Surgery – Miscellaneous – Devices placed entirely within body and means used therewith
Reexamination Certificate
1999-04-28
2001-11-20
Lacyk, John P. (Department: 3736)
Surgery
Miscellaneous
Devices placed entirely within body and means used therewith
Reexamination Certificate
active
06318375
ABSTRACT:
RELATED APPLICATION
This application claims priority to European Patent Application No. 99830032.1, filed on Jan. 28, 1999, the entire teachings of which are incorporated herein by reference.
The present invention relates in general to techniques for operating on the heart which are performed transvenously with the use of catheters.
During these transvenous heart procedures performed with the use of catheters, it is very important to be able to locate the pole of the catheter used—generally within a three-dimensional space. This need is very marked in radio-frequency ablation and electro-physiological mapping procedures which require so-called “navigation” of the catheter along a complex endocardial surface.
Recently, non-fluoroscopic locating systems based on magnetic systems for mapping the catheter-pole position have been proposed. Devices of this type have been used in the electro-physiological mapping of the endocardium with simultaneous recording of the pole position and of the electrogram. In this connection, the work “A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart” by L. Gepstem, G. Hayam and S. A. Ben-Haim in Circ., Vol. 95, No. 6, Pages 1611-1622, 1977 may usefully be consulted.
The device concerned has been clinically evaluated and has demonstrated its usefulness in reducing exposure to X-rays so that it is possible to return to a specific anatomical site of interest.
A system based on sonomicrometry recently proposed for the same purpose consists of a scanning catheter fitted with a piezoelectric transducer which can send ultrasound pulses to seven reference sensors fitted on the epicardial surface of a sheep's heart. In this connection, the work “Application of sonomicrometry and multidimensional scaling to cardiac catheter tracking” by Scott A. Meyer and Patrick D. Wolf in IEEE transactions on Biomedical Engineering, Vol. 44, No. 11 November 1997 may usefully be consulted.
The present invention fits into this line of research which is directed towards locating the pole of a catheter operating in an endocardial site whilst avoiding fluoroscopic location.
According to the present invention, this object is achieved by means of a device having the characteristics recited specifically in the following claims.
Briefly, the solution according to the invention is based—in the currently preferred embodiment—on the principle of the vectorial de-composition of an electric field onto three axes, the electric field being generated by pulses below the stimulation threshold, delivered to the endocardial surface by the pole of a scanning catheter.
The device according to the invention, which is intended preferably for temporary use in acute situations, preferably comprises a four-pole, triaxial geometric reference system, associated with a lead having at least one core for scanning the endocardial surface, as well as an external unit for processing data in real time. The device, again preferably, is for use in combination with a pulse generator for generating direct-current pulses of programmable frequency and duration, and with a system for displaying and printing maps of the endocardial surface or of the physiological signals detected thereon.
Again in the currently-preferred embodiment, the system is based upon the detection, within a heart chamber, of the vectorial projections, onto a triaxial spatial reference system, of the electrical potential generated between a pole or electrode of a scanning lead (which is positioned at different sites of the endocardium by the operator) and a central pole acting as an origin of the triaxial reference system. The reference lead is also positioned inside the same heart chamber or in any case in a position such as to lead to little distortion of the electric field between the reference lead and the scanning pole.
The external data-processing unit analyzes the three vectorial components of the potential. This is done with reference to the inclination of the axes which, although they are fixed, are not necessarily perpendicular. The relative position of the scanning pole, which is guided by the operator so as to describe the endocardial surface under investigation, can thus be calculated by a suitable algorithm.
External electrical stimulation or electrotonic inhibition devices and/or devices for measuring electro-physiological quantities may optionally be connected to the scanning pole, enabling the respective data to be transmitted to the processing unit, possibly for association with the respective spatial position. This enables three-dimensional maps or two-dimensional developments of the parameter investigated to be displayed.
Whilst keeping the reference lead in situ, it is possible to replace the scanning lead with a lead of a different type, for example, having radio-frequency ablation electrodes, optical fibres for endoscopy and/or for topical application of radiation, or devices for performing microscopic surgical operations. Such a lead may nevertheless have a conductive pole with the same characteristics as the previous scanning lead to enable the lead to be positioned and a display to be provided on the previously-constructed map, by similar methods.
In order to be able to insert the reference system with its three axes and the respective poles in the blood vessel, it is possible to use, for example, two coaxial leads of which the outer one has the function of a movable sheath with facilitated relative sliding.
This facilitates transvenous insertion into the heart chamber under investigation and the subsequent opening-out in situ of a reference system having intrinsic mechanical stability. This stability can also be achieved actively, for example, by associating with each of the axes respective pole tubules made of a material and by techniques similar to those used for balloon catheters for angioplasty treatments (PTCA). These soft tubules can easily be housed inside a retractable sheath and can subsequently become stiff after being pressurized by a suitable gas or liquid. The reverse operation enables the reference lead to be recovered in each of the systems described.
Although the currently preferred embodiment provides for the production of a three-dimensional positioning system, the invention may also be implemented—in simplified versions—by means of two-dimensional reference systems or, potentially, even one-dimensional systems. Naturally, in this case, the greater ease of implementation compensates for the reduced richness of the data.
In this connection, it is again pointed out that the reference system does not necessarily have to be a perpendicular Cartesian system. Three-dimensional reference systems of different types, for example polar or cylindrical systems, may in fact be used within the scope of the invention.
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Gepstein et al., “A Novel Method for Nonfluoroscopic Catheter-Based Electroanatomical Mapping of the Heart”,Circulation, 95(6) :1611-1622 (Mar. 18, 1997).
Meyer et al., “Application of Sonomicrometery andMultidimensional Scaling to Cardiac Catheter Tracking”,Transactions on Biomedical Engineering 44(11) :1061-1067 (Nov. 1997).
Gaggini Guido
Garberoglio Bruno
Marcelli Emanuela
Plicchi Gianni
Vallana Franco
Dorsey & Whitney LLP
Lacyk John P.
Ministero dell' Universita' e della Ricera Scientifica
Szmal Brian
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