|Publication number||WO2001076479 A1|
|Publication date||18 Oct 2001|
|Filing date||6 Apr 2001|
|Priority date||6 Apr 2000|
|Publication number||PCT/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|
|Inventors||Gheorghe Aurel Marie Pop|
|Applicant||Martil Instruments B.V.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (34), Classifications (4), Legal Events (8)|
|External Links: Patentscope, Espacenet|
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.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|WO1994022367A1 *||6 Jan 1994||13 Oct 1994||Pfizer Inc.||Radiotelemetry impedance plethysmography device|
|WO2000074775A1||5 Jun 2000||14 Dec 2000||Martil Instruments B.V.||Method, device and catheter for in vivo determining blood properties such as blood viscosity|
|EP0384060A2 *||25 Aug 1989||29 Aug 1990||Cardiac 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 1982||20 Mar 1984||Cordis Corporation||Method for making multiconductor coil and the coil made thereby|
|US4836214 *||1 Dec 1986||6 Jun 1989||Bomed Medical Manufacturing, Ltd.||Esophageal electrode array for electrical bioimpedance measurement|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|WO2003077759A1||20 Mar 2003||25 Sep 2003||Martil Instruments B.V.||Catheter with integrated signal-processing device|
|WO2009123508A1 *||31 Mar 2008||8 Oct 2009||St. Jude Medical Ab||Anti-arrhythmia implantable medical device|
|US8103326||7 Apr 2008||24 Jan 2012||Cardiac Pacemakers, Inc.||Device for monitoring fluid status|
|US8388541||25 Nov 2008||5 Mar 2013||C. R. Bard, Inc.||Integrated system for intravascular placement of a catheter|
|US8388546||21 Apr 2009||5 Mar 2013||Bard Access Systems, Inc.||Method of locating the tip of a central venous catheter|
|US8437833||7 Oct 2009||7 May 2013||Bard Access Systems, Inc.||Percutaneous magnetic gastrostomy|
|US8478382||11 Feb 2009||2 Jul 2013||C. R. Bard, Inc.||Systems and methods for positioning a catheter|
|US8512256||9 Sep 2010||20 Aug 2013||Bard Access Systems, Inc.||Method of locating the tip of a central venous catheter|
|US8774907||9 Jan 2013||8 Jul 2014||Bard Access Systems, Inc.||Method of locating the tip of a central venous catheter|
|US8781555||2 Mar 2010||15 Jul 2014||C. R. Bard, Inc.||System for placement of a catheter including a signal-generating stylet|
|US8784336||23 Aug 2006||22 Jul 2014||C. R. Bard, Inc.||Stylet apparatuses and methods of manufacture|
|US8801693||27 Oct 2011||12 Aug 2014||C. R. Bard, Inc.||Bioimpedance-assisted placement of a medical device|
|US8849382||10 Sep 2009||30 Sep 2014||C. R. Bard, Inc.||Apparatus and display methods relating to intravascular placement of a catheter|
|US8858455||16 Aug 2013||14 Oct 2014||Bard Access Systems, Inc.||Method of locating the tip of a central venous catheter|
|US8971994||8 Apr 2013||3 Mar 2015||C. R. Bard, Inc.||Systems and methods for positioning a catheter|
|US9125578||2 Feb 2011||8 Sep 2015||Bard Access Systems, Inc.||Apparatus and method for catheter navigation and tip location|
|US9211107||7 Nov 2012||15 Dec 2015||C. R. Bard, Inc.||Ruggedized ultrasound hydrogel insert|
|US9265443||5 May 2014||23 Feb 2016||Bard Access Systems, Inc.||Method of locating the tip of a central venous catheter|
|US9339206||14 Jun 2010||17 May 2016||Bard Access Systems, Inc.||Adaptor for endovascular electrocardiography|
|US9345422||3 Oct 2014||24 May 2016||Bard Acess Systems, Inc.||Method of locating the tip of a central venous catheter|
|US9415188||31 Jul 2014||16 Aug 2016||C. R. Bard, Inc.||Bioimpedance-assisted placement of a medical device|
|US9445734||10 Aug 2010||20 Sep 2016||Bard Access Systems, Inc.||Devices and methods for endovascular electrography|
|US9456766||27 May 2011||4 Oct 2016||C. R. Bard, Inc.||Apparatus for use with needle insertion guidance system|
|US9492097||6 Jul 2012||15 Nov 2016||C. R. Bard, Inc.||Needle length determination and calibration for insertion guidance system|
|US9521961||23 Dec 2011||20 Dec 2016||C. R. Bard, Inc.||Systems and methods for guiding a medical instrument|
|US9526440||19 Jun 2014||27 Dec 2016||C.R. Bard, Inc.||System for placement of a catheter including a signal-generating stylet|
|US9532724||22 Sep 2011||3 Jan 2017||Bard Access Systems, Inc.||Apparatus and method for catheter navigation using endovascular energy mapping|
|US9549685||26 Sep 2014||24 Jan 2017||C. R. Bard, Inc.||Apparatus and display methods relating to intravascular placement of a catheter|
|US9554716||27 May 2011||31 Jan 2017||C. R. Bard, Inc.||Insertion guidance system for needles and medical components|
|US9636031||29 Sep 2010||2 May 2017||C.R. Bard, Inc.||Stylets for use with apparatus for intravascular placement of a catheter|
|US9649048||17 Apr 2009||16 May 2017||C. R. Bard, Inc.||Systems and methods for breaching a sterile field for intravascular placement of a catheter|
|US9681823||11 May 2012||20 Jun 2017||C. R. Bard, Inc.||Integrated system for intravascular placement of a catheter|
|USD699359||1 Aug 2012||11 Feb 2014||C. R. Bard, Inc.||Ultrasound probe head|
|USD754357||24 Jan 2014||19 Apr 2016||C. R. Bard, Inc.||Ultrasound probe head|
|International Classification||A61B5/145, A61B5/15|
|18 Oct 2001||AK||Designated states|
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