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Publication numberWO2001076479 A1
Publication typeApplication
Application numberPCT/NL2001/000281
Publication date18 Oct 2001
Filing date6 Apr 2001
Priority date6 Apr 2000
Publication numberPCT/2001/281, PCT/NL/1/000281, PCT/NL/1/00281, PCT/NL/2001/000281, PCT/NL/2001/00281, PCT/NL1/000281, PCT/NL1/00281, PCT/NL1000281, PCT/NL100281, PCT/NL2001/000281, PCT/NL2001/00281, PCT/NL2001000281, PCT/NL200100281, WO 0176479 A1, WO 0176479A1, WO 2001/076479 A1, WO 2001076479 A1, WO 2001076479A1, WO-A1-0176479, WO-A1-2001076479, WO0176479 A1, WO0176479A1, WO2001/076479A1, WO2001076479 A1, WO2001076479A1
InventorsGheorghe Aurel Marie Pop
ApplicantMartil Instruments B.V.
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
Catheter for measuring the impedance of surrounding blood
WO 2001076479 A1
Abstract
The present invention relates to a catheter (1) for measuring the impedance of surrounding blood, comprising a catheter body (2), which comprises close to the distal end (3) thereof at least four electrodes (4) at mutual distances from each other, and connecting lines (5) extending through the catheter body from the electrodes to the proximal end of the catheter.
Claims  (OCR text may contain errors)
1. Catheter for measuring the impedance of surrounding blood, comprising a catheter body, which comprises close to the distal end thereof at least four electrodes at mutual distances from each other, and connecting lines extending through the catheter body from the electrodes to the proximal end of the catheter.
2. Catheter as claimed in claim 1, characterized in that the at least four electrodes comprise at least two voltage electrodes, which can be connected via the connecting lines to an alternating voltage source, and two measuring electrodes situated therebetween, which can be connected to a measuring unit via the connecting lines .
3. Catheter as claimed in claim 1 or 2 , characterized in that the measuring electrodes are arranged symmetrically relative to the centre between the voltage electrode.
4. Catheter as claimed in claim 1, 2 or 3 , characterized in that the mutual distance between the four electrodes is equal.
5. Catheter as claimed in any of the claims 1-4, characterized in that at least one shielding wire is arranged between two connecting wires.
6. Catheter as claimed in any of the claims 1-5, characterized in that each connecting wire is enclosed by two parallel shielding wires.
7. Catheter as claimed in any of the foregoing claims, characterized in that the connecting wires are carried helically at a mutual distance from each other as a "flat cable" from the distal end, where the electrodes are arranged, to the proximal end around a central core in the catheter body.
8. Catheter as claimed in any of the foregoing claims, characterized in that six electrodes are arranged at a mutual distance from each other close to the distal end of the catheter body.
9. Catheter as claimed in any of the foregoing claims, characterized in that the catheter body comprises an elongate intravascular part intended for placing in the blood, which part is embodied such that the at least four electrodes for performing the impedance measurement can be placed in the right-hand atrium of the heart.
10. Catheter as claimed in claim 9, characterized in that the most distal of the at least four electrodes is arranged at least about 1 mm from the distal end of the catheter body.
11. Catheter as claimed in claim 9 or 10, characterized in that the distal end with the at least four electrodes can be placed in the right-hand atrium of the heart at an angle of between 0 and 180 C relative to the catheter body.
12. Catheter as claimed in any of the foregoing claims, characterized in that the electrodes are annular electrodes.
13. Catheter as claimed in any of the foregoing claims, characterized in that the electrodes are platinum or stainless steel electrodes.
14. Use of a catheter as claimed in any of the foregoing claims for determining the blood viscosity of a human or animal .
Description  (OCR text may contain errors)

CATHETER FOR MEASURING THE IMPEDANCE OF SURROUNDING BLOOD

The present invention relates to a catheter for measuring the impedance of surrounding blood.

Atherosclerosis is the most common disease in the western world and thereby represents one of the most significant problems of our health care services and our society. Atherosclerosis is a generalized disorder of the blood vessels, which can manifest itself for instance in the coronaries in unstable angina pectoris, myocardial infarction or even acute heart death. Atherosclerosis in the head is for instance responsible for the largest number of strokes (cerebral infarction) , while elsewhere in the body atherosclerosis can be the cause of reduced blood circulation in for instance the legs or the kidneys. Significant factors in the development of atherosclerotic complications are, amongst others, thrombotic processes. The treatment of atherosclerosis therefore generally focusses on suppressing such thrombotic processes. More recently it has been further discovered that inflammatory processes also appear to play a part in the occurrence of atherosclerotic complications .

The present invention has for its object to provide a catheter for measuring the impedance of surrounding blood, in particular for the purpose of determining the blood viscosity, whereby it is possible to monitor such thrombotic and/or inflammatory processes.

This object is achieved with the present invention by providing a catheter, comprising a catheter body, which comprises close to the distal end thereof at least four electrodes at mutual distances from each other, and connecting lines extending through the catheter body from the electrodes to the proximal end of the catheter. Using the catheter according to the invention impedance measurements of surrounding tissue, such as blood, can be performed, for instance in the heart, via the electrodes. It is known that blood has electrical properties. These electrical properties are different for the plasma and the blood cells. The plasma and the interior of the cells consist of conductive fluids with a determined electrical resistance and the cell membranes consist of phospholipids and proteins with dielectric properties. The electrical impedance of blood is primarily determined by three parameters: the plasma resistance, the internal resistance in the cell, and the capacitance of the cell membrane. The electrical impedance of the blood increases with an increased viscosity of the blood. The electrical impedance of blood is also found to be closely related to the fibrinogen content and the erythrocyte sedimentation rate, significant "markers" for the presence of inflammatory processes. The application of the catheter for instance for in vivo determining of the blood viscosity is based on the determining of the blood impedance as described in the Netherlands patent application number 1012223 and the international PCT application PCT/NL00/00378.

In a particular embodiment of the catheter according to the present invention the at least four electrodes comprise at least two voltage electrodes, which can be connected via the connecting lines to an alternating voltage source, and two measuring electrodes situated therebetween, which can be connected to a measuring unit via the connecting lines. Using the alternating voltage source connected to the voltage electrodes, an electric alternating voltage field with a determined frequency is generated for instance in the blood for a determined time, wherein using the measuring electrodes connected to the measuring unit a measuring signal of the electrical impedance of the blood is measured during this determined time. The measured measuring signal is then compared to a predetermined relation between the measured impedance and the blood viscosity.

In order to obtain reliable measurement results, the measuring electrodes are preferably arranged symmetrically relative to the centre between the voltage electrode. In a particularly suitable embodiment the mutual distances between the four electrodes are equal . The mutual distance between the measuring electrodes is preferably as small as possible, for instance between 0.5 and 2 mm, wherein the signal/noise ratio must be such that reliable measurements can still be made. Limiting the distance between the measuring electrodes as much as possible ensures that the field around the catheter in which measurement is taking place is as small as possible. The most reliable possible measurement of the impedance of the surrounding blood is hereby obtained, and for instance the vascular wall or the wall of the atrium are prevented from influencing the impedance measurement of the blood.

Each electrode is connected to a connecting wire which runs from the electrode through the catheter body to the proximal end of the catheter. In order to obtain shielding against stray capacitance, which can occur particularly when measurement takes place using alternating voltage, at least one shielding wire is arranged between two connecting wires. In a particularly suitable embodiment each connecting wire is enclosed by two parallel shielding wires. Herein the connecting wires are preferably carried helically at a mutual distance from each other as a " flat cable" from the distal end, where the electrodes are arranged, to the proximal end around a central core in the catheter body. The connecting wire is here thus enclosed by a "layer" of shielding wires. The shielding wires can remain loose, i.e. not connected, or be connected to the proximal end with a zero potential. A charge can also be applied to the shielding wires in order to obtain "active shielding" . This is especially relevant when higher frequencies are used, particularly at frequencies above 1 MHz.

In a special preferred embodiment of the catheter six electrodes are arranged at a mutual distance from Φ

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catheter the catheter body is for instance adapted such that the outer distal end of the catheter body comes to rest on the apex of the right-hand ventricle, wherein the electrodes are situated in the atrium of the heart . In this case the most distal electrode must be arranged further from the extreme distal end such that the most distal electrode comes to lie above the level of the tricuspid valve, so that the impedance measurement is performed in the right-hand atrium. According to a further preferred embodiment the electrodes are annular electrodes which are arranged close to the distal end of the catheter body. The electrodes are preferably platinum or stainless steel electrodes. The transfer resistance which results on the electrode surface increases as the surface decreases.

This resistance (impedance) may not become too great in respect of the compliance (operating range) of the voltage source.

The catheter according to the invention as described above can be suitably used for instance for in vivo determining of the blood viscosity of human or animal, as described earlier in for instance PCT/NL00/00378. Determining the blood viscosity in a patient can be used to evaluate the chance of thrombosis formation, and thereby the risk of thrombotic disorders such as a myocardial or cerebral infarction. When the measurement indicates a high viscosity, it may for instance be decided to apply viscosity-reducing therapy, such as the administering of a fibrinogen-reducing agent. By monitoring the effect of the administered agent on the viscosity, the ideal dosage of the agent can be precisely determined.

The invention is further elucidated with reference to the annexed figures, in which: Fig. 1 shows a schematic view of a preferred embodiment of the catheter with four electrodes;

Fig. 2 is a schematic, partly cut-away view of the human heart provided with the catheter shown in Fig. 1; Fig. 3 shows a schematic view of another preferred embodiment of the catheter according to the invention, provided with six electrodes.

Fig. 1 shows a schematic representation of a preferred embodiment of catheter 1 according to the invention. Catheter 1 herein comprises a catheter body 2, which close to the distal end 3 thereof comprises four annular platinum or stainless steel electrodes 4 (for instance 0.8 mm wide) at mutual distances from each other. Connecting lines 5 extend from electrodes 4 through the catheter body to the proximal end 6 thereof, where they can be connected to for instance an alternating voltage source and a measuring unit .

In the shown embodiment the mutual distances between the electrodes are equal (about 2 mm from the centre of a first electrode to the centre of a subsequent electrode) . The distal end on which the electrodes are arranged is situated during the impedance measurement in for instance the right-hand atrium at an angle relative to the rest of catheter body 2, as shown in figure 2. The most distal electrode is herein arranged at least 1 mm from the end, and the top of the distal end is preferably soft so as to prevent damage of the atrium wall by the most distal electrode. The other part of the catheter body is preferably made from a stiff material so as to ensure that the catheter can be repositioned from the outside such that the distal end with the electrodes remains centrally in the atrium.

As shown in Fig. 2, catheter 1 comprises an intravascular part 2 intended for placing in the bloodstream, which part is embodied such that the distal end with the at least four electrodes for performing the impedance measurement can be placed in the right-hand atrium 8 of a human heart 7. By way of orientation the right-hand ventricle is further designated in figure 2 with 9, the sino-atrial node with 10, and the atrioventricular bundle with 11. The distal end of catheter body 2 with the four electrodes is shown in area 12. During the impedance measurement the distal end is situated in right-hand atrium 8 at an angle relative to the rest of catheter body 2, such that the electrodes lie as centrally as possible in the atrium.

Finally, Fig. 3 shows a schematic representation of another preferred embodiment of catheter 1 according to the invention. Six electrodes 4 are herein arranged close to the distal end 3 of catheter body 2, wherein a connecting wire 5 runs from each electrode through the catheter body to the proximal end 6 of the catheter, and wherein each electrode is enclosed by two shielding wires. The most distal electrode is herein arranged at a greater distance, for instance about 12 cm, from the distal end. The embodiment of the catheter shown in these figures is for instance particularly suitable for use in the application where the tip of the distal end comes to rest on the apex of the right-hand ventricle. Because the electrodes are arranged at a greater distance from the distal end it is possible to ensure that the voltage electrodes and the measuring electrodes measure the impedance of the blood in the atrium. If the dimensions of the heart for sampling are for instance such that the most distal electrode or electrodes do not lie above the level of the tricuspid valve, four more proximally situated electrodes can be used for the measurement. It will be further understood that the dimensions given above can be varied, for instance depending on the size of the heart for which the catheter is intended, such as for instance human or animal.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
WO1994022367A1 *6 Jan 199413 Oct 1994Pfizer Inc.Radiotelemetry impedance plethysmography device
WO2000074775A15 Jun 200014 Dec 2000Martil Instruments B.V.Method, device and catheter for in vivo determining blood properties such as blood viscosity
EP0384060A2 *25 Aug 198929 Aug 1990Cardiac Pacemakers, Inc. (a Minnesota corporation)Method and apparatus for matching the sensed length of an impedance measuring catheter to a ventricular chamber
NL1012223C2 Title not available
US4437474 *16 Jul 198220 Mar 1984Cordis CorporationMethod for making multiconductor coil and the coil made thereby
US4836214 *1 Dec 19866 Jun 1989Bomed Medical Manufacturing, Ltd.Esophageal electrode array for electrical bioimpedance measurement
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
WO2003077759A120 Mar 200325 Sep 2003Martil Instruments B.V.Catheter with integrated signal-processing device
WO2009123508A1 *31 Mar 20088 Oct 2009St. Jude Medical AbAnti-arrhythmia implantable medical device
US81033267 Apr 200824 Jan 2012Cardiac Pacemakers, Inc.Device for monitoring fluid status
US838854125 Nov 20085 Mar 2013C. R. Bard, Inc.Integrated system for intravascular placement of a catheter
US838854621 Apr 20095 Mar 2013Bard Access Systems, Inc.Method of locating the tip of a central venous catheter
US84378337 Oct 20097 May 2013Bard Access Systems, Inc.Percutaneous magnetic gastrostomy
US847838211 Feb 20092 Jul 2013C. R. Bard, Inc.Systems and methods for positioning a catheter
US85122569 Sep 201020 Aug 2013Bard Access Systems, Inc.Method of locating the tip of a central venous catheter
US87749079 Jan 20138 Jul 2014Bard Access Systems, Inc.Method of locating the tip of a central venous catheter
US87815552 Mar 201015 Jul 2014C. R. Bard, Inc.System for placement of a catheter including a signal-generating stylet
US878433623 Aug 200622 Jul 2014C. R. Bard, Inc.Stylet apparatuses and methods of manufacture
US880169327 Oct 201112 Aug 2014C. R. Bard, Inc.Bioimpedance-assisted placement of a medical device
US884938210 Sep 200930 Sep 2014C. R. Bard, Inc.Apparatus and display methods relating to intravascular placement of a catheter
US885845516 Aug 201314 Oct 2014Bard Access Systems, Inc.Method of locating the tip of a central venous catheter
US89719948 Apr 20133 Mar 2015C. R. Bard, Inc.Systems and methods for positioning a catheter
US91255782 Feb 20118 Sep 2015Bard Access Systems, Inc.Apparatus and method for catheter navigation and tip location
US92111077 Nov 201215 Dec 2015C. R. Bard, Inc.Ruggedized ultrasound hydrogel insert
US92654435 May 201423 Feb 2016Bard Access Systems, Inc.Method of locating the tip of a central venous catheter
US933920614 Jun 201017 May 2016Bard Access Systems, Inc.Adaptor for endovascular electrocardiography
US93454223 Oct 201424 May 2016Bard Acess Systems, Inc.Method of locating the tip of a central venous catheter
US941518831 Jul 201416 Aug 2016C. R. Bard, Inc.Bioimpedance-assisted placement of a medical device
US944573410 Aug 201020 Sep 2016Bard Access Systems, Inc.Devices and methods for endovascular electrography
US945676627 May 20114 Oct 2016C. R. Bard, Inc.Apparatus for use with needle insertion guidance system
US94920976 Jul 201215 Nov 2016C. R. Bard, Inc.Needle length determination and calibration for insertion guidance system
US952196123 Dec 201120 Dec 2016C. R. Bard, Inc.Systems and methods for guiding a medical instrument
US952644019 Jun 201427 Dec 2016C.R. Bard, Inc.System for placement of a catheter including a signal-generating stylet
US953272422 Sep 20113 Jan 2017Bard Access Systems, Inc.Apparatus and method for catheter navigation using endovascular energy mapping
US954968526 Sep 201424 Jan 2017C. R. Bard, Inc.Apparatus and display methods relating to intravascular placement of a catheter
US955471627 May 201131 Jan 2017C. R. Bard, Inc.Insertion guidance system for needles and medical components
US963603129 Sep 20102 May 2017C.R. Bard, Inc.Stylets for use with apparatus for intravascular placement of a catheter
US964904817 Apr 200916 May 2017C. R. Bard, Inc.Systems and methods for breaching a sterile field for intravascular placement of a catheter
US968182311 May 201220 Jun 2017C. R. Bard, Inc.Integrated system for intravascular placement of a catheter
USD6993591 Aug 201211 Feb 2014C. R. Bard, Inc.Ultrasound probe head
USD75435724 Jan 201419 Apr 2016C. R. Bard, Inc.Ultrasound probe head
Classifications
International ClassificationA61B5/145, A61B5/15
Cooperative ClassificationA61B5/02035
European ClassificationA61B5/02F2
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