conductive material, which wires are electrically insulated and twisted one with respect to the other, to avoid, except for the electrodes, electromagnetic field generation along the catheter during the induction of electromagnetic dipoles at the distal end of the catheter, and a substantially cylindrical flexible tube that sheaths said wires and electrodes, at the distal end thereof leaving exposed a section of the electrode tips and, onto the side wall, near the distal end, a section of said at least one ring-shaped more proximal electrode.
Besides the lumen housing the electrodes and the wires, the flexible tube can provide a plurality of other lumens, each running along the catheter body in parallel and separate thereamong—with tip andor lateral eyelets—to insert other wires, e.g. ablation wires or biopsy tubes, or fiberoptics, or for fluid infusion and/or suction.
The equivalent surface of the electrodes ranges according to the molecular structure of the material used.
The distance between the distal electrodes and the proximal ring-shaped ones can vary.
The material used for the electrodes should be amagnetic and non-polarizable, e.g., platinated platinum or amorphous carbon. The molecular structure can be such as to increase, electrode diameters being equal, the equivalent surface.
The material used for the wires can be twisted copper, diameter about 200 &mgr;m, or other amagnetic equivalent.
The flexible tube can be made of biocompatible, non-thrombogenic plastic material. For instance, good results were obtained with materials selected from the group comprising polyurethane, polyvinyl chloride, polyether amide.
The internal gauge of the electrocatheter can range between 2.0 and 2.7 mm (6 F and 8 F, F meaning French).
All the embodiments of the amagnetic catheter according to
Bennett Henry
Consiglio Nazionale delle Richerche
Robinson Daniel
LandOfFree
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